阅读说明：本技术 一种能够用于同步cot模式开关电源开关频率的锁相环电路 (Phase-locked loop circuit capable of being used for synchronizing switching frequency of COT mode switching power supply ) 是由 明鑫 张�杰 黄佳晖 贾丽伟 梁华 程政 王卓 张波 于 2020-05-15 设计创作，主要内容包括：一种能够用于同步COT模式开关电源开关频率的锁相环电路,通过使能逻辑模块在检测到外部同步时钟存在时使能锁相环电路,否则关闭锁相环电路防止误触发；利用鉴相器检测外部同步时钟和开关信号的相位差,并将误差信息通过低通滤波器反映到滤波电容电压上,包含鉴相信息的滤波电容电压再通过电压-电流转换模块转换成电流信息,与包含开关电源输入电压信息的电流叠加后为计时电容充电来调整导通时间,从而调整开关电源的开关动作使得其与外部同步时钟的上升沿重合,达到外部时钟频率与内部开关频率相同的目的。本发明提出的锁相环电路在开关电源输入电压发生跳变时能够通过直接采样输入电压的信息来快速改变计时电容的充电电流,提高了锁频速度。(A phase-locked loop circuit capable of being used for synchronizing the switching frequency of a COT mode switching power supply enables the phase-locked loop circuit when an enabling logic module detects that an external synchronous clock exists, otherwise, the phase-locked loop circuit is closed to prevent false triggering; the phase discriminator is used for detecting the phase difference between an external synchronous clock and a switching signal, error information is reflected to the voltage of a filter capacitor through a low-pass filter, the voltage of the filter capacitor containing the phase discrimination information is converted into current information through a voltage-current conversion module, the current information is superposed with the current containing the input voltage information of the switching power supply and then charges a timing capacitor to adjust the conduction time, and therefore the switching action of the switching power supply is adjusted to enable the switching power supply to coincide with the rising edge of the external synchronous clock, and the purpose that the frequency of the external clock is the same as the frequency of the internal switch is achieved. The phase-locked loop circuit provided by the invention can rapidly change the charging current of the timing capacitor by directly sampling the information of the input voltage when the input voltage of the switching power supply jumps, thereby improving the frequency locking speed.)

1. A phase-locked loop circuit capable of being used for synchronizing the switching frequency of a COT mode switching power supply is characterized in that the COT mode switching power supply charges a timing capacitor by using charging current containing input voltage information of the COT mode switching power supply, and generates a switching signal for controlling a power tube in the COT mode switching power supply by comparing the voltage on the timing capacitor with a first reference voltage;

it is characterized in that the phase-locked loop circuit comprises an enabling logic module, a phase discriminator, a low-pass filter and a voltage-current conversion module,

the enabling logic module is used for enabling the phase-locked loop circuit when detecting that an external synchronous clock exists and closing the phase-locked loop circuit when not detecting the external synchronous clock;

the phase discriminator is used for detecting the phase difference between the external synchronous clock and the switching signal;

the low-pass filter comprises a first resistor, a second capacitor and a third capacitor, one end of the first resistor is connected with an output signal of the phase discriminator, one end of the third capacitor and the input end of the voltage-current conversion module, and the other end of the first resistor is grounded after passing through the second capacitor; the other end of the third capacitor is grounded;

the voltage-current conversion module comprises a sixth NMOS tube, a seventh NMOS tube, an eighth NMOS tube, a ninth NMOS tube, a tenth NMOS tube, an eleventh NMOS tube, a twelfth NMOS tube, a fifth PMOS tube, a sixth PMOS tube, a seventh PMOS tube, an eighth PMOS tube and a ninth PMOS tube,

the grid electrode of the twelfth NMOS tube is connected with the grid electrodes of the tenth NMOS tube and the eleventh NMOS tube and is connected with the enabling signal generated by the enabling logic module, the drain electrode of the twelfth NMOS tube is connected with the grid electrode of the fifth PMOS tube and the third reference voltage, and the source electrode of the twelfth NMOS tube is connected with the grid electrode of the sixth PMOS tube and serves as the input end of the voltage-current conversion module;

the grid electrode of the ninth PMOS tube is connected with bias voltage, the source electrode of the ninth PMOS tube is connected with the source electrodes of the seventh PMOS tube and the eighth PMOS tube and power supply voltage, and the drain electrode of the ninth PMOS tube is connected with the source electrodes of the fifth PMOS tube and the sixth PMOS tube; the bias voltage is proportional to the COT mode switching power supply input voltage;

the grid electrode of the sixth NMOS tube is connected with the grid electrode and the drain electrode of the seventh NMOS tube, the drain electrode of the fifth PMOS tube and the drain electrode of the tenth NMOS tube, the drain electrode of the sixth NMOS tube is connected with the grid electrode and the drain electrode of the seventh PMOS tube and the grid electrode of the eighth PMOS tube, and the source electrode of the sixth NMOS tube is connected with the source electrodes of the seventh NMOS tube, the eighth NMOS tube, the ninth NMOS tube, the tenth NMOS tube and the eleventh NMOS tube and is grounded;

the grid electrode of the ninth NMOS tube is connected with the grid electrode and the drain electrode of the eighth NMOS tube, the drain electrode of the sixth PMOS tube and the drain electrode of the eleventh NMOS tube, and the drain electrode of the ninth NMOS tube is connected with the drain electrode of the eighth PMOS tube and generates an output signal of the phase-locked loop circuit to be superposed on the charging current.

2. The phase-locked loop circuit capable of being used to synchronize the switching frequency of a COT-mode switching power supply of claim 1, wherein said enable logic block comprises a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, a sixth inverter, a seventh inverter, a first delay unit, a second delay unit, a third delay unit, a comparator, and a first NAND gate,

the input end of the first inverter is connected with the external synchronous clock and the first input end of the first NAND gate, and the output end of the first inverter is connected with the positive input end of the comparator after passing through the first delay unit;

the negative input end of the comparator is connected with a second reference voltage, and the output end of the comparator is connected with the input end of the second inverter;

the input end of the third inverter is connected with the output end of the second inverter, and the output end of the third inverter is connected with the second input end of the first NAND gate;

the input end of the second delay unit is connected with the output end of the first NAND gate, and the output end of the second delay unit is connected with the input end of the third delay unit after passing through the fourth inverter and the fifth inverter in sequence;

the output end of the third delay unit generates the enable signal after passing through the sixth inverter and the seventh inverter in sequence;

and when the high level duration of the external synchronous clock is longer than the delay time of the first delay unit and the low level duration of the external synchronous clock is shorter than the sum of the delay time of the second delay unit and the delay time of the third delay unit, enabling the enable signal to be effective and controlling the phase-locked loop circuit to start working.

3. The phase-locked loop circuit capable of being used for synchronizing switching frequency of a COT mode switching power supply according to claim 1 or 2, wherein the phase detector comprises a first D flip-flop, a second D flip-flop, a first AND gate, a fourth capacitor, a fifth capacitor, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a fourth NMOS transistor, a fifth NMOS transistor, a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a fourth PMOS transistor and a first constant current source,

the clock input end of the first D trigger is connected with the external synchronous clock, the data input end of the first D trigger is connected with power supply voltage, and the Q output end of the first D trigger is connected with the grid electrode of the first PMOS tube and the first input end of the first AND gate;

the clock input end of the second D trigger is connected with the switching signal, the data input end of the second D trigger is connected with power supply voltage, and the Q output end of the second D trigger is connected with the grid electrode of the second NMOS tube and the second input end of the first AND gate;

the output end of the first AND gate is connected with the reset ends of the first D trigger and the second D trigger;

the grid electrode of the third PMOS tube is connected with the grid electrode and the drain electrode of the second PMOS tube and the drain electrode of the fourth NMOS tube and is connected with the grid electrode of the first PMOS tube after passing through the fourth capacitor, the source electrode of the third PMOS tube is connected with the drain electrode of the first PMOS tube, and the drain electrode of the third PMOS tube is connected with the source electrode of the fourth PMOS tube;

the grid electrode of the fourth PMOS tube is connected with the source electrodes of the first PMOS tube and the second PMOS tube and the power supply voltage, and the drain electrode of the fourth PMOS tube is connected with the drain electrode of the fifth NMOS tube and generates an output signal of the phase discriminator;

the grid electrode of the fifth NMOS tube is connected with the grid electrode of the fourth NMOS tube, the grid electrode and the drain electrode of the third NMOS tube, the drain electrode of the first NMOS tube and the first constant current source, and is connected with the grid electrode of the second NMOS tube after passing through the fifth capacitor, and the source electrode of the fifth NMOS tube is connected with the drain electrode of the second NMOS tube;

the grid electrode of the first NMOS tube is connected with the enabling signal, and the source electrode of the first NMOS tube is connected with the source electrodes of the second NMOS tube, the third NMOS tube and the fourth NMOS tube and is grounded.

4. The phase-locked loop circuit capable of being used for synchronizing the switching frequency of a COT mode switching power supply of claim 3, wherein the fourth PMOS transistor, the third NMOS transistor, the fourth NMOS transistor and the fifth NMOS transistor are high-voltage-tolerant devices, and the width-to-length ratios of the third NMOS transistor and the fourth NMOS transistor are the same.

Technical Field

The invention belongs to the technical field of electronic circuits, and relates to a phase-locked loop circuit which can be used for synchronizing the switching frequency of a COT mode switching power supply according to an external synchronous clock.

Background

The conventional PWM control mode is difficult to meet the requirements of point loads (PO L) On the performance of the power supply, and a Constant On Time (COT) control mode is widely applied in the industry due to excellent transient response capability and high light load efficiency.

Disclosure of Invention

Aiming at the problem of switching frequency drift of a COT control switching power supply and the defect of low frequency locking speed of the traditional phase-locked loop, the invention designs the phase-locked loop circuit capable of being used for switching frequency of an external synchronous COT mode switching power supply, and the circuit introduces a generated P LL control signal into the COT control switching power supply to contain an input voltage V_INOn-Time generation of information (On-Time)r) module, which makes the switching frequency generated by the COT mode switching power supply have good frequency locking precision and faster transient response speed; the phase-locked loop circuit provided by the invention can well synchronize the external synchronous clock with the rising edge of the internal switch action; and an input voltage V of an external power supply, i.e. a COT mode switching power supply_INWhen jumping occurs, the phase-locked loop circuit provided by the invention can directly sample V_INThe current flowing into the on-time timer module is quickly changed by the voltage information, and quick transient response is realized.

The technical scheme of the invention is as follows:

a phase-locked loop circuit capable of being used for synchronizing the switching frequency of a COT mode switching power supply is characterized in that the COT mode switching power supply charges a timing capacitor by using charging current containing input voltage information of the COT mode switching power supply, and generates a switching signal for controlling a power tube in the COT mode switching power supply by comparing the voltage on the timing capacitor with a first reference voltage;

the phase-locked loop circuit comprises an enabling logic module, a phase discriminator, a low-pass filter and a voltage-current conversion module,

the enabling logic module is used for enabling the phase-locked loop circuit when detecting that an external synchronous clock exists and closing the phase-locked loop circuit when not detecting the external synchronous clock;

the phase discriminator is used for detecting the phase difference between the external synchronous clock and the switching signal;

the low-pass filter comprises a first resistor, a second capacitor and a third capacitor, one end of the first resistor is connected with an output signal of the phase discriminator, one end of the third capacitor and the input end of the voltage-current conversion module, and the other end of the first resistor is grounded after passing through the second capacitor; the other end of the third capacitor is grounded;

the voltage-current conversion module comprises a sixth NMOS tube, a seventh NMOS tube, an eighth NMOS tube, a ninth NMOS tube, a tenth NMOS tube, an eleventh NMOS tube, a twelfth NMOS tube, a fifth PMOS tube, a sixth PMOS tube, a seventh PMOS tube, an eighth PMOS tube and a ninth PMOS tube,

the grid electrode of the twelfth NMOS tube is connected with the grid electrodes of the tenth NMOS tube and the eleventh NMOS tube and is connected with the enabling signal generated by the enabling logic module, the drain electrode of the twelfth NMOS tube is connected with the grid electrode of the fifth PMOS tube and the third reference voltage, and the source electrode of the twelfth NMOS tube is connected with the grid electrode of the sixth PMOS tube and serves as the input end of the voltage-current conversion module;

the grid electrode of the ninth PMOS tube is connected with bias voltage, the source electrode of the ninth PMOS tube is connected with the source electrodes of the seventh PMOS tube and the eighth PMOS tube and power supply voltage, and the drain electrode of the ninth PMOS tube is connected with the source electrodes of the fifth PMOS tube and the sixth PMOS tube; the bias voltage is proportional to the COT mode switching power supply input voltage;

the grid electrode of the sixth NMOS tube is connected with the grid electrode and the drain electrode of the seventh NMOS tube, the drain electrode of the fifth PMOS tube and the drain electrode of the tenth NMOS tube, the drain electrode of the sixth NMOS tube is connected with the grid electrode and the drain electrode of the seventh PMOS tube and the grid electrode of the eighth PMOS tube, and the source electrode of the sixth NMOS tube is connected with the source electrodes of the seventh NMOS tube, the eighth NMOS tube, the ninth NMOS tube, the tenth NMOS tube and the eleventh NMOS tube and is grounded;

the grid electrode of the ninth NMOS tube is connected with the grid electrode and the drain electrode of the eighth NMOS tube, the drain electrode of the sixth PMOS tube and the drain electrode of the eleventh NMOS tube, and the drain electrode of the ninth NMOS tube is connected with the drain electrode of the eighth PMOS tube and generates an output signal of the phase-locked loop circuit to be superposed on the charging current.

Specifically, the enable logic module comprises a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, a sixth inverter, a seventh inverter, a first delay unit, a second delay unit, a third delay unit, a comparator and a first nand gate,

the input end of the first inverter is connected with the external synchronous clock and the first input end of the first NAND gate, and the output end of the first inverter is connected with the positive input end of the comparator after passing through the first delay unit;

the negative input end of the comparator is connected with a second reference voltage, and the output end of the comparator is connected with the input end of the second inverter;

the input end of the third inverter is connected with the output end of the second inverter, and the output end of the third inverter is connected with the second input end of the first NAND gate;

the input end of the second delay unit is connected with the output end of the first NAND gate, and the output end of the second delay unit is connected with the input end of the third delay unit after passing through the fourth inverter and the fifth inverter in sequence;

the output end of the third delay unit generates the enable signal after passing through the sixth inverter and the seventh inverter in sequence;

and when the high level duration of the external synchronous clock is longer than the delay time of the first delay unit and the low level duration of the external synchronous clock is shorter than the sum of the delay time of the second delay unit and the delay time of the third delay unit, enabling the enable signal to be effective and controlling the phase-locked loop circuit to start working.

Specifically, the phase discriminator comprises a first D trigger, a second D trigger, a first AND gate, a fourth capacitor, a fifth capacitor, a first NMOS tube, a second NMOS tube, a third NMOS tube, a fourth NMOS tube, a fifth NMOS tube, a first PMOS tube, a second PMOS tube, a third PMOS tube, a fourth PMOS tube and a first constant current source,

the clock input end of the first D trigger is connected with the external synchronous clock, the data input end of the first D trigger is connected with power supply voltage, and the Q output end of the first D trigger is connected with the grid electrode of the first PMOS tube and the first input end of the first AND gate;

the clock input end of the second D trigger is connected with the switching signal, the data input end of the second D trigger is connected with power supply voltage, and the Q output end of the second D trigger is connected with the grid electrode of the second NMOS tube and the second input end of the first AND gate;

the output end of the first AND gate is connected with the reset ends of the first D trigger and the second D trigger;

the grid electrode of the third PMOS tube is connected with the grid electrode and the drain electrode of the second PMOS tube and the drain electrode of the fourth NMOS tube and is connected with the grid electrode of the first PMOS tube after passing through the fourth capacitor, the source electrode of the third PMOS tube is connected with the drain electrode of the first PMOS tube, and the drain electrode of the third PMOS tube is connected with the source electrode of the fourth PMOS tube;

the grid electrode of the fourth PMOS tube is connected with the source electrodes of the first PMOS tube and the second PMOS tube and the power supply voltage, and the drain electrode of the fourth PMOS tube is connected with the drain electrode of the fifth NMOS tube and generates an output signal of the phase discriminator;

the grid electrode of the fifth NMOS tube is connected with the grid electrode of the fourth NMOS tube, the grid electrode and the drain electrode of the third NMOS tube, the drain electrode of the first NMOS tube and the first constant current source, and is connected with the grid electrode of the second NMOS tube after passing through the fifth capacitor, and the source electrode of the fifth NMOS tube is connected with the drain electrode of the second NMOS tube;

the grid electrode of the first NMOS tube is connected with the enabling signal, and the source electrode of the first NMOS tube is connected with the source electrodes of the second NMOS tube, the third NMOS tube and the fourth NMOS tube and is grounded.

Specifically, the fourth PMOS transistor, the third NMOS transistor, the fourth NMOS transistor, and the fifth NMOS transistor are high voltage tolerant devices, and the width-to-length ratios of the third NMOS transistor and the fourth NMOS transistor are the same.

The invention has the advantages that the invention can effectively prevent the P LL loop from being opened by mistake by monitoring the external synchronous clock signal, realizes the accurate synchronization of the external clock and the internal switch signal, has good frequency locking precision, and switches the power supply input voltage V in the COT mode_INWhen jumping occurs, the phase-locked loop circuit provided by the invention can directly sample V_INThe charging current of the timing capacitor is quickly changed by the voltage information, the conduction time is changed, the quick transient response is realized, and the P LL loop at V can be effectively improved_INThe frequency locking speed when jumping occurs, and meanwhile, the frequency locking range of the P LL loop is effectively improved.

Drawings

Fig. 1 is a schematic diagram of a control loop of a COT control mode switching power supply and a control loop of a phase-locked loop P LL according to the present invention.

Fig. 2 is a circuit structure diagram of an implementation of an enable logic block in a phase-locked loop circuit capable of synchronizing the switching frequency of a COT switching power supply according to the present invention.

Fig. 3 is a structural diagram of an implementation circuit of a phase detector in a phase-locked loop circuit that can be used for synchronizing the switching frequency of a COT mode switching power supply according to the present invention.

Fig. 4 is a schematic diagram of a specific circuit structure of a voltage-current conversion module in a phase-locked loop circuit capable of synchronizing the switching frequency of a COT switching power supply according to the present invention.

FIG. 5 is V_INThe simulation verification schematic diagram of the rapid frequency locking effect of the phase-locked loop is shown when the jump is changed from 5V to 12V.

FIG. 6 is V_INThe simulation verification schematic diagram of the rapid frequency locking effect of the phase-locked loop is shown when the jump is changed from 36V to 5V.

Detailed Description

The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in the COT control loop On the right of FIG. 1, the On-time generation (On-timeTimer) module of the COT mode switching power supply includes the input voltage V of the COT mode switching power supply_INCharging current I of information_VIN-IFor timing capacitor C₁Charging is carried out by charging a timing capacitor C₁Voltage on and a first reference voltage V_REF1The P LL control loop on the left side of fig. 1 is a phase-locked loop circuit provided by the present invention, and includes an enable logic module, a phase discriminator, a low-pass filter, and a voltage-current conversion module (V-I converter), the phase difference between the internal switching signal D of the COT mode switching power supply and the external synchronous clock can be discriminated by the phase discriminator, and then the error information obtained by the phase discriminator is passed through I_PFDIs a filter capacitor in a low-pass filter, i.e. a second capacitor C₂Charging to reflect the filter capacitor voltage V_LPFV containing phase discrimination information_LPFThen converting the current information into current information by a voltage-current conversion module, and then enabling the current information to contain V with an on-time timer module in a COT mode switching power supply_INCurrent I of information_VIN-IBy superimposing each other to adjust the conduction time T_ONTherefore, the switching action D is adjusted to be coincident with the rising edge of the external synchronous clock, and the purpose that the frequency of the external clock is the same as that of the internal switching frequency is achieved.

The specific structure and operation of each module are described in detail below.

The enabling logic module activates a P LL loop by detecting the high pulse width of an external synchronous clock, and when no clock signal is at the input end of the external synchronous clock, namely the external synchronous clock is not detected to exist, the enabling logic module can close a phase-locked loop circuit, and at the moment, the switching frequency of the COT mode switching power supply is switched on by the conduction time of an upper tube of the COT mode switching power supplyT_ONAnd otherwise, when the external synchronous clock is detected to exist, the enabling logic module generates an effective enabling signal to activate the P LL loop, and the external synchronous clock determines the switching frequency of the COT mode switching power supply.

As shown in fig. 2, an implementation circuit diagram of an enable logic module is provided, which includes a first inverter INV1, a second inverter INV2, a third inverter INV3, a fourth inverter INV4, a fifth inverter INV5, a sixth inverter INV6, a seventh inverter INV7, a first delay unit, a second delay unit, a third delay unit, a comparator and a first nand gate, wherein an input end of the first inverter INV1 is connected to an external synchronous clock and a first input end of the first nand gate, and an output end of the first inverter INV1 is connected to a positive input end of the comparator after passing through the first delay unit; the negative input end of the comparator is connected with a second reference voltage V_REF2The output end of the inverter is connected with the input end of the second inverter INV 2; the input end of the third inverter INV3 is connected to the output end of the second inverter INV2, and the output end of the third inverter INV3 is connected to the second input end of the first nand gate; the input end of the second delay unit is connected with the output end of the first nand gate, and the output end of the second delay unit is connected with the input end of the third delay unit after passing through the fourth inverter INV4 and the fifth inverter INV5 in sequence; the output end of the third delay unit generates an enable signal EN' after passing through the sixth inverter INV6 and the seventh inverter INV7 in sequence.

The enabling logic module detects whether a pulse signal exists at the input end of the external synchronous clock so as to determine whether to activate the P LL loop, the P LL loop is disconnected when the generated enabling signal EN ' is high, and the P LL loop is activated when the generated enabling signal EN ' is low, when the input end of the external synchronous clock, namely the end C L K is kept to be 0, the output of the first NAND gate is 1, the enabling signal EN ' is 1, the enabling is invalid, the related module of the P LL loop does not work, the P LL loop is disconnected, and when the end C L K is 1, the point A, namely the positive input end of the comparator reaches a second reference voltage V after passing through the delay t1 of the first delay unit_REF2When the output of the comparator is turned high, the point B, namely the output end of the third inverter INV3, is turned high, both the inputs of the first nand gate are high level, the output is 0, the point C, namely the output end of the second delay unit is turned high, then the gate level of the MN13 transistor in the third delay unit is raised, and the point D, namely the third inverter INV3When the end C L K is turned down to 0, the logic transmission process tends to pull the enable signal EN 'high, namely tends to disable the enable, but the process needs to pass through the high delay t2+ t3 of the second delay unit and the third delay unit, if the external clock is turned up again within the delay time (namely the low signal maintaining time of the section C L K is less than t2+ t3), the enable EN' will not be pulled high, even if the external clock can be kept active (0) all the time, the analysis is summarized, so that the condition that the high level duration of the external synchronous clock is greater than the delay time t1 of the first delay unit, and the low pulse duration is less than the delay time t2 of the second delay unit and the delay time t 49323 of the third delay unit can avoid the false activation of the P LL.

The phase discriminator is used for detecting the phase difference between the external synchronous clock and the internal switch action. Fig. 3 shows an implementation form of the phase detector, which includes a first D flip-flop, a second D flip-flop, a first and gate, and a fourth capacitor C₄A fifth capacitor C₅The transistor comprises a first NMOS transistor MN1, a second NMOS transistor MN2, a third NMOS transistor MN3, a fourth NMOS transistor MN4, a fifth NMOS transistor MN5, a first PMOS transistor MP1, a second PMOS transistor MP2, a third PMOS transistor MP3, a fourth PMOS transistor MP4 and a first constant current source I_CHThe clock input end of the first D trigger is connected with an external synchronous clock, and the data input end of the first D trigger is connected with a power supply voltage V_CCThe Q output end of the first PMOS tube MP1 is connected with the grid electrode of the first PMOS tube MP1 and the first input end of the first AND gate; the clock input end of the second D trigger is connected with a switching signal D, and the data input end of the second D trigger is connected with a power supply voltage V_CCThe Q output end of the first NMOS transistor is connected with the grid electrode of the second NMOS transistor MN2 and the second input end of the first AND gate; the output end of the first AND gate is connected with the reset ends of the first D trigger and the second D trigger; the gate of the third PMOS transistor MP3 is connected to the gate and the drain of the second PMOS transistor MP2 and the drain of the fourth NMOS transistor MN4 via a fourth capacitor C₄The grid electrode of the first PMOS tube MP1 is connected at the back, the source electrode of the first PMOS tube MP1 is connected with the drain electrode of the first PMOS tube MP1, and the drain electrode of the first PMOS tube MP4 is connected with the source electrode of the fourth PMOS tube MP 4; grid connection of fourth PMOS pipe MP4Sources of the first and second PMOS transistors MP1 and MP2 and a power supply voltage V_CCThe drain electrode of the phase discriminator is connected with the drain electrode of a fifth NMOS tube MN5 and generates an output signal of the phase discriminator; the grid electrode of the fifth NMOS transistor MN5 is connected with the grid electrode of the fourth NMOS transistor MN4, the grid electrode and the drain electrode of the third NMOS transistor MN3, the drain electrode of the first NMOS transistor MN1 and the first constant current source I_CHAnd through a fifth capacitor C₅The grid electrode of the second NMOS transistor MN2 is connected, and the source electrode of the second NMOS transistor MN2 is connected; the gate of the first NMOS transistor MN1 is connected to the enable signal EN', and the source thereof is connected to the sources of the second, third, and fourth NMOS transistors MN2, MN3, and MN4 and grounded.

The purpose of the phase detector is to discriminate the phase difference between the switching signal D and the external synchronous clock and to react the error information to the voltage V of the low pass filter (L PF)_LFPUpper, V_LPFIs regulated by a first constant current source I_CHAnd a first PMOS pipe MP1 and a second NMOS pipe MN 2. The third NMOS transistor MN3, the fourth NMOS transistor MN4 and the fifth NMOS transistor MN5 form a current mirror, and the second PMOS transistor MP2 and the third PMSO transistor MP3 also form a current mirror, i.e. I_CHConversion to L PF Filter capacitor C₂The charging and discharging current of (1). As shown in FIG. 1, the low-pass filter includes a second capacitor C₂A third capacitor C₃And a first resistor R and a second capacitor C₂A first resistor R and a second capacitor C as main filter capacitors and P LL loop compensation capacitors₂A low-frequency zero point is generated in series for P LL loop compensation, and a third capacitor C₃The third capacitor C can filter voltage spikes generated when the charging and discharging current flows through the first resistor R₃Is much smaller than the second capacitor C₂Since the values of the filter capacitor and the compensation resistor are large, L PF is usually connected to the outside of the chip, it is preferable to use the fourth PMOS transistor MP4 and the fifth NMOS transistor MN5 as high-voltage transistors to bear high-voltage static electricity, in order to ensure the matching of the current mirror, the third NMOS transistor MN3 and the third NMOS transistor MN4 also use the same high-voltage transistor, and in addition, it is also possible to select other ways to achieve withstand voltageWhen the gate voltage of the second NMOS transistor MN2 is rapidly increased, the parasitic gate-drain capacitor couples the DV/DT at the gate terminal of the second NMOS transistor MN2 to the source terminal of the fifth NMOS transistor MN5, and the fifth capacitor C5 can be used to couple the DV/DT to the gate terminal of the fifth NMOS transistor MN5 at the same time, that is, the DV/DT does not cause the gate-source voltage VGS of the fifth NMOS transistor MN5 to generate a large spike instantaneously, thereby avoiding the generation of a current spike.

The charging current calculation module inputs the phase discrimination result to an on-time timer module in the COT mode switching power supply in a current mode to change T_ONAnd time, and further adjusting the switching frequency. The charging current calculating module includes a low pass filter and a voltage-current converting module, as shown in fig. 4, which is a schematic structural diagram of the voltage-current converting module, and includes a sixth NMOS transistor MN6, a seventh NMOS transistor MN7, an eighth NMOS transistor MN8, a ninth NMOS transistor MN9, a tenth NMOS transistor MN10, an eleventh NMOS transistor MN11, a twelfth NMOS transistor MN12, a fifth PMOS transistor MP5, a sixth PMOS transistor MP6, a seventh PMOS transistor MP7, an eighth PMOS transistor MP8 and a ninth PMOS transistor MP9, a gate of the twelfth NMOS transistor MN12 is connected to gates of the tenth NMOS transistor MN10 and the eleventh NMOS transistor MN11 and is connected to an enable signal EN' generated by the enable logic module, and a drain thereof is connected to a gate of the fifth PMOS transistor MP5 and a third reference voltage V_ERF3The source electrode of the first PMOS tube MP6 is connected with the grid electrode of the sixth PMOS tube MP6 and is used as the input end of the voltage-current conversion module; the gate of the ninth PMOS transistor MP9 is connected with a bias voltage V_BIASThe source electrodes of the seventh and eighth PMOS transistors MP7 and MP8 are connected to a power supply voltage V_CCThe drain electrode of the PMOS transistor is connected with the source electrodes of the fifth PMOS transistor MP5 and the sixth PMOS transistor MP 6; bias voltage V_BIASInput voltage V of switching power supply in COT mode_INProportioning; the gate of the sixth NMOS transistor MN6 is connected to the gate and the drain of the seventh NMOS transistor MN7, the drain of the fifth PMOS transistor MP5 and the drain of the tenth NMOS transistor MN10, the drain of the sixth NMOS transistor MN6 is connected to the gate and the drain of the seventh PMOS transistor MP7 and the gate of the eighth PMOS transistor MP8, the source of the sixth NMOS transistor MN6 is connected to the sources of the seventh NMOS transistor MN7, the eighth NMOS transistor MN8, the ninth NMOS transistor MN9, the tenth NMOS transistor MN10 and the eleventh NMOS transistor MN11 and is grounded; a gate of the ninth NMOS transistor MN9 is connected to the gate and the drain of the eighth NMOS transistor MN8, the drain of the sixth PMOS transistor MP6 and the drain of the eleventh NMOS transistor MN11, and a drain thereof is connected to the drain of the eighth PMOS transistor MP8Drain electrode and output signal I of phase-locked loop circuit_PLLSuperimposed on the charging current I_VIN-IThe above.

Voltage-current converter for converting V containing phase discrimination information_LPFConversion into current information I_LPF. In this embodiment, the voltage-current converter has a fully differential structure, and the gate signals of the input pair transistors MP5 and MP6 are the third reference voltage V_REF3And the signal V output by the low-pass filter_LPFLet G be the DC transconductance of the whole voltage-to-current converter_mV-IThen an output current I can be obtained_PLLAnd an input voltage V_LPFThe relationship of (1) is:

I_PLL＝G_mV-I(V_REF3-V_LPF) (1)

before the P LL is released, even if the enable signal EN' is 1, the second NMOS transistor MN2 is turned on and V is turned off_LPFWill be quickly charged to the third reference voltage V_REF3Again, this process is a precharge process, if not, V_LPFNeed to use a small current I_CH1Is a second capacitor C₂Charging, P LL starting process is seriously slowed down, output current I_PLLCurrent I with the on-time timer itself_VIN-IA timing capacitor C after superposition₁Charging to determine the on-time T_ONThe size of (2). T can be obtained from FIG. 1_ONAnd I_PLL，V_INThe relationship of (1) is:

wherein K can be understood as the DC transimpedance of V-I in the on-time timer. The switching power supply takes the BUCK converter as an example, and the switching frequency and T can be obtained by the BUCK control mode_ONAnd an input voltage V_INAn output voltage V_OThe relationship between them is:

it can be seen that the frequency of the external synchronous clock C L K is assumed to be constant, and the voltage-current is changedBias current I of the switching module_BIASAnd the input voltage V of the switching power supply_INNot related, then when V_INOccurrence of V_IN2＝K₂V_IN1(V_IN1Jump to V_IN2) Fsw changes instantaneously (due to C)₂For larger compensation capacitance, V_LPFAnd I_PLLNot instantaneously), i.e., the external clock will be offset from the internal switching action, the P LL loop will detect the corresponding phase difference and adjust V in response_LPFAnd I_PLLTo make I_PLL2＝K₂I_PLL1And further synchronize fsw with the external clock, I_PLL2Is the output of the adjusted phase-locked loop circuit, I_PLL1Is the output of a phase-locked loop circuit before adjustment, K₂Is V_INBut due to the low bandwidth of the P LL loop, this adjustment process can be slow and frequency locking can take a long time to achieve, and moreover, assume I_BIASAt V_INDoes not change at the transition, then due to V_INBefore and after jumping I_PLLA large change occurs, so V_LPFAnd V_REF3Will increase to satisfy I_PLLThe transconductance of the voltage-to-current conversion module is degraded, and the frequency-locked range of P LL (i.e., the externally supportable clock frequency range) is severely reduced_BIASInstead of a fixed bias current, the bias current is related to the input voltage V of the COT mode switching power supply_INRelated, as shown in fig. 1. As can be seen in connection with FIG. 4, the bias current I_BIASThat is, the current flowing through the ninth PMOS transistor MP9 satisfies I_BIAS＝V_IN/K₁In which K is₁The value of (A) needs to be compromised, K₁The output current of the voltage-current converter is limited if the voltage-current converter is too large, the frequency locking range of P LL is limited, K₁Too small a value will result in the on-time T of the COT mode switching power supply operating in DCM_ONThe size is greatly reduced. Then when V is_INOccurrence of V_IN2＝K₂V_IN1At time of jump of, I_BIASWill instantaneously become the original K₂Due to V_LPFAnd V_REF3Are all unchanged, so I_PLLWill thus become the original K₂The numerator and denominator of the formula (3) are changed to the original K₂Multiple, therefore fsw at V_INThe change hardly occurs during the jump, that is, the phase-locked loop can quickly complete the frequency locking process after the jump. Furthermore, due to I_BIASWill follow V_INIs changed proportionally, the input V of the voltage-current converter_LPFAnd V_REF3The transconductance does not degrade, so P LL can be at all V_INThe method has a larger frequency locking range under the condition.

FIG. 5 is V_INA simulation verification diagram of the fast frequency locking effect of the phase-locked loop when the 5V jump is changed into 12V; FIG. 6 is V_INThe simulation verification chart of the fast frequency locking effect of the phase-locked loop when the jump is changed from 36V to 5V shows that the frequency locking is completed instantly after the jump, and V is_LPFHardly changed.

In summary, the phase-locked loop circuit provided by the invention is realized based on a classical charge pump phase-locked loop, has the advantages of good transient response speed of pseudo-constant frequency and high precision of the phase-locked loop, and can be used for synchronizing the switching frequency of a COT mode switching power supply, the invention can effectively monitor an external synchronous clock signal and effectively prevent a P LL loop from being opened by mistake by an enabling logic module, and introduces a generated P LL control signal into an input voltage V which already contains the COT switching power supply_INAn On-time Timer (ON-TIME) module of the information realizes the accurate synchronization of an external clock and an internal switching signal, so that the switching frequency generated by a COT switching voltage loop has good frequency locking precision and faster transient response speed; switching power supply input voltage V in COT mode_INThe proportional bias current is used as the bias current of the voltage-current converter, and the input voltage V of an external power supply, namely a COT mode switching power supply_INWhen jumping occurs, the phase-locked loop circuit provided by the invention can directly sample V_INThe current flowing into the on-time timer module is quickly changed by the voltage information, so that the voltage on a low-pass filter in a loop is not required to be changed, namely, the self slow loop adjustment process is skipped, and the quick transient response is realizedThe loop of the P LL can be effectively improved at V_INThe frequency locking speed when jumping occurs can effectively improve the frequency locking range of P LL.

It will be appreciated by those of ordinary skill in the art that the foregoing examples are intended to assist the reader in understanding the principles of the invention, and are to be construed as being without limitation to such specifically recited examples and embodiments. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.