Novel power conversion circuit and device

Abstract

The invention provides a novel power conversion circuit and device, and relates to the technical field of power circuits, the novel power conversion circuit is mainly composed of a rectification circuit, a first capacitor C1, an isolation unit and a gate drive circuit, rectification is carried out through an MOS tube, voltage and current phases are synchronously adjusted, a power factor is improved, and reactive power loss is reduced; the secondary control MOS tube is matched with the isolation unit, so that the primary circuit is simplified, and the stability and the reliability are enhanced. A discharge path is arranged to protect the switch tube, so that reverse bias breakdown is avoided; meanwhile, multiple novel isolation modes are supported, an optocoupler is not adopted, the response speed is increased, the service life is prolonged, and the anti-interference performance is improved. On the whole, the AC-DC power supply conversion efficiency can be effectively improved, the cost is reduced, a large inductor and a capacitor device required by a traditional PFC (Power Factor Correction) are prevented from being used, unnecessary space occupation and element stacking are reduced, and the overall circuit is lighter.

Description

Technical Field

[0001] This application relates to the technical field of power circuits, and particularly to a novel power conversion circuit and device. Background Art

[0002] With the increasingly wide application range of electronic devices, the requirements for miniaturization of appearance and high power of electronic devices are also becoming stronger and stronger. This also requires that every link in the charging path of electronic devices should consider losses. Otherwise, for a high-power power supply above 75W, a loss of 1W is almost a one-percentage-point loss; and because it is a high-power power supply, the impact on the power grid and load also needs to be considered. The current way to deal with the impact on the power grid is to add a power factor correction (PFC) circuit to prevent the electronic device from affecting the power grid efficiency of the power supply side due to charging and discharging. The common practice now is to detect the phase difference between the voltage and current at the primary side to ensure that it does not affect the power grid. This method does not guarantee the efficiency from the power supply to the load end. Although many current methods can reduce the total harmonic distortion (THD) to ensure that the efficiency from the power supply to the load end can meet the requirements, at the secondary side of the load, it still needs to be detected from the secondary side and then feedback to the primary side; the change rate of the load and the response speed of the primary detection feedback will both affect the THD value; and there are several types of electronic devices in the charging system: resistive load, capacitive load, inductive load, or a combination of these three types of loads; if the load type of the electronic device is capacitive or inductive or a combination of the two, it will affect the voltage and current phases of the alternating current. In order to improve the conversion efficiency and not affect the power grid of the power supply side, it is necessary to calibrate back the voltage and current phase deviations caused by capacitive and inductive loads. The method of calibration is called power factor correction (PFC).

[0003] See the attached Figure 1, in order to solve the problem that load variation affects the power grid or to improve the PF value, existing power converters add devices or circuits to the power conversion path. However, adding devices or circuits will reduce the conversion efficiency of the input and output of the power converter. The common practice is to add an LLC resonant circuit after the PFC. By utilizing the resonance of inductors and capacitors, the efficiency of the AC-DC converter is improved. However, generally, the LLC resonant circuit requires the input and output voltages to be fixed within a certain range. The output voltage range of 3.3V to 48V of the USB PD power converter will increase the complexity of the LLC resonant circuit design. Therefore, in current high-power PD power converters, additional circuits are required to achieve dynamic changes in the load voltage and current, which will also cause a reduction in the measured conversion efficiency at the load end and the AC input end. The more obvious this phenomenon is with higher power. Moreover, in PD power converters, due to the addition of these two circuits, PFC and LLC, multiple large inductors and capacitors need to be added. Additionally, the current control circuits for PFC and LLC are in a low-voltage domain. Placing them on the primary side requires peripheral circuits to isolate the high voltage of the mains power and meet the low-voltage domain requirements of the PFC and LLC control circuits. Therefore, it is not easy to achieve the goals of being lightweight and miniaturized. Summary of the Invention

[0004] To overcome the deficiencies in the prior art, the present application provides a novel power conversion circuit and device, which can improve the PF value of the PFC and the conversion efficiency of the power input and output, and make the overall circuit lighter.

[0005] A novel power conversion circuit provided by the present application, a rectifier circuit, is connected to an AC power supply and is used to convert the alternating current input by the AC power supply into direct current;

[0006] A first capacitor C1 is connected to the output end of the rectifier circuit and is in parallel with the primary winding of the transformer, and is used to filter the rectified direct current; wherein, the secondary winding of the transformer includes an output winding and an auxiliary winding, and the primary winding of the transformer is also connected in series with a switching element;

[0007] An isolation unit includes a transmitting module arranged on the output winding side and a receiving module arranged on the auxiliary winding side, so as to send the feedback signal on the secondary winding side of the transformer to the receiving module through the transmitting module;

[0008] A drive circuit, whose input end is connected to the receiving module and the output end is connected to the switching element, and is used to control the conduction and cut-off of the switching element according to the feedback signal sent by the receiving module.

[0009] In a possible implementation manner, the drive circuit is integrated in the self-excited soft-start unit or the isolation unit;

[0010] The self-excited soft-start unit includes an unconventional RC oscillator and a comparison selector; one path of the receiving module is connected to the comparison selector, and the other path is connected to the driving circuit; one path of the unconventional RC oscillator is connected to the comparison selector, and the other path is connected to the driving circuit; wherein, when the comparison selector does not receive the feedback signal sent by the receiving module, the unconventional RC oscillator is turned on and outputs a clock frequency with a duty cycle other than 50 / 50 as the clock of the driving circuit; when the comparison selector receives the feedback signal sent by the receiving module, the unconventional RC oscillator is turned off, and the driving circuit controls the conduction and cutoff of the switching element according to the feedback signal sent by the receiving module.

[0011] In a possible implementation manner, the rectification circuit adopts a bridge rectification circuit composed of four diodes.

[0012] In a possible implementation manner, the rectification circuit adopts a bridge rectification circuit composed of four MOS transistors, and the conduction and cutoff of the four MOS transistors are controlled by the driving circuit to adjust the voltage and current phases output by the rectification circuit to be synchronized.

[0013] In a possible implementation manner, a discharge path is provided between the head and tail ends of the primary winding for discharging the reverse current when the reverse electromotive force is generated in the primary winding of the transformer.

[0014] In a possible implementation manner, the discharge path adopts a diode or a MOS transistor.

[0015] In a possible implementation manner, the switching element adopts a MOS transistor or a full-bridge switching transistor composed of four MOS transistors.

[0016] In a possible implementation manner, the self-excited soft-start unit is powered by the auxiliary winding.

[0017] In a possible implementation manner, the isolation unit adopts a magnetic coupler, a capacitive coupler, or a digital isolator.

[0018] A novel power conversion device provided by the present application adopts any one of the above-mentioned novel power conversion circuits.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] The novel power conversion circuit and device provided in this embodiment save the large inductors and capacitor components required by traditional PFCs, reduce unnecessary space occupation and component stacking, making the overall circuit lighter; and in some embodiments, MOS transistors are used for rectification, and at the same time, the phases of the output voltage and current are adjusted to be synchronized to improve the power factor; and in some embodiments, the control signal of the MOS transistor is generated on the secondary winding side of the transformer and transmitted to the primary winding side through the isolation unit to control the MOS transistor, improving the dynamic response ability of the power supply and simplifying the circuit structure on the primary winding side of the transformer. Description of the Drawings

[0021] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0022] Figure 1 Shows the schematic diagram of the existing high-power power supply structure with PFC + LLC in an embodiment of the present application;

[0023] Figure 2 Shows the schematic diagram of the power supply structure with PFC function at the first level in an embodiment of the present application;

[0024] Figure 3 Shows the schematic diagram of the structure of the self-excited soft start unit in an embodiment of the present application;

[0025] Figure 4 Shows the schematic diagram of the structure of the self-excited soft start unit in another embodiment of the present application;

[0026] Figure 5 Shows the schematic diagram of the structure of the first-level bridge-less PFC power supply in an embodiment of the present application;

[0027] Figure 6 Shows the schematic diagram of the structure of the discharge path formed by diodes in an embodiment of the present application;

[0028] Figure 7 Shows the schematic diagram of the structure of the discharge path formed by MOS transistors in an embodiment of the present application;

[0029] Figure 8 Shows the schematic diagram of the structure with full-bridge switching transistors as switching elements in an embodiment of the present application;

[0030] Figure 9 and Figure 10 Shows the schematic diagram of the structure in which the control signal of the MOS transistor is controlled by the secondary in an embodiment of the present application. Detailed Implementation Modes

[0031] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application.

[0032] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0033] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0034] In the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0036] In view of the technical problems proposed in the background art, the present application provides a novel power conversion circuit and device, which can improve the PF value of the PFC, the power input and output conversion efficiency, and make the overall circuit lighter and more compact.

[0037] See the attached drawings of the specification Figure 2 A novel power conversion circuit provided by an embodiment of the present application mainly consists of a rectification circuit, a first capacitor C1, an isolation unit, and a drive circuit. Among them, the rectification circuit is connected to an AC power supply and is used to convert the alternating current input by the AC power supply into direct current, providing a DC input for subsequent circuits; the first capacitor C1 is connected to the output end of the rectification circuit and is in parallel with the primary winding of the transformer, and is used to filter the rectified direct current to make the DC voltage smoother, reduce voltage fluctuations, and provide a stable DC power supply for the primary winding side of the transformer; among them, the secondary winding of the transformer includes an output winding and an auxiliary winding. The output winding is used to provide a stable DC voltage after voltage transformation, rectification, filtering, etc., to provide the required electrical energy for the load. It transfers the energy of the primary winding to the secondary according to the turns ratio relationship of the transformer, and transforms the voltage to an appropriate value to meet the voltage requirements of different loads; the auxiliary winding mainly provides a stable DC power supply for the self-excited soft start unit. In addition, a switching element is also connected in series to the primary winding of the transformer. In this embodiment, the switching element uses a first MOS transistor Q1. The gate of the first MOS transistor Q1 is connected to the output end of the drive circuit, its source is grounded, and its drain is connected to the end of the primary winding of the transformer. The isolation unit includes a transmitting module arranged on the output winding side and a receiving module arranged on the auxiliary winding side, and is used to achieve electrical isolation and signal transmission between the primary winding side and the secondary winding side of the transformer. Among them, the feedback signal of the output voltage on the secondary winding side is transmitted to the receiving module after being converted by the transmitting module, and then transmitted to the drive circuit. Since the switching element is a MOS transistor, the drive circuit here can be called a gate drive circuit, so that the gate drive circuit can adjust the control of the first MOS transistor Q1 according to the change of the output voltage to form a closed loop.

[0038] It should be noted that in the attached drawings of the specification Figure 2 the gate drive circuit is integrated in the self-excited soft start unit. The self-excited soft start unit also includes an unconventional RC oscillator, a comparison selector, high-voltage power extraction, an X-CAP discharge circuit, and overcurrent, over-temperature, over-voltage, under-voltage, and over-power protection. As for high-voltage power extraction, the X-CAP discharge circuit, and some overcurrent, over-temperature, over-voltage, under-voltage, and over-power protection are necessary functions of the power converter, which will not be elaborated here. Among them, see the attached drawings of the specification Figure 3, one path of the receiving module is connected to the comparison selector, and the other path is connected to the driving circuit; one path of the unconventional RC oscillator is connected to the comparison selector, and the other path is connected to the driving circuit. The unconventional RC oscillator outputs a clock frequency with a duty cycle other than 50 / 50. When the receiving module detects that no signal is received, this unconventional duty cycle clock is used as the clock for the gate driving circuit. In addition to being used as the input signal for driving the gate driving circuit in the standby mode, this unconventional RC oscillator is also used in the timing logic circuit of the self-excited soft start circuit; this means that the circuit part of the timing logic controlled by the clock needs to ensure whether the change of the clock will cause the logic of the control circuit to conform to the design specifications. The comparison selector unit detects whether the receiving module has received a signal. If a signal is received, the comparison selector will turn off the unconventional RC oscillator, that is, the output of the gate driving circuit is based on the signal received by the receiving module; if the comparison selector does not detect the signal of the receiving module unit, it will select the output of the unconventional RC oscillator to the gate driving circuit, that is, in the standby mode, the output of the gate driving circuit is based on the signal received by the unconventional RC oscillator.

[0039] In other embodiments, the gate driving circuit is integrated in the isolation unit. Refer to the accompanying Figure 4 , the self-excited soft start unit includes an unconventional RC oscillator and a comparison selector. The connection relationship between the unconventional RC oscillator, the comparison selector, the gate driving circuit, and the receiving module is the same as above and will not be elaborated here. In this way, the control signal is directly generated by the secondary winding of the transformer according to the actual output situation and fed back to the primary winding to control the MOS tube, which can achieve more accurate control. Compared with the primary winding control method, this method can respond faster to the changes in the output voltage and load, timely adjust the working state of the MOS tube, improve the dynamic response ability of the power supply, and make the output voltage more stable; and by adopting this primary winding control method, the complexity of the primary winding side control circuit is reduced, and the primary winding side circuit design is made more concise.

[0040] In addition, it should be noted that in the accompanying Figure 2 of the specification, the rectifier circuit uses a bridge rectifier composed of four diodes. In other embodiments, the diodes can be replaced by MOS tube bodies to form a first-stage bridgeless PFC circuit. In one embodiment, refer to the accompanying Figure 5, This is a topology structure of a medium and small power AC-DC power converter applied in the range of 65W - 300W. Among them, the rectifier circuit consists of the third MOS transistor M3, the fourth MOS transistor M4, the fifth MOS transistor M5, and the sixth MOS transistor M6. The gates of the four MOS transistors are controlled by a gate drive circuit. In this circuit, while the MOS transistors shape the AC wave into a flat-topped wave, by controlling the conduction time and conduction degree of the MOS transistors, the phases of the output voltage and current can be kept consistent, thereby improving the power factor, reducing the loss of reactive power, and enabling the power supply to work more efficiently. That is, the attached Figure 5 Compared with the attached Figure 2 , it can better meet the requirements of medium and small power power converters for efficiency and power quality.

[0041] It should be noted that when the first MOS transistor M1 is turned off, due to the inductance characteristic, a reverse electromotive force will be generated in the primary winding of the transformer. This reverse electromotive force will be superimposed on both ends of the first MOS transistor M1 with the power supply voltage, resulting in an excessive reverse bias voltage (possibly reaching 800V - 900V) borne by the first MOS transistor M1. When the reverse bias voltage exceeds the breakdown voltage of the first MOS transistor M1, the first MOS transistor M1 will be broken down and damaged. Therefore, a discharge path needs to be set between the head and the tail of the primary winding of the transformer to discharge the reverse current generated when the primary winding of the transformer generates a reverse electromotive force.

[0042] In one embodiment, referring to the attached Figure 6 In the attached Figure 5 , a discharge path is set on this basis. The discharge path includes a diode and a first resistor R1. The two ends of the first resistor R1 are respectively connected to the head and the tail of the primary winding of the transformer. The anode of the diode is connected to the tail of the primary winding of the transformer, and its cathode is connected to the head of the primary winding of the transformer. When the first MOS transistor M1 conducts normally, the diode is in the reverse cut-off state and does not affect the normal operation of the first MOS transistor M1; when a reverse bias voltage appears, the diode conducts forward, providing a discharge path for the reverse current.

[0043] In another embodiment, referring to the attached Figure 7 In the attached Figure 5 , a discharge path is set on this basis. The discharge path includes a seventh MOS transistor M7. The source of the seventh MOS transistor M7 is connected to the tail of the primary winding of the transformer, its drain is connected to the head of the primary winding of the transformer, and its gate is connected to the gate drive circuit. When the first MOS transistor M1 is turned off and a reverse electromotive force is generated in the primary winding of the transformer, the seventh MOS transistor M7 conducts, discharging the reverse current, thereby reducing the stress borne by the first MOS transistor M1.

[0044] Furthermore, referring to the attached Figure 8, in the attached drawings of the specification Figure 2 Based on this, the switching element is changed from the first MOS transistor M1 to a full-bridge switching transistor for control. The full-bridge switching transistor is composed of the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, and the fifth MOS transistor M5, and its gate is also controlled by a gate drive circuit. Among them, compared with a single switching transistor, the full-bridge switching transistor can allow a larger current to pass through the primary winding of the transformer under the same input voltage and switching frequency, so that higher power transmission can be achieved. And through a reasonable control strategy, the switching loss of the switching transistor can be further reduced, and the overall conversion efficiency of the power supply can be improved.

[0045] In addition, referring to the attached drawings of the specification Figure 9 , the difference from the attached drawings of the specification Figure 7 lies in the adopted self-excited soft-start unit as shown in the attached drawings of the specification Figure 4 . Among them, the control signals of MOS transistors such as the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, the fifth MOS transistor M5, the sixth MOS transistor M6, and the seventh MOS transistor M7 are controlled by the secondary winding side of the transformer. After the isolation unit isolates the control signals of the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, the fifth MOS transistor M5, and the sixth MOS transistor M6 controlled by the secondary winding side of the transformer, they are transmitted to the primary winding side of the transformer to directly control the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, the fifth MOS transistor M5, the sixth MOS transistor M6, and the seventh MOS transistor M7.

[0046] Similarly, referring to the attached drawings of the specification Figure 10 , the difference from the attached drawings of the specification Figure 8 lies in the adopted self-excited soft-start unit as shown in the attached drawings of the specification Figure 4 . The control signals of MOS transistors such as the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, and the fifth MOS transistor M5 are controlled by the secondary winding side of the transformer. After the isolation unit isolates the control signals of the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, and the fifth MOS transistor M5 controlled by the secondary winding side of the transformer, they are transmitted to the primary winding side of the transformer to directly control the first MOS transistor M1, the third MOS transistor M3, the fourth MOS transistor M4, and the fifth MOS transistor M5.

[0047] In this method, power is supplied to the self-excited soft-start unit through an auxiliary coil. The isolation unit supports isolation methods such as magnetic coupling, capacitive coupling, and digital isolators, and does not support traditional opto-coupler isolation.

[0048] It can be seen that the novel power conversion circuit provided by the present application rectifies through MOS transistors and synchronously adjusts the phase of voltage and current, improving the power factor and reducing the reactive power loss; controls the MOS transistors at the secondary side and cooperates with the isolation unit to simplify the primary circuit and enhance the stability and reliability. Moreover, a discharge path is set to protect the switching transistor from being broken down by reverse bias voltage; at the same time, it supports a variety of novel isolation methods without using optocouplers, improving the response speed, service life and anti-interference ability. Overall, it can effectively improve the AC-DC power conversion efficiency, reduce the cost, and avoid the large inductors and capacitor components required by traditional PFCs, reducing unnecessary space occupation and component stacking, making the overall circuit lighter and more compact.

[0049] The present invention also provides a novel power conversion device, which adopts the above novel power conversion circuit, can improve the PF value of the PFC and the power input and output conversion efficiency, and makes the overall circuit lighter and more compact. Since the principle of solving problems of the power supply device in the embodiments of the present application is similar to that of the above power supply circuit in the embodiments of the present application, the implementation of the power supply device can refer to the implementation of the power supply circuit, and the repeated parts will not be described again.

[0050] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0051] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A novel power conversion circuit, characterized in that, Comprising: A rectification circuit, connected to an AC power supply, for converting the alternating current input by the AC power supply into direct current; A first capacitor C1, connected to the output terminal of the rectification circuit and in parallel with the primary winding of the transformer, for filtering the rectified direct current; wherein, the secondary winding of the transformer includes an output winding and an auxiliary winding, and the primary winding of the transformer is also connected in series with a switching element; An isolation unit, including a transmitting module disposed on the output winding side and a receiving module disposed on the auxiliary winding side, for transmitting the feedback signal on the secondary winding side of the transformer to the receiving module through the transmitting module; A drive circuit, with its input terminal connected to the receiving module and its output terminal connected to the switching element, for controlling the conduction and cutoff of the switching element according to the feedback signal sent by the receiving module.

2. The novel power conversion circuit according to claim 1, wherein The drive circuit is integrated in a self-excited soft start unit or the isolation unit; The self-excited soft start unit includes an unconventional RC oscillator and a comparison selector; one path of the receiving module is connected to the comparison selector, and the other path is connected to the drive circuit; one path of the unconventional RC oscillator is connected to the comparison selector, and the other path is connected to the drive circuit; wherein, when the comparison selector does not receive the feedback signal sent by the receiving module, the unconventional RC oscillator is turned on and outputs a clock frequency with a duty cycle not of 50 / 50 as the clock of the drive circuit; when the comparison selector receives the feedback signal sent by the receiving module, the unconventional RC oscillator is turned off, and the drive circuit controls the conduction and cutoff of the switching element according to the feedback signal sent by the receiving module.

3. The novel power conversion circuit according to claim 2, wherein The rectification circuit adopts a bridge rectification circuit composed of four diodes.

4. The novel power conversion circuit according to claim 2, wherein The rectification circuit adopts a bridge rectification circuit composed of four MOS tubes, and the conduction and cutoff of the four MOS tubes are controlled by the drive circuit to adjust the voltage and current phases output by the rectification circuit to be synchronized.

5. The novel power conversion circuit according to claim 4, wherein A discharge path is provided between the head end and the tail end of the primary winding, for discharging the reverse current when the primary winding of the transformer generates a reverse electromotive force.

6. The novel power conversion circuit according to claim 5, characterized in that The discharge path adopts a diode or a MOS tube.

7. The novel power conversion circuit according to claim 5, wherein The switching element adopts a single MOS tube or a full-bridge switching tube composed of four MOS tubes.

8. The novel power conversion circuit according to claim 2, wherein The self-excited soft start unit is powered by the auxiliary winding.

9. The novel power conversion circuit according to claim 2, wherein The isolation unit adopts magnetic coupling, capacitive coupling, or a digital isolator.

10. A novel power conversion device, characterized in that, Including the novel power conversion circuit according to any one of claims 1-9.

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