CN-122001207-A - THD compensation circuit and control method thereof

Abstract

The application relates to a THD compensation circuit and a control method thereof, comprising a THD compensation main control circuit; the first input end of the THD compensation main control circuit receives the voltage loop compensation voltage output by the voltage loop amplifier, the second input end of the THD compensation main control circuit receives the slope signal, the output end of the THD compensation main control circuit is connected with the in-phase input end of the PWM comparator, the THD compensation main control circuit generates compensation quantity according to the voltage loop compensation voltage and superimposes the compensation quantity on the slope signal to generate a compensated slope signal, the compensated slope signal is output to the in-phase input end of the PWM comparator and is compared with the current loop compensation voltage signal to generate a logic control signal for modulating the PWM control signal. The scheme provided by the application can dynamically and adaptively compensate harmonic waves, automatically adjust compensation quantity, improve the reliability and stability of a switching power supply system and optimize THD value.

Inventors

• WANG CHAO
• SHEN YANG

Assignees

• 广州博之源科技有限公司

Dates

Publication Date

20260508

Application Date

20251231

Claims (7)

1. 1. A THD compensation circuit comprising a PFC main power circuit and a power factor correction main control circuit, characterized by comprising: THD compensates the master control circuit; a first input end of the THD compensation main control circuit receives voltage loop compensation voltage output by a voltage loop amplifier in the power factor correction main control circuit; a second input end of the THD compensation main control circuit receives a slope signal; the output end of the THD compensation main control circuit is connected with the non-inverting input end of a PWM comparator in the power factor correction main control circuit; The THD compensation main control circuit generates compensation quantity according to the voltage loop compensation voltage, and the compensation quantity is added to the slope signal to generate a compensated slope signal, the compensated slope signal is output to the non-inverting input end of the PWM comparator, and the non-inverting input end of the compensated slope signal is compared with the current loop compensation voltage signal to generate a logic control signal for modulating the PWM control signal.
2. 2. The THD compensation circuit according to claim 1, comprising: the THD compensation master control circuit generates compensation quantity positively correlated with the amplitude of the voltage loop compensation voltage.
3. 3. The THD compensation circuit according to claim 1, wherein: The ramp signal is controlled by a phase drive clock signal CLK.
4. 4. A THD compensation circuit control method adapted to the THD compensation circuit according to any one of claims 1 to 3, comprising: acquiring a voltage loop compensation voltage of a power factor correction main control circuit; generating THD compensation quantity according to the voltage loop compensation voltage; superposing the THD compensation quantity on a slope signal to generate a compensated slope signal; And comparing the compensated slope signal with the current loop compensation voltage to generate a logic level signal, modulating the duty ratio of the PWM control signal and driving the power switching device to be turned on and off.
5. 5. The THD compensation circuit control method according to claim 4, wherein the generating the THD compensation amount from the voltage loop compensation voltage includes: The THD compensation quantity is positively correlated with the amplitude of the voltage loop compensation voltage, and the THD compensation quantity is obtained by multiplying the voltage loop compensation voltage with a dynamic gain factor; the dynamic gain factor increases with an increase in the voltage loop compensation voltage; the THD compensated ramp signal is: V2=VRAMP+(VCOMP*K)(3) where VRAMP is the initial ramp signal, VCOMP is the voltage loop compensation voltage, and K is the dynamic gain factor.
6. 6. The THD compensation circuit control method according to claim 4, wherein the generating a logic level signal comprises: comparing the compensated ramp signal with a current loop compensation voltage signal; when the compensated slope signal is larger than the current loop compensation voltage, the logic level signal is in a high level; When the compensated ramp signal is at the current loop compensation voltage, the logic level signal is at a low level.
7. 7. The THD compensation circuit control method according to claim 4, wherein the duty ratio of the modulated PWM control signal comprises: The voltage of the ramp signal after adding compensation is raised, and exceeds the current loop compensation voltage signal in advance, so that the output logic level signal determining the switching tube starting time of the PFC main power circuit is changed into high level in advance, the output setting of the RS trigger is changed into high level in advance, the duty ratio of the PWM control signal is increased, the switching tube is controlled to be started in advance, the conduction time is increased, the charge of the input filter capacitor of the PFC main power circuit is consumed, and the THD value is optimized; When CLK is high, the output reset of RS trigger RS1 becomes low, PWMP signal becomes low, and the switching tube is completed in one switching cycle.

Description

THD compensation circuit and control method thereof Technical Field The application relates to the technical field of switching power supplies, in particular to a THD compensation circuit and a control method thereof. Background In the technical field of switching power supplies, a Power Factor Correction (PFC) technology is widely applied to an alternating current-direct current (AC-DC) converter to improve an input current waveform so as to be in phase with an input voltage, thereby improving a power factor, reducing harmonic distortion (THD), and improving power quality of a power grid. Total Harmonic Distortion (THD) is an important index for measuring the deviation degree of a current waveform from a sine wave, and a higher THD not only affects the stability of a power supply system, but also can cause the problems of overheating of equipment, efficiency reduction and the like. The traditional PFC control scheme generally adopts a voltage loop and current loop double-loop control structure, and the input current is shaped by adjusting the duty ratio of a switching tube. However, near the zero crossing point of the input voltage, the input current is easily distorted due to the fact that the residual charge on the input filter capacitor cannot be consumed in time and the conduction voltage drop of the rectifier diode is affected, resulting in the deterioration of THD. To improve this problem, a fixed compensation voltage is superimposed on the ramp signal of the PWM comparator in the conventional THD compensation technique to start the power switching transistor in advance and increase the on time thereof, so as to consume the charge on the input filter capacitor near the zero crossing point and improve the current waveform. However, in the THD compensation mode with the fixed compensation amount, under the working conditions of system start, light load or protection recovery, the current loop is not completely established, and if the fixed THD compensation voltage is directly applied, the ramp signal may exceed the current loop compensation voltage too early, so that the output of the PWM comparator is continuously high, and the switching tube is caused to be conducted for a long time with the maximum or near the maximum duty ratio, so that an excessive inductance current peak is generated. Not only the damage risk of the power device is increased, but also the unstable operation of the power supply system can be caused. Therefore, a control circuit and a control method for realizing effective dynamic compensation of THD without introducing a start-up current surge are needed. Disclosure of Invention In order to solve or partially solve the problems existing in the related art, the application provides a THD compensation circuit and a control method thereof, and aims to solve the problems of low full-working-condition performance and low system safety caused by adopting a fixed compensation quantity mode. A first aspect of the application provides a THD compensation circuit comprising: The PFC main power circuit, the power factor correction main control circuit and the THD compensation main control circuit; The PFC main power circuit comprises a rectifier bridge, an input filter capacitor CIN, a power inductor L, a power switch tube Q1, a rectifier diode D5 and an output filter capacitor COUT, wherein the rectifier bridge is composed of input alternating voltage rectifier diodes D1, D2, D3 and D4 and is used for rectifying input alternating voltage to be changed into direct voltage VIN. The input filter capacitor CIN is connected in parallel with the output end of the rectifier bridge and mainly used for rectifying and filtering the rectified voltage. The power inductor L is connected with one end of the input filter capacitor CIN, the drain electrode of the power switch tube Q1 is connected with one end of the power inductor L, the source electrode of the power switch tube Q1 is connected with the other end of the input filter capacitor CIN, the grid electrode of the power switch tube Q1 is connected with the output end of the power factor correction main control circuit, the anode of the rectifier diode D5 is connected with the drain electrode of the power switch tube Q1, and the chopper and boost control of the input voltage are realized. One end of the output filter capacitor COUT is connected with the cathode of the rectifying diode D5, the other end of the output filter capacitor COUT is connected with the source electrode of the power switch tube Q1 and grounded, and the output voltage is filtered to obtain a stable direct-current output voltage. The power factor correction main control circuit comprises an inductance current sampling resistor RS, an inductance current sampling voltage inverse proportional amplifier A1, a current loop amplifier IEA, RC compensation networks R1 and C1 of the current loop amplifier IEA, a voltage loop amplifier VEA, RC compensation networks R2 and C2 of the voltag