A quasi-resonant flyback power supply circuit and power conversion device with a floating structure

Abstract

This invention relates to a quasi-resonant flyback power supply circuit and power conversion device with a floating ground structure. The circuit includes: a power switching device with a built-in integrated gallium nitride power device and a quasi-resonant flyback controller, and a transformer; the transformer includes: 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 circuit's power supply ground to form a floating ground structure; when the gallium nitride power device is turned on, an on-loop is formed by the circuit's power supply voltage input terminal, the first primary winding, the gallium nitride power device's drain pin, source pin, current sampling resistor, the second primary winding, and the circuit's power supply ground; at this time, the first primary winding and the second primary winding are connected in series to form the primary main winding; when the gallium nitride power device is turned off, the secondary winding forms a loop with the output rectifier and filter circuit to maintain power supply to the load; the second primary winding is used as a power supply winding, forming a loop with the power supply loop to power the power switching device.

Description

Technical Field

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

[0002] With the miniaturization and increasing efficiency of electronic devices, switching power supplies have been widely used in consumer electronics, communication equipment, and industrial applications. Among them, flyback topologies are widely adopted due to their simple structure, low cost, and suitability for low power ranges. However, traditional fixed-frequency flyback topologies tend to generate high switching losses under high-frequency operating conditions, and the presence of transformer leakage inductance causes voltage spikes when power devices are turned on and off, further increasing system power losses and electromagnetic interference (EMI) problems. To address these issues, the industry has gradually introduced quasi-resonant flyback topologies.

[0003] The quasi-resonant flyback topology detects the oscillation signal of the primary winding of the transformer, and then... (The sentence is incomplete and requires more context to translate accurately.) DS By turning on the power transistor only when the voltage reaches its valley, the efficiency of the power supply system can be improved. This method not only significantly reduces switching losses but also mitigates the impact of voltage spikes on power devices, improving power conversion efficiency and system reliability. However, despite the significant efficiency advantages of quasi-resonant topologies, existing designs often require complex control circuits and precise voltage detection mechanisms, placing high demands on circuit integration. Furthermore, traditional silicon-based power devices still face switching losses and thermal management issues at high frequencies, limiting the overall performance of the power supply.

[0004] To further improve the switching efficiency and power density of power supplies, the application of gallium nitride (GaN) power devices is gradually attracting attention. Compared with traditional silicon-based devices, gallium nitride devices have lower on-resistance and faster switching speeds, enabling higher conversion efficiency at high frequencies.

[0005] In traditional quasi-resonant flyback topologies, the power transistor's switching on and off is achieved by controlling the current in the primary winding of the transformer. Typically, the primary winding of the transformer is separate from the winding used to power the control chip. While this design effectively isolates power transmission and control circuitry, it also increases the transformer's size and cost.

[0006] Existing quasi-resonant flyback circuits suffer from 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 this invention is to address the shortcomings of existing technologies by providing a quasi-resonant flyback power supply circuit and power conversion device with a floating ground structure. By using a floating ground structure and winding reuse, 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 objectives, 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 switching device and a transformer that integrates a gallium nitride power device and a quasi-resonant flyback controller;

[0009] The power switching device with built-in integrated gallium nitride 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, gallium nitride power device drain pin SW, gallium nitride power device source pin CS, and high-voltage start-up and X capacitor discharge pin HV.

[0010] The transformer includes: 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 start-up 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 source pin CS of the gallium nitride power device through a current sampling resistor RCS1;

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

[0014] When the gallium nitride power device is turned on, the voltage at the opposite terminals of each winding is higher than that at the same terminals. Starting from the power supply voltage input terminal of the circuit, the voltage returns to the power supply ground PGND of the circuit through the first primary winding Np1, the drain pin SW of the gallium nitride power device, the source pin CS of the gallium nitride power device, the current sampling resistor RCS1, and the second primary winding Np2, forming a turn-on loop. In the turn-on loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form the primary main winding.

[0015] When the gallium nitride power device is turned off, the coils on both sides of the transformer generate an induced electromotive force, and the voltage at the same-name terminal of each winding is higher than that at the opposite-name terminal; 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, forming a loop with the power supply circuit to supply power to 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 terminal of the rectifier diode D1 is connected to the same terminal of the second primary winding Np2, and the negative terminal 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 connected to the chip power supply pin VCC.

[0018] The other end of capacitor C2 is connected to the chip reference ground pin GND and the opposite terminal 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 terminal of the rectifier diode D1 is connected to the same terminal of the second primary winding Np2, and the negative terminal 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 connected to the chip power supply pin VCC.

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

[0022] Preferably, the output rectifier filter circuit includes: a rectifier diode D2 and a capacitor EC2;

[0023] One end of the capacitor EC2 is connected to the same-name terminal of the secondary winding Ns, and the other end is connected to the positive terminal of the rectifier diode D2, and simultaneously connected to signal ground SGND. The negative terminal of the rectifier diode D2 is connected to the opposite-name terminal 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 supply 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 terminal 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. The other end of the second resistor R2 is connected to the opposite-name terminal 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 gallium nitride power device is turned on, the source pin CS of the gallium nitride power device is also used to monitor the current flowing through the primary winding. When the monitored current reaches a set limit, the quasi-resonant flyback controller in the power switching device controls the gallium nitride power device to turn off.

[0031] Preferably, when the gallium nitride power device is turned off, the power switching 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 gallium nitride power device to be turned on at the quasi-resonant point.

[0032] Secondly, embodiments of the present invention provide a power conversion device, the power conversion device including the quasi-resonant flyback power supply circuit with a floating ground structure as described in the first aspect above.

[0033] The quasi-resonant flyback power supply circuit with a floating ground structure provided in this invention, through optimized circuit structure design, achieves the following: when the gallium nitride (GaN) power device is on, the first primary winding Np1 and the second primary winding Np2 are connected in series through the GaN power device to form the primary main winding; when the GaN power device is off, the second primary winding Np2 serves as the power supply winding to power the quasi-resonant flyback controller of the power switching device. This design simplifies the circuit structure, eliminates the need for additional windings to provide power to the quasi-resonant flyback controller, and reduces the size of the transformer and the complexity of the circuit. The circuit of this invention can be applied to high power density, high frequency power conversion equipment, such as switching power supplies and DC-DC converters. Attached Figure Description

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

[0035] Figure 2 This is a block diagram of the internal circuit structure of a power switching device specifically used in this invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] This invention provides a quasi-resonant flyback power supply circuit with a floating ground structure. Figure 1 The circuit structure diagram of a quasi-resonant flyback power supply circuit with a floating ground structure is provided for an embodiment of the present invention. The following is in conjunction with... Figure 1 The technical solution of the present invention will be described below.

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

[0040] The power switching device U1, which integrates gallium nitride power devices and a 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, gallium nitride power device drain pin SW, gallium nitride power device source pin CS, and high-voltage start-up and X capacitor discharge pin HV.

[0041] In one specific embodiment of the present invention, the power switching device U1 is implemented using the DK065G power switching chip. The DK065G is a highly integrated quasi-resonant flyback controlled AC-DC power switching chip with a 650V / 260mΩ GaN HEMT. In addition to the aforementioned chip pins, it also includes an unused pin NC.

[0042] Those skilled in the art will understand that, in addition to the DK065G power switch chip used in the specific embodiments 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 achieve the technical solution of the present invention.

[0043] 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 start-up 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, and the positive terminal of the input capacitor EC1 is connected to the voltage input voltage Vi n_dc. The negative terminal of the input capacitor EC1 is connected to the power supply ground PGND of the circuit.

[0045] Input capacitor EC1, serving as the capacitor at the power input terminal, is used for filtering and energy storage. It is responsible for filtering out high-frequency noise and power ripple from the input power supply, ensuring a relatively stable voltage input to the circuit and reducing interference to subsequent circuits. Simultaneously, in the power supply circuit, input capacitor EC1 also acts as an energy reserve, providing energy support when transient voltage drops occur at the power input, maintaining the stability of the input voltage.

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

[0047] The same-named terminal D of the second primary winding Np2 is connected to the power ground PGND of the circuit and is connected to the power supply pin VCC of the chip through the power supply loop; the opposite-named terminal of the second primary winding Np2 is connected to the power ground PGND, and the opposite-named terminal C of the second primary winding Np2 is connected to the source pin CS of the gallium nitride power device through the 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 terminal of the rectifier diode D1 is connected to the same-name terminal D of the second primary winding Np2, and the negative terminal 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 then to the chip's power supply pin VCC. The other end of the capacitor C2 is connected to the chip's reference ground pin GND and the opposite-name terminal C of the second primary winding Np2. The function of capacitor C2 in this circuit is to provide a stable operating voltage for the power switching device U1 (DK065G), especially after the circuit starts up, to ensure stable power supply to 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 the startup voltage to the VCC pin of the power switching device U1. The presence of the current-limiting resistor R3 helps to stabilize voltage changes during startup, ensuring that the startup voltage of the power switching device U1 can be established smoothly, avoiding instability caused by voltage overshoot or oscillation.

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

[0050] The quasi-resonant flyback power supply circuit with a floating ground structure of the present invention 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 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; 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, eliminate noise and high-frequency interference, ensure that the signal fed back to the controller is more stable and accurate, and at the same time help 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 realizing the quasi-resonant flyback power supply circuit with floating ground structure of the present invention. Those skilled in the art can add the required components or peripheral circuits or modify the use of some components according to actual needs, which are all common technical means in the field.

[0053] The circuit structure has been introduced above; the working principle of the circuit will be explained below.

[0054] To better understand the working principle of the circuit, the following will use... Figure 1 Combination Figure 2 The diagram shows the internal circuit structure of the DK065G.

[0055] During power-on startup, the power switching device U1 supplies power to the internal power circuit and control logic of the quasi-resonant flyback controller through a high-voltage startup circuit (such as the HV pin of the DK065G). The HV pin extracts a small portion 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 switching device U1 enters the working state, shuts off the high-voltage current source, and the startup process ends. At this time, the gallium nitride power device ( Figure 2 The power transistor between the SW pin and the CS pin remains off.

[0056] After the quasi-resonant flyback controller completes startup, it begins monitoring the voltage of the primary winding. Based on the detected voltage, the gallium nitride power device is turned on for the first time when the quasi-resonant point is reached. At this time, the current on the primary winding side forms a power supply circuit through the gallium nitride power device, and begins to store the energy at the input end in the magnetic field of transformer T1, preparing to transfer it to the secondary side later.

[0057] Specifically, when the gallium nitride (GaN) power device is turned on, the voltages at the opposite terminals of each winding of transformer T1 are higher than those at the same terminals; the voltages across the first primary winding Np1 (VA > VB), the voltages across the second primary winding Np2 (VC > VD), and the voltages across the secondary winding Ns (VE > VF) are all in reverse cutoff mode. Therefore, at this time, rectifier diodes D1 and D2 are both in reverse cutoff mode. Starting from the power supply voltage input terminal of the circuit, the voltage flows through the first primary winding Np1, the drain pin SW of the GaN power device, the source pin CS of the GaN power device, the current sampling resistor RCS1, and the second primary winding Np2, returning to the power ground PGND of the circuit, forming a turn-on loop. In the turn-on loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form the primary main winding.

[0058] When the gallium nitride power device is in the ON state, the source pin CS of the gallium nitride power device is also used to monitor the current flowing through the primary winding. The voltage across the current sampling resistor RCS1 can detect the current flowing through the entire primary winding. When the detected current reaches a set limit, the quasi-resonant flyback controller in the power switching device U1 controls the gallium nitride power device to turn off.

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

[0060] When the gallium nitride power device is off, the power switching 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 gallium nitride power device to turn on again at the quasi-resonant point.

[0061] Therefore, it can be seen that in the quasi-resonant flyback power supply circuit with a floating ground structure of the present invention, Np2 in the primary winding of transformer T1 has a dual function: when the power transistor is turned on, Np2, as part of the primary winding, is connected in series with Np1 and participates in energy storage; when the power transistor is turned off, Np1 and Np2 participate in energy transfer simultaneously, with the main energy transferred to the secondary NS winding. At the same time, Np2 also acts as a power supply winding, providing the operating voltage for the quasi-resonant flyback controller. This reused structure effectively reduces the number of windings, simplifies transformer design, reduces size and cost, and increases the power density of the power supply. This design, through the rational reuse of windings, not only saves hardware resources but also improves the efficiency and stability of the entire power supply system.

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

[0063] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment 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 within 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 structure includes: a power switching device and a transformer with a built-in integrated gallium nitride power device and a quasi-resonant flyback controller; The power switching device with built-in integrated gallium nitride 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, gallium nitride power device drain pin SW, gallium nitride power device source pin CS, and high-voltage start-up and X capacitor discharge pin HV. The transformer includes: 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 start-up 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 chip reference ground pin GND, and the opposite-name terminal of the second primary winding Np2 is connected to the source pin CS of the gallium nitride power device through a current sampling resistor RCS1; The secondary winding Ns is connected to the load after the output rectifier and filter circuit; When the gallium nitride power device is turned on, the voltage at the opposite terminals of each winding is higher than that at the same terminals. Starting from the power supply voltage input terminal of the circuit, the voltage returns to the power supply ground PGND of the circuit through the first primary winding Np1, the drain pin SW of the gallium nitride power device, the source pin CS of the gallium nitride power device, the current sampling resistor RCS1, and the second primary winding Np2, forming a turn-on loop. In the turn-on loop, the first primary winding Np1 and the second primary winding Np2 are connected in series to form the primary main winding. When the gallium nitride power device is turned off, the coils on both sides of the transformer generate an induced electromotive force, and the voltage at the same-name terminal of each winding is higher than that at the opposite-name terminal; 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, forming a loop with the power supply circuit to supply power to 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 terminal of the rectifier diode D1 is connected to the same terminal of the second primary winding Np2, and the negative terminal 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 connected to the chip power supply pin VCC. The other end of capacitor C2 is connected to the chip reference ground pin GND and the opposite terminal 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 rectifier and filter circuit includes: rectifier diode D2 and capacitor EC2; One end of the capacitor EC2 is connected to the same-name terminal of the secondary winding Ns, and the other end is connected to the positive terminal of the rectifier diode D2, and simultaneously connected to signal ground SGND. The negative terminal of the rectifier diode D2 is connected to the opposite-name terminal 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 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 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. The other end of the second resistor R2 is connected to the opposite-name terminal 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 gallium nitride power device is in the ON state, the source pin CS of the gallium nitride power device is also used to monitor the current flowing through the primary winding. When the current is detected to reach a set limit, the quasi-resonant flyback controller in the power switching device controls the gallium nitride power device to turn off.

8. The quasi-resonant flyback power supply circuit with a floating ground structure according to claim 1, characterized in that, When the gallium nitride power device is off, the power switching 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 gallium nitride power device to be turned on at the quasi-resonant point.

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

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