CN206422704U - Intelligent half-bridge sine voltage change-over circuit based on PFC interleaving inverse excitations - Google Patents

Abstract

The utility model discloses an intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback, which includes: an input rectification filter unit; a PFC boost unit; an interleaved flyback isolation transformation unit, including a first switch tube, The second switch tube, the first transformer, the second transformer, the first diode, the second diode, the third diode and the fourth diode; the DC filtering unit, including the first capacitor and the second capacitor, The cathode of the third diode is connected to the rear end ground through the first capacitor, and the anode of the fourth diode is connected to the rear end ground through the second capacitor; the inverter inverter unit includes the fourth switch tube and the fifth switch tube , the third electrolytic capacitor, the fourth electrolytic capacitor and the filter inductance, the rear end of the filter inductance and the negative pole of the third electrolytic capacitor serve as the output end of the inverter unit. The utility model utilizes the filtering inductance to filter out high-frequency pulses, so that the load can obtain high-quality industrial frequency sinusoidal alternating current, and at the same time reduce the circuit cost.

Description

Intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback

technical field

The utility model relates to a voltage conversion circuit, in particular to an intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback.

Background technique

In the prior art, the intelligent buck-boost conversion device from AC to AC is also called a travel plug-in strip. In this device, the voltage conversion circuit is the key circuit, which is a circuit that can realize AC-AC conversion. In the AC-AC conversion, the function of realizing buck-boost and stabilizing voltage and frequency. However, most of the current AC-AC portable equipment market is a non-isolated topology circuit with low PF value, low output voltage quality, and poor safety and reliability. Especially in the voltage conversion process, more ripple interference will be generated, which will affect the voltage quality. In addition, the existing sine wave voltage conversion circuit has defects such as complex circuit structure, slow response speed, and high cost. In practical applications, due to the high-speed switching of the switching tube during the voltage conversion process, there will be a certain high-frequency pulse signal on the output side of the circuit, which will affect the quality of the output voltage, so it is difficult to meet the conversion requirements.

Utility model content

The technical problem to be solved by the utility model is to provide a circuit that can reduce the ripple in the circuit, simplify the circuit structure, reduce the cost of the circuit, filter out high-frequency crosstalk, and improve the quality of the output voltage in view of the deficiencies of the prior art. And a safe and reliable intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback.

In order to solve the above technical problems, the utility model adopts the following technical solutions.

An intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback, which includes an input rectification and filtering unit for rectifying and filtering the grid voltage, and an input rectification and filtering unit for step-up conversion of the output voltage of the input rectification and filtering unit PFC step-up unit, and: an interleaved flyback isolation conversion unit, including a first switch tube, a second switch tube, a first transformer, a second transformer, a first diode, a second diode, a third two pole tube and a fourth diode, the first end of the primary winding of the first transformer is connected to the output end of the PFC step-up unit, and the second end of the primary winding of the first transformer is connected to the drain of the first switching tube , the source of the first switch tube is connected to the front-end ground, the drain of the first switch tube is connected to the anode of the first diode, and the cathode of the first diode is connected to the PFC through a first resistor The output end of the step-up unit, the first resistor is connected in parallel with a third capacitor, the first end of the primary winding of the second transformer is connected to the output end of the PFC step-up unit, the second end of the primary winding of the second transformer connected to the drain of the second switch tube, the source of the second switch tube is connected to the front-end ground, the drain of the second switch tube is connected to the anode of the second diode, and the second diode The cathode of the PFC is connected to the output end of the PFC step-up unit through a second resistor, the second resistor is connected in parallel with a fourth capacitor, and the grid of the first switching tube and the grid of the second switching tube are respectively used to connect to the two PWM pulse signals with opposite phases, the first end of the secondary winding of the first transformer is connected to the anode of the third diode, the second end of the secondary winding of the first transformer is connected to the back-end ground, the The first end of the secondary winding of the second transformer is connected to the rear end, the second end of the secondary winding of the second transformer is connected to the cathode of the fourth diode, the cathode of the third diode and the fourth The anode of the diode is used as the output end of the interleaved flyback isolation conversion unit; a DC filter unit includes a first capacitor and a second capacitor, and the cathode of the third diode is connected to the back-end ground through the first capacitor, The anode of the fourth diode is connected to the rear end ground through the second capacitor; an inverter inverter unit includes a fourth switching tube, a fifth switching tube, a third electrolytic capacitor, a fourth electrolytic capacitor and a filter inductor , the drain of the fourth switching tube is connected to the positive pole of the output terminal of the interleaved flyback isolation conversion unit, the source of the fourth switching tube is connected to the drain of the fifth switching tube, and the source of the fifth switching tube The pole is connected to the negative pole of the output terminal of the interleaved flyback isolation conversion unit, the gate of the fourth switch tube and the gate of the fifth switch tube are respectively used to access two PWM pulse signals with opposite phases, and the fourth switch The source of the tube is also connected to the front end of the filter inductor, the positive pole of the third electrolytic capacitor is connected to the drain of the fourth switching tube, the negative pole of the third electrolytic capacitor is connected to the rear end ground, and the The negative pole is also connected to the positive pole of the fourth electrolytic capacitor, the negative pole of the fourth electrolytic capacitor is connected to the source of the fifth switching tube, the rear end of the filter inductor and the negative pole of the third electrolytic capacitor serve as the inverter inverter unit output.

Preferably, a first resistor is connected between the gate and source of the fourth switch transistor, and a second resistor is connected between the gate and source of the fifth switch transistor.

Preferably, the input rectifying and filtering unit includes a socket, an insurance, a lightning protection resistor, a common-mode suppression inductor, a safety capacitor and a rectifier bridge, the insurance is connected in series with the neutral wire or live wire of the socket, and the common-mode suppression The front end of the inductance is connected in parallel to the socket, the lightning protection resistor is connected in parallel to the front end of the common mode suppression inductor, the safety capacitor and the input end of the rectifier bridge are connected in parallel to the rear end of the common mode suppression inductor, and the output end of the rectifier bridge A filter capacitor is connected in parallel.

Preferably, the PFC boost unit includes a boost inductor, a third switch tube, a first rectifier diode and a second electrolytic capacitor, the front end of the boost inductor is connected to the output terminal of the input rectifier filter unit, and the boost The rear end of the piezoelectric inductance is connected to the drain of the third switching tube, the source of the third switching tube is connected to the front ground, and the gate of the third switching tube is used to access a PWM control signal. The drain of the switch tube is connected to the anode of the first rectifier diode, the cathode of the first rectifier diode is used as the output end of the PFC boost unit, and the cathode of the first rectifier diode is connected to the positive pole of the second electrolytic capacitor, and the second electrolytic capacitor The negative terminal of the terminal is connected to the ground.

Preferably, it also includes an MCU control unit, the grid of the first switch tube, the grid of the second switch tube and the grid of the third switch tube are respectively connected to the MCU control unit, and the MCU control unit is used for respectively Outputting PWM signals to the first switch tube, the second switch tube and the third switch tube to control the on-off states of the first switch tube, the second switch tube and the third switch tube.

Preferably, the MCU control unit includes a single-chip microcomputer and its peripheral circuits.

Preferably, an AC sampling unit is also included, the AC sampling unit is connected between the input terminal of the input rectification and filtering unit and the MCU control unit, and the AC sampling unit is used to collect the voltage on the AC side of the input rectification and filtering unit and feed it back to MCU control unit.

Preferably, the AC sampling unit includes an operational amplifier, the two input terminals of the operational amplifier are respectively connected to the input terminals of the input rectification and filtering unit through a current limiting resistor, and the output terminal of the operational amplifier is connected to the MCU control unit .

Preferably, a first sampling resistor is connected between the source of the third switching tube and the front-end ground, the source of the third switching tube is connected to the MCU control unit, and the MCU is controlled by the first sampling resistor. The control unit collects the electrical signal of the source of the third switch tube.

Preferably, it also includes a DC voltage sampling unit, the DC voltage sampling unit includes a second sampling resistor and a third sampling resistor connected in series in sequence, and the front end of the second sampling resistor is connected to the output of the interleaved flyback isolation conversion unit The rear end of the third sampling resistor is connected to the MCU control unit, and the MCU control unit collects the electrical signal output by the interleaved flyback isolation conversion unit through the second sampling resistor and the third sampling resistor.

In the intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback disclosed by the utility model, the input rectification and filtering unit is used to rectify and filter the grid voltage to output the pulsating DC voltage, and then the PFC booster unit is used to rectify the pulsating DC voltage Step-up processing, in the interleaved flyback isolation conversion unit, the first switching tube and the second switching tube are turned on alternately, when the first switching tube is turned on, the second switching tube is turned off, and the current is supplied by the primary winding of the first transformer, The first switch tube forms a loop to the front end, and the primary winding of the first transformer starts to store energy; when the second switch tube is turned on, the first switch tube is cut off, and the current is composed of the second transformer primary winding, the second switch tube, and the front end ground loop, the primary winding of the second transformer starts to store energy, and at the same time, the primary winding of the first transformer is coupled to the secondary winding through the first transformer core, and then charges the first capacitor through the third diode, forming a positive current on the first capacitor. Then the first switch tube is turned on again, the second switch tube is turned off, the first transformer stores energy, and the secondary winding of the second transformer charges the second capacitor through the fourth diode, forming a negative phase on the second capacitor Voltage; in this way, positive and negative DC voltages are formed on the DC bus. The first diode, the second diode, the first resistor, the second resistor, the third capacitor, and the fourth capacitor in the above circuit are the absorption circuits of the first switching tube and the second switching tube respectively, and are used to absorb the first switching tube and the second switching tube. The peak voltage generated by the leakage inductance of the first transformer and the second transformer is used to reduce the voltage stress of the switch tube. The above interleaved flyback isolation unit has achieved the following beneficial effects: due to the use of alternating conduction, the current ripple in the circuit is smaller and the application is more flexible. At the same time, the EMI and EMC interference in the circuit are small, and the circuit operating frequency is higher. Therefore, the power density can be improved. In addition, the output voltage can be changed by changing the primary-to-secondary turn ratio of the first transformer and the second transformer, thereby realizing step-up or step-down. Based on the above features, the utility model has the beneficial effects of reducing the ripple in the circuit, simplifying the circuit structure, reducing the cost of the circuit, improving the quality of the output voltage, and being safe and reliable. On this basis, the utility model is equipped with a filter inductor at the output end of the inverter unit, and the high-frequency pulse of the alternating current can be filtered out by using the filter inductor, so that the load can obtain high-quality industrial frequency sinusoidal alternating current, thereby improving the output Voltage quality to meet power supply needs.

Description of drawings

Figure 1 is a circuit schematic diagram of a sine wave voltage conversion circuit.

Fig. 2 is a schematic circuit diagram of an AC sampling unit in a preferred embodiment of the present invention.

Fig. 3 is a schematic circuit diagram of the MCU control unit in the preferred embodiment of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment the utility model is described in more detail.

The utility model discloses an intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback, as shown in Fig. 1 to Fig. 3 , it includes an input rectifying and filtering unit 10, A PFC step-up unit 20 for step-up conversion of the output voltage input to the rectification and filtering unit 10, and:

An interleaved flyback isolation conversion unit 30, including a first switch tube Q6, a second switch tube Q7, a first transformer T1, a second transformer T2, a first diode D6, a second diode D5, a third two Diode D7 and fourth diode D8, the first end of the primary winding of the first transformer T1 is connected to the output end of the PFC step-up unit 20, the second end of the primary winding of the first transformer T1 is connected to the first The drain of the switching tube Q6, the source of the first switching tube Q6 is connected to the front-end ground, the drain of the first switching tube Q6 is connected to the anode of the first diode D6, and the first diode The cathode of D6 is connected to the output end of the PFC step-up unit 20 through the first resistor R26, the first resistor R26 is connected in parallel with the third capacitor C5, and the first end of the primary winding of the second transformer T2 is connected to the PFC step-up unit 20, the second end of the primary winding of the second transformer T2 is connected to the drain of the second switching tube Q7, the source of the second switching tube Q7 is connected to the front-end ground, and the second switching tube Q7 The drain of the second diode D5 is connected to the anode of the second diode D5, and the cathode of the second diode D5 is connected to the output terminal of the PFC boost unit 20 through the second resistor R27, and the second resistor R27 is connected in parallel with a fourth Capacitor C6, the gate of the first switching tube Q6 and the gate of the second switching tube Q7 are respectively used to access two PWM pulse signals with opposite phases, and the first end of the secondary winding of the first transformer T1 is connected to At the anode of the third diode D7, the second end of the secondary winding of the first transformer T1 is connected to the back-end ground, the first end of the secondary winding of the second transformer T2 is connected to the back-end ground, and the The second terminal of the secondary winding of the second transformer T2 is connected to the cathode of the fourth diode D8, and the cathode of the third diode D7 and the anode of the fourth diode D8 serve as the interleaved flyback isolation conversion unit 30 output terminal;

A DC filtering unit 40, including a first capacitor C7 and a second capacitor C8, the cathode of the third diode D7 is connected to the back-end ground through the first capacitor C7, and the anode of the fourth diode D8 is connected to the rear end through the The second capacitor C8 is connected to the back-end ground;

An inverter and phase inverting unit 60, including a fourth switching tube Q2, a fifth switching tube Q4, a third electrolytic capacitor C3, a fourth electrolytic capacitor C4 and a filter inductor L3, the drain of the fourth switching tube Q2 is connected to The positive pole of the output terminal of the interleaved flyback isolation conversion unit 30, the source of the fourth switching transistor Q2 is connected to the drain of the fifth switching transistor Q4, and the source of the fifth switching transistor Q4 is connected to the interleaved flyback isolation conversion The negative pole of the output terminal of the unit 30, the gate of the fourth switching tube Q2 and the gate of the fifth switching tube Q4 are respectively used to access two PWM pulse signals with opposite phases, and the source of the fourth switching tube Q2 It is also connected to the front end of the filter inductor L3, the positive pole of the third electrolytic capacitor C3 is connected to the drain of the fourth switching transistor Q2, the negative pole of the third electrolytic capacitor C3 is connected to the rear end ground, and the third electrolytic capacitor C3 The negative pole of the fourth electrolytic capacitor C4 is also connected to the positive pole of the fourth electrolytic capacitor C4, the negative pole of the fourth electrolytic capacitor C4 is connected to the source of the fifth switching tube Q4, the rear end of the filter inductor L3 and the negative pole of the third electrolytic capacitor C3 serve as Inverting the output terminal of the inverter unit 60 .

In the above sine wave voltage conversion circuit, the input rectification and filtering unit 10 is used to rectify and filter the grid voltage to output the pulsating DC voltage, and then the PFC boost unit 20 is used to boost the pulsating DC voltage, and the interleaved flyback isolation conversion unit 30, wherein the first switching tube Q6 and the second switching tube Q7 are turned on alternately, when the first switching tube Q6 is turned on, the second switching tube Q7 is cut off, and the current flows from the primary winding of the first transformer T1, the first switching tube Q6 to The front-end ground forms a loop, and the primary winding of the first transformer T1 starts to store energy; when the second switch tube Q7 is turned on, the first switch tube Q6 is turned off, and the current is composed of the primary winding of the second transformer T2, the second switch tube Q7, and the front-end ground loop, the primary winding of the second transformer T2 starts to store energy, and at the same time the primary winding of the first transformer T1 is coupled to the secondary winding through the magnetic core of the first transformer T1, and then charges the first capacitor C7 through the third diode D7. A forward voltage is formed on a capacitor C7; then the first switching tube Q6 is turned on again, the second switching tube Q7 is turned off, the first transformer T1 stores energy, and the secondary winding of the second transformer T2 supplies energy to the second transformer through the fourth diode D8. The capacitor C8 is charged to form a negative voltage on the second capacitor C8; thus, positive and negative DC voltages are formed on the DC bus. The first diode D6, the second diode D5, the first resistor R26, the second resistor R27, the third capacitor C5, and the fourth capacitor C6 in the above circuit are respectively the first switching tube Q6 and the second switching tube Q7 The absorption circuit is used to absorb the peak voltage generated by the leakage inductance of the first transformer T1 and the second transformer T2, so as to reduce the voltage stress of the switch tube. The above interleaved flyback isolation unit has achieved the following beneficial effects: due to the use of alternating conduction, the current ripple in the circuit is smaller and the application is more flexible. At the same time, the EMI and EMC interference in the circuit are small, and the circuit operating frequency is higher. Therefore, the power density can be improved. In addition, the output voltage can be changed by changing the primary-to-secondary turn ratio of the first transformer T1 and the second transformer T2, thereby realizing step-up or step-down. Based on the above features, the utility model has the beneficial effects of reducing the ripple in the circuit, simplifying the circuit structure, reducing the cost of the circuit, improving the quality of the output voltage, and being safe and reliable. On this basis, the utility model is provided with a filter inductance L3 at the output end of the inverter unit 60, and the high-frequency pulse in the AC can be filtered out by using the filter inductance L3, so that the load can obtain a high-quality industrial frequency sinusoidal AC, and then Improve output voltage quality to meet power supply needs.

Further, a first resistor R17 is connected between the gate and source of the fourth switching transistor Q2, and a second resistor R23 is connected between the gate and source of the fifth switching transistor Q4.

In the inverter inverter unit 60, when the fourth switching tube Q2 is turned on, the fourth switching tube Q2, the load, and the fourth electrolytic capacitor C4 form a loop to generate the first high-frequency pulse level to the load. When the switching tube Q2 is turned off, a freewheeling circuit is formed through the fourth electrolytic capacitor C4, the body diode of the fifth switching tube Q4, and the filter inductor L3; when the fifth switching tube Q4 is turned on, it passes through the fifth switching tube Q4, the load, the third The electrolytic capacitor C3 forms a loop, and the second high-frequency pulse level is formed on the load. When the fifth switching tube Q4 is turned off, the body diode of the fourth switching tube Q2, the third electrolytic capacitor C3, the load, and the filter inductor L3 forms a freewheeling circuit. The high-frequency driving PWM signals of the fourth switching tube Q2 and the fifth switching tube Q4 are sent to the GATE poles of the fourth switching tube Q2 and the fifth switching tube Q4 after being changed by power frequency modulation. The driving signals of the fourth switching tube Q2 and the fifth switching tube Q4 are modulated by power frequency, and the current flowing through the fourth switching tube Q2 and the fifth switching tube Q4 changes sinusoidally. Since the filter inductor L3 has a high-resistance characteristic for high-frequency pulses, the high-frequency components are filtered out by the filter inductor L3, and a power frequency sinusoidal AC voltage is formed on the load. At the same time, the third electrolytic capacitor C3 and the fourth electrolytic capacitor C4 also have the function of filtering, and can form a DC filter circuit with the filter inductor L3. The control of the inverter circuit is simple, the circuit only uses two MOS tubes, and the cost is low.

Regarding the input part, as shown in Figure 1, the input rectification and filtering unit 10 includes a socket, insurance F2, lightning protection resistor RV1, common mode suppression inductor L1, safety capacitor CX1 and rectifier bridge DB1, and the insurance F2 is connected in series On the neutral line or live line of the socket, the front end of the common mode suppression inductor L1 is connected in parallel to the socket, the lightning protection resistor RV1 is connected in parallel with the front end of the common mode suppression inductor L1, the input of the safety capacitor CX1 and the rectifier bridge DB1 Both terminals are connected in parallel to the rear end of the common mode suppression inductor L1, and the output terminal of the rectifier bridge DB1 is connected in parallel with a filter capacitor C1.

Regarding the boost part, the PFC boost unit 20 includes a boost inductor L2, a third switch tube Q5, a first rectifier diode D1 and a second electrolytic capacitor C2, and the front end of the boost inductor L2 is connected to the input rectifier filter The output end of the unit 10, the back end of the boost inductor L2 is connected to the drain of the third switching tube Q5, the source of the third switching tube Q5 is connected to the front end, and the gate of the third switching tube Q5 For connecting a PWM control signal, the drain of the third switching tube Q5 is connected to the anode of the first rectifying diode D1, the cathode of the first rectifying diode D1 is used as the output end of the PFC boost unit 20, and the first The cathode of a rectifier diode D1 is connected to the positive pole of the second electrolytic capacitor C2, and the negative pole of the second electrolytic capacitor C2 is connected to the terminal ground.

The above-mentioned PFC boost unit 20, when sampling the filter capacitor C1 to output a half-wave AC voltage, the PFC enters the boost mode to increase the PF value of the AC-to-AC intelligent step-down conversion topology circuit, and after boosting, it is filtered by the second electrolytic capacitor C2 The final voltage is 400V, and the specific boost principle is as follows: when the third switch tube Q5 is turned on, the current on the filter capacitor C1 forms a loop through the boost inductor L2 and the third switch tube Q5 to GND, and the boost inductor L2 stores energy ; When the third switching tube Q5 is turned off, an induced electromotive force much higher than the input voltage will be formed on the boost inductor, and the induced electromotive force will be rectified by the freewheeling tube D1 to form a one-way pulse voltage and then sent to the second electrolytic capacitor C2 Into filtering, filtering into 400V DC voltage. And the third switching tube Q5 increases or decreases the conduction time of the third switching tube Q5 according to the change of the input AC correction wave collected by the control chip, so that the phase of the current and the voltage become consistent to increase the PF value.

As a preferred manner, please refer to FIG. 3 , this embodiment also includes an MCU control unit 80, the gate of the first switch Q6, the gate of the second switch Q7 and the gate of the third switch Q5 Respectively connected to the MCU control unit 80, the MCU control unit 80 is used to respectively output PWM signals to the first switch tube Q6, the second switch tube Q7 and the third switch tube Q5, so as to control the first switch tube Q6, the second switch tube The switch Q7 and the third switch Q5 are in the on-off state. Further, the MCU control unit 80 includes a single-chip microcomputer U1 and its peripheral circuits.

For the convenience of monitoring the electrical signal of the AC side, please refer to Fig. 2, the present embodiment also includes an AC sampling unit 70, and the AC sampling unit 70 is connected between the input end of the input rectification filter unit 10 and the MCU control unit 80, so The AC sampling unit 70 is used to collect the voltage input to the AC side of the rectifying and filtering unit 10 and feed it back to the MCU control unit 80 .

Further, the AC sampling unit 70 includes an operational amplifier U9B, the two input terminals of the operational amplifier U9B are respectively connected to the input terminals of the input rectification and filtering unit 10 through a current limiting resistor, and the output terminals of the operational amplifier U9B Connected to the MCU control unit 80 .

In order to facilitate real-time collection of current, a first sampling resistor R2A is connected between the source of the third switching tube Q5 and the front-end ground, and the source of the third switching tube Q5 is connected to the MCU control unit 80, by The first sampling resistor R2A enables the MCU control unit 80 to collect the electrical signal of the source of the third switching transistor Q5.

As a preferred manner, in order to collect the DC side electric signal, this embodiment also includes a DC voltage sampling unit 50, the DC voltage sampling unit 50 includes a second sampling resistor R13 and a third sampling resistor R15 connected in series in sequence , the front end of the second sampling resistor R13 is connected to the output end of the interleaved flyback isolation conversion unit 30, the rear end of the third sampling resistor R15 is connected to the MCU control unit 80, through the second sampling resistor R13 and The third sampling resistor R15 enables the MCU control unit 80 to collect the electrical signal output by the interleaved flyback isolation conversion unit 30 .

The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback disclosed by the utility model has a high PF value, can realize the isolation of the power grid and the output terminal, and has very high safety. The output voltage can be automatically adjusted within the full input voltage range, the output frequency can be fixed, and the output voltage is output as a sine wave, which has an automatic shaping function for the AC voltage. In addition, the utility model has a simple circuit, convenient control, and contains voltage and Current sampling circuit can prevent surge voltage and current.

The above is only a preferred embodiment of the utility model, and is not intended to limit the utility model. All modifications, equivalent replacements or improvements made within the technical scope of the utility model should be included in the protection of the utility model. In the range.

Claims (10)

1. An intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback, characterized in that it includes an input rectification and filtering unit for rectifying and filtering grid voltage, an output voltage for input rectification and filtering unit A PFC boost unit for boost conversion, and: An interleaved flyback isolation conversion unit, including a first switch tube, a second switch tube, a first transformer, a second transformer, a first diode, a second diode, a third diode and a fourth diode tube, the first end of the primary winding of the first transformer is connected to the output end of the PFC step-up unit, the second end of the primary winding of the first transformer is connected to the drain of the first switching tube, and the first switching tube The source of the first switch tube is connected to the front-end ground, the drain of the first switch tube is connected to the anode of the first diode, and the cathode of the first diode is connected to the output terminal of the PFC boost unit through a first resistor, The first resistor is connected in parallel with a third capacitor, the first end of the primary winding of the second transformer is connected to the output end of the PFC step-up unit, and the second end of the primary winding of the second transformer is connected to the second switch tube Drain, the source of the second switch tube is connected to the front-end ground, the drain of the second switch tube is connected to the anode of the second diode, and the cathode of the second diode is connected to the second resistor At the output end of the PFC step-up unit, the second resistor is connected in parallel with a fourth capacitor, and the grid of the first switching tube and the grid of the second switching tube are respectively used to access two PWM pulse signals with opposite phases. , the first end of the secondary winding of the first transformer is connected to the anode of the third diode, the second end of the secondary winding of the first transformer is connected to the rear end ground, and the secondary winding of the second transformer The first end is connected to the rear end ground, the second end of the secondary winding of the second transformer is connected to the cathode of the fourth diode, and the cathode of the third diode and the anode of the fourth diode are used as an alternate The output terminal of the flyback isolation conversion unit; A DC filtering unit, including a first capacitor and a second capacitor, the cathode of the third diode is connected to the rear ground through the first capacitor, and the anode of the fourth diode is connected to the rear ground through the second capacitor end; An inverter inverter unit, including a fourth switch tube, a fifth switch tube, a third electrolytic capacitor, a fourth electrolytic capacitor and a filter inductor, the drain of the fourth switch tube is connected to the interleaved flyback isolation conversion unit The positive pole of the output terminal, the source of the fourth switch tube is connected to the drain of the fifth switch tube, the source of the fifth switch tube is connected to the negative pole of the output terminal of the interleaved flyback isolation conversion unit, the fourth switch The grid of the tube and the grid of the fifth switching tube are respectively used to access two PWM pulse signals with opposite phases, the source of the fourth switching tube is also connected to the front end of the filter inductor, the third electrolytic capacitor The positive pole is connected to the drain of the fourth switching tube, the negative pole of the third electrolytic capacitor is connected to the back-end ground, the negative pole of the third electrolytic capacitor is also connected to the positive pole of the fourth electrolytic capacitor, and the negative pole of the fourth electrolytic capacitor Connected to the source of the fifth switching tube, the rear end of the filter inductor and the negative electrode of the third electrolytic capacitor serve as the output end of the inverter unit. 2. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 1, wherein a first resistor is connected between the grid and the source of the fourth switching tube, so A second resistor is connected between the gate and the source of the fifth switch tube. 3. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 1, wherein said input rectification filter unit includes socket, insurance, lightning protection resistor, common mode suppression inductor, A safety capacitor and a rectifier bridge, the insurance is connected in series to the zero line or live line of the socket, the front end of the common mode suppression inductor is connected in parallel to the socket, the lightning protection resistor is connected in parallel to the front end of the common mode suppression inductor, the safety Both the gauge capacitor and the input end of the rectifier bridge are connected in parallel to the rear end of the common-mode suppression inductor, and the output end of the rectifier bridge is connected in parallel with a filter capacitor. 4. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 1, wherein the PFC boost unit includes a boost inductor, a third switch tube, a first rectifier diode and the second electrolytic capacitor, the front end of the boost inductor is connected to the output end of the input rectification filter unit, the rear end of the boost inductor is connected to the drain of the third switching tube, and the source of the third switching tube connected to the front-end ground, the gate of the third switch tube is used to access a PWM control signal, the drain of the third switch tube is connected to the anode of the first rectifier diode, and the cathode of the first rectifier diode is used as a PFC booster The output terminal of the voltage unit, and the cathode of the first rectifier diode is connected to the positive pole of the second electrolytic capacitor, and the negative pole of the second electrolytic capacitor is connected to the terminal ground. 5. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 4, further comprising an MCU control unit, the gate of the first switching tube, the second switching tube The gate of the gate and the gate of the third switch tube are respectively connected to the MCU control unit, and the MCU control unit is used to output PWM signals to the first switch tube, the second switch tube and the third switch tube respectively to control the first switch tube tube, the second switch tube and the third switch tube are on and off. 6. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback according to claim 5, wherein the MCU control unit includes a single-chip microcomputer and its peripheral circuits. 7. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 5, further comprising an AC sampling unit connected to the input terminal of the input rectification filter unit Between the MCU control unit, the AC sampling unit is used to collect the voltage input to the AC side of the rectification and filtering unit and feed it back to the MCU control unit. 8. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 7, wherein the AC sampling unit includes an operational amplifier, and the two input terminals of the operational amplifier pass through the The current limiting resistor is connected to the input end of the input rectification filter unit, and the output end of the operational amplifier is connected to the MCU control unit. 9. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 5, wherein a first sampling resistor is connected between the source of the third switch tube and the front-end ground, The source of the third switch tube is connected to the MCU control unit, and the MCU control unit collects the electrical signal of the source of the third switch tube through the first sampling resistor. 10. The intelligent half-bridge sine wave voltage conversion circuit based on PFC interleaved flyback as claimed in claim 5, further comprising a DC voltage sampling unit, said DC voltage sampling unit comprising a second series connected in series A sampling resistor and a third sampling resistor, the front end of the second sampling resistor is connected to the output end of the interleaved flyback isolation conversion unit, and the rear end of the third sampling resistor is connected to the MCU control unit, by the second sampling resistor resistor and the third sampling resistor so that the MCU control unit collects the electrical signal output by the interleaved flyback isolation conversion unit.