Quasi-resonant flyback power supply circuit with floating ground structure and power conversion equipment

Abstract

The invention relates to a quasi-resonant flyback power supply circuit with a floating structure and power conversion equipment. The circuit comprises a power switch device and a transformer, wherein a gallium nitride power device and a quasi-resonant flyback controller are integrated in the power switch device; the transformer comprises a first primary winding, a second primary winding and a secondary winding; the second primary winding is connected in series between the chip reference ground pin and the power ground of the circuit to form a floating ground structure; when the gallium nitride power device is turned on, the power supply voltage input end of the circuit, the first primary winding, the drain electrode pin and the source electrode pin of the gallium nitride power device, the current sampling resistor, the second primary winding and the power supply ground of the circuit form a turn-on loop. The first primary winding and the second primary winding are connected in series to form a primary main winding; when the gallium nitride power device is turned off, the secondary winding and the output rectification filter circuit form a loop to maintain power supply to the load. And the second primary winding is used as a power supply winding and forms a loop for supplying power to the power switching device with the power supply loop.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a quasi-resonant flyback power supply circuit and a power conversion device with a floating ground structure. Background Art

[0002] With the development of miniaturization and high efficiency of electronic devices, switching power supplies have been widely used in consumer electronics, communication equipment and industrial applications. Among them, the flyback topology is widely used due to its simple structure, low cost and suitability for small power range. However, the traditional fixed-frequency flyback topology is prone to high switching losses under high-frequency working conditions, and due to the presence of transformer leakage inductance, power devices will generate voltage spikes when turning on and off, further increasing the power loss and electromagnetic interference (EMI) problems of the system. In order to solve these problems, the industry has gradually introduced the quasi-resonant flyback topology.

[0003] The quasi-resonant flyback topology detects the oscillation signal of the primary winding of the transformer and DS When the resonance reaches the valley voltage, the power tube is turned on, thereby improving the efficiency of the power system. This method can not only significantly reduce switching losses, but also reduce the impact of voltage spikes on power devices, improve power conversion efficiency and system reliability. However, despite the obvious efficiency advantages of the quasi-resonant topology, existing designs often require complex control circuits and precise voltage detection mechanisms, which places high demands on the integration of the circuit. In addition, traditional silicon-based power devices still face switching losses and thermal management issues when working at high frequencies, which limits the overall performance of the power supply.

[0004] In order to further improve the switching efficiency and power density of power supplies, the application of gallium nitride (GaN) power devices has gradually attracted attention. Compared with traditional silicon-based devices, gallium nitride devices have lower on-resistance and faster switching speed, and can achieve higher conversion efficiency at high frequencies.

[0005] In the traditional quasi-resonant flyback topology circuit, the power tube is turned on and off by controlling the current of the primary winding of the transformer. Usually, the primary winding of the transformer and the winding used to power the control chip are separated. Although such a design can effectively isolate the power transmission and control circuits, it also increases the size and cost of the transformer.

[0006] The existing quasi-resonant flyback circuit has problems such as complex structure and high cost, and cannot meet the development needs of miniaturization, high efficiency and high density of switching power supplies. Summary of the invention

[0007] The purpose of the present invention is to address the defects of the prior art and provide a quasi-resonant flyback power supply circuit and a power conversion device with a floating ground structure. Through the floating ground structure and winding multiplexing, the structure of the quasi-resonant flyback power supply circuit is simplified and the cost is reduced, providing a new solution for miniaturized, efficient and high-density power conversion applications.

[0008] To achieve the above-mentioned object, in a first aspect, the present invention provides a quasi-resonant flyback power supply circuit with a floating ground structure, the quasi-resonant flyback power supply circuit comprising: a power switch device and a transformer with a built-in integrated gallium nitride power device and a quasi-resonant flyback controller;

[0009] The power switch device with built-in integrated GaN power device and quasi-resonant flyback controller includes: an auxiliary winding voltage detection pin VS, a feedback input pin FB, a chip power supply pin VCC, a chip reference ground pin GND, a GaN power device drain pin SW, a GaN power device source pin CS and a high-voltage startup and X-capacitor discharge pin HV;

[0010] The transformer comprises: a first primary winding Np1, a second primary winding Np2 and a secondary winding Ns;

[0011] The same-name terminal of the first primary winding Np1 is connected to the drain pin SW of the gallium nitride power device, and the opposite-name terminal is connected to the high-voltage startup and X-capacitor discharge pin HV and the power supply voltage input terminal of the circuit;

[0012] The second primary winding Np2 is connected in series between the chip reference ground pin GND and the circuit power ground PGND to form a floating ground structure; wherein the same-name terminal of the second primary winding Np2 is connected to the circuit power ground PGND, and is connected to the chip power supply pin VCC through a power supply loop; the opposite-name terminal of the second primary winding Np2 is connected to the power ground PGND, and the opposite-name terminal of the second primary winding Np2 is connected to the gallium nitride power device source pin CS through a current sampling resistor RCS1;

[0013] The secondary winding Ns is connected to the output rectifier filter circuit and then to the load;

[0014] When the GaN power device is turned on, the voltage at the opposite-name end of each winding is higher than that at the same-name end; starting from the power supply voltage input end of the circuit, through the first primary winding Np1, the GaN power device drain pin SW, the GaN power device source pin CS, the current sampling resistor RCS1 and the second primary winding Np2, back to the power supply ground PGND of the circuit, forming an open loop; in the open loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form a primary main winding;

[0015] When the gallium nitride power device is turned off, the coils on both sides of the transformer generate induced electromotive force, and the voltage at the same-name end of each winding is higher than that at the opposite-name end; the secondary winding Ns forms a loop with the output rectifier and filter circuit to maintain the output voltage to the load; the second primary winding Np2 is used as a power supply winding, and forms a loop with the power supply loop to power the power switching device.

[0016] Preferably, the power supply circuit includes: a rectifier diode D1, a current limiting resistor R3 and a capacitor C2;

[0017] The positive electrode of the rectifier diode D1 is connected to the same-name terminal of the second primary winding Np2, and the negative electrode is connected to one end of the current limiting resistor R3. The other end of the current limiting resistor R3 is connected to one end of the capacitor C2 and to the chip power supply pin VCC.

[0018] The other end of the capacitor C2 is connected to the chip reference ground pin GND and the opposite-name end of the second primary winding Np2.

[0019] Preferably, the power supply circuit includes: a rectifier diode D1, a current limiting resistor R3 and a capacitor C2;

[0020] The positive electrode of the rectifier diode D1 is connected to the same-name terminal of the second primary winding Np2, and the negative electrode is connected to one end of the current-limiting resistor. The other end of the current-limiting resistor is connected to one end of the capacitor C2 and to the chip power supply pin VCC.

[0021] The other end of the capacitor C2 is connected to the chip reference ground pin GND and the opposite-name end of the second primary winding Np2.

[0022] Preferably, the output rectification and filtering circuit comprises: a rectification diode D2 and a capacitor EC2;

[0023] One end of the capacitor EC2 is connected to the same-name end of the secondary winding Ns, and the other end is connected to the positive electrode of the rectifier diode D2 and the signal ground SGND. The cathode of the rectifier diode D2 is connected to the opposite-name end of the secondary winding Ns.

[0024] Preferably, the power supply voltage input terminal is the positive terminal of the input capacitor EC1, the positive terminal of the input capacitor EC1 is connected to the voltage input voltage Vin_dc, and the negative terminal of the input capacitor EC1 is connected to the power ground PGND of the circuit.

[0025] Preferably, the quasi-resonant flyback power supply circuit with a floating ground structure further includes an auxiliary winding voltage detection branch;

[0026] The auxiliary winding voltage detection branch includes a first resistor R1 and a second resistor R2;

[0027] One end of the first resistor R1 is connected to the same-name end of the second primary winding Np2, and the other end is connected to one end of the second resistor R2 at the auxiliary winding voltage detection reference point, and the other end of the second resistor R2 is connected to the opposite-name end of the second primary winding Np2;

[0028] The auxiliary winding voltage detection reference point is connected to the auxiliary winding voltage detection reference point pin VS.

[0029] Preferably, a feedback filter capacitor C1 is connected between the feedback input pin FB and the chip reference ground pin GND.

[0030] Preferably, when the GaN power device is turned on, the source pin CS of the GaN power device is also used to monitor the current flowing through the primary main winding. When it is monitored that the current reaches a set limit value, the quasi-resonant flyback controller in the power switch device controls to turn off the GaN power device.

[0031] Preferably, when the GaN power device is turned off, the power switch device monitors the demagnetization condition of the transformer by monitoring the voltage of the auxiliary winding voltage detection pin VS, so that the quasi-resonant flyback controller controls the GaN power device to be turned on at the quasi-resonant point.

[0032] In a second aspect, an embodiment of the present invention provides a power conversion device, wherein the power conversion device includes the quasi-resonant flyback power supply circuit with a floating ground structure as described in the first aspect.

[0033] The quasi-resonant flyback power supply circuit with a floating ground structure provided in an embodiment of the present invention realizes, through the design optimization of the circuit structure, that when the gallium nitride power device is turned on, the first primary winding Np1 and the second primary winding Np2 are connected in series through the gallium nitride power device to form a primary main winding, and when the gallium nitride power device is turned off, the second primary winding Np2 is used as a power supply winding to power the quasi-resonant flyback controller of the power switching device. This design simplifies the structure of the circuit, does not require additional windings to provide power for the quasi-resonant flyback controller, and reduces the size of the transformer and the complexity of the circuit. The circuit of the present invention can be applied to high power density, high frequency power conversion equipment, such as switching power supplies, DC-DC converters, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A circuit structure diagram of a quasi-resonant flyback power supply circuit with a floating ground structure provided by an embodiment of the present invention;

[0035] Figure 2 The figure is a block diagram of the internal circuit structure of a power switch device specifically adopted in the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0038] An embodiment of the present invention provides a quasi-resonant flyback power supply circuit with a floating ground structure. Figure 1 The circuit structure diagram of the quasi-resonant flyback power supply circuit with a floating ground structure provided by the embodiment of the present invention. Figure 1 , the technical solution of the present invention is described.

[0039] The quasi-resonant flyback power supply circuit with a floating ground structure of the present invention is shown in the figure, and includes: a power switch device U1 and a transformer T1 with a built-in integrated gallium nitride power device and a quasi-resonant flyback controller;

[0040] The power switch device U1 with built-in integrated GaN power device and quasi-resonant flyback controller includes: auxiliary winding voltage detection pin VS, feedback input pin FB, chip power supply pin VCC, chip reference ground pin GND, GaN power device drain pin SW, GaN power device source pin CS and high-voltage startup and X-capacitor discharge pin HV.

[0041] In a specific embodiment of the present invention, the power switch device U1 is implemented by using a DK065G power switch chip. DK065G is a highly integrated 650V / 260mΩGaN HEMT quasi-resonant flyback control AC-DC power switch chip. In addition to the above chip pins, it also includes a vacant pin NC.

[0042] Those skilled in the art can understand that, in addition to the DK065G power switch chip used in the specific embodiment of the present invention, other power switch devices with built-in integrated gallium nitride power devices and quasi-resonant flyback controllers disclosed in the prior art can also be applied to the present invention to implement the technical solution of the present invention.

[0043] The transformer T1 includes a first primary winding Np1, a second primary winding Np2 and a secondary winding Ns.

[0044] The same-name terminal B of the first primary winding Np1 is connected to the drain pin SW of the gallium nitride power device, and the opposite-name terminal A is connected to the high-voltage startup and X-capacitor discharge pin HV and the power supply voltage input terminal of the circuit. As shown in the figure, the power supply voltage input terminal is the positive terminal of the input capacitor EC1, the positive terminal of the input capacitor EC1 is connected to the voltage input voltage Vin_dc, and the negative terminal of the input capacitor EC1 is connected to the power ground PGND of the circuit.

[0045] The input capacitor EC1 is used as a capacitor at the power input end for filtering and energy storage. It is responsible for filtering out the high-frequency noise and power ripple of the input power supply, ensuring that the voltage input to the circuit is relatively stable and reducing interference to subsequent circuits. At the same time, in the power supply circuit, the input capacitor EC1 also acts as an energy reserve, providing energy support when there is a transient voltage drop in the power input, and maintaining the stability of the input voltage.

[0046] The second primary winding Np2 is connected in series between the chip reference ground pin GND and the circuit power ground PGND to form a floating ground structure. Here, the power ground PGND (Power Ground) is the grounding of the power part in the circuit and is used in large current and high power signal loops.

[0047] The same-name terminal D of the second primary winding Np2 is connected to the power ground PGND of the circuit, and is connected to the chip power supply pin VCC through a power supply loop; the opposite-name terminal of the second primary winding Np2 is connected to the power ground PGND, and the opposite-name terminal C of the second primary winding Np2 is connected to the gallium nitride power device source pin CS through a current sampling resistor RCS1.

[0048] The power supply circuit includes: a rectifier diode D1, a current limiting resistor R3 and a capacitor C2; the positive electrode of the rectifier diode D1 is connected to the same-name terminal D of the second primary winding Np2, the negative electrode is connected to one end of the current limiting resistor R3, the other end of the current limiting resistor R3 is connected to one end of the capacitor C2, and is connected to the chip power supply pin VCC. The other end of the capacitor C2 is connected to the chip reference ground pin GND and the opposite-name terminal C of the second primary winding Np2. The function of the capacitor C2 in this circuit is to provide a stable working voltage for the power switch device U1 (DK065G), especially after the circuit is started, to ensure the stability of the power supply of the chip. The rectifier diode D1 and the current limiting resistor R3 form a resistor-diode loop, the main function of which is to provide a starting voltage for the VCC pin of the power switch device U1. The existence of the current limiting resistor R3 helps to stabilize the voltage change during the startup process, ensuring that the startup voltage of the power switch device U1 can be established smoothly, and avoiding instability caused by voltage overshoot or oscillation.

[0049] The secondary winding Ns is connected to the output rectifier filter circuit and then to the load. The output rectifier filter circuit includes: a rectifier diode D2 and a capacitor EC2; one end of the capacitor EC2 is connected to the same-name terminal F of the secondary winding Ns, and the other end is connected to the positive electrode of the rectifier diode D2 and the signal ground SGND, and the negative electrode of the rectifier diode D2 is connected to the opposite-name terminal of the secondary winding Ns. The output rectifier filter circuit is responsible for rectifying the AC power generated by the secondary winding of the transformer into DC power, and filtering through the capacitor EC2 to smooth the output voltage and ensure the stability of the output voltage.

[0050] The quasi-resonant flyback power supply circuit with a floating ground structure of the present invention also includes an auxiliary winding voltage detection branch; the auxiliary winding voltage detection branch includes a first resistor R1 and a second resistor R2; one end of the first resistor R1 is connected to the same-name terminal D of the second primary winding Np2, and the other end is connected to one end of the second resistor R2 at the auxiliary winding voltage detection reference point VS1, and the other end of the second resistor R2 is connected to the opposite-name terminal C of the second primary winding Np2. The auxiliary winding voltage detection reference point VS1 is connected to the auxiliary winding voltage detection reference point pin VS.

[0051] In addition, a feedback filter capacitor C1 is connected between the feedback input pin FB and the chip reference ground pin GND. The feedback filter capacitor C1 is used to filter the signal fed back from the output end, eliminate noise and high-frequency interference, and ensure that the signal fed back to the controller is more stable and accurate. At the same time, it helps to improve the dynamic response of the feedback loop, prevent transient changes in the feedback signal from causing circuit instability or oscillation, and improve the stability of the power supply output.

[0052] The above is the basic circuit structure for implementing the quasi-resonant flyback power supply circuit with a floating structure of the present invention. On this basis, those skilled in the art can add required components or peripheral circuits according to actual needs, or modify the use of some components, which are all commonly used technical means in the field.

[0053] The structure of the circuit is introduced above, and the working principle of the circuit is explained below.

[0054] In order to understand the working principle of the circuit more clearly, the following Figure 1 Combination Figure 2 The internal circuit structure block diagram of DK065G is shown in the figure.

[0055] When the circuit is powered on, the power switch device U1 supplies power to the internal power circuit and control logic of the quasi-resonant flyback controller through the high-voltage startup circuit (such as the HV pin of DK065G). The HV pin extracts a small amount of current from the input voltage to charge the chip's power supply capacitor (such as capacitor C2). When the threshold voltage is reached, the quasi-resonant flyback controller of the power switch device U1 enters the working state, turns off the high-voltage current source, and the startup process ends. At this time, the gallium nitride power device ( Figure 2 The power tube between the SW pin and the CS pin remains turned off.

[0056] When the quasi-resonant flyback controller completes startup, it begins to monitor the voltage of the primary winding. Based on the detected voltage, when the quasi-resonant point is reached, the GaN power device is turned on for the first time. At this time, the current on the primary winding side forms a power supply loop through the GaN power device, and begins to store the energy at the input end in the magnetic field of transformer T1, ready to be transferred to the secondary side later.

[0057] Specifically, when the GaN power device is turned on, the voltages at the opposite ends of each winding of the transformer T1 are higher than those at the same end; the voltages at both ends of the first primary winding Np1 are VA>VB, the voltages at both ends of the second primary winding Np2 are VC>VD, and the voltages at both ends of the secondary winding Ns are VE>VF. Therefore, at this time, the rectifier diodes D1 and D2 are both in a reverse cut-off state. Starting from the power supply voltage input end of the circuit, through the first primary winding Np1, the GaN power device drain pin SW, the GaN power device source pin CS, the current sampling resistor RCS1 and the second primary winding Np2, back to the power supply ground PGND of the circuit, forming an open loop. In the open loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form a primary main winding.

[0058] When the GaN power device is turned on, the source pin CS of the GaN power device is also used to monitor the current flowing through the primary main winding, and the voltage across the current sampling resistor RCS1 can detect the current flowing through the entire primary main winding. When the current reaches the set limit, the quasi-resonant flyback controller in the power switch device U1 controls the GaN power device to be turned off.

[0059] When the GaN power device is turned off, the coils on both sides of the transformer T1 generate induced electromotive force, and the voltage of the same-name end of each winding is higher than that of the opposite-name end; the voltage across Np1 VA<VB, the voltage across Np2 VC<VD, and the voltage across Ns VE<VF. At this time, the rectifier diode D1 and the rectifier diode D2 are both subjected to forward voltage and turned on. The secondary winding Ns forms a loop with the output rectifier filter circuit (rectifier diode D2 and capacitor EC2) to maintain the output voltage to the load; the second primary winding Np2 is used as a power supply winding, and forms a loop with the power supply loop (rectifier diode D1, current limiting resistor R3 and capacitor C2) to supply power to the power switch device U1.

[0060] When the GaN power device is turned off, the power switch device monitors the demagnetization of the transformer by monitoring the voltage of the auxiliary winding voltage detection pin VS, so that the quasi-resonant flyback controller can control the GaN power device to be turned on again at the quasi-resonant point.

[0061] It can be seen from this that in the quasi-resonant flyback power supply circuit with a floating ground structure of the present invention, Np2 in the primary main winding of the transformer T1 has a dual function: when the power tube is turned on, Np2, as part of the main winding, is connected in series with Np1 to jointly participate in energy storage, and when the power tube is turned off, Np1 and Np2 participate in energy transfer at the same time, and the main energy is transferred to the secondary NS winding. At the same time, Np2 also acts as a power supply winding to provide a working voltage for the quasi-resonant flyback controller. This reuse structure effectively reduces the number of windings, simplifies the transformer design, reduces the volume and cost, and improves the power density of the power supply. This design not only saves hardware resources through the reasonable reuse of windings, but also improves the efficiency and stability of the entire power supply system.

[0062] The circuit of the present invention can be applied to high power density and high frequency power conversion equipment, such as switching power supplies, DC-DC converters, etc.

[0063] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quasi-resonant flyback power supply circuit with a floating ground structure, characterized in that: The quasi-resonant flyback power supply circuit with a floating ground structure comprises: a power switch device and a transformer with a built-in integrated gallium nitride power device and a quasi-resonant flyback controller; The power switch device with built-in integrated GaN power device and quasi-resonant flyback controller includes: an auxiliary winding voltage detection pin VS, a feedback input pin FB, a chip power supply pin VCC, a chip reference ground pin GND, a GaN power device drain pin SW, a GaN power device source pin CS and a high-voltage startup and X-capacitor discharge pin HV; The transformer comprises: a first primary winding Np1, a second primary winding Np2 and a secondary winding Ns; The same-name terminal of the first primary winding Np1 is connected to the drain pin SW of the gallium nitride power device, and the opposite-name terminal is connected to the high-voltage startup and X-capacitor discharge pin HV and the power supply voltage input terminal of the circuit; The second primary winding Np2 is connected in series between the chip reference ground pin GND and the circuit power ground PGND to form a floating ground structure; wherein the same-name terminal of the second primary winding Np2 is connected to the circuit power ground PGND, and is connected to the chip power supply pin VCC through a power supply loop; the opposite-name terminal of the second primary winding Np2 is connected to the power ground PGND, and the opposite-name terminal of the second primary winding Np2 is connected to the gallium nitride power device source pin CS through a current sampling resistor RCS1; The secondary winding Ns is connected to the output rectifier filter circuit and then to the load; When the GaN power device is turned on, the voltage at the opposite-name end of each winding is higher than that at the same-name end; starting from the power supply voltage input end of the circuit, through the first primary winding Np1, the GaN power device drain pin SW, the GaN power device source pin CS, the current sampling resistor RCS1 and the second primary winding Np2, back to the power supply ground PGND of the circuit, forming an open loop; in the open loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form a primary main winding; When the gallium nitride power device is turned off, the coils on both sides of the transformer generate induced electromotive force, and the voltage at the same-name end of each winding is higher than that at the opposite-name end; the secondary winding Ns forms a loop with the output rectifier and filter circuit to maintain the output voltage to the load; the second primary winding Np2 is used as a power supply winding, and forms a loop with the power supply loop to power the power switching device.

2. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: The power supply circuit includes: a rectifier diode D1, a current limiting resistor R3 and a capacitor C2; The positive electrode of the rectifier diode D1 is connected to the same-name terminal of the second primary winding Np2, and the negative electrode is connected to one end of the current-limiting resistor. The other end of the current-limiting resistor is connected to one end of the capacitor C2 and to the chip power supply pin VCC. The other end of the capacitor C2 is connected to the chip reference ground pin GND and the opposite-name end of the second primary winding Np2.

3. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: The output rectification and filtering circuit comprises: a rectification diode D2 and a capacitor EC2; One end of the capacitor EC2 is connected to the same-name end of the secondary winding Ns, and the other end is connected to the positive electrode of the rectifier diode D2 and the signal ground SGND. The cathode of the rectifier diode D2 is connected to the opposite-name end of the secondary winding Ns.

4. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: The power supply voltage input terminal is the positive terminal of the input capacitor EC1 . The positive terminal of the input capacitor EC1 is connected to the voltage input voltage Vin_dc, and the negative terminal of the input capacitor EC1 is connected to the power ground PGND of the circuit.

5. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: The quasi-resonant flyback power supply circuit with a floating ground structure further includes an auxiliary winding voltage detection branch; The auxiliary winding voltage detection branch includes a first resistor R1 and a second resistor R2; One end of the first resistor R1 is connected to the same-name end of the second primary winding Np2, and the other end is connected to one end of the second resistor R2 at the auxiliary winding voltage detection reference point, and the other end of the second resistor R2 is connected to the opposite-name end of the second primary winding Np2; The auxiliary winding voltage detection reference point is connected to the auxiliary winding voltage detection reference point pin VS.

6. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: A feedback filter capacitor C1 is connected between the feedback input pin FB and the chip reference ground pin GND.

7. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: When the GaN power device is in the on state, the source pin CS of the GaN power device is also used to monitor the current flowing through the primary main winding. When it is monitored that the current reaches a set limit, the quasi-resonant flyback controller in the power switch device controls to turn off the GaN power device.

8. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that: When the GaN power device is in the off state, the power switch device monitors the demagnetization of the transformer by monitoring the voltage of the auxiliary winding voltage detection pin VS, so that the quasi-resonant flyback controller controls the GaN power device to be turned on at the quasi-resonant point.

9. A power conversion device, characterized in that: The power conversion device comprises the quasi-resonant flyback power supply circuit with a floating ground structure as described in any one of claims 1 to 8.

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