阅读说明：本技术 一种谐波失真补偿电路、相关电路及系统和方法 (Harmonic distortion compensation circuit, related circuit, system and method ) 是由 赵汗青 于 2020-04-27 设计创作，主要内容包括：本发明公开了一种谐波失真补偿电路、相关电路及系统和方法,该谐波失真补偿电路,包括：去磁状态检测电路、时间采样电路和时间调节电路；去磁状态检测电路,用于在开关周期内检测电感去磁状态,并在电感去磁结束时刻向所述时间采样电路输出电感去磁结束信号；时间采样电路,用于采样脉冲宽度调制器的输出信号以及根据接收的电感去磁结束信号,得到表征开关导通时间、电感去磁时间以及开关启动等待时间的时间信号,并输出到时间调节电路；所述时间调节电路,用于根据所述时间信号,确定导通时间控制信号,并输出到所述脉冲宽度调制器,以控制开关电源系统的开关导通时间。降低了电路的THD,提高了开关电源系统向被控负载供电的稳定性。(The invention discloses a harmonic distortion compensation circuit, a related circuit, a system and a method, wherein the harmonic distortion compensation circuit comprises: the demagnetization detection circuit comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the demagnetization state detection circuit is used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the moment of the demagnetization ending of the inductor; the time sampling circuit is used for sampling an output signal of the pulse width modulator, obtaining time signals representing switch conduction time, inductor demagnetization time and switch starting waiting time according to the received inductor demagnetization finishing signal and outputting the time signals to the time adjusting circuit; and the time adjusting circuit is used for determining a conduction time control signal according to the time signal and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switching power supply system. The THD of the circuit is reduced, and the stability of the power supply of the switching power supply system to the controlled load is improved.)

1. A harmonic distortion compensation circuit, comprising: the demagnetization detection circuit comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the time sampling circuit is respectively connected with the demagnetization state detection circuit and the time adjusting circuit;

the demagnetization state detection circuit is connected with an inductor of the switching power supply system and used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the moment when the demagnetization of the inductor is ended;

the time sampling circuit is connected with a pulse width modulator of the switching power supply system and is used for sampling an output signal of the pulse width modulator, obtaining time signals representing switch conduction time, inductor demagnetization time and switch starting waiting time according to a received inductor demagnetization finishing signal and outputting the time signals to the time adjusting circuit;

and the time adjusting circuit is connected with the pulse width modulator and used for determining a conduction time control signal according to the time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time, and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switch power supply system.

2. The harmonic distortion compensation circuit of claim 1, wherein the demagnetization detection circuit comprises a first operational amplifier and an RS flip-flop, wherein a reverse input terminal of the first operational amplifier is connected to the inductor, a forward input terminal of the first operational amplifier is grounded, an output terminal of the first operational amplifier is connected to a reset terminal of the RS flip-flop, a set terminal of the RS flip-flop is connected to a reference level, and an output terminal of the RS flip-flop is connected to the time sampling circuit.

3. The harmonic distortion compensation circuit of claim 1 wherein the time sampling circuit comprises a first current source, a time sampling switch, a first capacitor; the first current source is connected with one end of a first capacitor, the other end of the first capacitor is grounded, one end of a time sampling switch is connected with the common end of the first current source and the first capacitor, and the other end of the time sampling switch is grounded; the time sampling switch samples the trigger signal and conducts, and the first capacitor discharges and outputs a time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time.

4. The harmonic distortion compensation circuit of claim 3 wherein the time sampling switch samples the output signal of the pulse width modulator as a switch on signal and turns on, the first capacitor discharges and outputs a time signal indicative of the switch on time;

the time sampling switch samples an output signal of the pulse width modulator as a switch closing signal and conducts, and the first capacitor discharges and outputs a time signal representing the demagnetization time of the inductor;

the time sampling switch samples an inductor demagnetization ending signal and is conducted, and the first capacitor discharges and outputs a time signal representing the starting waiting time of the switch.

5. The harmonic distortion compensation circuit as claimed in claim 1, wherein the time adjustment circuit comprises a logical operation unit and a signal output circuit;

the logic operation unit is used for obtaining the switch conduction time, the inductance demagnetization time and the switch starting waiting time according to the received time signal, and determining the compensation duty ratio according to the switch conduction time, the inductance demagnetization time and the switch starting waiting time, wherein the compensation duty ratio D is T_on/(T_on+T_dmg+K*T_wait) Wherein K is greater than or equal to 1, T_onIndicating the switch on-time, T_dmgRepresenting the demagnetization time of the inductor, T_waitIndicating a switch activation latency;

the signal output circuit comprises a second current source and a third capacitor, the common end of the second current source and the third capacitor is an adjusting signal output end, the second current source determines constant output current according to the compensation duty ratio and preset reference current, and charges the third capacitor, so that the signal output end outputs a conduction time control signal corresponding to the constant output current.

6. The harmonic distortion compensation circuit of claim 5 wherein the adjustment signal output is connected to a positive input of a second operational amplifier of the pulse width modulator, an inverting input of the second operational amplifier being connected to an output of a feedback detection circuit of the switching power supply system, and receiving the comparison voltage output by the feedback detection circuit; and the second operational amplifier outputs a driving signal for adjusting the conduction time according to the conduction time control signal and the comparison voltage.

7. A load driving circuit, comprising: a feedback detection circuit, a pulse width modulator, a driver, and the harmonic distortion compensation circuit of any of claims 1-6;

the pulse width modulator is respectively connected with the feedback detection circuit and the driver.

8. The load driving circuit of claim 7, wherein the feedback detection circuit samples a sampled voltage representative of the output current, derives a comparison voltage from the sampled voltage, and outputs the comparison voltage to the pulse width modulator;

the pulse width modulator outputs a driving signal for adjusting the conduction time according to the comparison voltage and a conduction time control signal of the harmonic distortion compensation circuit;

and the driver drives a switching tube of the switching power supply system to be conducted according to the driving signal.

9. The load driving circuit of claim 8, wherein the pulse width modulator comprises a second operational amplifier;

the positive input end of the second operational amplifier is connected with the output end of the time regulating circuit of the harmonic distortion compensation circuit, and the inverting input end of the second operational amplifier is connected with the output end of the feedback detection circuit and receives the comparison voltage output by the feedback detection circuit; and the second operational amplifier outputs a driving signal for adjusting the conduction time according to the received conduction time control signal of the harmonic distortion compensation circuit and the comparison voltage of the feedback detection circuit.

10. A switching power supply system, comprising: a rectifier module, an inductor, a switching tube, a sampling resistor and the load driving circuit of any one of claims 7 to 9 connected with an alternating current power supply;

the rectifier module is connected with the input end of a controlled load, the input end of the inductor is connected with the output end of the controlled load, the output end of the inductor is connected with the drain electrode of the switch tube, the source electrode of the switch tube is connected with the sampling resistor, and the grid electrode of the switch tube is connected with the output end of the load driving circuit and receives a driving signal for adjusting the conduction time; the output end of the sampling resistor is grounded.

11. The switching power supply system according to claim 10, wherein the inductor is a common mode inductor, two ends of a primary coil of the common mode inductor are respectively connected to the controlled load and a drain of the switching tube, one end of a secondary coil of the common mode inductor is connected to the demagnetization state detection circuit, and the other end of the secondary coil of the common mode inductor is grounded.

12. A harmonic distortion compensation method, comprising:

detecting the demagnetization state of the inductor in a switching period, and outputting an inductor demagnetization ending signal to the time sampling circuit at the moment of the demagnetization ending of the inductor;

sampling an output signal of the pulse width modulator and obtaining a time signal representing switch conduction time, inductor demagnetization time and switch starting waiting time according to a received inductor demagnetization finishing signal;

and determining a conduction time control signal according to the time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system.

Technical Field

The invention relates to a harmonic distortion compensation circuit, a related circuit, a system and a method.

Background

In the prior art, because the second Harmonic, the third Harmonic and the noise test Harmonic generated by the inevitable oscillation or other resonance of the circuit are superimposed on the actual input signal, the signal output at the output end is not only the exact same component as the input signal, but also includes the Harmonic components, and the comparison of these excessive Harmonic components with the actual input signal is expressed by percentage and is called Total Harmonic Distortion (THD).

When the input voltage is in the wave trough interval, the peak current of the inductor is reduced along with the input voltage, so that the demagnetization time T of the inductor is caused_dmgHowever, due to the frequency limitation of the switching tube, for example, the frequency of the switching tube is generally between several khz and several hundred khz, the switching period Ts of the switching tube has a minimum limit. The circuit enters a Discontinuous Conduction Mode (DCM) from a Critical Conduction Mode (CRM), and the current harmonic distortion characteristic changes. At present, the on-time T of the switch is adopted_onThe mode of superimposing the input voltage waveform cannot compensate the harmonic distortion caused by the change of the circuit conduction mode. Therefore, how to compensate the current harmonic distortion when the circuit enters the DCM mode and reduce the total harmonic distortion of the circuit in the DCM mode is a problem to be solved.

Disclosure of Invention

The embodiment of the invention aims to provide a harmonic distortion compensation circuit, a related circuit, a system and a method, which can reduce the total harmonic distortion when a circuit enters a DCM mode.

As a first aspect of an embodiment of the present invention, an embodiment of the present invention provides a harmonic distortion compensation circuit, including: the demagnetization detection circuit comprises a demagnetization state detection circuit, a time sampling circuit and a time adjusting circuit; the time sampling circuit is respectively connected with the demagnetization state detection circuit and the time adjusting circuit;

the demagnetization state detection circuit is connected with an inductor of the switching power supply system and used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit at the moment when the demagnetization of the inductor is ended;

the time sampling circuit is connected with a pulse width modulator of the switching power supply system and is used for sampling an output signal of the pulse width modulator, obtaining time signals representing switch conduction time, inductor demagnetization time and switch starting waiting time according to a received inductor demagnetization finishing signal and outputting the time signals to the time adjusting circuit;

and the time adjusting circuit is connected with the pulse width modulator and used for determining a conduction time control signal according to the time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time, and outputting the conduction time control signal to the pulse width modulator so as to control the switch conduction time of the switch power supply system.

In some optional embodiments, the demagnetization detection circuit includes a first operational amplifier and an RS flip-flop, where a reverse input end of the first operational amplifier is connected to the inductor, a forward input end of the first operational amplifier is grounded, an output end of the first operational amplifier is connected to a reset end of the RS flip-flop, a set end of the RS flip-flop is connected to a reference level, and an output end of the RS flip-flop is connected to the time sampling circuit.

In some optional embodiments, the time sampling circuit comprises a first current source, a time sampling switch, a first capacitor; the first current source is connected with one end of a first capacitor, the other end of the first capacitor is grounded, one end of a time sampling switch is connected with the common end of the first current source and the first capacitor, and the other end of the time sampling switch is grounded; the time sampling switch samples the trigger signal and conducts, and the first capacitor discharges and outputs a time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time.

In some optional embodiments, the time sampling switch samples the output signal of the pulse width modulator as a switch conducting signal and conducts, and the first capacitor discharges and outputs a time signal representing the switch conducting time;

the time sampling switch samples an output signal of the pulse width modulator as a switch closing signal and conducts, and the first capacitor discharges and outputs a time signal representing the demagnetization time of the inductor;

the time sampling switch samples an inductor demagnetization ending signal and is conducted, and the first capacitor discharges and outputs a time signal representing the starting waiting time of the switch.

In some optional embodiments, the time adjustment circuit includes a logic operation unit and a signal output circuit;

the logic operation unit is used for obtaining the switch conduction time, the inductance demagnetization time and the switch starting waiting time according to the received time signal, and determining the compensation duty ratio according to the switch conduction time, the inductance demagnetization time and the switch starting waiting time, wherein the compensation duty ratio D is T_on/(T_on+T_dmg+K*T_wait) Wherein K is greater than or equal to 1, T_onIndicating the switch on-time, T_dmgRepresenting the demagnetization time of the inductor, T_waitIndicating a switch activation latency;

the signal output circuit comprises a second current source and a third capacitor, the common end of the second current source and the third capacitor is an adjusting signal output end, the second current source determines constant output current according to the compensation duty ratio and preset reference current, and charges the third capacitor, so that the signal output end outputs a conduction time control signal corresponding to the constant output current.

In some optional embodiments, the adjusting signal output end is connected to a positive input end of a second operational amplifier in the pulse width modulator, and an inverting input end of the second operational amplifier is connected to an output end of a feedback detection circuit of the switching power supply system, and receives a comparison voltage output by the feedback detection circuit; and the second operational amplifier outputs a driving signal for adjusting the conduction time according to the conduction time control signal and the comparison voltage.

As a second aspect of the embodiments of the present invention, an embodiment of the present invention provides a load driving circuit, including: the circuit comprises a feedback detection circuit, a pulse width modulator, a driver and the harmonic distortion compensation circuit;

the pulse width modulator is respectively connected with the feedback detection circuit and the driver.

In some optional embodiments, the feedback detection circuit samples a sampling voltage representing the output current, obtains a comparison voltage according to the sampling voltage, and outputs the comparison voltage to the pulse width modulator;

the pulse width modulator outputs a driving signal for adjusting the conduction time according to the comparison voltage and a conduction time control signal of the harmonic distortion compensation circuit;

and the driver drives a switching tube of the switching power supply system to be conducted according to the driving signal.

In some alternative embodiments, the pulse width modulator comprises a second operational amplifier;

the positive input end of the second operational amplifier is connected with the output end of the time regulating circuit of the harmonic distortion compensation circuit, and the inverting input end of the second operational amplifier is connected with the output end of the feedback detection circuit and receives the comparison voltage output by the feedback detection circuit; and the second operational amplifier outputs a driving signal for adjusting the conduction time according to the received conduction time control signal of the harmonic distortion compensation circuit and the comparison voltage of the feedback detection circuit.

As a third aspect of the embodiments of the present invention, an embodiment of the present invention provides a switching power supply system, including: the load driving circuit comprises a rectifier module, an inductor, a switching tube, a sampling resistor and a load driving circuit, wherein the rectifier module, the inductor, the switching tube and the sampling resistor are connected with an alternating current power supply;

the rectifier module is connected with the input end of a controlled load, the input end of the inductor is connected with the output end of the controlled load, the output end of the inductor is connected with the drain electrode of the switch tube, the source electrode of the switch tube is connected with the sampling resistor, and the grid electrode of the switch tube is connected with the output end of the load driving circuit and receives a driving signal for adjusting the conduction time; the output end of the sampling resistor is grounded.

In some optional embodiments, the inductor is a common mode inductor, two ends of a primary coil of the common mode inductor are respectively connected to the controlled load and the drain of the switching tube, one end of a secondary coil of the common mode inductor is connected to the demagnetization state detection circuit, and the other end of the secondary coil of the common mode inductor is grounded.

As a fourth aspect of the embodiments of the present invention, an embodiment of the present invention provides a harmonic distortion compensation method, including:

detecting the demagnetization state of the inductor in a switching period, and outputting an inductor demagnetization ending signal to the time sampling circuit at the moment of the demagnetization ending of the inductor;

sampling an output signal of the pulse width modulator and obtaining a time signal representing switch conduction time, inductor demagnetization time and switch starting waiting time according to a received inductor demagnetization finishing signal;

and determining a conduction time control signal according to the time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system.

The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:

the harmonic distortion compensation circuit provided by the embodiment of the invention detects the demagnetization state of the inductor of the switching power supply system, respectively detects the time signals of the demagnetization time of the inductor and the starting waiting time of the switch within the turn-off time of the switching tube, and obtains the control signal of the turn-on time according to the determined switch turn-on time, the demagnetization time of the inductor and the starting waiting time of the switch, thereby realizing the adjustment of the turn-on time of the switch. By adjusting the switch conduction time in the switching period of the switching tube, the current harmonic distortion of the circuit in the CRM mode and the DCM mode is compensated, so that the input current is closer to an ideal sine half-wave waveform. For a switching power supply system, the THD of the circuit is reduced, the input current is closer to an ideal sine half-wave waveform, and the stability of supplying power to a controlled load by the switching power supply system is improved.

Drawings

FIG. 1 is a schematic diagram of a prior art LED driving circuit;

FIG. 2 is a timing diagram of a switching cycle in the LED driving circuit shown in FIG. 1;

FIG. 3 is a diagram illustrating the waveforms and fundamental frequency components of the actual input current and the ideal input current in the LED driving circuit shown in FIG. 1;

fig. 4 is a schematic structural diagram of a switching power supply system according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a medium inductance L and a demagnetization detection circuit according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of voltage waveforms at different detection terminals during a switching period according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a time sampling circuit according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of a signal output circuit according to an embodiment of the present invention;

fig. 9 is a schematic diagram of waveforms to be compensated of the input current obtained by performing a difference and translation on waveforms of the actual input current and the ideal input current shown in fig. 3;

FIG. 10 is a schematic diagram of the switch on-time adjustment in the switching power supply system shown in FIG. 4;

fig. 11 is a schematic structural diagram of another switching power supply system according to an embodiment of the present invention;

fig. 12 is a schematic structural diagram of a signal conversion circuit according to an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Referring to fig. 1, an LED load driving circuit for implementing constant current driving in the prior art includes a rectifier 10, an LED load 20 and a regulating circuit, where an input of the rectifier 10 is connected to an ac power supply, an output of the rectifier 10 is connected to the LED load 20, the LED load 20 is connected to a drain of a transistor M0, a source of the transistor M0 passes through a sampling resistor R_csGround, the regulation circuit including the feedback detection circuit 30, the pulse width regulator 40 and the driver U0, the input of the feedback detection circuit 30 and the source of the transistor M0 and the sampling resistor R_csIs connected to the common terminal, the output of the feedback detection circuit 30 is connected to the input of the pulse width modulator 40, the output of the pulse width modulator 40 is connected to the input of the driver U0, and the output of the driver U0 is connected to the gate of the transistor M0. Specifically, the feedback detection circuit 30 samples a sampling resistor R in the circuit representing the input current_csOn a feedback voltage V_csThe feedback detection circuit 30 feeds back the voltage V_csProcessing to obtain a compensation signal V_compAnd input into a pulse width modulator 40, the pulse width modulator 40 being responsive to a compensation signal V_compAnd obtaining a driving signal for adjusting the output conduction time, and adjusting the conduction time of the transistor M0 by the control driver U0 according to the driving signal, thereby realizing constant current driving control. Wherein the input current I_inAnd an input voltage V_inThere is the following relationship, equation 1:wherein L represents inductance, T_onIndicating the on-time, T, of the switching tube_sIndicating the switching period of the switching tube. Referring to FIG. 2, it is shown as T_on、T_offAnd T_sIn a conceptual timing diagram of (1), wherein T_offIndicating the off-time, T, of the switching tube_sIs a conduction time T_onAnd off time T_offAnd (4) summing. Equation 1 can also be expressed as equation 2:wherein D is the duty cycle, andreferring to FIG. 3, with the LED load driving circuit shown in FIG. 1, the input current I_inThe difference between the actual waveform 1 and the ideal sine waveform 2 is larger, which indicates that the THD in the circuit is larger and the power factor is reduced. And during one cycle of the input current, the circuit will operate in either CRM mode or DCM mode. At present, the conduction time T of a switch tube is adopted_onThe harmonic distortion in DCM cannot be compensated by superimposing the input voltage waveform. Therefore, how to work with DCMThe difficulty solved by the invention is that the voltage output signal in the middle zero-crossing stage is compensated, and the input current signal is closer to an ideal semi-circular waveform. The invention aims to provide a harmonic distortion compensation circuit, so that a switching power supply system can ensure lower THD in any working mode, and the THD compensation circuit has a simple and reliable structure.

In order to solve the problem of harmonic distortion in the prior art, an embodiment of the present invention provides a harmonic distortion compensation circuit, and as shown in fig. 4, the harmonic distortion compensation circuit includes: a demagnetization state detection circuit 51, a time sampling circuit 52, and a time adjustment circuit 53; the time sampling circuit 52 is respectively connected with the demagnetization state detection circuit 51 and the time adjusting circuit 53;

the demagnetization state detection circuit 51 is connected with an inductor L of the switching power supply system, and is used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization ending signal to the time sampling circuit 52 at the moment when the demagnetization of the inductor is ended;

the time sampling circuit 52 is connected with the pulse width modulator of the switching power supply system, and is used for sampling an output signal of the pulse width modulator, obtaining time signals representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time according to the received inductor demagnetization finishing signal, and outputting the time signals to the time adjusting circuit 53;

and the time adjusting circuit 53 is connected with the pulse width modulator of the switching power supply system, and is used for determining an on-time control signal according to the time signal representing the switch on-time, the inductor demagnetization time and the switch starting waiting time, and outputting the on-time control signal to the pulse width modulator of the switching power supply system so as to control the switch on-time of the switching power supply system.

The harmonic distortion compensation circuit provided by the embodiment of the invention detects the demagnetization state of the inductor of the switching power supply system, respectively detects the time signals of the demagnetization time of the inductor and the starting waiting time of the switch within the turn-off time of the switching tube, and obtains the control signal of the turn-on time according to the determined switch turn-on time, the demagnetization time of the inductor and the starting waiting time of the switch, thereby realizing the adjustment of the turn-on time of the switch. By adjusting the switch conduction time in the switching period of the switching tube, the current harmonic distortion of the circuit in the CRM mode and the DCM mode is compensated, so that the input current is closer to an ideal sine half-wave waveform. For a switching power supply system, the THD of the circuit is reduced, the input current is closer to an ideal sine half-wave waveform, and the stability of supplying power to a controlled load by the switching power supply system is improved.

For more convenient illustration of the specific implementation manner of the embodiment of the present invention, referring to fig. 4, the embodiment of the present invention is described in detail by using a switching power supply system including the harmonic distortion compensation circuit. The switching power supply system is used for controlling the working state of a controlled load, specifically, the controlled load may be the LED load 20 and the regulating circuit. The switching power supply system includes: a rectifier module 10 connected with an alternating current power supply, an inductor L, a switch tube M0 and a sampling resistor R_csA feedback detection circuit 30, a pulse width modulator 40, a driver U0, and the harmonic distortion compensation circuit 50; the harmonic distortion compensation circuit 50 includes: a demagnetization state detection circuit 51, a time adjustment circuit 53, and a time sampling circuit 52 connected to the demagnetization state detection circuit 51 and the time adjustment circuit 53, respectively;

the rectifier module 10 is connected with the input end of the LED load 20;

the input end of the inductor L is connected with the output end of the LED load 20, and the output end of the inductor L is connected with the drain electrode of the switching tube M0;

the source electrode of the switching tube M0 is connected with a sampling resistor R_csThe grid of the switch tube M0 is connected with the output end of the driver U0 and is used for adjusting the conduction time T_onThe drive signal of (1);

sampling resistor R_csThe output end of the transformer is grounded;

the feedback detection circuit 30 is connected to the pulse width modulator 40, the source of the switch transistor M0 and the sampling resistor R_csAt the common terminal between, sampling a sampling voltage V representing the output current_csAccording to said sampling voltage V_csObtain a comparison voltage V_compAnd output to the pulse width modulator 40;

the demagnetization state detection circuit 51 is connected with the inductor L and used for detecting the demagnetization state of the inductor in a switching period and outputting an inductor demagnetization finishing signal to the time sampling circuit;

the time sampling circuit 52 is connected to the pulse width modulator 40 and is configured to sample an output signal of the pulse width modulator 40 and obtain a time signal V representing a switch on time, an inductor demagnetization time, and a switch start waiting time according to the received inductor demagnetization end signal_capAnd output to the time adjustment circuit 53;

the time adjustment circuit 53 is coupled to the pulse width modulator 40 for adjusting the time of the switch on-time, the inductor demagnetization time and the switch on-latency based on a time signal V representing the switch on-time, the inductor demagnetization time and the switch on-latency_capDetermines the on-time control signal SD and outputs it to the pulse width modulator 40;

the pulse width modulator 40 is connected to a driver U0 based on a received comparison voltage V_compAnd an on-time control signal SD for outputting an on-time T_onThe drive signal of (1);

driver U0 adjusts the on-time T based on the received signal_onThe driving signal drives the switch tube to be conducted.

In an embodiment, referring to fig. 5, an inductor L of the switching power supply system is a common mode inductor, two ends of a primary coil of the inductor L are respectively connected to the controlled load 20 and the drain of the switching tube M0, one end of a secondary coil of the inductor L is connected to the demagnetization state detection circuit, and the other end is grounded.

In one embodiment, referring to FIG. 5, the demagnetization detection circuit 51 comprises a first operational amplifier U1 and an RS flip-flop, wherein the inverting input terminal of the first operational amplifier U1 is connected to the secondary winding of the inductor L, the forward input terminal of the first operational amplifier is grounded, the output terminal of the first operational amplifier is connected to the reset terminal of the RS flip-flop, and the set terminal of the RS flip-flop is connected to the reference levelThe output of the RS flip-flop is connected to a time sampling circuit 52. When the switch tube M0 is switched from on to offIn the state, the first operational amplifier U1 detects that the inductor L is discharged and is in the inductor demagnetizing state, at the moment of the inductor demagnetization ending, the inverting input end of the first operational amplifier U1 detects a level falling edge and sends a high level signal to the reset end of the RS flip-flop, and the output end of the RS flip-flop outputs an inductor demagnetization ending signal to the time sampling circuit 52 according to the high level signal.

Referring to fig. 6, when the circuit of the switching power supply system operates in DCM, the switching transistor M has a switching period T_sIncluding the switch on-time T_onTime of demagnetization of inductor_dmgAnd a switch activation wait time T_wait. When the switch tube M0 is in the switch conduction time T_onInternal time, grid voltage V of switch tube_driverFor high level signal, when the switch tube M0 is turned off, the gate voltage V of the switch tube_driverFor switching from a high level signal to a low level signal; on the contrary, when the switch tube M0 is turned on, the drain voltage V of the switch tube_drainFor low level signal, when the switch tube M0 is turned off, the gate voltage V of the switch tube_driverThe time for the inductor L to enter a demagnetizing state is the inductor demagnetizing time T for converting from a low level signal to a high level signal_dmgAnd when the demagnetization time of the inductor is over, the drain voltage V of the switching tube cannot compensate more voltage due to insufficient energy of the inductor L in the circuit_drainWhen oscillation occurs, the inductor L needs to wait for the switch starting waiting time T_waitThe switching tube is conducted and enters the next switching period for recharging; for the secondary winding of the inductor L, the voltage waveform and the drain voltage V of the switch tube_drainIn accordance, the voltage V at the output end is made to be equal by connecting the output end to the common end of the two voltage-dividing resistors_auxWhen the falling edge of the first voltage oscillation occurs, the output voltage reaches 0V, so that the inverting input end of the first operational amplifier U1 detects a first level falling edge at the moment when the inductor demagnetization time is ended, the inverting input end of the first operational amplifier U1 detects the level falling edge, a high level signal is sent to the reset end of the RS trigger, and the output end of the RS trigger outputs an inductor demagnetization junction to the time sampling circuit 52 according to the high level signalA beam signal.

Referring to FIG. 7, the time sampling circuit 52 includes a first current source I_chgA time sampling switch SN, a first capacitor C1, the first current source I_chgOne end of a first capacitor C1, the other end of the first capacitor C1 is grounded, and one end of a time sampling switch SN is connected with a first current source I_chgConnected to the common terminal of the first capacitor C1, the other terminal of the time sampling switch SN is grounded, and a first current source I_chgThe first capacitor C1 can be charged, the time sampling switch SN samples the trigger signal and is conducted, at the moment, the first capacitor C1 discharges and outputs a time signal V representing the sampling time_cap。

Specifically, the time sampling switch SN may sample the output signal of the pwm 40 as a switch on signal and turn on, the first capacitor C1 discharges, and the time signal V representing the switch on time is output_cap1(ii) a The output signal sampled by the time sampling switch SN to the pulse width modulator 40 is a switch off signal and turned on, the first capacitor discharges, and a time signal V representing the demagnetization time of the inductor is output_cap2(ii) a The time sampling switch SN samples an inductor demagnetization ending signal and is conducted, the first capacitor discharges, and a time signal V representing the starting waiting time of the switch is output_cap3。

In order to prevent the time sampling circuit 52 from signal disturbance when sampling different trigger signals, in the embodiment of the present invention, the time sampling circuit includes 3 sets of circuit structures shown in fig. 7, where the trigger signal of the time sampling switch SN of the first set of circuits is the switch on signal of the output signal of the pulse width modulator 40, the trigger signal of the time sampling switch SN of the second set of circuits is the switch off signal of the output signal of the pulse width modulator 40, and the trigger signal of the time sampling switch SN of the third set of circuits is the inductance demagnetization end signal output by the RS flip-flop of the demagnetization state detection circuit 51.

In the embodiment of the present invention, the time adjusting circuit 53 includes a logic operation unit and a signal output circuit 531;

logic operation unit of the time adjustment circuit 53 for characterizing the switch based on the received time signalTime signal V of the on-time_cap1Time signal V representing the demagnetization time of the inductor_cap2And a time signal V characterizing the switch activation latency_cap3Obtaining the switch on-time T_onTime of demagnetization of inductor_dmgAnd a switch activation wait time T_waitAnd according to the switch on-time T_onTime of demagnetization of inductor_dmgAnd a switch activation wait time T_waitDetermining a compensation duty cycle D ', where D' is T_on/(T_on+T_dmg+K*T_wait) Wherein K is greater than or equal to 1, T_onIndicating the switch on-time, T_dmgRepresenting the demagnetization time of the inductor, T_waitIndicating a switch activation latency.

In one embodiment, referring to FIG. 8, the signal output circuit 531 of the time adjustment circuit 53 includes a second current source I_sdAnd a second capacitor C2, a second current source I_sdAnd the common terminal of the second capacitor C2 is a regulating signal output terminal, and the second current source I_sdAnd determining a constant output current according to the compensation duty ratio and a preset reference current, and charging the second capacitor C2 to enable a signal output end to output an on-time control signal corresponding to the constant output current.

In the embodiment of the present invention, in order to make the compensated waveform closer to the ideal waveform, the size of the waveform to be compensated needs to be determined first, and when the compensation waveform is actually determined, a difference operation may be performed using the ideal sinusoidal waveform 2 shown in fig. 3 and the measured actual waveform 1, for example, a fourier transform algorithm is performed on the obtained ideal sinusoidal waveform 1 and the actual waveform 2, and the mathematical formula of the actual waveform is subtracted from the mathematical formula of the obtained ideal sinusoidal waveform, so as to obtain the original waveform to be compensated. When the on-off time of the switch is adopted to carry out waveform compensation, only forward compensation can be carried out, but reverse compensation cannot be carried out, and the conduction T of the switching period is adjusted_onThis is equivalent to reducing the difference between the input current of the next cycle and the ideal value, thereby reducing THD. Therefore, in the embodiment of the invention, the inventor innovatively adopts the original method which needs compensationThe shape is translated upwards to obtain the waveform to be compensated shown in fig. 9. According to the waveform to be compensated shown in fig. 9, in each half-wave period, at two sides of the approximate "W" waveform, the circuit enters into DCM mode, the inductor L has insufficient energy at the end of the period, and cannot compensate more voltage, at this time, due to the limitation of the frequency of the switching tube M0, when the switching tube M0 is turned off, the inductor demagnetizing time T is longer_dmgAfter the end, the switch tube M0 still needs to wait for a certain time to start again, and the time for the switch to start is marked as T_waitThen at this time, the switch is turned off for a time T_off＝T_dmg+T_wait. Knowing the actual duty cycleWhen forward compensation is needed in the DCM mode, the switch conducting time T needs to be changed by controlling the charging time of the second capacitor C2_on. At switch on time T_onThe compensation is performed, and the equivalent to the input current is changed. The inventor proposes to adjust the charging current of the second capacitor C2 by using the compensation duty ratio D', and further control the charging time of the second capacitor C2 to realize the switch on time T_onAnd (4) adjusting. The above-mentioned compensation duty ratioWherein K is greater than 1. The value of K in the embodiment of the invention can be selected according to manual experience, or can be obtained by software simulation screening.

The time adjusting circuit 53 uses the logical operation unit to adjust the time according to the time signal V representing the switch conducting time_cap1Time signal V representing the demagnetization time of the inductor_cap2And a time signal V characterizing the switch activation latency_cap3Obtaining the switch on-time T_onTime of demagnetization of inductor_dmgAnd a switch activation wait time T_waitAnd according to the switch on-time T_onTime of demagnetization of inductor_dmgAnd a switch activation wait time T_waitDetermining the compensated duty cycle D', and then, the signal output circuit 531 second current source I_sdDetermining constant output current according to the compensation duty ratio D' and preset reference current, charging a second capacitor C2 to obtain voltage on a second capacitor C2, obtaining a voltage parameter U ═ f (T) related to time, and outputting an on-time control signal SD to the pulse width modulator 40 to realize adjustment of T of the next period_on。

Referring to fig. 10, in the DCM mode, when the on-time control signal SD reaches the compensation voltage, the switch on-time reaches the maximum value, and the adjustment of the switch on-time T is achieved by controlling the slope of the on-time control signal SD_on. By characterizing the on-time T for the current switching period_onDemagnetization time T_dmgAnd switch actuation latency time T_waitTo realize the adjustment of T of the next period_onThis is equivalent to reducing the difference between the input current of the next cycle and the ideal value, thereby reducing THD.

In CRM mode, when the switch tube M0 is turned off, the switch waits for the starting time T_waitIs 0, inductance demagnetization time T_dmgEqual to the switch-off time T_offAt this time, the compensation duty D' is equal to the actual duty D. Time adjusting circuit 53 for time signal V_capCalculating to obtain an on-time adjusting signal SD inversely proportional to the duty ratio D, and outputting the on-time adjusting signal SD to the pulse width modulator 40 to adjust the on-time T of the next cycle_onFurther adjusting the on-time T of the switch_onIs inversely proportional to the duty ratio D, and realizes the switch on-time T_onThe product of duty ratio D is constant value, so that input current I_inAnd an input voltage V_inThe direct proportion relation is formed, and the switching power supply system can be ensured to have a smaller THD value.

In one particular embodiment, referring to FIG. 8, the pulse width modulator 40 includes a second operational amplifier U2; the positive input terminal of the second operational amplifier U2 is connected to the output terminal of the time adjustment circuit 53 of the harmonic distortion compensation circuit 50, the negative input terminal of the second operational amplifier U2 is connected to the output terminal of the feedback detection circuit 30, and receives the comparison voltage output by the feedback detection circuit 30V_comp(ii) a The second operational amplifier U2 is controlled according to the received on-time control signal SD of the harmonic distortion compensation circuit 50 and the comparison voltage V of the feedback detection circuit 30_compThe output is used for regulating the on-time T_onThe drive signal of (1).

In the embodiment of the present invention, the above-described embodiment shown in fig. 4 is only a specific implementation manner of the embodiment of the present invention. In the embodiment of the present invention, the specific implementation schemes of the rectification module 10, the switching tube M0, the driver U0, and the feedback detection circuit 30 may refer to the manners described in the prior art, and the specific circuit implementation manners in the embodiment of the present invention are not strictly limited herein, as long as the technical purpose of the present invention can be achieved, and no further description is given in the embodiment of the present invention.

It should be noted that, although the circuit of the switching power supply system including the harmonic distortion compensation circuit in the above embodiment is a buck type circuit, which is only a specific implementation manner of the embodiment of the present invention, the harmonic distortion compensation circuit in the embodiment of the present invention may also be applied to a fly-back type circuit or a boost type circuit.

Example two

In a specific implementation manner of the first embodiment, in the time sampling circuit shown in fig. 7, when the first capacitor C1 discharges, the output time signal V is output_capFor voltage signals, in order to facilitate subsequent signal processing, referring to fig. 11, the harmonic distortion compensation circuit 50 of the switching power supply system according to the second embodiment of the present invention further includes a signal conversion circuit 54 disposed between the time sampling circuit 52 and the time adjustment circuit 53, wherein the signal conversion circuit 54 is configured to convert the voltage signal output by the time sampling circuit 52 into a current signal, and the current signal is input to the time adjustment circuit 53 for signal calculation processing.

In a specific embodiment, referring to fig. 12, the signal conversion circuit 54 includes a current sampling switch SH, a third capacitor C3, a third operational amplifier U3, a conversion transistor M1 and a first resistor R1, wherein one end of the current sampling switch SH is connected to the time signal V outputted by the time sampling circuit 52_capThe other end of the current sampling switch SH is connected with the positive input of a third operational amplifier U3The other end of the current sampling switch SH is grounded through a third capacitor C3 at the input end, the output of a third operational amplifier U3 is connected with the grid electrode of a conversion transistor M1, the source electrode of the conversion transistor M1 is grounded through a first resistor R1, the common end of the source electrode of the conversion transistor M1 and the first resistor R1 is connected with the inverting input end of the third operational amplifier U3, and the drain electrode of the conversion transistor M1 outputs a sampling current I representing the sampling time_out. The time signal V in the form of a voltage which can be input by the signal conversion circuit 54_capSampled current I converted into current form_outThereby facilitating signal processing by the subsequent time adjustment circuit 53.

In a specific embodiment, according to the description of the time sampling circuit 52 in the first embodiment, the time sampling circuit 52 includes 3 sets of circuit structures shown in fig. 7, and respectively outputs the time signals V representing the on-time of the switches_cap1Time signal V representing the demagnetization time of the inductor_cap2And a time signal V characterizing the switch activation latency_cap3. Accordingly, the signal conversion circuit 54 in the second embodiment of the present invention may also include 3 sets of circuit structures shown in fig. 12 to respectively convert the time signals V representing the switch on-times into the time signals V representing the switch on-times_cap1Time signal V representing the demagnetization time of the inductor_cap2And a time signal V characterizing the switch activation latency_cap3Converted into a corresponding current signal. The signal conversion circuit 54 has good working effect and ensures the stability of the whole circuit.

In the embodiment of the present invention, a detailed circuit implementation and a detailed implementation manner of other components of the circuit in fig. 11 have been described in detail in the first embodiment, and will not be described in detail here.

EXAMPLE III

Based on the same inventive concept, the embodiment of the present invention further provides a load driving circuit, including the feedback detection circuit 30, the pulse width modulator 40, the driver U0, and the harmonic distortion compensation circuit 50 described in the above-mentioned first embodiment or second embodiment;

the pulse width modulator 40 is connected to the feedback detection circuit 30 and the driver U0, respectively.

In one embodiment, feedback detection circuit 30 samples a sampled voltage V that is representative of the output current_csAccording to the sampling voltage V_csObtain a comparison voltage V_compAnd output to the pulse width modulator 40;

the pulse width modulator 40 is based on the received comparison voltage V_compAnd an on-time control signal SD of the harmonic distortion compensation circuit 50 for outputting a control signal for adjusting the on-time T_onThe drive signal of (1);

driver U0 adjusts the on-time T according to the application_onThe driving signal of (2) drives the switching tube M0 of the switching power supply system to be conducted.

In a particular embodiment, the pulse width modulator includes a second operational amplifier U2;

the positive input end of the second operational amplifier U2 is connected with the output end of the time adjusting circuit of the harmonic distortion compensating circuit, the negative input end of the second operational amplifier U2 is connected with the output end of the feedback detecting circuit 30, and receives the comparison voltage V output by the feedback detecting circuit 30_comp(ii) a The second operational amplifier U2 is controlled according to the received on-time control signal SD of the harmonic distortion compensation circuit and the comparison voltage V of the feedback detection circuit 30_compThe output is used for regulating the on-time T_onThe drive signal of (1).

The specific structure and implementation manner of the load driving circuit according to the embodiment of the present invention may refer to the description of the specific circuit implementation schemes of the switching power supply system in the first embodiment and the second embodiment, and are not described herein again.

Example four

Based on the same inventive concept, an embodiment of the present invention further provides a harmonic distortion compensation method, including:

detecting the demagnetization state of the inductor in a switching period, and outputting an inductor demagnetization ending signal at the moment of finishing the demagnetization of the inductor;

sampling an output signal of the pulse width modulator and obtaining a time signal representing switch conduction time, inductor demagnetization time and switch starting waiting time according to a received inductor demagnetization finishing signal;

and determining a conduction time control signal according to the time signal representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time so as to control the switch conduction time of the switch power supply system.

In one embodiment, the determining the on-time control signal according to the time signals representing the switch on-time, the inductor demagnetization time and the switch starting waiting time to control the switch on-time of the switching power supply system includes:

obtaining the switch conduction time, the inductor demagnetization time and the switch starting waiting time according to the time signals representing the switch conduction time, the inductor demagnetization time and the switch starting waiting time;

determining a compensation duty ratio according to the switch conduction time, the inductor demagnetization time and the switch starting waiting time, wherein the compensation duty ratio D is T_on/(T_on+T_dmg+K*T_wait) Wherein K is greater than or equal to 1, T_onIndicating the switch on-time, T_dmgRepresenting the demagnetization time of the inductor, T_waitIndicating a switch activation latency;

and determining a constant output current according to the compensation duty ratio and a preset reference current so as to output a conduction time control signal corresponding to the constant output current.

The specific implementation of the harmonic distortion compensation method provided in the embodiment of the present invention may refer to the detailed description of the first embodiment and the second embodiment of the present invention. The embodiments of the present invention will not be described in detail herein.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.