阅读说明：本技术 并联有源滤波器的高pf定开关频率升压变换器 (High PF (positive-frequency) fixed switching frequency boost converter of parallel active filter ) 是由 杨坚 姚凯 刘劲滔 刘乐 王泽松 李家镇 高阳 于 2020-04-30 设计创作，主要内容包括：本发明公开了一种并联有源滤波器的高PF定开关频率升压变换器,包括主功率电路、有源滤波电路以及控制电路,其中控制电路包括输入电压采样电路、输入电压峰值采样电路、输出电压采样电路、输出电压反馈电路、有源滤波电容电压反馈电路、第一减法电路、第二减法电路、第一乘法器、第二乘法器、第三乘法器、第四乘法器、峰值电流比较电路、平均电流反馈电路、RS锁存器及驱动电路和锯齿波比较器及驱动电路；由前馈运算电路提供峰值电流控制和平均电流控制所需的电流包络和电流基准,实行定开关频率控制方式对变换器进行控制及平均电流控制方式对有源滤波器进行控制。本发明提高了定开关频率CRM Boost PFC变换器的PF值,简化了EMI设计。(The invention discloses a high PF constant switching frequency boost converter connected with an active filter in parallel, which comprises a main power circuit, an active filter circuit and a control circuit, wherein the control circuit comprises an input voltage sampling circuit, an input voltage peak value sampling circuit, an output voltage feedback circuit, an active filter capacitor voltage feedback circuit, a first subtraction circuit, a second subtraction circuit, a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a peak current comparison circuit, an average current feedback circuit, an RS latch, a driving circuit, a sawtooth wave comparator and a driving circuit; the current envelope and the current reference required by peak current control and average current control are provided by a feedforward operation circuit, and a constant switching frequency control mode is adopted to control the converter and an average current control mode is adopted to control the active filter. The method improves the PF value of the CRM Boost PFC converter with the fixed switching frequency, and simplifies the EMI design.)

1. A high PF constant switching frequency boost converter with parallel active filters, comprising: the active filter circuit comprises a main power circuit (1), an active filter circuit (2) and a control circuit, wherein the control circuit comprises an input voltage sampling circuit (3), an input voltage peak value sampling circuit (11), an output voltage sampling circuit (4), an output voltage feedback circuit (10), an active filter capacitor voltage feedback circuit (17), a first subtraction circuit (6), a second subtraction circuit (12), a first multiplier (5), a second multiplier (7), a third multiplier (13), a fourth multiplier (14), a peak current comparison circuit (9), an average current feedback circuit (16), an RS latch and drive circuit (8) and a sawtooth wave comparator and drive circuit (15);

the main power circuit (1) is respectively connected with an active filter circuit (2), an input voltage sampling circuit (3), an output voltage sampling circuit (4), an RS latch and drive circuit (8), a peak current comparison circuit (9) and an output voltage feedback circuit (10), the active filter circuit (2) is respectively connected with a sawtooth wave comparator and drive circuit (15), an average current feedback circuit (16) and an active filter capacitor voltage feedback circuit (17), the input voltage sampling circuit (3) is respectively connected with a first multiplier (5), a first subtraction circuit (6), an input voltage peak sampling circuit (11), a second subtraction circuit (12) and a third multiplier (13), the output voltage sampling circuit (4) is connected with the first subtraction circuit (6), the first multiplier (5) is respectively connected with the first subtraction circuit (6) and the second multiplier (7), the second multiplier (7) is respectively connected with a peak current comparison circuit (9) and an output voltage feedback circuit (10), the RS latch and drive circuit (8) is connected with the peak current comparison circuit (9), the output voltage feedback circuit (10) is connected with a fourth multiplier (14), the input voltage peak value sampling circuit (11) is connected with a second subtraction circuit (12), the second subtraction circuit (12) is connected with a third multiplier (13), the third multiplier (13) is connected with the fourth multiplier (14), the fourth multiplier (14) is connected with an average current feedback circuit (16), the sawtooth wave comparator and drive circuit (15) is connected with the average current feedback circuit (16), and the average current feedback circuit (16) is connected with an active filter capacitor voltage feedback circuit (17);

a feed-forward operation circuit is used for providing a peak current envelope and an average current reference required for carrying out peak current control and average current control, a constant switching frequency control mode of variable conduction time is carried out for controlling the converter, and an average current control mode is carried out for controlling the active filter.

2. The parallel active filter high PF fixed switching frequency boost converter of claim 1, wherein: the main power circuit (1) comprises an input voltage source v_inEMI filter, rectifying circuit RB, LC filter and boost inductor L_bBoost switching tube Q_bAnd a boost diode D_bA first sampling resistor R_s1An output capacitor C_oAnd a load R_Ld(ii) a Said input voltage source v_inThe output port of the EMI filter is connected with the input port of the rectifier bridge RB, the output positive port of the rectifier bridge RB is connected with the input positive port of the LC filter, the output negative port of the rectifier bridge RB is connected with the input negative port of the LC filter, and the output positive ports of the LC filter are respectively connected with the boost inductor L_bIs connected with the active filter circuit (2) and the input voltage sampling circuit (3), and the output negative port of the LC filter is respectively connected with the first sampling resistor R_s1One terminal of (1), an output capacitor C_oNegative terminal of and load R_LdIs connected with the negative terminal of the LC filter, the negative port of the LC filter is a reference potential zero point, and a boost inductor L_bThe other end of the first and second switches is respectively connected with a boost switch tube Q_bDrain terminal of and boost diode D_bIs connected with the positive end of the boost switching tube Q_bRespectively with the first sampling resistor R_s1The other end of the voltage boosting switch tube Q is connected with a peak current comparison circuit (9)_bIs connected to the RS latch and the drive circuit (8), and a boost diode D_bNegative terminal of and output capacitor C_oAnd a load R_LdIs connected to the positive terminal of a load R_LdThe voltage at both ends is output voltage V_oLoad R_LdThe positive terminal of the voltage regulator is connected with the output voltage sampling circuit (4) and the output voltage feedback circuit (10).

3. The parallel active filter high PF fixed switching frequency boost converter of claim 1, wherein: the active filter circuit (2) comprises an active filter inductor L_fA first MOS transistor Q₁A second MOS transistor Q₂Active filter capacitor C_fAnd a second sampling resistor R_s2(ii) a The active filter inductor L_fOne end of the active filter is connected with the output positive port of the LC filter of the main power circuit (1), and the active filter inductor L_fThe other end of the first MOS transistor and the second MOS transistor are respectively connected with a first MOS transistor Q₁Drain terminal and second MOS transistor Q₂Source terminal of the first MOS transistor Q₁Source terminals of the first and second capacitors are connected to an active filter capacitor C_fNegative terminal of (1), second sampling resistor R_s2Is connected with an average current feedback circuit (16), and a second MOS transistor Q₂Drain terminal and active filter capacitor C_fIs connected with the positive end of a first MOS tube Q₁And a second MOS transistor Q₂The grid terminal of the first sampling resistor R is connected with a sawtooth wave comparator and a driving circuit (15)_s2The other end of the active filter is connected with the negative port of an LC filter of the main power circuit (1), the negative port of the LC filter is a reference potential zero point, and an active filter capacitor C_fThe voltage of the positive terminal is the voltage v of the active filter capacitor_CfActive filter capacitor C_fThe positive terminal is connected with an active filter capacitor voltage feedback circuit (17).

4. The parallel active filter high PF fixed switching frequency boost converter of claim 1, wherein: the control circuit comprises a peak current envelope feedforward operation circuit, an average current reference feedforward operation circuit, an active filter capacitor voltage feedback circuit (17), a peak current comparison circuit (9), an average current feedback circuit (16), an RS latch and drive circuit (8) and a sawtooth wave comparator and drive circuit (15), wherein the peak current envelope feedforward operation circuit comprises an input voltage sampling circuit (3), an output voltage sampling circuit (4), a first subtracter (6), a first multiplier (5), an output voltage feedback circuit (10) and a second multiplier (7), and the average current reference feedforward operation circuit comprises an input voltage peak sampling circuit (11), a second subtracter (12), a third multiplier (13) and a fourth multiplier (14);

the signal input end A of an input voltage sampling circuit (3) in the peak current envelope feedforward operation circuit passes through a first resistor R₁With the voltage v of the positive port of the LC filter in the main power circuit (1)_gThe output end B of the input voltage sampling circuit is respectively connected with one input end of the first subtracter (6) and one input end of the first multiplier (5); the signal input end C of the output voltage sampling circuit (4) passes through a third resistor R₃And a load R in the main power circuit (1)_LdVoltage V on the positive terminal_oThe output end D of the output voltage sampling circuit (4) is connected with the other input end of the first subtracter (6), the output end E of the first subtracter (6) is connected with the first multiplier (5)) Is connected with one input end of the second multiplier (7), and the output end F of the first multiplier (5) is connected with one input end of the second multiplier (7); an inverting input terminal G of the output voltage feedback circuit (10) is connected to the tenth resistor R₁₀And a load R in the main power circuit (1)_LdVoltage V on the positive terminal_oConnected to the non-inverting input of an output voltage feedback circuit (10) and to an output voltage reference V_{ref_1}The output end I of the output voltage feedback circuit (10) is connected with the other input end of the second multiplier (7), and the output end H of the second multiplier (7) is connected with the non-inverting input end of the peak current comparison circuit (9);

the non-inverting input end of the peak current comparison circuit (9) is connected with the output end H of the second multiplier (7); the inverting input terminals are respectively connected with the first sampling resistors R_s1And a boost switching tube Q_bThe source terminal of the peak current comparison circuit (9) is connected with the R terminal of the RS latch and the driving circuit (8);

the R end of the RS latch and the drive circuit (8) is connected with the output end of the peak current comparison circuit (9), and the S end of the RS latch and the drive circuit (8) is connected with the current limiting resistor R_zIs connected to a current limiting resistor R_zAnd the other end of the auxiliary inductor L_zOne end of the auxiliary winding is connected with the reference potential zero point, the output end of the RS latch and drive circuit (8) is connected with the boost switching tube drive resistor R_dIs connected with the boost switching tube driving resistor R_dAnd the other end of the voltage boosting switch tube Q_bIs connected with the grid terminal;

an input end a of an input voltage peak voltage sampling circuit (11) in the average current reference feedforward operation circuit is connected with an output end B of the input voltage sampling circuit (3), an output end B of the input voltage peak voltage sampling circuit (11) is connected with one input end of a second subtracter (12), the other input end of the second subtracter (12) is connected with the output end B of the input voltage sampling circuit (3), and an output end c of the second subtracter (12) is connected with an input end v of a third multiplier (13)_yConnected to the input v of a third multiplier (13)_xIs connected with the output end B of the input voltage sampling circuit (3), and the output end d of the third multiplier (13) is connected with the input end v of the fourth multiplier (14)_xConnected to the input v of a fourth multiplier (14)_yConnected to the output terminal I of the output voltage sampling circuit (10), the output terminal e of the fourth multiplier (14) is connected via a twentieth resistor R₂₀Is connected with the input end f of the average current feedback circuit (16);

the inverting input terminal g of the active filter capacitor voltage feedback circuit (17) passes through a twenty-second resistor R₂₂And the voltage v on the positive end of an active filter capacitor in the active filter circuit (2)_CfConnected with the same-phase input end of an active filter capacitor voltage feedback control circuit (17) and an active filter capacitor voltage reference V_{ref_2}Connected, the output h of the active filter capacitor voltage feedback circuit (17) passes through a twenty-fourth resistor R₂₄Is connected with the input end f of the average current feedback circuit (16);

the other input end of the average current feedback circuit (16) and an active filter capacitor C_fAnd a second sampling resistor R_s2One end of the average current feedback circuit (16) is connected with the input end of the sawtooth wave comparator and drive circuit (15);

two paths of outputs of the sawtooth wave comparator and the drive circuit (15) are respectively connected with a first MOS tube drive resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS transistor and the second MOS transistor are respectively connected with a first MOS transistor Q₁And a second MOS transistor Q₂Is connected to the gate terminal.

5. The parallel active filter high PF fixed switching frequency boost converter of claim 1, wherein: output signals of a feedforward operation circuit comprising a peak current envelope feedforward operation circuit and an average current reference feedforward operation circuit are respectively input into a peak current comparator (9) and an average current feedback circuit (16), and different driving signals are generated according to two different control modes of peak current control and average current control, so that the purposes of controlling boost inductive current and active filter inductive current are achieved; the boosting switching tube Q under the control of the fixed switching frequency_bConduction time t_{on_b}Comprises the following steps:

wherein L is_bFor boost inductance, P_oTo output power, V_mFor input voltage amplitude, V_oIs the output voltage, omega is the grid voltage angular frequency, t is the time;

the first MOS transistor Q₁And a second MOS transistor Q₂Complementary conduction, the relationship between duty ratios is:

d₁(t)＝1-d₂(t)

wherein d is₁Is a first MOS transistor Q₁Duty ratio of d₂Is a second MOS transistor Q₂Duty ratio of C_fIs an active filter capacitor, v_cfIs an active filter capacitor C_fUpper capacitor voltage, v_gIs the voltage across the LC filter, V_{Cf_min}Is an active filter capacitor C_fMinimum value of upper capacitor voltage, v_gIs the voltage of the positive terminal of the LC filter, t₀＝2T_linearcsin(8/3π)，T_lineIs the grid voltage cycle.

6. The parallel active filter high PF fixed switching frequency boost converter of claim 4, wherein: the input voltage sampling circuit (3) comprises a first operational amplifier A₁A first resistor R₁And a second resistor R₂(ii) a The first resistor R₁One end of the primary power circuit (1) and the output positive port voltage v of the LC filter of the primary power circuit_gConnected by a first resistor R₁And the other end of the first resistor and a second resistor R₂And a first operational amplifier A₁Is connected with the non-inverting input terminal of the second resistorR₂Is connected to a reference potential zero point, a first operational amplifier A₁Output terminal B and first operational amplifier A₁Is connected to the inverting input terminal of the first operational amplifier A of the input voltage sampling circuit (3)₁The output end B of the voltage sampling circuit is respectively connected with an output voltage sampling circuit (4), a first multiplier (5), a first subtraction circuit (6), an input voltage peak value sampling circuit (11), a second subtraction circuit (12) and a third multiplier (13);

the output voltage sampling circuit (4) comprises a second operational amplifier A₂A third resistor R₃And a fourth resistor R₄(ii) a Third resistor R₃And a load R of the main power circuit (1)_LdPositive terminal voltage V_oConnected, third resistor R₃And the other end of the first resistor and a fourth resistor R₄And a second operational amplifier A₂Is connected to the same-direction input end of the fourth resistor R₄Is connected to a reference potential zero point, a second operational amplifier A₂Output terminal D and second operational amplifier A₂Is connected to the inverting input terminal of the first operational amplifier A of the output voltage sampling circuit (4)₂Is connected with a first subtraction circuit (6);

the first subtraction circuit (6) comprises a fifth resistor R₅A sixth resistor R₆A seventh resistor R₇An eighth resistor R₈And a third operational amplifier A₃(ii) a The fifth resistor R₅Is connected with the output terminal B of the input sampling circuit (3) and is connected with the other end to the third operational amplifier A₃The inverting input terminal of (1); eighth resistor R₈And a third operational amplifier A₃Is connected to the inverting input terminal of the eighth resistor R₈And the other end of the first operational amplifier A and a third operational amplifier A₃The output end E of the switch is connected; a sixth resistor R₆One end of the output voltage sampling circuit is connected with the output end D of the output voltage sampling circuit (4), and the other end of the output voltage sampling circuit is connected with the third operational amplifier A₃The positive phase input end of the switch is connected; a seventh resistor R₇And a third operational amplifier A₃Is connected with the positive input end of the seventh resistor R₇Is connected to a reference potential zero point, a third operational amplifier A₃The output end of (2) is the output end E of the first subtraction circuit (6); the output end E of the first subtraction circuit (6) is connected with the first multiplier (5);

the output voltage feedback circuit (10) comprises a ninth resistor R₉A tenth resistor R₁₀An eleventh resistor R₁₁A first capacitor C₁And a fourth operational amplifier A₄(ii) a The tenth resistor R₁₀And a load R of the main power circuit (1)_LdPositive terminal voltage V_oConnected to the other end of the ninth resistor R₉And a fourth operational amplifier A₄Is connected to the inverting input terminal of the ninth resistor R₉The other end of the reference potential zero point is connected with a reference potential zero point; eleventh resistor R₁₁And a fourth operational amplifier A₄Is connected to the inverting input terminal of the eleventh resistor R₁₁And the other end of the first capacitor C₁Is connected to a first capacitor C₁And the other end of the first operational amplifier A and a fourth operational amplifier A₄The output end is connected; fourth operational amplifier A₄Non-inverting input terminal and output voltage reference V_{ref_1}Connected, fourth operational amplifier A₄I.e. the output terminal I of the output voltage feedback circuit (10), a fourth operational amplifier A of the output voltage feedback circuit (10)₄Are connected to the second and fourth multipliers (14) respectively.

7. The parallel active filter high PF fixed switching frequency boost converter of claim 4, wherein: the peak current comparison circuit (9) comprises a first comparator Cp₁Said first comparator Cp₁Is connected to the output of a second multiplier (7), a first comparator Cp₁And a first sampling resistor R of the main power circuit (1)_s1And boost switching tube Q_bIs connected to the source terminal of a first comparator Cp₁An output terminal of the peak current comparison circuit (9), and a first comparator Cp of the peak current comparison circuit (9)₁The output end of the comparator is connected with the RS latch and the driving circuit (8).

8. The parallel active filter high PF fixed switching frequency boost converter of claim 4, wherein: the input voltage peak value sampling circuit (11) comprises a twelfth resistor R₁₂A thirteenth resistor R₁₃Diode D₁A second capacitor C₂And a fifth operational amplifier A₅(ii) a The twelfth resistor R₁₂One end of the resistor is connected with the output end B of the input voltage sampling circuit (3) and a twelfth resistor R₁₂Another terminal of (1) and a diode D₁Is connected to the positive terminal of a diode D₁Negative terminal of and a second capacitor C₂A thirteenth resistor R₁₃And a fifth operational amplifier A₅Is connected with the non-inverting input terminal of the second capacitor C₂And a thirteenth resistance R₁₃Is connected to a reference potential zero point, a fifth operational amplifier A₅The output end of the voltage regulator is connected with the inverting input end of the voltage regulator; fifth operational amplifier A of input voltage peak value sampling circuit 11₅Is connected with a second subtraction circuit (12);

the second subtraction circuit (12) comprises a fourteenth resistor R₁₄A fifteenth resistor R₁₅Sixteenth resistor R₁₆Seventeenth resistor R₁₇And a sixth operational amplifier A₆(ii) a The sixteenth resistor R₁₆Is connected with the output terminal b of the input voltage peak value sampling circuit (11), and the other end is connected with a sixth operational amplifier A₆The inverting input terminal of (1); seventeenth resistor R₁₇And a third operational amplifier A₃Is connected to the inverting input terminal of the seventeenth resistor R₁₇And the other end of the first operational amplifier A and a third operational amplifier A₃The output end c of the switch is connected; a fifteenth resistor R₁₅One end of the first operational amplifier is connected with the output end B of the input voltage sampling circuit (3), and the other end of the first operational amplifier is connected with the sixth operational amplifier A₆The non-inverting input end of the input terminal is connected; a fourteenth resistance R₁₄And a sixth operational amplifier A₆Is connected to the fourteenth resistor R₁₄Is connected to a reference potential zero point, a sixth operational amplifier A₆Is the output c of the second subtraction circuit (12); sixth operational amplifier A of second subtraction circuit (12)₆Is connected to a third multiplier (13).

9. The parallel active filter high PF fixed switching frequency boost converter of claim 4, wherein: the active filter capacitor voltage feedback circuit (17) comprises a twenty-first resistor R₂₁A twenty-second resistor R₂₂Twenty-fifth resistor R₂₅A fifth capacitor C₅A sixth capacitor C₆And a seventh operational amplifier A₇(ii) a The twenty-second resistor R₂₂And a positive terminal voltage v of an active filter capacitor of the active filter circuit (2)_CfConnected with the other end connected with a twenty-first resistor R₂₁And a seventh operational amplifier A₇The inverting input terminal of (1), the twenty-first resistor R₂₁The other end of the reference potential zero point is connected with a reference potential zero point; twenty-fifth resistor R₂₅And a seventh operational amplifier A₇Is connected to the inverting input terminal of the resistor R, a twenty-fifth resistor R₂₅And the other end of the first capacitor C and a sixth capacitor C₆Is connected to a sixth capacitor C₆And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected to a fifth capacitor C₅And a seventh operational amplifier A₇An inverting input terminal connected to a fifth capacitor C₅And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected, seventh operational amplifier A₇With the same-phase input terminal and the active filter capacitor voltage reference V_{ref_2}Connected, a seventh operational amplifier A₇The output end of the active filter capacitor voltage feedback circuit (17); seventh operational amplifier A of active filter capacitor voltage feedback circuit (17)₇Is connected with an average current feedback circuit (16);

the average current feedback circuit (16) comprises an eighteenth resistor R₁₈Nineteenth resistor R₁₉Twentieth resistor R₂₀Twenty third resistor R₂₃Twenty-fourth resistor R₂₄A third capacitor C₃A fourth capacitor C₄And an eighth operational amplifier A₈(ii) a The nineteenth resistor R₁₉And the negative end of the active filter capacitor of the active filter circuit (2)And a second sampling resistor R_s2Connected with the other end connected with an eighteenth resistor R₁₈And an eighth operational amplifier A₈The eighteenth resistor R₁₈Is connected with a reference potential zero point, a twenty-third resistor R₂₃And an eighth operational amplifier A₈Is connected to the inverting input terminal of the first resistor, a twenty-third resistor R₂₃The other end of the first capacitor and a fourth capacitor C₄Is connected to a fourth capacitor C₄And the other end of the same with an eighth operational amplifier A₈Output terminal connected to a third capacitor C₃And an eighth operational amplifier A₈A third capacitor C connected to the inverting input terminal₃And the other end of the same with an eighth operational amplifier A₈Connected, twentieth resistor R₂₀Is connected to a fourth multiplier, a twenty-fourth resistor R₂₄One end of the second resistor is connected with the output end of the active filter capacitor voltage feedback circuit (17), and the twentieth resistor R₂₀And a twenty-fourth resistor R₂₄And the other end of the same with an eighth operational amplifier A₈Is connected to the non-inverting input terminal of the eighth operational amplifier A₈I.e. the output of the average current feedback circuit (16), an eighth operational amplifier A of the average current feedback circuit (16)₈The output end of the voltage regulator is connected with a sawtooth wave comparator and a driving circuit (15);

the sawtooth comparator and drive circuit (15) includes a second comparator Cp₂RS trigger and drive circuit, the second comparator Cp₂Is connected to the output of the average current feedback circuit (16), a second comparator Cp₂Is connected to the sawtooth wave, a second comparator Cp₂The output end of the RS trigger is connected with the R end of the RS trigger, the S end of the RS trigger is connected with the pulse wave with fixed frequency, and the output end of the RS trigger is connected with the driving circuit. Output of the driving circuit and the first MOS tube driving resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS tube Q is respectively connected with the first MOS tube Q of the active filter circuit (2)₁And a second MOS transistor Q₂Is connected to the gate terminal.

10. The parallel active filter high PF fixed switching frequency boost converter of claim 4, wherein: the RS latch and drive circuit (8) and the peak current comparison circuit (9) are integrated IC circuits of L6561 or L6562 type; the RS latch and the drive circuit (8) are respectively connected with the main power circuit (1) and the peak current comparison circuit (9), and the peak current comparison circuit (9) is respectively connected with the main power circuit (1) and the second multiplier (7);

the sawtooth wave comparator in the sawtooth wave comparator and drive circuit (15) adopts an integrated IC circuit of UC3843 or UC3525 model. The generation circuit of the driving signal selects a logic chip with SN74HC08N, CD4069 or 74HC32N models, the driving circuit selects a driving chip with IR2110 or TLP250 models or a totem-pole driving circuit, and the sawtooth wave comparator and the driving circuit (15) are respectively connected with the active filter circuit (2) and the average current feedback circuit (16);

the first operational amplifier A₁A second operational amplifier A₂A third operational amplifier A₃A fourth operational amplifier A₄A fifth operational amplifier A₅A sixth operational amplifier A₆A seventh operational amplifier A₇And an eighth operational amplifier A₈Selecting operational amplifiers of TL074, TL072, LM358 or LM324 models;

the first multiplier (4), the second multiplier (7), the third multiplier (13) and the fourth multiplier (14) are formed by Integrated Circuit (IC) circuits or discrete devices, the first multiplier (5) is respectively connected with the input voltage sampling circuit (3), the first subtraction circuit (6) and the second multiplier (7), the second multiplier (7) is respectively connected with the peak current comparison circuit (9) and the output voltage feedback circuit (10), the third multiplier (13) is respectively connected with the input voltage sampling circuit (3), the second subtraction circuit (12) and the fourth multiplier (14), and the fourth multiplier (14) is respectively connected with the output voltage feedback circuit (10) and the average current feedback circuit (16).

Technical Field

The invention relates to the technical field of alternating current-direct current converters of electric energy conversion devices, in particular to a high-PF (pulse-frequency) fixed switching frequency boost converter connected with an active filter in parallel.

Background

Boost converter of inductive current Critical Continuous (CRM) switch tube Q due to Boost_bZero current turn-on, boost diode D_bThe method has no reverse recovery, can realize unit Power Factor and the like, and is widely applied to occasions of Power Factor Correction (PFC) of medium and small Power. The constant on-time controlled CRMBoost PFC can theoretically reach unity power factor. However, the switching frequency of the filter has a large variation range within a half power frequency period, which results in complicated design of the inductor and the EMI filter. In order to reduce the variation range of the Switching Frequency, the YaoKai proposes a CRM Boost PFC Converter which adopts variable on-time Control to realize Fixed Switching Frequency in Critical reduction Mode Boost PFC Converter With Fixed Switching Frequency Control. The CRMBoost PFC controlled by the variable conduction time has fixed switching frequency theoretically, so that the design of an inductor and an EMI filter is facilitated, and the loss of a converter is reduced. However, the input current of the converter contains a large amount of harmonic waves, and when the input voltage of the converter is high, the power factor of the converter is particularly low, so that the design technical requirements cannot be met.

Disclosure of Invention

The invention aims to provide a CRM Boost PFC converter controlled by peak current of a parallel active filter, which has sinusoidal input current, high power factor and low cost, and can improve the PF value to be close to 1 in the whole 90-264V AC input voltage range.

The technical solution for realizing the purpose of the invention is as follows: a high PF fixed switching frequency boost converter connected in parallel with an active filter. The converter comprises a main power circuit, an active filter circuit and a control circuit, wherein the control circuit comprises an input voltage sampling circuit, an input voltage peak value sampling circuit, an output voltage feedback circuit, an active filter capacitor voltage feedback circuit, a first subtraction circuit, a second subtraction circuit, a first multiplier, a second multiplier, a third multiplier, a fourth multiplier, a peak current comparison circuit, an average current feedback circuit, an RS latch, a driving circuit, a sawtooth wave comparator and a driving circuit;

furthermore, the main power circuit is respectively connected with an active filter circuit, an input voltage sampling circuit, an output voltage sampling circuit, an RS latch and drive circuit, a peak current comparison circuit and an output voltage feedback circuit, the active filter circuit is respectively connected with a sawtooth wave comparator and drive circuit, an average current feedback circuit and an active filter capacitor voltage feedback circuit, the input voltage sampling circuit is respectively connected with a first multiplier, a first subtraction circuit, an input voltage peak sampling circuit, a second subtraction circuit and a third multiplier, the output voltage sampling circuit is connected with the first subtraction circuit, the first multiplier is respectively connected with the first subtraction circuit and the second multiplier, the second multiplier is respectively connected with the peak current comparison circuit and the output voltage feedback circuit, the RS latch and the drive circuit are connected with the peak current comparison circuit, the output voltage feedback circuit is connected with a fourth multiplier, the input voltage peak value sampling circuit is connected with a second subtraction circuit, the second subtraction circuit is connected with a third multiplier, the third multiplier is connected with a fourth multiplier, the fourth multiplier is connected with an average current feedback circuit, the sawtooth wave comparator and the driving circuit are connected with the average current feedback circuit, and the average current feedback circuit is connected with the active filter capacitor voltage feedback circuit;

a feed-forward operation circuit is used for providing a peak current envelope and an average current reference required for carrying out peak current control and average current control, a constant switching frequency control mode of variable conduction time is carried out for controlling the converter, and an average current control mode is carried out for controlling the active filter.

Further, the main power circuit comprises an input voltage source v_inEMI filter, rectifying circuit RB,LC filter and boost inductor L_bBoost switching tube Q_bAnd a boost diode D_bA first sampling resistor R_s1An output capacitor C_oAnd a load R_Ld(ii) a Said input voltage source v_inThe output port of the EMI filter is connected with the input port of the rectifier bridge RB, the output positive port of the rectifier bridge RB is connected with the input positive port of the LC filter, the output negative port of the rectifier bridge RB is connected with the input negative port of the LC filter, and the output positive ports of the LC filter are respectively connected with the boost inductor L_bOne end of the LC filter is connected with the active filter circuit and the input voltage sampling circuit, and the output negative port of the LC filter is respectively connected with the first sampling resistor R_s1One terminal of (1), an output capacitor C_oNegative terminal of and load R_LdIs connected with the negative terminal of the LC filter, the negative port of the LC filter is a reference potential zero point, and a boost inductor L_bThe other end of the first and second switches is respectively connected with a boost switch tube Q_bDrain terminal of and boost diode D_bIs connected with the positive end of the boost switching tube Q_bRespectively with the first sampling resistor R_s1The other end of the voltage boosting switch tube Q is connected with a peak current comparison circuit_bThe gate terminal of the voltage boosting diode D is connected with the RS latch and the driving circuit_bNegative terminal of and output capacitor C_oAnd a load R_LdIs connected to the positive terminal of a load R_LdThe voltage at both ends is output voltage V_oLoad R_LdThe positive terminal of the voltage sampling circuit is connected with the output voltage sampling circuit and the output voltage feedback circuit.

Further, the active filter circuit comprises an active filter inductor L_fA first MOS transistor Q₁A second MOS transistor Q₂Active filter capacitor C_fAnd a second sampling resistor R_s2. The active filter inductor L_fOne end of the active filter inductor is connected with the output positive port of the LC filter of the main power circuit, and the active filter inductor L_fThe other end of the first MOS transistor and the second MOS transistor are respectively connected with a first MOS transistor Q₁Drain terminal and second MOS transistor Q₂Source terminal of the first MOS transistor Q₁Source terminals of the first and second capacitors are connected to an active filter capacitor C_fNegative terminal of (1), second sampling resistor R_s2And average current feedbackCircuit connection, second MOS transistor Q₂Drain terminal and active filter capacitor C_fIs connected with the positive end of a first MOS tube Q₁And a second MOS transistor Q₂The grid end of the first sampling resistor R is connected with the sawtooth wave comparator and the driving circuit_s2The other end of the active filter is connected with the negative port of the LC filter of the main power circuit, the negative port of the LC filter is a reference potential zero point, and an active filter capacitor C_fThe voltage of the positive terminal is the voltage v of the active filter capacitor_CfActive filter capacitor C_fThe positive end is connected with the voltage feedback circuit of the active filter capacitor.

Further, the control circuit comprises a peak current envelope feedforward operation circuit, an average current reference feedforward operation circuit, an active filter capacitor voltage feedback circuit, a peak current comparison circuit, an average current feedback circuit, an RS latch and driving circuit, a sawtooth wave comparator and driving circuit, wherein the peak current envelope feedforward operation circuit comprises an input voltage sampling circuit, an output voltage sampling circuit, a first subtracter, a first multiplier, an output voltage feedback circuit and a second multiplier, and the average current reference feedforward operation circuit comprises an input voltage peak sampling circuit, a second subtracter, a third multiplier and a fourth multiplier.

Furthermore, the signal input end A of the input voltage sampling circuit in the peak current envelope feedforward operation circuit passes through a first resistor R₁Voltage v of positive port of LC filter in main power circuit_gThe output end B of the input voltage sampling circuit is respectively connected with the input ends of the first subtracter and the first multiplier; the signal input end C of the output voltage sampling circuit passes through a third resistor R₃And a load R in the main power circuit_LdVoltage V on the positive terminal_oThe output end D of the output voltage sampling circuit is connected with the other input end of the first subtracter, the output end E of the first subtracter is connected with the other input end of the first multiplier, and the output end F of the first multiplier is connected with one input end of the second multiplier; the inverting input terminal G of the output voltage feedback circuit passes through a tenth resistor R₁₀And a load R in the main power circuit_LdVoltage V on the positive terminal_oConnected, output voltage feedbackNon-inverting input terminal and output voltage reference V of circuit_{ref_1}And the output end I of the output voltage feedback circuit is connected with the other input end of the second multiplier, and the output end H of the second multiplier is connected with the non-inverting input end of the peak current comparison circuit.

Further, the non-inverting input end of the peak current comparison circuit is connected with the output end H of the second multiplier; the inverting input terminals are respectively connected with the first sampling resistors R_s1And a boost switching tube Q_bThe source terminal of the peak current comparison circuit is connected with the output terminal of the RS latch and the R terminal of the driving circuit.

Furthermore, the R end of the RS latch and the driving circuit is connected with the output end of the peak current comparison circuit, and the S end of the RS latch and the driving circuit is connected with the current limiting resistor R_zIs connected to a current limiting resistor R_zAnd the other end of the auxiliary inductor L_zOne end of the auxiliary winding is connected with the reference potential zero point, the output ends of the RS latch and the driving circuit are connected with the boost switching tube driving resistor R_dIs connected with the boost switching tube driving resistor R_dAnd the other end of the voltage boosting switch tube Q_bIs connected to the gate terminal.

Furthermore, an input end a of an input voltage peak voltage sampling circuit in the average current reference feedforward operation circuit is connected with an output end B of the input voltage sampling circuit, an output end B of the input voltage peak voltage sampling circuit is connected with one input end of a second subtracter, the other input end of the second subtracter is connected with the output end B of the input voltage sampling circuit, and an output end c of the second subtracter is connected with an input end v of a third multiplier_yConnected to the input v of a third multiplier_xThe output end d of the third multiplier is connected with the input end v of the fourth multiplier_xConnected to the input v of a fourth multiplier_yThe output end e of the fourth multiplier is connected with the output end I of the output voltage sampling circuit through a twentieth resistor R₂₀Is connected with the input terminal f of the average current feedback circuit.

Further, the reverse phase input of the active filter capacitor voltage feedback circuitTerminal g passes through a twenty-second resistor R₂₂And the voltage v on the positive end of an active filter capacitor in the active filter circuit_CfThe non-inverting input end of the active filter capacitor voltage feedback control circuit is connected with the active filter capacitor voltage reference V_{ref_2}Connected, the output end h of the voltage feedback circuit of the active filter capacitor passes through a twenty-fourth resistor R₂₄Is connected with the input terminal f of the average current feedback circuit.

Furthermore, the other input end of the average current feedback circuit is connected with an active filter capacitor C_fNegative terminal and second sampling resistor R_s2One end of the average current feedback circuit is connected with the output end of the average current feedback circuit, and the output end of the average current feedback circuit is connected with the input ends of the sawtooth wave comparator and the driving circuit.

Furthermore, two paths of outputs of the sawtooth wave comparator and the drive circuit are respectively connected with a first MOS tube drive resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS transistor and the second MOS transistor are respectively connected with a first MOS transistor Q₁And a second MOS transistor Q₂Is connected to the gate terminal.

Further, output signals of a feedforward operation circuit comprising a peak current envelope feedforward operation circuit and an average current reference feedforward operation circuit are respectively input into a peak current comparator and an average current feedback circuit, and different driving signals are generated according to two different control modes of peak current control and average current control, so that the purposes of controlling boost inductive current and active filter inductive current are achieved; the boosting switching tube Q under the control of the fixed switching frequency_bConduction time t_{on_b}Comprises the following steps:

wherein L is_bFor boost inductance, P_oTo output power, V_mFor input voltage amplitude, V_oTo output voltage, ω is the grid voltage angular frequency and t is time.

The first MOS transistor Q₁And a second MOS transistor Q₂Complementary conduction between duty cyclesThe relationship is as follows:

d₁(t)＝1-d₂(t)

wherein d is₁Is a first MOS transistor Q₁Duty ratio of d₂Is a second MOS transistor Q₂Duty ratio of C_fIs an active filter capacitor, v_cfIs an active filter capacitor C_fUpper capacitor voltage, v_gIs the voltage across the LC filter, V_{Cf_min}Is an active filter capacitor C_fMinimum value of upper capacitor voltage, v_gIs the voltage of the positive terminal of the LC filter, t₀＝2T_linearcsin(8/3π)，T_lineIs the grid voltage cycle.

Further, the input voltage sampling circuit comprises a first operational amplifier A₁A first resistor R₁And a second resistor R₂(ii) a The first resistor R₁One end of the primary power circuit and the output positive port voltage v of the LC filter of the primary power circuit_gConnected by a first resistor R₁And the other end of the first resistor and a second resistor R₂And a first operational amplifier A₁Is connected with the non-inverting input terminal of the first resistor R₂Is connected to a reference potential zero point, a first operational amplifier A₁Output terminal B and first operational amplifier A₁Is connected to the first operational amplifier A of the input voltage sampling circuit₁The output end B of the voltage sampling circuit is respectively connected with the output voltage sampling circuit, the first multiplier, the first subtraction circuit, the input voltage peak value sampling circuit, the second subtraction circuit and the third multiplier.

Further, the output voltage sampling circuit comprises a second operational amplifier A₂A third resistor R₃And a fourth resistor R₄(ii) a Third resistor R₃And a load R of the main power circuit_LdPositive terminal ofVoltage V_oConnected, third resistor R₃And the other end of the first resistor and a fourth resistor R₄And a second operational amplifier A₂Is connected to the same-direction input end of the fourth resistor R₄Is connected to a reference potential zero point, a second operational amplifier A₂Output terminal D and second operational amplifier A₂Is connected to the inverting input terminal of the first operational amplifier A, and outputs a voltage sampling circuit₂Is connected to the first subtraction circuit.

Further, the first subtraction circuit comprises a fifth resistor R₅A sixth resistor R₆A seventh resistor R₇An eighth resistor R₈And a third operational amplifier A₃(ii) a The fifth resistor R₅Is connected with the output terminal B of the input sampling circuit, and the other end is connected with the third operational amplifier A₃The inverting input terminal of (1); eighth resistor R₈And a third operational amplifier A₃Is connected to the inverting input terminal of the eighth resistor R₈And the other end of the first operational amplifier A and a third operational amplifier A₃The output end E of the switch is connected; a sixth resistor R₆One end of the output voltage sampling circuit is connected with the output end D of the output voltage sampling circuit, and the other end of the output voltage sampling circuit is connected with the third operational amplifier A₃The positive phase input end of the switch is connected; a seventh resistor R₇And a third operational amplifier A₃Is connected with the positive input end of the seventh resistor R₇Is connected to a reference potential zero point, a third operational amplifier A₃The output end of the first subtraction circuit is the output end E of the first subtraction circuit; the output E of the first subtraction circuit is connected to the first multiplier.

Furthermore, the output voltage feedback circuit comprises a ninth resistor R₉A tenth resistor R₁₀An eleventh resistor R₁₁A first capacitor C₁And a fourth operational amplifier A₄(ii) a The tenth resistor R₁₀And a load R of the main power circuit_LdPositive terminal voltage V_oConnected to the other end of the ninth resistor R₉And a fourth operational amplifier A₄Is connected to the inverting input terminal of the ninth resistor R₉The other end of the reference potential zero point is connected with a reference potential zero point; eleventh resistor R₁₁And a fourth operational amplifier A₄Is connected to the inverting input terminal of the eleventh resistor R₁₁And the other end of the first capacitor C₁Is connected to a first capacitor C₁And the other end of the first operational amplifier A and a fourth operational amplifier A₄The output end is connected; fourth operational amplifier A₄Non-inverting input terminal and output voltage reference V_{ref_1}Connected, fourth operational amplifier A₄I.e. the output terminal I of the output voltage feedback circuit. Fourth operational amplifier A of output voltage feedback circuit₄The output end I is respectively connected with the second multiplier and the fourth multiplier.

Further, the peak current comparison circuit includes a first comparator Cp₁Said first comparator Cp₁Is connected to the output of the second multiplier, a first comparator Cp₁And a first sampling resistor R of the main power circuit_s1And boost switching tube Q_bIs connected to the source terminal of a first comparator Cp₁I.e. the output of the peak current comparison circuit, the first comparator Cp of the peak current comparison circuit₁The output end of the latch is connected with the RS latch and the drive circuit.

Further, the input voltage peak value sampling circuit comprises a twelfth resistor R₁₂A thirteenth resistor R₁₃Diode D₁A second capacitor C₂And a fifth operational amplifier A₅(ii) a The twelfth resistor R₁₂One end of the resistor is connected with the output end B of the input voltage sampling circuit (3) and a twelfth resistor R₁₂Another terminal of (1) and a diode D₁Is connected to the positive terminal of a diode D₁Negative terminal of and a second capacitor C₂A thirteenth resistor R₁₃And a fifth operational amplifier A₅Is connected with the non-inverting input terminal of the second capacitor C₂And a thirteenth resistance R₁₃Is connected to a reference potential zero point, a fifth operational amplifier A₅The output end of the voltage regulator is connected with the inverting input end of the voltage regulator; fifth operational amplifier A of input voltage peak value sampling circuit₅Is connected to the second subtraction circuit.

Further, the air conditioner is provided with a fan,the second subtraction circuit comprises a fourteenth resistor R₁₄A fifteenth resistor R₁₅Sixteenth resistor R₁₆Seventeenth resistor R₁₇And a sixth operational amplifier A₆(ii) a The sixteenth resistor R₁₆Is connected with the output end b of the input voltage peak value sampling circuit, and the other end is connected with a sixth operational amplifier A₆The inverting input terminal of (1); seventeenth resistor R₁₇And a third operational amplifier A₃Is connected to the inverting input terminal of the seventeenth resistor R₁₇And the other end of the first operational amplifier A and a third operational amplifier A₃The output end c of the switch is connected; a fifteenth resistor R₁₅One end of the first operational amplifier is connected with the output end B of the input voltage sampling circuit, and the other end of the first operational amplifier is connected with the sixth operational amplifier A₆The non-inverting input end of the input terminal is connected; a fourteenth resistance R₁₄And a sixth operational amplifier A₆Is connected to the fourteenth resistor R₁₄Is connected to a reference potential zero point, a sixth operational amplifier A₆The output end of the first subtraction circuit is the output end c of the second subtraction circuit; sixth operational amplifier A of the second subtracting circuit₆Is connected to the third multiplier.

Further, the active filter capacitor voltage feedback circuit comprises a twenty-first resistor R₂₁A twenty-second resistor R₂₂Twenty-fifth resistor R₂₅A fifth capacitor C₅A sixth capacitor C₆And a seventh operational amplifier A₇(ii) a The twenty-second resistor R₂₂And the positive end voltage v of the active filter capacitor of the active filter circuit_CfConnected with the other end connected with a twenty-first resistor R₂₁And a seventh operational amplifier A₇The inverting input terminal of (1), the twenty-first resistor R₂₁The other end of the reference potential zero point is connected with a reference potential zero point; twenty-fifth resistor R₂₅And a seventh operational amplifier A₇Is connected to the inverting input terminal of the resistor R, a twenty-fifth resistor R₂₅And the other end of the first capacitor C and a sixth capacitor C₆Is connected to a sixth capacitor C₆And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected to a fifth capacitor C₅And a seventh operational amplifier A₇Reverse phase transmissionInput terminal connection, a fifth capacitor C₅And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected, seventh operational amplifier A₇With the same-phase input terminal and the active filter capacitor voltage reference V_{ref_2}Connected, a seventh operational amplifier A₇The output end of the active filter capacitor voltage feedback circuit is the output end of the active filter capacitor voltage feedback circuit; seventh operational amplifier A of active filter capacitor voltage feedback circuit₇Is connected with the average current feedback circuit.

Further, the average current feedback circuit comprises an eighteenth resistor R₁₈Nineteenth resistor R₁₉Twentieth resistor R₂₀Twenty third resistor R₂₃Twenty-fourth resistor R₂₄A third capacitor C₃A fourth capacitor C₄And an eighth operational amplifier A₈(ii) a The nineteenth resistor R₁₉One end of the first sampling resistor, the negative end of the active filter capacitor of the active filter circuit and the second sampling resistor R_s2Connected with the other end connected with an eighteenth resistor R₁₈And an eighth operational amplifier A₈The eighteenth resistor R₁₈Is connected with a reference potential zero point, a twenty-third resistor R₂₃And an eighth operational amplifier A₈Is connected to the inverting input terminal of the first resistor, a twenty-third resistor R₂₃The other end of the first capacitor and a fourth capacitor C₄Is connected to a fourth capacitor C₄And the other end of the same with an eighth operational amplifier A₈Output terminal connected to a third capacitor C₃And an eighth operational amplifier A₈A third capacitor C connected to the inverting input terminal₃And the other end of the same with an eighth operational amplifier A₈Connected, twentieth resistor R₂₀Is connected to a fourth multiplier, a twenty-fourth resistor R₂₄One end of the second resistor is connected with the output end of the voltage feedback circuit of the active filter capacitor, and the twentieth resistor R₂₀And a twenty-fourth resistor R₂₄And the other end of the same with an eighth operational amplifier A₈Is connected to the non-inverting input terminal of the eighth operational amplifier A₈I.e. the output of the average current feedback circuit, the eighth operational amplifier a of the average current feedback circuit₈Output terminal of the comparator and the sawtooth wave comparatorAnd a drive circuit;

furthermore, the sawtooth wave comparator and the driving circuit comprise a second comparator Cp₂RS trigger and drive circuit, the second comparator Cp₂Is connected to the output of the average current feedback circuit, a second comparator Cp₂Is connected to the sawtooth wave, a second comparator Cp₂The output end of the RS trigger is connected with the R end of the RS trigger, the S end of the RS trigger is connected with the pulse wave with fixed frequency, and the output end of the RS trigger is connected with the driving circuit. Output of the driving circuit and the first MOS tube driving resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS transistor and the other end of the second MOS transistor are respectively connected with a first MOS transistor Q of an active filter circuit₁And a second MOS transistor Q₂Is connected to the gate terminal.

Furthermore, the RS latch, the driving circuit and the peak current comparison circuit are integrated IC circuits of L6561 or L6562 type; the RS latch and the driving circuit are respectively connected with the main power circuit and the peak current comparison circuit, and the peak current comparison circuit is respectively connected with the main power circuit and the second multiplier.

Furthermore, the sawtooth wave comparator in the sawtooth wave comparator and driving circuit adopts an integrated IC circuit of a model of UC3843 or UC 3525. The generation circuit of the driving signal selects a logic chip with SN74HC08N, CD4069 or 74HC32N models, the driving circuit selects a driving chip with IR2110 or TLP250 models or a totem pole driving circuit, and the sawtooth wave comparator and the driving circuit are respectively connected with the active filter circuit and the average current feedback circuit.

Further, the first operational amplifier A₁A second operational amplifier A₂A third operational amplifier A₃A fourth operational amplifier A₄A fifth operational amplifier A₅A sixth operational amplifier A₆A seventh operational amplifier A₇And an eighth operational amplifier A₈Operational amplifiers of TL074, TL072, LM358 or LM324 models are selected.

Furthermore, the first multiplier, the second multiplier, the third multiplier and the fourth multiplier are formed by integrated IC circuits or discrete devices, the first multiplier is respectively connected with the input voltage sampling circuit, the first subtraction circuit and the second multiplier, the second multiplier is respectively connected with the peak current comparison circuit and the output voltage feedback circuit, the third multiplier is respectively connected with the input voltage sampling circuit, the second subtraction circuit and the fourth multiplier, and the fourth multiplier is respectively connected with the output voltage feedback circuit and the average current feedback circuit.

Compared with the prior art, the invention has the remarkable advantages that: (1) the feedforward operation circuit is used for providing peak current envelope and average current reference required by implementing peak current control and average current control, a constant switching frequency control mode of variable conduction time is implemented to control the converter, and an average current control mode is implemented to control the active filter, so that the power factor of the converter can be improved to be close to 1 in the whole 90V-264V AC input voltage range, and the feedforward operation circuit has the advantages of high input power factor and low cost; (2) the switching frequency range of the CRM Boost PFC converter is reduced, and output voltage ripples are reduced.

Drawings

Fig. 1 is a diagram of a main circuit and a control circuit of a CRM Boost PFC converter connected with an active filter in parallel according to the present embodiment of the invention.

Fig. 2 is a schematic diagram of a CRM Boost PFC converter main circuit with parallel active filters in an embodiment of the present invention.

Fig. 3 is a waveform diagram of an inductive current, a switching tube or a MOS tube driving of the CRM Boost PFC converter connected in parallel with the active filter in a switching period in the embodiment of the present invention, where fig. (a) is a waveform diagram of the CRM Boost PFC converter during operation, and fig. (b) is a waveform diagram of the active filter during operation.

Fig. 4 is a diagram of the variation of the switching frequency of the CRM Boost PFC converter within a half power frequency period under the control of the conventional fixed on-time in the embodiment of the present invention.

Fig. 5 is a diagram of the input current and the harmonic current component in the input current of the CRM Boost PFC converter under the control of the fixed switching frequency in the embodiment of the present invention.

Fig. 6 is a PF-value comparison of a fixed switching frequency controlled down-converter and a parallel active filter converter in an embodiment of the invention.

Fig. 7 is a diagram of a CRM Boost PFC converter main circuit and a control circuit for implementing fixed switching frequency control with variable on-time in the embodiment of the present invention.

Fig. 8 is a graph of input voltage and current, current and harmonic components of the Boost inductor, input instantaneous power, active filter inductor current, and active filter capacitor voltage waveforms for the CRM Boost PFC converter in parallel with the active filter in the embodiment of the present invention.

Fig. 9 is a graph of the variation of the switching frequency of the fixed switching frequency CRM Boost PFC converter in a half power frequency cycle in the embodiment of the present invention.

Fig. 10 is a graph showing the variation of the per unit value of input power in a half power frequency period under the conventional constant on-time control method and constant switching frequency control in the embodiment of the present invention.

Fig. 11 is a graph showing the variation of the ratio of the output voltage ripple under the control of the conventional constant on-time control method and the constant switching frequency control according to the embodiment of the present invention.

Main symbol names in the above figures: v. of_inAnd a power supply voltage. i.e. i_inAnd inputting the current. RB, a rectifier bridge. v. of_gAnd the input voltage after the LC filter. i.e. i_LbAnd boosting the inductor current. L is_bAnd a boost inductor. Q_bAnd a boost switching tube. R_s1And a first sampling resistor. D_bAnd a boost diode. C_oAnd an output capacitor. R_LdAnd a load. V_oAnd outputting the voltage. i.e. i_LfAnd active filtering of the inductor current. L is_fAnd an active filter inductor. Q₁And a first MOS transistor. Q₂And a second MOS transistor. R_s2And a second sampling resistor. C_fAnd an active filter capacitor. V_CfActive filter capacitor voltage. v. of_gsAnd a driving signal of the boost switching tube. v. of_gs1And a driving signal of the first MOS tube. v. of_gs2And a driving signal of the second MOS tube. i.e. i_{Lb_pk}And boost inductor current peak. t is t_{on_b}Of step-up switching tubeThe on time. t is t_{off_b}And the turn-off time of the boost switching tube. t is t_{s_b}And the switching period of the boost switching tube. d₁And the duty ratio of the first MOS tube. d₂And the duty ratio of the second MOS tube. t is t_{s_f}And switching period of the MOS tube. f. of_{s_b}And the switching frequency of the boost switching tube. f. of_{s_1}And the switching frequency of the boost switching tube is controlled by the fixed conduction time. ω, angular frequency of the input voltage. i.e. i_{in_b}And a fixed switching frequency converter input current. i.e. i_{in_h}And the fixed switching frequency converter inputs harmonic current. i.e. i_{in_h1}The fixed switching frequency converter inputs fundamental wave current. i.e. i_{in_h3}And the fixed switching frequency converter inputs third harmonic current. i.e. i_{in_h5}The fixed switching frequency converter inputs fifth harmonic current. i.e. i_{in_h7}And the fixed switching frequency converter inputs seventh harmonic current. V_rmsAnd an input voltage effective value. V_{ref_1}And outputting the voltage reference voltage. i.e. i_{Lb_b}And boosting the inductive current by the fixed switching frequency converter. i.e. i_{Lb_h}And boosting the harmonic current of the inductor by the fixed switching frequency converter. p is a radical of_inAnd instantaneous input power of the power grid. p is a radical of_{in_b}Instantaneous input power of the converter. p is a radical of_{in_f}Active filter instantaneous input power. i.e. i_{in_f}An active filter input current. V_{ref_2}And voltage reference voltage of the active filter capacitor. v. of_EAAnd outputting the error voltage signal controlled by the output voltage feedback.The fixed on-time controls the instantaneous input power per unit value of the converter.The variable on-time controls the instantaneous input power per unit value of the converter. ω t_c2And the electrical angle of the intersection point of the instantaneous input power per unit value and 1 under the control of the fixed switching frequency. Δ V_{o_1}Output voltage ripple value delta V under control of fixed on-time_{o_2}And the output voltage ripple value under the control of the fixed switching frequency.

Detailed Description

The invention is described in further detail below with reference to the figures and the embodiments.

1CRM Boost PFC converter

1.1 working principle of CRM Boost PFC converter with fixed switching frequency

Fig. 2 is a high PF fixed switching frequency CRM Boost PFC converter main circuit with parallel active filters.

Setting: 1. all devices are ideal elements; 2. the output voltage ripple is very small compared to its dc amount; 3. the switching frequency is much higher than the input voltage frequency.

Fig. 3 shows the inductor current waveform during one switching period of the converter, wherein (a) is the waveform of the CRM Boost PFC converter during operation. When the boost switch tube Q_bWhen conducting, the boost diode D_bCut-off and boost inductor L_bThe voltage at both ends is LC filter post-voltage v_gCurrent of i thereof_LbStarting from zero with v_g/L_bIs linearly increased, the load R_LdPowered by an output capacitor Co. When Q is_bAt the time of cut-off, D_bConduction, i_LbBy D_bFollow current, L_bVoltage across v_g-V_o，i_LbWith (v)_g-V_o)/L_bThe slope of (c) decreases. When i is_LbAfter the voltage drops to zero, the boost switch tube Q_bAnd is turned on again.

Without loss of generality, define the input AC voltage v_inThe expression of (a) is:

v_in＝V_msinωt (1)

wherein V_mAnd ω is the amplitude and angular frequency of the input ac voltage, respectively.

The voltage v rectified by the input voltage and passing through the LC filter_gComprises the following steps:

v_g＝V_m|sinωt| (2)

by analyzing the working mode of the converter, the peak value i of the boost voltage inductive current can be obtained_{Lb_pk}Average value of boost inductor current i_{Lb_avg}And an input current i_inExpression (c):

wherein t is_onIndicating boost switch tube Q_bThe on-time of (c).

In each switching cycle, the boost inductor L_bBoth ends satisfy the volt-second area balance, then Q_bOff time t of_offAnd a switching frequency f_sThe expression is as follows:

from the equation (5), the input current of the conventional CRM Boost PFC converter controlled by the fixed on-time automatically follows the output voltage, and the theoretical PF value is 1. However, the switching frequency of the converter is constantly changing, and the switching frequency of a conventional fixed on-time controlled down-converter can be plotted by equation (7), as shown in fig. 4. As can be seen from the figure, the switching frequency of the converter constantly changes within a half power frequency cycle, and when the input voltage is 264VAC, the switching frequency change range is: 30kHz to 454 kHz.

In order to realize the fixation of the switching frequency of the CRM Boost PFC converter, the combination formula (7) is used for determining the on-time t if the on-time t is changed_{on_b}：

Switching frequency expression f of converter for determining switching frequency_{s_b}The following were used:

where k is a constant, and the input voltage V of the CRM Boost PFC converter_mAn output voltage V_oOutput power P_oAnd boost inductance value L_bAnd the like.

Input current average value i of CRM Boost PFC converter with fixed switching frequency_{in_b}The expression of (a) is:

combining power balance and equation (10):

the formula (12) is replaced by the formula (8), and the switch tube Q is boosted under the control_bOn-time t of_{on_b}Expression (c):

input current i_{in_b}The expression of (a) is:

by performing fourier decomposition on equation (15), the input current can be written as the sum of the fundamental and harmonic, as shown in fig. 5:

where n represents the number of harmonics.

As can be seen from equation (16), the input current of the CRM Boost PFC converter with a fixed switching frequency contains a large amount of harmonic components, so that the THD of the converter increases and the power factor decreases, as shown in fig. 6. As can be seen from the figure, V_mThe larger the PF value, the lower the PF value. In the 90V-264V AC input voltage range, when the input voltage is 264V AC and the output voltage is 400V, the PF value is only 0.79.

1.2 control circuit

Fig. 7 is a circuit for implementing constant switching frequency control with variable on-time. Input voltage v after LC filter_gThrough a first resistor R₁And a first resistor R₂Dividing the voltage and inputting the voltage into a voltage sampling circuit to obtain v_B＝k_vgV_m|sinωt|，k_vgIs the coefficient of partial pressure, k_vg＝R₂/(R₁+R₂). Output voltage V_oThrough a third resistor R₃And a fourth resistor R₄Voltage division, obtaining v by an output voltage sampling circuit_D＝k_vgV_oWherein R is₃/R₄＝R₁/R₂。v_BAnd v_DV is obtained by a first subtraction circuit_E＝k_vg(V_o-V_msin ω t), and R₇＝R₈＝R₅＝R₆. Output v of the first multiplier_F＝k_vg ²V_msinωt(V_o-V_msin ω t). On the other hand, the output voltage V in the output voltage feedback circuit_oThrough a ninth resistor R₉And a tenth resistor R₁₀Divided sampling, and reference voltage V of output voltage of error amplifier_{ref_1}In contrast, here V_{ref_1}＝2.5V，R₁₀＝159R₉Via the eleventh R₁₁And a first capacitor C₁The constituent regulator deriving an error signal v_EA，v_EAAnd v_FAnd after the second multiplier is connected, the potential of the H point is obtained as follows:

the control chip uses L6561, and the control circuit adopts peak current control. Comparing formula (17) with formula (15), v_HThe change rule of the boost inductance current peak value under the control of fixed switching frequency is consistent with the change rule of the boost inductance current peak value under the control of adopting variable conduction time. v. of_HThe positive phase input end of a peak current comparator in the control chip L6561 is connected, and the negative phase input end of the comparator is the detection voltage v of the switching tube loop_S. The conduction time t of the converter_{on_b}Comprises the following steps:

after the converter is stably operated, the error adjusting signal v can be approximately considered_EAIs constant, thereby realizing the variable on-time control shown in the equation (14).

Further, the converter for realizing fixed switching frequency by changing the conduction time comprises a main power circuit 1 and a control circuit, wherein the control circuit comprises an input voltage sampling circuit 3, an output voltage sampling circuit 4, an output voltage feedback circuit 10, a first subtraction circuit 6, a first multiplier 5, a second multiplier 7, a peak current comparison circuit 9 and an RS latch and drive circuit 8; a feed-forward operation circuit is used to provide a peak current envelope required for peak current control, and a constant switching frequency control mode of variable conduction time is used to control the converter.

Further, the main power circuit 1 is connected to an input voltage sampling circuit 3, an output voltage sampling circuit 4, an RS latch and drive circuit 8, a peak current comparison circuit 9, and an output voltage feedback circuit 10, respectively, the input voltage sampling circuit 3 is connected to a first multiplier 5 and a first subtraction circuit 6, the output voltage sampling circuit 4 is connected to the first subtraction circuit 6, the first multiplier 5 is connected to the first subtraction circuit 6 and a second multiplier 7, the second multiplier 7 is connected to the peak current comparison circuit 9 and the output voltage feedback circuit 10, respectively, and the RS latch and drive circuit 8 is connected to the peak current comparison circuit 9.

Further, a main power circuit 1Comprising an input voltage source v_inEMI filter, rectifying circuit RB, LC filter and boost inductor L_bBoost switching tube Q_bAnd a boost diode D_bA first sampling resistor R_s1An output capacitor C_oAnd a load R_Ld(ii) a Said input voltage source v_inThe output port of the EMI filter is connected with the input port of the rectifier bridge RB, the output positive port of the rectifier bridge RB is connected with the input positive port of the LC filter, the output negative port of the rectifier bridge RB is connected with the input negative port of the LC filter, and the output positive ports of the LC filter are respectively connected with the boost inductor L_bIs connected with the input voltage sampling circuit 3, and the output negative port of the LC filter is respectively connected with the first sampling resistor R_s1One terminal of (1), an output capacitor C_oNegative terminal of and load R_LdIs connected with the negative terminal of the LC filter, the negative port of the LC filter is a reference potential zero point, and a boost inductor L_bThe other end of the first and second switches is respectively connected with a boost switch tube Q_bDrain terminal of and boost diode D_bIs connected with the positive end of the boost switching tube Q_bRespectively with the first sampling resistor R_s1The other end of the voltage boosting switch tube Q is connected with a peak current comparison circuit_bHas its gate terminal connected to the RS latch and the driving circuit 8, and a boost diode D_bNegative terminal of and output capacitor C_oAnd a load R_LdIs connected to the positive terminal of a load R_LdThe voltage at both ends is output voltage V_oLoad R_LdIs connected to the output voltage sampling circuit 4 and the output voltage feedback circuit 10.

Further, the control circuit comprises a peak current envelope feedforward operation circuit, a peak current comparison circuit 9 and an RS latch and drive circuit 8, wherein the peak current envelope feedforward operation circuit comprises an input voltage sampling circuit 3, an output voltage sampling circuit 4, a first subtracter 6, a first multiplier 5, an output voltage feedback circuit 10 and a second multiplier 7.

Further, the signal input end A of the input voltage sampling circuit 3 in the peak current envelope feedforward operation circuit passes through a first resistor R₁And the positive port of the LC filter in the main power circuit 1Voltage v of_gThe output end B of the input voltage sampling circuit 3 is respectively connected with the first subtracter 6 and one input end of the first multiplier 5; the signal input end C of the output voltage sampling circuit 4 passes through a third resistor R₃And a load R in the main power circuit 1_LdVoltage V on the positive terminal_oThe output end D of the output voltage sampling circuit 4 is connected with the other input end of the first subtracter 6, the output end E of the first subtracter 6 is connected with the other input end of the first multiplier 5, and the output end F of the first multiplier 5 is connected with one input end of the second multiplier 7; the inverting input terminal G of the output voltage feedback circuit 10 passes through the tenth resistor R₁₀And a load R in the main power circuit 1_LdVoltage V on the positive terminal_oConnected to output voltage feedback circuit 10_{ref_1}The output end I of the output voltage feedback circuit 10 is connected with the other input end of the second multiplier 7, and the output end H of the second multiplier 7 is connected with the non-inverting input end of the peak current comparison circuit 9.

Further, the non-inverting input terminal of the peak current comparing circuit 9 is connected to the output terminal H of the second multiplier; the inverting input terminals are respectively connected with the first sampling resistors R_s1And a boost switching tube Q_bThe source terminal of which is connected, and the output terminal of the peak current comparison circuit 9 is connected with the R terminal of the RS latch and drive circuit 8.

Furthermore, the R terminal of the RS latch and driving circuit 8 is connected to the output terminal of the peak current comparing circuit 9, and the S terminal of the RS latch and driving circuit 8 is connected to the current limiting resistor R_zIs connected to a current limiting resistor R_zAnd the other end of the auxiliary inductor L_zOne end of the auxiliary winding is connected with the reference potential zero point, the output end of the RS latch and drive circuit 8 is connected with the boost switching tube drive resistor R_dIs connected with the boost switching tube driving resistor R_dAnd the other end of the voltage boosting switch tube Q_bIs connected to the gate terminal.

Further, an output signal of the peak current envelope feedforward operation circuit is input to the peak current comparator 9, and a driving signal is generated according to the peak current control, so that the purpose of controlling the boost inductive current is achieved; what is needed isBoost switching tube Q under control of fixed switching frequency_bConduction time t_{on_b}Comprises the following steps:

wherein L is_bFor boost inductance, P_oTo output power, V_mFor input voltage amplitude, V_oTo output voltage, ω is the grid voltage angular frequency and t is time.

Further, the input voltage sampling circuit 3 includes a first operational amplifier A₁A first resistor R₁And a second resistor R₂(ii) a The first resistor R₁And one end of the primary power circuit 1 and the output positive port voltage v of the LC filter of the primary power circuit 1_gConnected by a first resistor R₁And the other end of the first resistor and a second resistor R₂And a first operational amplifier A₁Is connected with the non-inverting input terminal of the first resistor R₂Is connected to a reference potential zero point, a first operational amplifier A₁Output terminal B and first operational amplifier A₁Is connected to the inverting input terminal of the first operational amplifier A of the input voltage sampling circuit 1₁The output terminal B of which is connected to the first multiplier 5, the first subtraction circuit 6, the input voltage peak value sampling circuit 11, the second subtraction circuit 12 and the third multiplier 13, respectively.

Further, the output voltage sampling circuit 4 comprises a second operational amplifier A₂A third resistor R₃And a fourth resistor R₄(ii) a Third resistor R₃And a load R of the main power circuit 1_LdPositive terminal voltage V_oConnected, third resistor R₃And the other end of the first resistor and a fourth resistor R₄And a second operational amplifier A₂Is connected to the same-direction input end of the fourth resistor R₄Is connected to a reference potential zero point, a second operational amplifier A₂Output terminal D and second operational amplifier A₂Is connected to the first subtraction circuit 6, and the output terminal D of the output voltage sampling circuit 4 is connected to the second subtraction circuit 6.

Further, the said firstA subtracting circuit 6 comprising a fifth resistor R₅A sixth resistor R₆A seventh resistor R₇An eighth resistor R₈And a third operational amplifier A₃(ii) a The fifth resistor R₅Is connected with the output terminal B of the input sampling circuit 3, and the other end is connected to the third operational amplifier a₃The inverting input terminal of (1); eighth resistor R₈And a third operational amplifier A₃Is connected to the inverting input terminal of the eighth resistor R₈And the other end of the first operational amplifier A and a third operational amplifier A₃The output end E of the switch is connected; a sixth resistor R₆One end of the output voltage sampling circuit is connected with the output end D of the output voltage sampling circuit 4, and the other end of the output voltage sampling circuit is connected with the third operational amplifier A₃The positive phase input end of the switch is connected; a seventh resistor R₇And a third operational amplifier A₃Is connected with the positive input end of the seventh resistor R₇Is connected to a reference potential zero point, a third operational amplifier A₃The output terminal of (a) is the output terminal E of the first subtraction circuit 6; the output E of the first subtraction circuit 6 is connected to the first multiplier 5.

Further, the output voltage feedback circuit 10 includes a ninth resistor R₉A tenth resistor R₁₀An eleventh resistor R₁₁A first capacitor C₁And a fourth operational amplifier A₄(ii) a The tenth resistor R₁₀And a load R of the main power circuit 1_LdPositive terminal voltage V_oConnected to the other end of the ninth resistor R₉And a fourth operational amplifier A₄Is connected to the inverting input terminal of the ninth resistor R₉The other end of the reference potential zero point is connected with a reference potential zero point; eleventh resistor R₁₁And a fourth operational amplifier A₄Is connected to the inverting input terminal of the eleventh resistor R₁₁And the other end of the first capacitor C₁Is connected to a first capacitor C₁And the other end of the first operational amplifier A and a fourth operational amplifier A₄The output end is connected; fourth operational amplifier A₄Non-inverting input terminal and output voltage reference V_{ref_1}Connected, fourth operational amplifier A₄I.e. the output I of the output voltage feedback circuit 10. Fourth operational amplifier a of output voltage feedback circuit 10₄The output I is connected to the second multiplier 7 and the fourth multiplier 14, respectively.

Further, the peak current comparing circuit 9 includes a first comparator Cp₁Said first comparator Cp₁Is connected to the output of the second multiplier 7, a first comparator Cp₁And the first sampling resistor R of the main power circuit 1_s1And boost switching tube Q_bIs connected to the source terminal of a first comparator Cp₁An output terminal of the peak current comparing circuit 9, a first comparator Cp of the peak current comparing circuit 9₁And the output terminal of which is connected to the RS latch and drive circuit 8.

Furthermore, the RS latch and driving circuit 8 and the peak current comparing circuit 9 are integrated IC circuits of L6561 or L6562 type, the RS latch and driving circuit 8 is connected to the main power circuit 1 and the peak current comparing circuit 9, and the peak current comparing circuit is connected to the main power circuit 1 and the second multiplier 7.

Further, the first operational amplifier A₁A second operational amplifier A₂A third operational amplifier A₃A fourth operational amplifier A₄Operational amplifiers of TL074, TL072, LM358 or LM324 models are selected.

Further, the first multiplier 5 and the second multiplier 7 are formed by integrated IC circuits or discrete devices, the first multiplier 5 is connected with the input voltage sampling circuit 3, the first subtraction circuit 6 and the second multiplier 7 respectively, and the second multiplier 7 is connected with the peak current comparison circuit 9 and the output voltage feedback circuit 10 respectively.

2 parallel active filter for improving PF value

2.1 operating principle of active Filter

Fig. 3 shows the boost inductor current waveform during one switching cycle of the converter, where diagram (b) is the waveform diagram of the active filter circuit in operation. The active filter inductor current of the active filter circuit operates in a continuous mode. When the first MOS transistor Q₁When conducting, the second MOS transistor Q₂Cut-off, active filter inductance L_fA voltage across isVoltage v after rectifier bridge_gCurrent of i thereof_LfWith v_g/L_bWhen the slope of the second MOS transistor Q rises linearly₂When conducting, the first MOS transistor Q₁Cut-off, active filter inductance L_fVoltage across v_g-v_Cf，i_LbWith (v)_g-V_o)/L_bThe slope of (c) decreases. When the first MOS transistor Q₁When the next on signal arrives, the active filter circuit enters the next switching period. First MOS transistor Q₁And a second MOS transistor Q₂And are always complementarily conducted.

In order to improve the power factor of the converter, the active filter cancels the harmonic component in the input current, fig. 8 shows the input voltage v of the CRM Boost PFC converter connected with the active filter in parallel_inAnd current i_inCurrent i of the boost inductor_{Lb_b}And a harmonic component i_{Lb_h}Input instantaneous power p_inActive filter inductor current i_LfAnd an active filter capacitor voltage v_cf. From equation (16), it can be seen that the harmonic component i that the active filter needs to cancel_{in_f}And an active filter inductor current i_LfComprises the following steps:

the instantaneous power p of the input active filter_{in_f}Comprises the following steps:

as can be seen from fig. 8: the active filter capacitor of the active filter is at t₁～t₂Charging in the section, and increasing the voltage of the capacitor; at t₂～t₃Discharge in the section, the capacitor voltage drops. Therefore, the maximum value and the minimum value of the capacitor voltage are respectively at t₂And t₁The moment is taken.

By time of dayt₁To time t₂Energy stored by an active filter capacitor Δ e_fComprises the following steps:

wherein V_{cf_min}Is the minimum value of the active filter capacitor voltage.

Solving the equation (22) to obtain a voltage expression on the output energy storage capacitor of the active filter:

wherein d is₁Is a first MOS transistor Q₁Duty ratio of d₂Is a second MOS transistor Q₂Duty ratio of C_fIs an active filter capacitor, v_cfIs an active filter capacitor C_fUpper capacitor voltage, v_gIs the voltage across the LC filter, V_{Cf_min}Is an active filter capacitor C_fMinimum value of upper capacitor voltage, v_gIs the voltage of the positive terminal of the LC filter, t₀＝2T_linearcsin(8/3π)，T_lineIs the grid voltage cycle.

The active filter adopts a Boost/Buck bidirectional converter, and the active filtering inductive current of the active filter is always continuous. First MOS transistor Q₁And a second MOS transistor Q₂And conducting complementarily. Second MOS transistor Q₂Duty ratio d of₂The relationship between the input voltage and the active filter capacitor voltage can be expressed as:

d₁(t)＝1-d₂(t) (25)

combining equation (20) and equation (16), connecting the input current i of the post-converter of the active filter in parallel_inExpressed as:

the PF value of the converter is expressed as:

PF curves of the fixed switching frequency CRM Boost PFC converter and the parallel active filter converter can be plotted according to equation (15), equation (26) and equation (27), as shown in fig. 6. As can be seen from the figure, the theoretical PF value is 1 in a wide input voltage range of 90V to 264VAC, and the PF value is greatly improved compared to the constant switching frequency control method of varying the on-time when a high voltage is input.

2.2 control Circuit

In order to ensure the normal work of a Boost/Buck bidirectional converter, namely an active filter, the voltage v on an active filter capacitor_cfMust always be greater than the LC filter back-voltage v_g。

v_Cf≥v_g＝V_m|sinωt| (28)

In the control circuit, this is achieved by a voltage closed loop.

In order to control the active filter inductor current to cancel the harmonic current component, average current control is used, and an average current reference feed-forward circuit is needed to provide a current reference of the active filter inductor current.

Fig. 1 incorporates a CRM Boost PFC circuit with fixed switching frequency control with variable on-time and an active filter with average current control. Input voltage sampling circuit obtains v_B＝k_vgV_mL sin ω t l, v is obtained by an input voltage peak value sampling circuit_b＝k_vgV_mWhere k is_vgIs the coefficient of partial pressure, k_vg＝R₂/(R₁+R₂)。v_BAnd v_bV is obtained after passing through a second subtraction circuit_c＝k_vg(V_msinωt-k₁V_m)，R₁₆＝(3π/8)R₁₇＝R₁₄＝(3π/8)R₅₇，k₁8/3 pi. Third multiplier output v_d＝k_vg ²V_msinωt(V_msinωt-k₁V_m). On the other hand, an error signal v of an output voltage feedback circuit_EAAnd v_dThe potential of the e point obtained after the fourth multiplier is connected is as follows:

the inductor current of the active filter is related to the output power of the fixed switching frequency CRM Boost PFC converter. To introduce an output power P_oThe output voltage feedback circuit of the CRM Boost PFC converter with the fixed switching frequency outputs v_EAA feed forward circuit is introduced. The control circuit of the constant switching frequency CRM Boost PFC converter meets the following formula:

likewise, the average current control circuit of the active filter in fig. 1 satisfies:

therefore, in conjunction with formula (17), when the resistor R is sampled_s1＝2R_s2Active filter capacitor voltage closed loop v_eaAnd v_eThe sum is the reference of the active filter inductor current. The output signal of the current loop intersects with the sawtooth-shaped carrier wave, the output signal of the comparator is sent to the RS trigger, and the output of the RS trigger is the first MOS transistor Q₁And a second MOS transistor Q₂The drive signal of (1).

Further, the bidirectional converter comprises an active filter circuit 2 and a control circuit, wherein the control circuit comprises an input voltage sampling circuit 3, an input voltage peak value sampling circuit 11, an active filter capacitor voltage feedback circuit 17, a second subtraction circuit 12, a third multiplier 13, a fourth multiplier 14, an average current feedback circuit 16 and a sawtooth wave comparator and drive circuit 15; a feedforward operation circuit is used to provide an average current reference required by average current control, and the active filter is controlled by the average current control mode.

Furthermore, the active filter circuit 2 is respectively connected with the main power circuit 1, the sawtooth wave comparator and drive circuit 15, the average current feedback circuit 16 and the active filter capacitor voltage feedback circuit 17, the input voltage sampling circuit 3 is respectively connected with the main power circuit 1, the input voltage peak value sampling circuit 11, the second subtraction circuit 12 and the third multiplier 13, the input voltage peak value sampling circuit 11 is connected with the second subtraction circuit 12, the second subtraction circuit 12 is connected with the third multiplier 13, the third multiplier 13 is connected with the fourth multiplier 14, the fourth multiplier 14 is connected with the output voltage feedback circuit 10 and the average current feedback circuit 16, the sawtooth wave comparator and drive circuit 15 is connected with the average current feedback circuit 16, and the average current feedback circuit 16 is connected with the active filter capacitor voltage feedback circuit 17.

Further, the active filter circuit 2 includes an active filter inductor L_fA first MOS transistor Q₁A first MOS transistor Q₂Active filter capacitor C_fAnd a second sampling resistor R_s2. The active filter inductor L_fOne end of the active filter is connected with the output positive port of the LC filter of the main power circuit 1, and the active filter inductor L_fThe other end of the first MOS transistor and the second MOS transistor are respectively connected with a first MOS transistor Q₁Drain terminal and second MOS transistor Q₂Source terminal of the second MOS transistor Q₂Drain terminal and active filter capacitor C_fIs connected with the positive end of a first MOS tube Q₁And a second MOS transistor Q₂The grid terminal of the active filter capacitor C is connected with a sawtooth wave comparator and a drive circuit 15_fRespectively with the first MOS transistor Q₁Source terminal, second sampling resistor R_s2Is connected to the average current feedback circuit 16, and a second sampling resistor R_s2Is connected with the negative port of the LC filter of the main power circuit 1, the negative port of the LC filter is a reference potential zero point, and the active filtering is carried outCapacitor C_fThe voltage of the positive terminal is the voltage v of the active filter capacitor_CfActive filter capacitor C_fThe positive terminal is connected with an active filter capacitor voltage feedback circuit 17.

Further, the control circuit comprises an average current reference feedforward operation circuit, an active filter capacitor voltage feedback circuit 17, an average current feedback circuit 16 and a sawtooth wave comparator and drive circuit 15, wherein the average current reference feedforward operation circuit comprises an input voltage peak value sampling circuit 11, a second subtracter 12, a third multiplier 13 and a fourth multiplier 14.

Further, an input end a of an input voltage peak voltage sampling circuit 11 in the average current reference feedforward operation circuit is connected with an output end B of the input voltage sampling circuit 3, an output end B of the input voltage peak voltage sampling circuit 11 is connected with an input end of a second subtracter 12, the other input end of the second subtracter 12 is connected with an output end B of the input voltage sampling circuit 3, an output end c of the second subtracter 12 is connected with an input end v of a third multiplier 13_yConnected to the input v of a third multiplier 13_xAn output terminal d of the third multiplier 13 is connected to an output terminal B of the input voltage sampling circuit 3, and an input terminal v of the fourth multiplier 14_xConnected to the input v of a fourth multiplier 14_yConnected to the output terminal I of the output voltage sampling circuit 10, the output terminal e of the fourth multiplier 14 is connected via a twentieth resistor R₂₀Is connected to the input f of the average current feedback circuit 16.

Further, the inverting input terminal g of the active filter capacitor voltage feedback circuit 17 passes through a twenty-second resistor R₂₂And the voltage v on the positive terminal of the active filter capacitor in the active filter circuit 2_CfThe non-inverting input terminal of the active filter capacitor voltage feedback control circuit 17 is connected with the active filter capacitor voltage reference V_{ref_2}Connected, the output terminal h of the active filter capacitor voltage feedback circuit 17 passes through a twenty-fourth resistor R₂₄Is connected to the input f of the average current feedback circuit 16.

Further, another input terminal of the average current feedback circuit 16 and the active filter capacitor C in the active filter circuit 2_fNegative terminal and second sampling resistor R_s2One end of the average current feedback circuit 16 is connected with the input end of the sawtooth wave comparator and drive circuit 15.

Further, the two outputs of the sawtooth wave comparator and the driving circuit 15 are respectively connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS transistor and the other end of the second MOS transistor are respectively connected with a first MOS transistor Q in the active filter circuit 2₁And a second MOS transistor Q₂Is connected to the gate terminal.

Further, the output signal of the average current reference feedforward operation circuit is input to the average current feedback circuit 16, and a driving signal is generated according to the control mode of average current control, so as to achieve the purpose of controlling the active filter inductive current.

The first MOS transistor Q₁And a second MOS transistor Q₂Complementary conduction, the relationship between duty ratios is:

d₁(t)＝1-d₂(t)

wherein d is₁Is a first MOS transistor Q₁Duty ratio of d₂Is a second MOS transistor Q₂Duty ratio of C_fIs an active filter capacitor, v_cfIs an active filter capacitor C_fUpper capacitor voltage, v_gIs the voltage across the LC filter, V_{Cf_min}Is an active filter capacitor C_fMinimum value of upper capacitor voltage, v_gIs the voltage of the positive terminal of the LC filter, t₀＝2T_linearcsin(8/3π)，T_lineIs the grid voltage cycle.

Further, the input voltage peak value sampling circuit 11 includes a twelfth resistor R₁₂A thirteenth resistor R₁₃Diode D₁A second capacitor C₂And a fifth operational amplifier A₅(ii) a The twelfth resistor R₁₂One end of the fourth resistor R is connected with the output end B of the input voltage sampling circuit 3, and the twelfth resistor R₁₂Another terminal of (1) and a diode D₁Is connected to the positive terminal of a diode D₁Negative terminal of and a second capacitor C₂A thirteenth resistor R₁₃And a fifth operational amplifier A₅Is connected with the non-inverting input terminal of the second capacitor C₂And a thirteenth resistance R₁₃Is connected to a reference potential zero point, a fifth operational amplifier A₅The output end of the voltage regulator is connected with the inverting input end of the voltage regulator; fifth operational amplifier a of input voltage peak value sampling circuit 11₅Is connected to second subtracting circuit 12.

Further, the second subtracting circuit 12 comprises a fourteenth resistor R₁₄A fifteenth resistor R₁₅Sixteenth resistor R₁₆Seventeenth resistor R₁₇And a sixth operational amplifier A₆(ii) a The sixteenth resistor R₁₆Is connected with the output terminal b of the input voltage peak value sampling circuit 11, and the other end is connected with the sixth operational amplifier a₆The inverting input terminal of (1); seventeenth resistor R₁₇And a third operational amplifier A₃Is connected to the inverting input terminal of the seventeenth resistor R₁₇And the other end of the first operational amplifier A and a third operational amplifier A₃The output end c of the switch is connected; a fifteenth resistor R₁₅One end of the first operational amplifier is connected with the output end B of the input voltage sampling circuit 3, and the other end of the first operational amplifier is connected with the sixth operational amplifier A₆The non-inverting input end of the input terminal is connected; a fourteenth resistance R₁₄And a sixth operational amplifier A₆Is connected to the fourteenth resistor R₁₄Is connected to a reference potential zero point, a sixth operational amplifier A₆Is the output c of the second subtraction circuit 12; sixth operational amplifier a of second subtracting circuit 12₆Is connected to the third multiplier 13.

Further, the active filter capacitor voltage feedback circuit 17 includes a twenty-first resistor R₂₁A twenty-second resistor R₂₂Twenty-fifth resistor R₂₅A fifth capacitor C₅A sixth capacitor C₆And a seventh operational amplifier A₇(ii) a The twenty-second resistor R₂₂And one end of the active filter circuit 2 is connected with the positive end voltage v of the active filter capacitor of the active filter circuit 2_CfConnected with the other end connected with a twenty-first resistor R₂₁And a seventh operational amplifier A₇The inverting input terminal of (1), the twenty-first resistor R₂₁The other end of the reference potential zero point is connected with a reference potential zero point; twenty-fifth resistor R₂₅And a seventh operational amplifier A₇Is connected to the inverting input terminal of the resistor R, a twenty-fifth resistor R₂₅And the other end of the first capacitor C and a sixth capacitor C₆Is connected to a sixth capacitor C₆And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected to a fifth capacitor C₅And a seventh operational amplifier A₇An inverting input terminal connected to a fifth capacitor C₅And the other end of the first operational amplifier and a seventh operational amplifier A₇Output terminal connected, seventh operational amplifier A₇With the same-phase input terminal and the active filter capacitor voltage reference V_{ref_2}Connected, a seventh operational amplifier A₇I.e. the output of the active filter capacitor voltage feedback circuit 17, a seventh operational amplifier a of the active filter capacitor voltage feedback circuit 17₇Is connected to an average current feedback circuit 16.

Further, the average current feedback circuit 16 includes an eighteenth resistor R₁₈Nineteenth resistor R₁₉Twentieth resistor R₂₀Twenty third resistor R₂₃Twenty-fourth resistor R₂₄A third capacitor C₃A fourth capacitor C₄And an eighth operational amplifier A₈(ii) a The nineteenth resistor R₁₉One end of the first sampling resistor, the negative end of the active filter capacitor of the active filter circuit 2 and the second sampling resistor R_s2Connected with the other end connected with an eighteenth resistor R₁₈And an eighth operational amplifier A₈The eighteenth resistor R₁₈Is connected with a reference potential zero point, a twenty-third resistor R₂₃And an eighth operational amplifier A₈Is connected to the inverting input terminal of the first resistor, a twenty-third resistor R₂₃The other end of the first capacitor and a fourth capacitor C₄Is connected at one end toFourth capacitor C₄And the other end of the same with an eighth operational amplifier A₈Output terminal connected to a third capacitor C₃And an eighth operational amplifier A₈A third capacitor C connected to the inverting input terminal₃And the other end of the same with an eighth operational amplifier A₈Connected, twentieth resistor R₂₀Is connected to a fourth multiplier, a twenty-fourth resistor R₂₄One end of the second resistor is connected with the output end of the active filter capacitor voltage feedback circuit 17, and the twentieth resistor R₂₀And a twenty-fourth resistor R₂₄And the other end of the same with an eighth operational amplifier A₈Is connected to the non-inverting input terminal of the eighth operational amplifier A₈I.e. the output of the average current feedback circuit 16, an eighth operational amplifier a of the average current feedback circuit 16₈The output terminal of which is connected to a sawtooth comparator and drive circuit 15.

Further, the sawtooth comparator and driving circuit 15 includes a second comparator Cp₂RS trigger and drive circuit, the second comparator Cp₂Is connected to the output of the average current feedback circuit 16, a second comparator Cp₂Is connected to the sawtooth wave, a second comparator Cp₂The output end of the RS trigger is connected with the R end of the RS trigger, the S end of the RS trigger is connected with the pulse wave with fixed frequency, and the output end of the RS trigger is connected with the driving circuit. Output of the driving circuit and the first MOS tube driving resistor R_d1And a second MOS transistor driving resistor R_d2Is connected with the first MOS transistor driving resistor R_d1And a second MOS transistor driving resistor R_d2The other end of the first MOS transistor Q is respectively connected with the first MOS transistor Q of the active filter circuit 2₁And a second MOS transistor Q₂Is connected to the gate terminal.

Further, the saw-tooth wave comparator in the saw-tooth wave comparator and driving circuit 15 adopts an integrated IC circuit of UC3843 or UC3525 model. The generation circuit of the driving signal selects a logic chip with SN74HC08N, CD4069 or 74HC32N model, the driving circuit selects a driving chip with IR2110 or TLP250 model or a totem pole driving circuit, and the sawtooth wave comparator and the driving circuit 15 are respectively connected with the active filter circuit 2 and the average current feedback circuit 16.

Further, the fifth operational amplifier A₅A sixth operational amplifier A₆A seventh operational amplifier A₇And an eighth operational amplifier A₈Operational amplifiers of TL074, TL072, LM358 or LM324 models are selected.

Further, the third multiplier 13 and the fourth multiplier are formed by integrated IC circuits or discrete devices, the third multiplier 13 is connected to the input voltage sampling circuit 3, the second subtraction circuit 12 and the fourth multiplier 14, respectively, and the fourth multiplier 14 is connected to the output voltage feedback circuit 10 and the average current feedback circuit 16, respectively.

3 advantages of novel control

3.1 improvement of Power factor

PF curves of the fixed switching frequency CRM Boost PFC converter and the parallel active filter converter can be plotted according to equation (15), equation (26) and equation (27), as shown in fig. 6. It can be seen from the figure that, in the wide input voltage range of 90V-264 VAC, the theoretical PF value is 1, and when high voltage is input, the PF value is greatly improved compared with the fixed switching frequency control mode of variable on-time, and the PF value improvement effect is obvious.

3.2 switching frequency conversion Range reduction

The expression of the switching frequency of the fixed switching frequency CRM Boost PFC converter is shown in formula (13), and if the lowest switching frequency f is limited_{s_min}A maximum inductance value L of 30kHz_bmaxThe expression of (a) is:

according to the design parameters of the converter: input voltage v_in: 90V-264V AC; output voltage V_o: 400V; output power P_o: 120W. In order to ensure that the switching frequency is not lower than 30kHz under the whole input voltage, the inductance value of the CRM Boost PFC converter with the fixed switching frequency is L_b＝0.79mH。

Mixing L with_bThe switching frequency of a CRM Boost PFC converter is determined to be half of that of a 0.79mH substitution formula (13) in combination with the parameters of the converterThe variation curve in the power frequency period is shown in fig. 9. As can be seen from the figure: 1) the switching frequency power frequency period is constant and is no longer a function changing along with the omegat, and the changing range in the power frequency period is successfully reduced to the minimum. 2) The switching frequency is only related to the input voltage, and the frequency changes from 29.9kHz to 34.1kHz in the whole input voltage range, and the frequency change range is small.

3.3 reduction of output Voltage ripple

When the constant on-time control is adopted, the instantaneous input power per unit value of the converter can be obtained by the formula (1) and the formula (5)(the reference value is the output power) is:

as shown in figure 10 of the drawings,there are 2 intersections with 1, where the first intersection corresponds to a time ω t_c1：

When the fixed switching frequency control is adopted, the instantaneous input power per unit value of the converter can be obtained by the formula (1) and the formula (15)(the reference value is the output power) is:

order toThe solution can be obtained:

as shown in figure 10 of the drawings,the time corresponding to the first intersection of 1 is ω t_c2：

When in useTime, energy storage capacitor C_oCharging; when in useWhen, C_oAnd (4) discharging. Under two control modes, the output capacitor C_oPer unit value of maximum energy stored in half power frequency periodAnd(the reference value is the output energy in a half power frequency period) respectively:

according to the calculation formula of the capacitance energy storage,andcan be expressed as:

wherein Δ V_{o_1}And Δ V_{o_2}The output voltage ripple values are respectively controlled by fixed conduction time and fixed switching frequency.

Fig. 11 is drawn from equation (41), and it can be seen from the graph that after the variable on-time control is adopted, when the input voltage is 90V AC, the output voltage ripple is reduced to 92.4% of the original output voltage ripple, when the input voltage is 110V AC, the output voltage ripple is reduced to 83.3% of the original output voltage ripple, when the input voltage is 176V AC, the output voltage ripple is reduced to 79.4% of the original output voltage ripple, and when the input voltage is 264V AC, the output voltage ripple is reduced to 50.8% of the original output voltage ripple.