A power conversion circuit and a charging gun circuit

Abstract

The present application relates to the field of circuit, particularly to a power conversion circuit and a charging gun circuit, and discloses a power conversion circuit and a charging gun circuit, wherein the power conversion circuit comprises a totem pole PFC circuit, and a synchronous rectifier tube of the totem pole PFC circuit is realized by a transistor with a body diode; a control strategy of the synchronous rectifier tube is that when the power conversion circuit works in a light load state, the synchronous rectifier tube is not controlled and is in an off state; when the power conversion circuit works in a heavy load state, the synchronous rectifier tube is controlled to follow the positive and negative of the input alternating current power and is correspondingly turned on. The present application can effectively reduce the heat loss of the synchronous rectifier tube, improve the overall working efficiency of the circuit, and improve the safety and reliability of the circuit.

Description

Technical Field

[0001] This invention belongs to the field of circuits, and specifically relates to a power conversion circuit and a charging gun circuit. Background Technology

[0002] In 2021, global sales of new energy vehicles exceeded 6.5 million units, a year-on-year increase of 108%; my country's sales exceeded 3.52 million units, a year-on-year increase of 157.5%. Driven by the rapid growth in new energy vehicle sales, the market demand for charging products for new energy vehicles has steadily increased. Charging products for new energy vehicles convert AC power into DC power to charge them. Because harmonic currents are generated during the conversion process, existing charging products typically include PFC (Power Factor Correction) circuits to reduce these harmonic currents. Totem-pole PFC circuits, due to their fewer components and simpler circuit structure, are increasingly widely used. However, the heat loss of the synchronous rectifier tubes in existing totem-pole PFC circuits is still relatively large, reducing the overall efficiency of the circuit and resulting in lower safety and reliability. Summary of the Invention

[0003] The purpose of this invention is to provide a power conversion circuit to solve the aforementioned technical problems.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a power conversion circuit, including a totem-pole PFC circuit, wherein the synchronous rectifier of the totem-pole PFC circuit is implemented by a transistor with a body diode, and the control strategy of the synchronous rectifier is as follows: when the power conversion circuit operates under light load, the synchronous rectifier is not controlled and is in the off state; when the power conversion circuit operates under heavy load, the synchronous rectifier is controlled to conduct accordingly following the positive and negative of the input AC power supply.

[0005] Furthermore, a pre-charge circuit is connected in series at the input terminal of the totem pole type PFC circuit. The pre-charge circuit includes a pre-charge resistor unit and a first pre-charge switch unit connected in parallel.

[0006] Furthermore, the pre-charge circuit also includes a second pre-charge switch unit, which is connected in series in the branch of the pre-charge resistor unit.

[0007] Furthermore, both the first precharge switch unit and the second precharge switch unit are implemented using relays.

[0008] Furthermore, the pre-charge resistor unit is implemented using a surge current protection resistor.

[0009] Furthermore, the pre-charge resistor unit is implemented using an NTC thermistor, a PTC thermistor, or a power resistor.

[0010] Furthermore, it also includes a full-bridge rectifier circuit, the input of which is connected to the input of the totem-pole PFC circuit, and the output of which is connected to the output of the totem-pole PFC circuit.

[0011] Furthermore, the upper and lower switching transistors of the totem-pole PFC circuit are both composed of two transistors connected in parallel.

[0012] Furthermore, the control strategy for the upper and lower switching transistors of the totem-pole PFC circuit is as follows: the feedback control of the input current is used as the inner loop PID, the feedback control of the output voltage is used as the outer loop PID, and the unit sine signal corresponding to the input AC power supply is multiplied by the output parameter of the outer loop PID as the input parameter of the inner loop PID.

[0013] Furthermore, it also includes a CLLLC resonant circuit, the input of which is connected to the output of the totem-pole PFC circuit.

[0014] The present invention also discloses a charging gun circuit, which includes the power conversion circuit described above.

[0015] Beneficial technical effects of the present invention: This invention can effectively reduce the heat loss of synchronous rectifier tubes, improve the overall working efficiency of the circuit, and enhance the safety and reliability of the circuit. Moreover, the circuit structure is simple and easy to implement. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a circuit diagram of a power conversion circuit according to a specific embodiment of the present invention; Figure 2 The waveform diagrams of control signals G3 and G4 are shown in a specific embodiment of the present invention. Figure 3 The waveform diagrams of control signals G1 and G2 are shown in a specific embodiment of the present invention. Figure 4 This is a block diagram illustrating the control principle of control signals G1 and G2 in a specific embodiment of the present invention. Figure 5 This is a block diagram of the inverter control principle of the totem-pole PFC circuit according to a specific embodiment of the present invention; Figure 6The AC output waveform obtained by simulation under the conditions of a sine wave frequency of 50Hz, a triangular wave frequency of 10kHz, and an amplitude ratio of 0.778 is shown in a specific embodiment of the present invention. Figure 7 The diagram shows the voltage gain ratio versus frequency of a CLLLC resonant circuit according to a specific embodiment of the present invention. Detailed Implementation

[0018] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0019] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown, a power conversion circuit includes a totem-pole PFC circuit 1, a CLLLC resonant circuit 2, a pre-charge circuit 3, and a full-bridge rectifier circuit 4. The pre-charge circuit 3 is connected in series with the input terminal of the totem-pole PFC circuit 1. The input terminal of the totem-pole PFC circuit 1 is used to connect to the input AC power supply. The input terminal of the full-bridge rectifier circuit 4 is connected to the input terminal of the totem-pole PFC circuit 1. The output terminal of the full-bridge rectifier circuit 4 is connected to the output terminal of the totem-pole PFC circuit 1. The input terminal of the CLLLC resonant circuit 2 is connected to the output terminal of the totem-pole PFC circuit 1.

[0021] Specifically, in this embodiment, the totem-pole PFC circuit 1 includes a power inductor L, an upper switch transistor, a lower switch transistor, a synchronous rectifier Q5, and a synchronous rectifier Q6. The upper switch transistor, the lower switch transistor, the synchronous rectifier Q5, and the synchronous rectifier Q6 form a double bridge arm. The node between the upper switch transistor and the lower switch transistor is connected to the first end of the power inductor L. The second end of the power inductor L serves as one input terminal of the totem-pole PFC circuit 1. The node between the synchronous rectifier Q5 and the synchronous rectifier Q6 serves as the other input terminal of the totem-pole PFC circuit 1.

[0022] Both synchronous rectifiers Q5 and Q6 are MOSFETs, which are easy to implement, have low power consumption, and low cost. However, they are not limited to this. In some embodiments, synchronous rectifiers Q5 and Q6 can also be implemented using other transistors with body diodes, such as IGBTs.

[0023] In this specific embodiment, the upper switch is composed of parallel MOSFETs Q1 and Q3, and the lower switch is composed of parallel MOSFETs Q2 and Q4. The use of two parallel MOSFETs for both the upper and lower switches helps to distribute energy consumption, reduce the heat generated by a single MOSFET, and protect MOSFETs Q1, Q2, Q3, and Q4 from burnout, thereby improving the safety and reliability of the circuit. However, this is not a limitation. In some embodiments, the upper and lower switches can be composed of a single MOSFET; in other embodiments, other transistors, such as IGBTs, can also be used.

[0024] The pre-charge circuit 3 is connected in series with the second terminal of the power inductor L. The pre-charge circuit 3 includes a pre-charge resistor unit and a first pre-charge switch unit connected in parallel. When the totem-pole PFC circuit 1 starts up, the pre-charge resistor unit can effectively suppress the surge current generated by it, reduce the transient impact on the switching components, and improve the robustness of the circuit operation. When the totem-pole PFC circuit 1 is working, the first pre-charge switch unit short-circuits the pre-charge resistor unit, so that the totem-pole PFC circuit 1 can work normally.

[0025] In this specific embodiment, the pre-charge resistor unit is preferably composed of an NTC thermistor R, which can greatly reduce the heat generation of the pre-charge resistor unit and improve reliability. Of course, in some embodiments, the pre-charge resistor unit can also be implemented using other surge current protection resistors such as PTC thermistors or power resistors. The first pre-charge switch unit is composed of a relay RLY1, which has high withstand voltage and low conduction energy consumption, but it is not limited to this. In some embodiments, the first pre-charge switch unit can also be implemented using other switching circuits, such as MOSFET switching circuits.

[0026] Furthermore, in this specific embodiment, the pre-charge circuit 3 also includes a second pre-charge switch unit. The second pre-charge switch unit is connected in series in the branch of the NTC thermistor R. That is, the second pre-charge switch unit is connected in series with the NTC thermistor R and then in parallel with the relay RLY1. By setting the second pre-charge switch unit, the pre-charge can be controlled to avoid automatic pre-charge upon power-on, thereby improving controllability.

[0027] The second precharge switch unit is composed of a relay RLY2, which has high withstand voltage and low conduction power consumption, but it is not limited to this. In some embodiments, the second precharge switch unit can also be implemented using other switching circuits, such as MOSFET switching circuits.

[0028] The specific working process of the pre-charging circuit 3 is as follows: When the power is turned on and the pre-charging circuit 3 is to be started, the control relay RLY2 is closed, and the input AC power is pre-charged through the NTC thermistor R until the DC voltage Udc at the output terminal of the totem pole PFC circuit 1 reaches the threshold (such as Udc>300V). Then, the relay RLY1 is closed and the relay RLY2 is opened, and the totem pole PFC circuit 1 works normally.

[0029] The full-bridge rectifier circuit 4 includes rectifier diodes D1, D2, D3, and D4, which form a rectifier bridge. One input terminal of the rectifier bridge is connected to the second terminal of the power inductor L, and the other input terminal is connected to the node between synchronous rectifier diodes Q5 and Q6. The two output terminals of the rectifier bridge are respectively connected to the two output terminals of the totem-pole PFC circuit 1. By setting up the full-bridge rectifier circuit 4, it is equivalent to connecting a diode with the same direction as its body diode in parallel to each of the subsequent MOSFETs (MOSFETs Q1-Q6). When the MOSFETs conduct current only through their body diodes, the full-bridge rectifier circuit 4 can also share some of the current, thus protecting the MOSFETs.

[0030] Compared to other DC / DC converter circuit structures, the CLLLC resonant circuit 2 can achieve zero-voltage turn-on and zero-current turn-off of the MOSFETs, reducing circuit heat loss and improving operating efficiency. In this specific embodiment, the CLLLC resonant circuit 2 adopts a fully symmetrical structure, including MOSFETs Q7-Q14, transformer T1, primary-side resonant capacitor Cr1, secondary-side resonant capacitor Cp1, primary-side resonant inductor Lp, secondary-side resonant inductor Lp1, and magnetizing inductor Lp2. For detailed connection structure, please refer to [link to detailed connection details]. Figure 1 This will not be discussed in detail. When the current is from... Figure 1 When the current flows from the left to the right, MOSFETs Q7-Q10 form an inverter full-bridge, and MOSFETs Q11-Q14 form a rectifier full-bridge; when the current flows from... Figure 1 When the current flows from the right side to the left side, MOSFETs Q7-Q10 form a rectifier bridge, and MOSFETs Q11-Q14 form an inverter bridge.

[0031] However, this is not the only option. In some embodiments, the CLLLC resonant circuit 2 can also be implemented using other existing CLLLC resonant circuits.

[0032] Preferably, in this specific embodiment, MOSFETs Q1-Q14 are all controlled by digital signals, which not only simplifies the hardware circuit, but also avoids hardware errors caused by environmental interference factors such as temperature, and the control method is more flexible.

[0033] Digital signals can be generated using a DSP controller or MCU processor and driven by an isolated driver output, which better separates high-voltage and low-voltage signals in the system and minimizes mutual interference between them.

[0034] In this specific embodiment, the control strategy for synchronous rectifier diodes Q5 and Q6 is as follows: When the power conversion circuit operates under light load, synchronous rectifier diodes Q5 and Q6 are not controlled and are in the off state. The body diodes of synchronous rectifier diodes Q5 and Q6 provide freewheeling current and thus achieve rectification. At this time, the heat loss generated by the body diodes of synchronous rectifier diodes Q5 and Q6 is less than the heat loss generated by the MOSFETs themselves. When the power conversion circuit operates under heavy load, synchronous rectifier diodes Q5 and Q6 are controlled to follow the input AC power supply... The synchronous rectifier operates according to the positive and negative signals. When the input AC power supply voltage Uac is in the positive half-cycle, the synchronous rectifier Q6 is turned on; when the input AC power supply voltage Uac is in the negative half-cycle, the synchronous rectifier Q5 is turned on. Rectification is performed by the synchronous rectifiers Q5 and Q6 themselves. At this time, the heat loss of the synchronous rectifiers Q5 and Q6 themselves is less than the heat loss generated by their body diodes, effectively reducing the heat loss of the synchronous rectifiers Q5 and Q6, improving the overall working efficiency of the circuit, and enhancing the safety and reliability of the circuit.

[0035] Specifically, by collecting the output current of the totem-pole PFC circuit 1, the system determines whether the totem-pole PFC circuit 1 is operating under light load or heavy load conditions based on the magnitude of the output current. For example, if the output current is less than 2.0 A, it is determined to be operating under light load conditions; if the output current is greater than or equal to 2.0 A, it is determined to be operating under heavy load conditions.

[0036] Preferably, an isolated current sensor is used to collect the output current of the totem-pole PFC circuit 1, so as to better separate the high voltage and low voltage in the system and minimize the mutual interference between them.

[0037] When the power conversion circuit operates under heavy load, synchronous rectifiers Q5 and Q6 are controlled by control signals G3 and G4, respectively. When the input AC power supply voltage Uac is in the positive half-cycle, synchronous rectifier Q6 is turned on by control signal G4 for output; when the input AC power supply voltage Uac is in the negative half-cycle, synchronous rectifier Q5 is turned on by control signal G3 for output. That is, the frequencies of control signals G3 and G4 are the same as the frequency of the AC power supply voltage Uac. In this embodiment, the frequency of the AC power supply voltage Uac is 50Hz, so control signals G3 and G4 are complementary control signals with a frequency of 50Hz and a duty cycle of 50%. Of course, to prevent synchronous rectifiers Q5 and Q6 from conducting simultaneously, a dead time needs to be set when synchronous rectifiers Q5 and Q6 alternately output. The specific waveform is as follows: Figure 2 As shown.

[0038] In this specific embodiment, the control signal G1 for MOSFETs Q1 and Q3 is complementary to the control signal G2 for MOSFETs Q2 and Q4. The frequencies of control signals G1 and G2 are fixed (65kHz in this embodiment, but not limited to this). Adjusting the duty cycles of control signals G1 and G2 directly affects the output voltage of the totem-pole PFC circuit 1. When the AC power supply voltage Uac input to the totem-pole PFC circuit 1 is in the positive half-cycle, the larger the duty cycle of control signal G2 and the smaller the duty cycle of control signal G1, the larger the output voltage of the totem-pole PFC circuit 1. When the input AC power supply voltage Uac is in the negative half-cycle, the larger the duty cycle of control signal G1 and the smaller the duty cycle of control signal G2, the larger the output voltage of the totem-pole PFC circuit 1.

[0039] Therefore, when the AC power supply voltage Uac input to the totem-pole PFC circuit 1 is in the positive half-cycle, the controlled object is control signal G2, and control signal G1 takes the complementary signal of control signal G2; when the AC power supply voltage Uac input to the totem-pole PFC circuit 1 is in the negative half-cycle, the controlled object is control signal G1, and control signal G2 takes the complementary signal of control signal G1. Similarly, to ensure that MOSFETs Q1 and Q3 cannot be turned on simultaneously with MOSFETs Q2 and Q4, a dead time needs to be set when the two pairs of MOSFETs alternate output. The specific waveform is as follows: Figure 3 As shown. Of course, in some embodiments, when the controlled object is control signal G2, control signal G1 may not be controlled; when the controlled object is control signal G1, control signal G1 may not be controlled, making the control algorithm simpler.

[0040] The control strategy for control signals G1 and G2 is as follows: the feedback control of the input current Iac of the totem-pole PFC circuit 1 is used as the inner loop PID, and the feedback control of the output voltage Udc of the totem-pole PFC circuit 1 is used as the outer loop PID. The unit sinusoidal signal W(z) corresponding to the input AC power supply voltage Uac of the totem-pole PFC circuit 1 is multiplied with the output parameter of the outer loop PID and used as the input parameter of the inner loop PID. This allows the input current to change with the input voltage, resulting in a higher power factor, further reducing heat generation, making the entire system more stable, and also reducing grid harmonics.

[0041] The specific control principle block diagrams for control signals G1 and G2 are as follows: Figure 4As shown, H2(z) is the sampling and transmission signal of the output voltage Udc of the totem-pole PFC circuit 1, H1(z) is the sampling and transmission signal of the input current Iac of the totem-pole PFC circuit 1, and Udct is the set expected value of the output voltage. First, the deviation between the expected value of the output voltage Udct and the output voltage is calculated, and the output parameters of the outer loop PID are updated. Then, the unit sine signal W(z) corresponding to the AC power supply voltage Uac is calculated, and the result is multiplied by the output parameters of the outer loop PID to obtain the input parameters of the inner loop PID. Then, based on the measured AC current magnitude H1(z), the current inner loop deviation is calculated, and the output of the inner loop PID is updated with the deviation value. Finally, the output of the inner loop PID is converted into the corresponding MOS transistor drive signal after output limiting processing. The signal is output to the control signal G2 in the positive half-cycle and to the control signal G1 in the negative half-cycle for corresponding control.

[0042] The totem-pole PFC circuit 1 inverter can achieve conversion via SPWM waveform modulation. The SPWM waveform can be configured through the SPWM peripheral port in the DSP controller. The principle is to compare and modulate a triangular wave with frequency f1 and amplitude U1 with a sine wave with frequency f2 and amplitude U2 to output the SPWM waveform (control block diagram as shown). Figure 5 As shown in the figure, the SPWM waveform is used to control MOSFETs Q1-Q6 to achieve the conversion of DC to AC. The relationship between AC output and DC input is as follows:

[0043] During SPWM waveform modulation, the sine wave frequency... This will determine the frequency of the output AC voltage. (Triangle wave frequency) This will affect the accuracy of the output AC voltage. The higher the frequency of the triangular wave, the lower the DC harmonics of the output AC voltage, and the higher the accuracy of the AC voltage output. If the input DC voltage... With a fixed modulation ratio between the sine wave and the triangular wave, the output AC voltage is directly determined. The G1 and G4 signals are controlled by the SPWM1 waveform (with a triangular wave modulation greater than the sine wave modulation), and the G2 and G4 signals are controlled by the SPWM2 waveform (with a triangular wave modulation less than the sine wave modulation), thus achieving inverter AC output.

[0044] Figure 6 The AC output waveform is obtained by simulation under the conditions of a sine wave frequency of 50Hz, a triangular wave frequency of 10kHz, and an amplitude ratio of 0.778.

[0045] The control strategy for MOSFETs Q11-Q14 (when used as rectifiers) in the CLLLC resonant circuit 2 is the same as that for synchronous rectifiers Q5 and Q6. For details, please refer to the control strategies for synchronous rectifiers Q5 and Q6 mentioned above. This will not be elaborated further. This will further reduce the heat loss of MOSFETs Q11-Q14, improve the overall efficiency of the circuit, and enhance the safety and reliability of the circuit.

[0046] The control and regulation methods for the CLLLC resonant circuit 2 can include controlling the output voltage by controlling the input voltage frequency, controlling the output voltage by phase shifting the input voltage, and simultaneously controlling both the input voltage frequency and phase shifting to regulate the output voltage. Among these: (1) Controlling the input voltage frequency to regulate the output voltage With the input DC voltage of the preamplifier fixed at 400V, and the duty cycles of the control signals G7, G8, G9, and G10 for MOSFETs Q7, Q8, Q9, and Q10 fixed at 50%, the relationship between the circuit output and input voltage frequencies can be calculated based on the parameters of the CLLLC resonant circuit and its corresponding model. Figure 7 As shown. Figure 7 As shown, the resonant circuit uses symmetrical parameters, meaning that the primary resonant inductor Lp and primary resonant capacitor Cr1 are the same as the secondary resonant inductor Lp1 and secondary resonant capacitor Cp1 in terms of model and parameters. At the circuit's resonant point ( There must be a voltage gain ratio of 1. When the load is greater than 50Ω, i.e., the power is less than 3.2kW, the voltage gain ratio is... The frequency range exhibits a basically monotonically decreasing trend, meaning that each frequency value corresponds to a unique output voltage value. Therefore, the frequency can be increased or decreased based on whether the output voltage reaches the desired value.

[0047] When MOSFETs Q7 and Q10 are outputting, MOSFETs Q8 and Q9 are turned off, and the secondary side current... The value is positive; when MOSFETs Q8 and Q9 are outputting, MOSFETs Q7 and Q10 are turned off, and the secondary side current is positive. It is a negative value.

[0048] (2) Controlling the input voltage phase shift to regulate the output voltage If the input DC voltage of the preamp is 400V, and the control signals G7, G8, G9, and G10 for the fixed MOSFETs Q7, Q8, Q9, and Q10 have a duty cycle of 50% and a fixed frequency (e.g., 150kHz), divide the four control signals into two groups: the first group consists of G7 and G10, and the second group consists of G8 and G9. The second group of signals lags behind the first group of signals in phase. ,exist When the output voltage reaches its maximum value, When the output voltage reaches its minimum value, the output voltage will change with the phase shift angle. It decreases as it increases.

[0049] In this specific embodiment, both the totem-pole PFC circuit 1 and the CLLLC resonant circuit 2 are equipped with soft-start control to further reduce the surge current generated by capacitor charging, reduce the transient impact on the switching components, and improve the robustness of the circuit operation. Specifically, when the totem-pole PFC circuit 1 and the CLLLC resonant circuit 2 are started, the duty cycle of control signals G1, G2, G7, G8, G9, and G10 gradually increases from 0% to a set value within a fixed time period (e.g., 100ms).

[0050] The present invention also discloses a charging gun circuit, which includes the power conversion circuit described above.

[0051] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A power conversion circuit, comprising a totem-pole PFC circuit, characterized in that: The synchronous rectifier in the totem-pole PFC circuit is implemented by a transistor with a body diode. The control strategy of the synchronous rectifier is as follows: when the power conversion circuit is operating under light load, the synchronous rectifier is not controlled and is in the cutoff state, so that the body diode of the synchronous rectifier can provide freewheeling current and perform rectification; when the power conversion circuit is operating under heavy load, the synchronous rectifier is controlled to conduct according to the positive and negative of the input AC power supply, so that the synchronous rectifier itself can perform rectification. The strategy for determining the light-load and heavy-load states of the power conversion circuit is as follows: the output current of the totem-pole PFC circuit is used to determine whether the totem-pole PFC circuit is operating under light-load or heavy-load conditions. The light load state is characterized by the heat loss of the body diode of the synchronous rectifier being less than the heat loss of the synchronous rectifier itself; the heavy load state is characterized by the heat loss of the synchronous rectifier itself being less than the heat loss of the body diode of the synchronous rectifier.

2. The power conversion circuit according to claim 1, characterized in that: A pre-charge circuit is connected in series at the input terminal of the totem pole type PFC circuit. The pre-charge circuit includes a pre-charge resistor unit and a first pre-charge switch unit connected in parallel.

3. The power conversion circuit according to claim 2, characterized in that: The pre-charge circuit also includes a second pre-charge switch unit, which is connected in series in the branch of the pre-charge resistor unit.

4. The power conversion circuit according to claim 3, characterized in that: Both the first precharge switch unit and the second precharge switch unit are implemented using relays.

5. The power conversion circuit according to claim 2, characterized in that: The pre-charge resistor unit is implemented using a surge current protection resistor.

6. The power conversion circuit according to claim 5, characterized in that: The pre-charge resistor unit is implemented using an NTC thermistor, a PTC thermistor, or a power resistor.

7. The power conversion circuit according to claim 1, characterized in that: It also includes a full-bridge rectifier circuit, the input of which is connected to the input of the totem-pole PFC circuit, and the output of which is connected to the output of the totem-pole PFC circuit.

8. The power conversion circuit according to claim 1, characterized in that: The upper and lower switching transistors of the totem-pole PFC circuit are both composed of two transistors connected in parallel.

9. The power conversion circuit according to claim 1, characterized in that: The control strategy for the upper and lower switching transistors of the totem-pole PFC circuit is as follows: the feedback control of the input current is used as the inner loop PID, the feedback control of the output voltage is used as the outer loop PID, and the unit sine signal corresponding to the input AC power supply is multiplied by the output parameter of the outer loop PID as the input parameter of the inner loop PID.

10. The power conversion circuit according to claim 1, characterized in that: It also includes a CLLLC resonant circuit, whose input terminal is connected to the output terminal of the totem-pole PFC circuit.

11. A charging gun circuit, characterized in that: The circuit is provided with any one of claims 1-10.

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