A switching power supply circuit based on harmonic compensation

Abstract

The present invention relates to the technical field of switching power supply control, and provides a switching power supply circuit based on harmonic compensation, including a rectifier module, a first filter module and a PWM half-bridge circuit connected in sequence, as well as a harmonic compensation module and a current detection module. The present invention adds a harmonic compensation module, and uses an energy storage capacitor EC1 or an energy storage capacitor EC2 to perform relay voltage compensation when a sinusoidal AC power is input, so that the diode in the rectifier bridge can be turned on during the time period from the instantaneous value of the AC input voltage (VEC3-2*n*VO) to the positive peak value, and during the time period from the positive peak value to the negative peak value, thereby widening the diode conduction angle in the rectifier bridge. Since the effective value of the input current will be reduced and the harmonic current will be suppressed, the reactive power will also be reduced and the power factor will be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supply control, and in particular to a switching power supply circuit based on harmonic compensation. Background Art

[0002] During the use of switching power supplies, semiconductor devices will generate harmonic interference when they are turned on and off. The AC rectifier filter circuit of the switching power supply needs to use large-capacity capacitors to filter and obtain smooth DC power, which increases reactive power, reduces the quality of the power grid, and affects the normal operation of other electrical equipment. Therefore, many countries have issued limit standards for limiting the current harmonics of electrical equipment. It is necessary to suppress the current harmonics of the switching power supply and compensate for the reactive power to meet the standards of various countries.

[0003] At present, the technologies for current harmonic suppression and reactive power compensation of switching power supplies mainly include passive compensation technology and active compensation technology, as follows:

[0004] (1) A passive network consisting of inductors and capacitors is used for harmonic suppression and reactive power compensation. Due to the large size and weight of the required filter capacitors and filter inductors, the power supply is large in size, low in efficiency and high in cost.

[0005] (2) Common passive current-following compensation technology can also suppress harmonics and compensate for reactive power, but the DC voltage obtained after filtering is low and the ripple is large, which makes the switching power supply low in efficiency and poor in output performance.

[0006] (3) A low harmonic switching power supply using a two-stage conversion circuit. The first stage is an active power factor correction circuit based on a Boost converter on the AC input side, and the second stage is an isolated DC-DC conversion circuit.

[0007] (4) A low harmonic switching power supply using a single-stage conversion circuit is a single-stage conversion circuit that uses a single-stage isolated PFC correction technology and operates in a discontinuous mode and a critical continuous mode.

[0008] These technologies all use active switching control technology, which can suppress current harmonics below the standard limit and the input power factor can be close to 1. However, these technologies all require a dedicated controller chip to drive the switch to control the energy storage or release of the inductor to achieve active power factor correction. Therefore, the control circuit of the switching power supply is relatively complex and the cost is relatively high. Among them, the switching power supply using single-stage isolation PFC correction technology has a relatively large output voltage ripple and poor output performance, which is not suitable for equipment with high voltage accuracy requirements. Summary of the invention

[0009] The present invention provides a switching power supply circuit based on harmonic compensation, which solves the technical problems that the existing active switch control is limited by a dedicated controller chip, has high circuit complexity, high cost, and relatively large voltage ripple.

[0010] In order to solve the above technical problems, the present invention provides a switching power supply circuit based on harmonic compensation, comprising: a rectifier module, a first filter module and a PWM half-bridge circuit connected in sequence, as well as a harmonic compensation module and a current detection module; the current detection module is connected to the primary circuit of the PWM half-bridge circuit; the input end of the harmonic compensation module is connected to the AC input, and the output end is connected to the output end of the rectifier module;

[0011] The harmonic compensation module performs voltage division detection through the current detection module, detects the fluctuation amplitude of the primary output voltage from the primary circuit, and then generates a compensation adjustment voltage that changes in the opposite direction of the fluctuation amplitude according to the fluctuation amplitude, and superimposes the compensation adjustment voltage to the output end of the rectifier module to perform harmonic compensation.

[0012] In a further embodiment, the harmonic compensation module includes a second filtering module, a rectifier bridge BDR2, an energy storage capacitor EC1 and an energy storage capacitor EC2; one end of the second filtering module is connected to the primary circuit of the PWM half-bridge circuit, and the other end is connected to the negative output end of the rectifier bridge BDR2;

[0013] The positive output end of the rectifier bridge BDR2 is connected to the output end of the rectifier module, its first input end is connected to the positive electrode of the energy storage capacitor EC1, and its second input end is connected to the positive electrode of the energy storage capacitor EC2; the negative electrode of the energy storage capacitor EC1 is connected to the first input end of the rectifier module and connected to the AC power supply input end L, and the negative electrode of the energy storage capacitor EC2 is connected to the second input end of the rectifier module and connected to the AC power supply input end N.

[0014] In a further implementation scheme, the second filtering module includes a filter capacitor C1 and a filter inductor L1, one end of the filter capacitor C1 is grounded, and the other end is connected to the negative output end of the rectifier bridge BDR2; one end of the filter inductor L1 is connected to the primary circuit of the PWM half-bridge circuit, and the other end is connected to the negative output end of the rectifier bridge BDR2; the filter capacitor C1 and the filter inductor L1 are used to filter out the high-frequency switching pulsation components detected from the primary output voltage.

[0015] In a further implementation scheme, the rectifier module includes a rectifier bridge BDR1, a first input terminal and a second input terminal of the rectifier bridge BDR1 are respectively connected to the AC power input terminal L and the AC power input terminal N, a positive output terminal is connected to the first filter module, and a negative output terminal is grounded; the rectifier bridge BDR1 is used to rectify the AC input and output a DC power supply.

[0016] In a further implementation scheme, the first filtering module includes an inductor L2 and a capacitor C3, one end of the inductor L2 is connected to the positive output end of the rectifier module, and the other end is connected to the PWM half-bridge circuit; one end of the capacitor C3 is connected to the positive output end of the rectifier module, and the other end is grounded; the inductor L2 and the capacitor C3 are used to form a high-frequency filtering circuit to filter out high-frequency interference signals in the rectified DC power supply.

[0017] In a further embodiment, the PWM half-bridge circuit includes a first switch tube Q1, a second switch tube Q2, a transformer TR1, a filter capacitor EC3 and a coupling capacitor C2;

[0018] The first end of the first switch tube Q1 is connected to the output end of the first filter module, and the second end is connected to the first end of the primary winding of the transformer TR1; the first end of the second switch tube Q2 is connected to the first end of the primary winding of the transformer TR1, and the second end is connected to the current detection module; one end of the coupling capacitor C2 is connected to the second end of the primary winding of the transformer TR1, and the other end is connected to the current detection module; the second end of the primary winding of the transformer TR1 is also connected to the harmonic compensation module; one end of the filter capacitor EC3 is connected between the first end of the first switch tube Q1 and the output end of the first filter module, and the other end is grounded.

[0019] In a further embodiment, the current detection module includes a resistor R1, one end of which is connected to the second end of the second switch tube Q2, and is also connected to the second end of the primary winding of the transformer TR1 through a coupling capacitor C2.

[0020] In a further embodiment, a third filtering module is further included, and the third filtering module includes a capacitor CX1 and a common-mode inductor L3 connected in sequence, the input end of the common-mode inductor L3 is connected to the AC power input terminal L and the AC power input terminal N, and the output end is connected to the rectification module and the harmonic compensation module, and the two ends of the capacitor CX1 are respectively connected to the AC power input terminal L and the AC power input terminal N.

[0021] In a further implementation scheme, the PWM half-bridge circuit also includes a secondary rectifier module, which includes a rectifier diode D9 and a filter capacitor EC4; the positive electrode of the rectifier diode D9 is connected to the DC output terminal VO-, and the negative electrode is connected to the first end of the secondary winding of the transformer TR1; the positive electrode of the filter capacitor EC4 is connected to the second end of the secondary winding of the transformer TR1 and the DC output terminal VO+, and the negative electrode is connected to the positive electrode of the rectifier diode D9 and the DC output terminal VO-.

[0022] In a further embodiment, the first switch tube Q1 is an N-channel MOS tube or a P-channel MOS tube, and the second switch tube Q2 is an N-channel MOS tube or a P-channel MOS tube.

[0023] The beneficial effects of the present invention are as follows:

[0024] By adding a harmonic compensation module, when a sinusoidal AC power is input, the energy storage capacitor EC1 or the energy storage capacitor EC2 is used for relay voltage compensation, so that the diodes in the rectifier bridge can be turned on during the time period from the instantaneous value of the AC input voltage (VEC3-2*n*VO) to the positive peak value and during the time period from the positive peak value to the negative peak value, thereby widening the diode conduction angle in the rectifier bridge. Since the effective value of the input current will be reduced and the harmonic current will be suppressed, the reactive power will also be reduced and the power factor will be improved; the filter capacitor C1 and the filter inductor L1 are set at the detection end of the rectifier bridge BDR2 to filter out the high-frequency switch pulsation components detected from the primary output voltage, which can further improve the compensation accuracy. Since the harmonic compensation mechanism is constructed with the rectifier bridge BDR2, the energy storage capacitor EC1 and the energy storage capacitor EC2 as the core, therefore:

[0025] (1) Compared with the switching power supply using the passive compensation technology of the common inductor and capacitor, the present application is smaller in size, more efficient and less expensive;

[0026] (2) Compared with the switching power supply using passive current-following compensation technology, the output ripple of this application is small, the efficiency is higher, and the output performance is higher;

[0027] (3) Compared with the switching power supply using active compensation technology based on Boost converter, the circuit of the present application is simple, uses fewer components and has lower cost;

[0028] (4) Compared with the switching power supply using single-stage isolated PFC correction technology, the output ripple of this application is smaller, the efficiency is higher, and the output performance is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a system framework diagram of a switching power supply circuit based on harmonic compensation provided by an embodiment of the present invention;

[0030] Figure 2 The embodiment of the present invention provides Figure 1 The hardware circuit diagram in ;

[0031] Among them: a rectifier module 1, a first filter module 2, a PWM half-bridge circuit 3, a harmonic compensation module 4, a current detection module 5, and a third filter module 6. DETAILED DESCRIPTION

[0032] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0033] An embodiment of the present invention provides a switching power supply circuit based on harmonic compensation, such as Figure 1 , Figure 2 As shown, in this embodiment, a rectifier module 1, a first filter module 2 and a PWM half-bridge circuit 3, as well as a harmonic compensation module 4 and a current detection module 5 are connected in sequence; the current detection module 5 is connected to the primary circuit of the PWM half-bridge circuit 3; the input end of the harmonic compensation module 4 is connected to the AC input, and the output end is connected to the output end of the rectifier module 1;

[0034] The harmonic compensation module 4 performs voltage division detection through the current detection module 5, detects the fluctuation amplitude of the primary output voltage from the primary circuit, and then generates a compensation adjustment voltage that changes in the opposite direction of the fluctuation amplitude according to the fluctuation amplitude, and superimposes the compensation adjustment voltage to the output end of the rectifier module 1 to perform harmonic compensation.

[0035] In this embodiment, the harmonic compensation module 4 includes a second filtering module, a rectifier bridge BDR2, an energy storage capacitor EC1 and an energy storage capacitor EC2; one end of the second filtering module is connected to the primary circuit of the PWM half-bridge circuit 3, and the other end is connected to the negative output end of the rectifier bridge BDR2;

[0036] The positive output end of the rectifier bridge BDR2 is connected to the output end of the rectifier module 1, its first input end is connected to the positive electrode of the energy storage capacitor EC1, and its second input end is connected to the positive electrode of the energy storage capacitor EC2; the negative electrode of the energy storage capacitor EC1 is connected to the first input end of the rectifier module 1 and connected to the AC power supply input end L, and the negative electrode of the energy storage capacitor EC2 is connected to the second input end of the rectifier module 1 and connected to the AC power supply input end N.

[0037] In this embodiment, the second filtering module includes a filter capacitor C1 and a filter inductor L1, one end of the filter capacitor C1 is grounded, and the other end is connected to the negative output end of the rectifier bridge BDR2; one end of the filter inductor L1 is connected to the primary circuit of the PWM half-bridge circuit 3, and the other end is connected to the negative output end of the rectifier bridge BDR2; the filter capacitor C1 and the filter inductor L1 are used to filter out the high-frequency switching pulsation components detected from the primary output voltage.

[0038] In this embodiment, the rectifier module 1 includes a rectifier bridge BDR1, a first input terminal and a second input terminal of the rectifier bridge BDR1 are respectively connected to the AC power input terminal L and the AC power input terminal N, a positive output terminal is connected to the first filter module 2, and a negative output terminal is grounded; the rectifier bridge BDR1 is used to rectify the AC input and output a DC power supply.

[0039] In this embodiment, the first filtering module 2 includes an inductor L2 and a capacitor C3, one end of the inductor L2 is connected to the positive output end of the rectifier module 1, and the other end is connected to the PWM half-bridge circuit 3; one end of the capacitor C3 is connected to the positive output end of the rectifier module 1, and the other end is grounded; the inductor L2 and the capacitor C3 are used to form a high-frequency filtering circuit to filter out high-frequency interference signals in the rectified DC power supply.

[0040] In this embodiment, the PWM half-bridge circuit 3 includes a first switch tube Q1, a second switch tube Q2, a transformer TR1, a filter capacitor EC3 and a coupling capacitor C2;

[0041] The control end of the first switch tube Q1 (the gate of the MOS tube as an example) and the control end of the second switch tube Q2 (the gate of the MOS tube as an example) are both connected to a main controller (not shown in this embodiment, such as a power chip of a switching power supply circuit). The main controller outputs a driving pulse according to a preset logic timing to control the first switch tube Q1 and the second switch tube Q2 to be alternately turned on to release the energy of the coupling capacitor C2.

[0042] The first end of the first switch tube Q1 is connected to the output end of the first filter module 2, and the second end is connected to the first end of the primary winding of the transformer TR1; the first end of the second switch tube Q2 is connected to the first end of the primary winding of the transformer TR1, and the second end is connected to the current detection module 5; one end of the coupling capacitor C2 is connected to the second end of the primary winding of the transformer TR1, and the other end is connected to the current detection module 5; the second end of the primary winding of the transformer TR1 is also connected to the harmonic compensation module 4; one end of the filter capacitor EC3 is connected between the first end of the first switch tube Q1 and the output end of the first filter module 2, and the other end is grounded.

[0043] In this embodiment, the current detection module 5 includes a resistor R1 , one end of which is connected to the second end of the second switch tube Q2 , and is also connected to the second end of the primary winding of the transformer TR1 through a coupling capacitor C2 .

[0044] In this embodiment, a third filtering module 6 is also included, and the third filtering module 6 includes a capacitor CX1 and a common-mode inductor L3 connected in sequence, the input end of the common-mode inductor L3 is connected to the AC power input terminal L and the AC power input terminal N, and the output end is connected to the rectifier module 1 and the harmonic compensation module 4, and the two ends of the capacitor CX1 are respectively connected to the AC power input terminal L and the AC power input terminal N.

[0045] In this embodiment, the PWM half-bridge circuit 3 also includes a secondary rectifier module 1, which includes a rectifier diode D9 and a filter capacitor EC4; the positive electrode of the rectifier diode D9 is connected to the DC output terminal VO-, and the negative electrode is connected to the first end of the secondary winding of the transformer TR1; the positive electrode of the filter capacitor EC4 is connected to the second end of the secondary winding of the transformer TR1 and the DC output terminal VO+, and the negative electrode is connected to the positive electrode of the rectifier diode D9 and the DC output terminal VO-.

[0046] In this embodiment, the first switch tube Q1 is an N-channel MOS tube or a P-channel MOS tube, and the second switch tube Q2 is an N-channel MOS tube or a P-channel MOS tube.

[0047] In this embodiment, the present invention further comprises a current fuse F1 connected in series to the live wire L.

[0048] Taking the first switch tube Q1 as an N-channel MOS tube and the second switch tube Q2 as an N-channel MOS tube as an example, the working principle of this embodiment is as follows:

[0049] 1. Stable working principle of switching power supply.

[0050] When the gate (GDH terminal) of the first switch tube Q1 receives a driving pulse with a duty cycle of D to turn on the first switch tube Q1, the voltage VEC3 across the filter capacitor EC3 is applied to the series circuit of the primary winding of the transformer TR1 and the coupling capacitor C2, and the primary winding of the transformer TR1 is excited to store energy.

[0051] When the gate (GDL end) of the second switch tube Q2 receives a driving pulse with a duty cycle of 1-D, the second switch tube Q2 is turned on, and the energy stored in the transformer TR1 is released to the coupling capacitor C2. At the same time, the rectifier diode D9 on the secondary side is turned on, and the energy stored in the transformer TR1 is also released to the output end, and the output voltage VO=VEC3×D / n (where n is the primary-to-secondary winding turns ratio of the transformer TR1). In this way, the voltage across the coupling capacitor C2 is clamped at about n*VO, which contains high-frequency switching pulsation components. Since the inductor L1 and capacitor C1 of the harmonic compensation circuit unit are used to filter out the high-frequency switching pulsation components, the terminal voltage VC1 of the capacitor C1 is approximately n*VO.

[0052] 2. Taking the negative half cycle of the AC input voltage as an example, the specific harmonic compensation process is as follows.

[0053] Since the potential of the AC input terminal N is higher than the potential of the AC input terminal L, the energy storage capacitor EC1 is charged and the energy storage capacitor EC2 is discharged. Near the peak value of the negative half cycle of the AC input voltage, the AC input voltage is rectified by the rectifier bridge BR1, and after being filtered by the high-frequency filter circuit composed of capacitor C3 and inductor L2, the filter capacitor EC3 is charged. The terminal voltage VEC3 of the filter capacitor EC3 is approximately equal to the peak value VAC of the AC input voltage. Since VAC-VEC2≈VEC3-n*VO, the terminal voltage of the energy storage capacitor EC1 is approximately n*VO. After the energy storage capacitor EC2 is completely discharged, its terminal voltage VEC2 is zero. As the AC input voltage changes from the negative peak to the positive direction, when the instantaneous value of the AC input voltage rises to (VEC3-2*n*VO), the voltage of the energy storage capacitor EC1 plus the instantaneous value of the input voltage will exceed the terminal voltage VEC3 of the capacitor EC3 at this time, and the diodes D5 and D7 in the rectifier bridge BDR2 are turned on to charge the filter capacitor EC3.

[0054] At this time, the energy storage capacitor EC1 starts to discharge, and the energy storage capacitor EC2 starts to charge. When the energy storage capacitor EC1 is fully released, its terminal voltage is zero (VEC1=0); the charging of the energy storage capacitor EC2 is completed and its terminal voltage is approximately VEC2=n*VO; the diodes D5 and D7 in the rectifier bridge BR2 are turned off. In this way, the AC input voltage continues to change toward the positive peak value, and the diodes D1 and D3 in the rectifier bridge BR1 will be turned on to continue charging the filter capacitor EC3. When the AC input voltage changes from the positive peak value to the negative peak value, the instantaneous value of the AC input voltage will be lower than the terminal voltage of the capacitor EC3, and the diodes D1 and D3 will be turned off.

[0055] From the above analysis, it can be seen that the rectifier tube is turned on during the time period from the instantaneous value of the AC input voltage (VEC3-2*n*VO) to the positive peak value, that is, the rectifier tube conduction angle becomes wider, the effective value of the input current will decrease, the harmonic current will be suppressed, the reactive power will also decrease, and the power factor will improve.

[0056] In the positive half cycle of the AC input voltage, the energy storage capacitor EC1 discharges and the energy storage capacitor EC2 charges. The circuit working principle during the period when the peak value of the positive half cycle changes to the negative half cycle is the same as the circuit working principle during the period when the peak value of the negative half cycle of the AC input voltage changes to the positive half cycle, and will not be repeated in this embodiment.

[0057] The beneficial effects of the present invention are as follows:

[0058] By adding a harmonic compensation module 4, when a sinusoidal AC power is input, the energy storage capacitor EC1 or the energy storage capacitor EC2 is used for relay voltage compensation, so that the diodes in the rectifier bridge can be turned on during the time period when the instantaneous value of the AC input voltage is (VEC3-2*n*VO) to the positive peak value and during the time period when the positive peak value changes to the negative peak value, thereby widening the diode conduction angle in the rectifier bridge. Since the effective value of the input current will be reduced and the harmonic current will be suppressed, the reactive power will also be reduced and the power factor will be improved. Since the harmonic compensation mechanism is constructed with the rectifier bridge BDR2, the energy storage capacitor EC1 and the energy storage capacitor EC2 as the core, therefore:

[0059] (1) Compared with the switching power supply using the passive compensation technology of the common inductor and capacitor, the present application is smaller in size, more efficient and less expensive;

[0060] (2) Compared with the switching power supply using passive current-following compensation technology, the output ripple of this application is small, the efficiency is higher, and the output performance is higher;

[0061] (3) Compared with the switching power supply using active compensation technology based on Boost converter, the circuit of the present application is simple, uses fewer components and has lower cost;

[0062] (4) Compared with the switching power supply using single-stage isolated PFC correction technology, the output ripple of this application is smaller, the efficiency is higher, and the output performance is higher.

[0063] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A switching power supply circuit based on harmonic compensation, characterized in that: It includes a rectifier module, a first filter module and a PWM half-bridge circuit, as well as a harmonic compensation module and a current detection module connected in sequence; the current detection module is connected to the primary circuit of the PWM half-bridge circuit; the input end of the harmonic compensation module is connected to the AC input, and the output end is connected to the output end of the rectifier module; The harmonic compensation module performs voltage division detection through the current detection module, detects the fluctuation amplitude of the primary output voltage from the primary circuit, and then generates a compensation adjustment voltage that changes in the opposite direction of the fluctuation amplitude according to the fluctuation amplitude, and superimposes the compensation adjustment voltage to the output end of the rectifier module to perform harmonic compensation; The harmonic compensation module includes a second filtering module, a rectifier bridge BDR2, an energy storage capacitor EC1 and an energy storage capacitor EC2; One end of the second filtering module is connected to the primary circuit of the PWM half-bridge circuit, and the other end is connected to the negative output end of the rectifier bridge BDR2; The positive output end of the rectifier bridge BDR2 is connected to the output end of the rectifier module, its first input end is connected to the positive electrode of the energy storage capacitor EC1, and its second input end is connected to the positive electrode of the energy storage capacitor EC2; the negative electrode of the energy storage capacitor EC1 is connected to the first input end of the rectifier module and connected to the AC power supply input end L, and the negative electrode of the energy storage capacitor EC2 is connected to the second input end of the rectifier module and connected to the AC power supply input end N.

2. A switching power supply circuit based on harmonic compensation as claimed in claim 1, characterized in that: The second filtering module includes a filter capacitor C1 and a filter inductor L1, one end of the filter capacitor C1 is grounded, and the other end is connected to the negative output end of the rectifier bridge BDR2; one end of the filter inductor L1 is connected to the primary circuit of the PWM half-bridge circuit, and the other end is connected to the negative output end of the rectifier bridge BDR2; the filter capacitor C1 and the filter inductor L1 are used to filter out the high-frequency switching pulsation components detected from the primary output voltage.

3. A switching power supply circuit based on harmonic compensation as claimed in claim 1, characterized in that: The rectifier module includes a rectifier bridge BDR1, a first input terminal and a second input terminal of the rectifier bridge BDR1 are respectively connected to an AC power input terminal L and an AC power input terminal N, a positive output terminal thereof is connected to a first filter module, and a negative output terminal is grounded; the rectifier bridge BDR1 is used to rectify the AC input and output a DC power supply.

4. A switching power supply circuit based on harmonic compensation as claimed in claim 3, characterized in that: The first filtering module includes an inductor L2 and a capacitor C3, one end of the inductor L2 is connected to the positive output end of the rectifier module, and the other end is connected to the PWM half-bridge circuit; one end of the capacitor C3 is connected to the positive output end of the rectifier module, and the other end is grounded; the inductor L2 and the capacitor C3 are used to form a high-frequency filtering circuit to filter out high-frequency interference signals in the rectified DC power supply.

5. A switching power supply circuit based on harmonic compensation as claimed in claim 4, characterized in that: The PWM half-bridge circuit includes a first switch tube Q1, a second switch tube Q2, a transformer TR1, a filter capacitor EC3 and a coupling capacitor C2; The first end of the first switch tube Q1 is connected to the output end of the first filter module, and the second end is connected to the first end of the primary winding of the transformer TR1; the first end of the second switch tube Q2 is connected to the first end of the primary winding of the transformer TR1, and the second end is connected to the current detection module; one end of the coupling capacitor C2 is connected to the second end of the primary winding of the transformer TR1, and the other end is connected to the current detection module; the second end of the primary winding of the transformer TR1 is also connected to the harmonic compensation module; one end of the filter capacitor EC3 is connected between the first end of the first switch tube Q1 and the output end of the first filter module, and the other end is grounded.

6. A switching power supply circuit based on harmonic compensation as claimed in claim 5, characterized in that: The current detection module includes a resistor R1 , one end of which is connected to the second end of the second switch tube Q2 , and is also connected to the second end of the primary winding of the transformer TR1 through a coupling capacitor C2 .

7. A switching power supply circuit based on harmonic compensation as claimed in claim 3, characterized in that: It also includes a third filtering module, which includes a capacitor CX1 and a common-mode inductor L3 connected in sequence, the input end of the common-mode inductor L3 is connected to the AC power input terminal L and the AC power input terminal N, and the output end is connected to the rectification module and the harmonic compensation module, and the two ends of the capacitor CX1 are respectively connected to the AC power input terminal L and the AC power input terminal N.

8. A switching power supply circuit based on harmonic compensation as claimed in claim 5, characterized in that: The PWM half-bridge circuit also includes a secondary rectifier module, which includes a rectifier diode D9 and a filter capacitor EC4; the positive electrode of the rectifier diode D9 is connected to the DC output terminal VO-, and the negative electrode is connected to the first end of the secondary winding of the transformer TR1; the positive electrode of the filter capacitor EC4 is connected to the second end of the secondary winding of the transformer TR1 and the DC output terminal VO+, and the negative electrode is connected to the positive electrode of the rectifier diode D9 and the DC output terminal VO-.

9. A switching power supply circuit based on harmonic compensation as claimed in claim 5, characterized in that: The first switch tube Q1 is an N-channel MOS tube or a P-channel MOS tube, and the second switch tube Q2 is an N-channel MOS tube or a P-channel MOS tube.

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