Flyback power supply circuit and power supply

Abstract

The application relates to a flyback power supply circuit and a power supply. The flyback primary side circuit comprises a primary side winding connected with a high-voltage power supply. The flyback secondary side circuit comprises a secondary side winding, a switching unit, an energy buffer unit and a charging unit. The switching unit is connected with the secondary side winding. The energy buffer unit is connected with the switching unit, the charging unit and a power supply output end respectively. The charging unit is used for charging the energy buffer unit before the flyback primary side circuit is connected with the high-voltage power supply. The charging unit arranged in the flyback secondary side circuit can charge the energy buffer unit in the flyback secondary side circuit before the flyback power supply circuit is connected with the high-voltage power supply, so that negative voltage of the flyback secondary side circuit is avoided. The application can reduce voltage stress of the switching unit when the flyback secondary side circuit starts, and improve stability and reliability of the flyback power supply circuit.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a flyback power supply circuit and a power supply. Background Technology

[0002] A flyback power supply is a common switching power supply topology widely used in various electronic devices. Currently, during startup, the secondary capacitor in a flyback power supply experiences excessive voltage stress on its diodes due to resonance and negative voltage phenomena, affecting the stability and reliability of the flyback power supply. Utility Model Content

[0003] This application provides a flyback power supply circuit and a power supply, which can reduce the voltage stress on the diodes when the flyback power supply circuit starts up, improve the stability and reliability of the flyback power supply, and at least partially solve the above-mentioned technical problems.

[0004] To achieve the above objectives, according to a first aspect of this application, a flyback power supply circuit is provided, comprising: a flyback primary circuit and a flyback secondary circuit, wherein: the flyback primary circuit includes: a primary winding connected to a high-voltage power supply; the flyback secondary circuit includes: a secondary winding, a switching unit, an energy buffer unit, and a charging unit, the switching unit being connected to the secondary winding, the energy buffer unit being connected to the switching unit, the charging unit, and a power output terminal, and the charging unit being used to charge the energy buffer unit before the flyback primary circuit is connected to the high-voltage power supply.

[0005] Optionally, the charging unit includes: a charging power supply; a voltage conversion circuit connected to the charging power supply, the voltage conversion circuit receiving a voltage signal output by the charging power supply and generating a converted voltage signal; a first switching circuit connected to the voltage conversion circuit and the energy buffer unit respectively, the first switching circuit receiving the converted voltage signal and outputting a charging voltage signal; and the energy buffer unit charging when receiving the charging voltage signal.

[0006] Optionally, the charging voltage signal output by the charging unit to the energy buffer unit is related to the output voltage signal of the flyback power supply circuit at the power output terminal.

[0007] Optionally, the first switching circuit includes a first diode, the cathode of which is connected to the energy buffer unit, and the anode of which is connected to the voltage conversion circuit.

[0008] Optionally, the voltage conversion circuit includes: a first resistor and a second resistor, a first end of the first resistor being connected to the charging power supply, a second end of the first resistor being connected to the first switching circuit and the first end of the second resistor respectively, and a second end of the second resistor being connected to the first ground terminal.

[0009] Optionally, the voltage conversion circuit includes a third resistor and a first Zener diode, the first end of the third resistor is connected to the charging power supply, the second end of the third resistor is connected to the first switching circuit and the cathode of the first Zener diode, and the anode of the first Zener diode is connected to the first ground terminal.

[0010] Optionally, the switching unit includes at least one diode, the cathode of which is connected to the secondary winding, and the anode of which is connected to the power output terminal and the energy buffer unit, respectively.

[0011] Optionally, the flyback primary-side circuit further includes: a second switching circuit, wherein the control terminal of the second switching circuit is connected to the power management chip, the first terminal of the second switching circuit is connected to the primary winding, and the second terminal of the second switching circuit is connected to the second ground terminal.

[0012] Optionally, the flyback power supply circuit further includes a feedback circuit, which includes an optocoupler primary circuit connected to the output terminal of the flyback secondary circuit and an optocoupler secondary circuit connected to the power management chip, wherein the optocoupler primary circuit is turned on when the voltage at the power output terminal is greater than a preset voltage, so that the optocoupler secondary circuit sends a feedback signal to the power management chip when the optocoupler primary circuit is turned on.

[0013] Optionally, the optocoupler primary-side circuit includes: a light-emitting element and a third switching circuit, wherein the control terminal of the third switching circuit is used to connect to the power output terminal, the first terminal of the third switching circuit is connected to the light-emitting element, and the second terminal of the third switching circuit is connected to the first ground terminal.

[0014] Optionally, the optocoupler secondary circuit includes: a photosensitive switch element, a first end of which is connected to the power management chip, a second end of which is connected to a second ground terminal, and the photosensitive switch element generating the feedback signal at the first end according to the conduction state of the light-emitting element.

[0015] According to a second aspect of this application, a power supply is provided, comprising: a power management chip, and a flyback power supply circuit as provided in the first aspect above.

[0016] In summary, the flyback power supply circuit in this application includes a flyback primary circuit and a flyback secondary circuit. The flyback primary circuit includes a primary winding connected to a high-voltage power supply. The flyback secondary circuit includes a secondary winding, a switching unit, an energy buffer unit, and a charging unit. The switching unit is connected to the secondary winding, and the energy buffer unit is connected to the switching unit, the charging unit, and the power output terminal. The charging unit charges the energy buffer unit before the flyback primary circuit is connected to the high-voltage power supply. The flyback power supply circuit of this application, by including a charging unit in the flyback secondary circuit, allows the energy buffer unit in the flyback secondary circuit to be charged before the flyback power supply is connected to the high-voltage power supply, preventing negative voltage from appearing in the flyback secondary circuit due to resonance or other reasons after the flyback power supply is started up. This application embodiment can reduce the voltage stress on the switching unit during the start-up of the flyback secondary circuit, improving the stability and reliability of the flyback power supply.

[0017] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0019] Figure 1 This is a schematic diagram of a flyback power supply circuit provided in an embodiment of this disclosure; Figure 2 This is a circuit diagram of a charging unit provided in an embodiment of this disclosure; Figure 3 This is a circuit diagram of another charging unit provided in an embodiment of this disclosure; Figure 4 This is a schematic diagram of another flyback power supply circuit provided in an embodiment of this disclosure; Figure 5 This is a schematic diagram of a feedback circuit provided in an embodiment of this disclosure; Figure 6 This is a connection diagram of a power management chip provided in an embodiment of this disclosure. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0021] In hybrid vehicles, drive circuits, emergency power supplies, and other components can be powered by a flyback power supply circuit. The high-voltage power supply is input to the flyback power supply circuit, and at its output terminal, a low-voltage power supply is generated and output from zero, following the input of the high-voltage power supply.

[0022] Please see Figure 1 , Figure 1 This is a schematic diagram of a flyback power supply circuit provided in an embodiment of this disclosure. For example... Figure 1 As shown, the flyback power supply circuit includes a flyback primary circuit and a flyback secondary circuit. The flyback primary circuit includes a primary winding, which is connected to a high-voltage power supply. The flyback secondary circuit includes a secondary winding, a switching unit 210, an energy buffer unit 220, and a charging unit 230. The switching unit 210 is connected to the secondary winding. The energy buffer unit 220 is connected to the switching unit 210, the charging unit 230, and the power output terminal, respectively. The charging unit 230 is used to charge the energy buffer unit 220 before the flyback primary circuit is connected to the high-voltage power supply.

[0023] Please continue reading. Figure 1 The primary winding of the flyback primary circuit is connected to the high-voltage power supply HV1+, which is used to input high-voltage power into the flyback power supply circuit so that the flyback power supply circuit can output low-voltage power in the flyback secondary circuit according to the high-voltage power input from the flyback primary circuit. The high-voltage power supply HV1+ can be obtained through voltage division on the high-voltage bus.

[0024] The flyback secondary circuit includes a secondary winding, a switching unit 210, an energy buffer unit 220, and a charging unit 230. The first terminal of the switching unit 210 is connected to the secondary winding, and the second terminal is connected to the energy buffer unit 220. The switching unit 210 rectifies the voltage signal output from the secondary winding through unidirectional conduction control, ensuring that the low-voltage power supply voltage output from the secondary winding provides a stable voltage signal to the load after rectification. The unidirectional conduction capability of the switching unit 210 also prevents energy from the energy buffer unit 220 from flowing into the secondary winding, which could damage the transformer.

[0025] The energy buffer unit 220 is connected to the second end of the switching unit 210. When the switching unit 210 is turned on, the energy buffer unit 220 is charged according to the low-voltage power supply output of the secondary winding. When the switching unit 210 is not turned on, the energy buffer unit 220 can continue to supply power to the load according to the stored power.

[0026] At the instant the flyback power supply circuit starts up, that is, when the high-voltage power supply is input to the primary winding, the switching unit 210 of the flyback secondary circuit undergoes reverse recovery, causing current to flow from the voltage output terminal of the flyback power supply circuit to the secondary winding, thus subjecting the switching unit 210 to reverse voltage stress. The junction capacitance in the switching unit 210 and the secondary winding also generate LC resonance, leading to a further increase in the reverse recovery current. At this time, the output voltage is low, and the energy buffer unit 220 stores very little charge, insufficient to stabilize the voltage fluctuations caused by the resonant current in the flyback secondary circuit. Simultaneously, because the output voltage is very low, resonance also causes a negative value at the output voltage terminal, causing current to flow from the first ground terminal through the resistor and capacitor to the output voltage terminal, further increasing the resonant current and resulting in even greater reverse voltage stress on the switching unit 210.

[0027] As can be seen from the above analysis, in the flyback power supply circuit of this application embodiment, the large voltage stress borne by the switching unit 210 is mainly due to the negative voltage formed at the power output terminal. The main reason for the negative voltage is the resonance between the junction capacitance of the switching unit 210 and the secondary winding. The amount of charge stored in the energy buffer unit 220 is related to the output voltage at the voltage output terminal. Since the flyback power supply circuit has just started, the output voltage at the power output terminal is relatively small, and the amount of charge stored in the energy buffer unit 220 is also relatively small, which cannot compensate for the resonant current, resulting in an increase in the resonant current and the formation of negative voltage. Therefore, in this application embodiment, the charging unit 230 is connected to the energy buffer unit 220. Before the flyback primary circuit is connected to the high-voltage power supply, the energy buffer unit 220 is charged through the charging unit 230, so that the energy buffer unit 220 can store enough charge through charging, and has sufficient voltage regulation capability when the switching unit 210 generates a resonant current, thus avoiding voltage fluctuations when the flyback power supply circuit starts.

[0028] This embodiment of the application includes a charging unit 230 in the flyback secondary circuit of the flyback power supply circuit. Before the flyback power supply circuit is connected to the high-voltage power supply, the charging unit 230 charges the energy buffer unit 220 in the flyback secondary circuit, giving the energy buffer unit 220 better voltage regulation capability. This prevents negative voltage from appearing in the flyback secondary circuit due to resonance or other reasons when the flyback power supply circuit is connected to the high-voltage power supply for startup. This embodiment of the application can reduce the voltage stress on the switching unit 210 during the startup of the flyback secondary circuit, improving the stability and reliability of the flyback power supply.

[0029] In some embodiments, the charging unit 230 includes a charging power supply, a voltage conversion circuit 231, and a first switching circuit 232. The voltage conversion circuit 231 is connected to the charging power supply, receives the voltage signal output by the charging power supply, and generates a converted voltage signal. The first switching circuit 232 is connected to both the voltage conversion circuit 231 and the energy buffer unit 220, receives the converted voltage signal, and outputs a charging voltage signal; the energy buffer unit 220 performs charging upon receiving the charging voltage signal.

[0030] Please see Figure 2 , Figure 2 This is a circuit diagram of a charging unit provided in an embodiment of this disclosure. Figure 2 As shown, the charging power supply is KL30. KL30 is a constant power line in the vehicle's electrical system, directly connected to the positive terminal of the battery. It can provide a voltage signal at any time without going through the ignition switch, even when the vehicle is off and the key is removed. Figure 2 As shown, the charging power supply is connected to the voltage conversion circuit 231. The voltage conversion circuit 231 converts the voltage signal received from the charging power supply to generate a converted voltage signal. The converted voltage signal is input to the first switching circuit 232 connected to the voltage conversion circuit 231. When the first switching circuit 232 is turned on, it outputs a charging voltage signal, and the energy buffer unit 220 charges upon receiving the charging voltage signal.

[0031] In some embodiments, please continue reading Figure 2 The voltage conversion circuit 231 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is connected to the charging power supply, and the second end of the first resistor R1 is connected to both the first switching circuit 232 and the first end of the second resistor R2. The second end of the second resistor R2 is connected to the first ground terminal DGND. In this case, the voltage conversion circuit 231 is a voltage divider circuit formed by resistors R1 and R2, and the voltage signal of the charging power supply KL30 is represented as V. KL30 After the voltage signal is divided by resistors R1 and R2, the resulting converted voltage signal can be expressed as V. KL30 *R2 / (R1+R2). When the converted voltage signal flows through the first switching circuit 232, it will generate a voltage loss signal △V, which will convert the converted voltage signal V. KL30 Subtracting the loss voltage signal ΔV flowing through the first switching circuit 232 from *R2 / (R1+R2) yields the charging voltage signal of the charging unit 230 to the energy buffer unit 220, denoted as V. KL30 *R2 / (R1+R2)-△V.

[0032] In some embodiments, the charging voltage signal output by the charging unit 230 to the energy buffer unit 220 is related to the output voltage signal of the flyback power supply circuit at the power output terminal.

[0033] Please continue reading. Figure 2 The first switching circuit 232 is a unidirectional conduction switch. Its first terminal is connected to the voltage conversion circuit 231, receiving the converted voltage signal output by the voltage conversion circuit 231. The second terminal of the first switching circuit 232 is connected to the power output terminal of the energy buffer unit 220 and the flyback power supply circuit. The output voltage signal of the flyback power supply circuit at its power output terminal is represented as V. backup Since the first switching circuit 232 is unidirectional, the charging voltage signal output by the first switching circuit 232 is greater than V. backup At this time, the first switching circuit 232 is turned on, and the charging unit 230 charges the energy buffer unit 220. This is in turn due to the output voltage signal V at the power output terminal. backup As the voltage increases, the charging voltage signal of the charging unit 230 charging the energy buffer unit 220 becomes less than the output voltage signal V at the power output terminal. backup When the output voltage signal of the flyback power supply circuit is stable and normal, the first switching circuit 232 is turned off, the charging unit 230 no longer charges the energy buffer unit 220, and the charging unit 230 exits.

[0034] After the charging unit 230 exits charging, if the flyback power supply unit short-circuits to ground, causing the first switching circuit 232 of the charging unit 230 to conduct, due to the voltage division effect of the voltage conversion circuit 231, assuming the maximum voltage of the charging power supply is 16V, the power consumption generated by the charging unit 230 is P=U*U / R=(8-0.7)* (8-0.7) / 1000 = 0.053W, which is very low.

[0035] In this embodiment, the charging unit 230 charges the energy buffer unit 220 before the flyback power supply circuit starts up. This increases the storage capacity of the energy buffer unit 220, improving its stability and preventing negative voltage from being generated in the flyback secondary circuit due to harmonic oscillations. This enhances the stability and reliability of the flyback power supply circuit. After the flyback power supply circuit starts up and outputs a normal power supply voltage, the charging unit 230 exits normally without affecting the normal operation of the flyback power supply circuit or incurring additional losses.

[0036] In some embodiments, the first switching circuit 232 includes a first diode, the cathode of which is connected to the energy buffer unit 220, and the anode of which is connected to the voltage conversion circuit 231.

[0037] Please continue reading. Figure 2The first switching circuit 232 is a unidirectional switching circuit that conducts power from the voltage conversion circuit 231 to the energy buffer unit 220. Taking the first diode included in the first switching circuit 232 as diode D7 as an example, when the converted voltage signal output by the voltage conversion circuit 231 minus the voltage drop of the first diode is greater than the output voltage signal of the flyback power supply circuit at the power output terminal, the first diode is turned on; when the converted voltage signal output by the voltage conversion circuit 231 minus the voltage drop of the first diode is less than or equal to the output voltage signal of the flyback power supply circuit at the power output terminal, the first diode is turned off.

[0038] Please see Figure 3 , Figure 3 This is a circuit diagram of another charging unit provided in an embodiment of this disclosure. In some embodiments, such as Figure 3 As shown, the voltage conversion circuit 231 includes a third resistor and a first Zener diode. The first end of the third resistor is connected to the charging power supply, the second end of the third resistor is connected to the first switching circuit 232 and the cathode of the first Zener diode, and the anode of the first Zener diode is connected to the first ground terminal.

[0039] The charging power supply KL30 of the charging unit 230 is externally powered, and there may be a voltage threshold greater than 16V. In this case, a first Zener diode can be set in the voltage conversion circuit 231 to ensure the stability of the charging voltage signal output by the charging unit 230.

[0040] Please continue reading. Figure 3 In the case where the voltage conversion circuit 231 includes a first Zener diode, the voltage conversion circuit 231 includes a third resistor R3 and a first Zener diode D8. The first end of the resistor R3 is connected to the charging power supply KL30, the second end of the resistor R3 is connected to the first switching circuit 232 and the cathode of the first Zener diode D8, and the anode of the first Zener diode D8 is connected to the first ground terminal DGND.

[0041] In some embodiments, the switching unit 210 includes at least one diode, the cathode of which is connected to the secondary winding, and the anode of which is connected to the power output terminal and the energy buffer unit 220, respectively.

[0042] Please continue reading. Figure 1 The switching unit 210 is a unidirectional conducting unit, transmitting the voltage generated by the secondary winding to the power output terminal and the energy buffer unit 220. For example... Figure 1 As shown, the switching unit 210 can be a diode D1 or multiple diodes D1 connected in parallel. When the switching unit 210 is a diode, the cathode of the diode is connected to the secondary winding, and the anode is connected to the power output terminal and the energy buffer unit 220.

[0043] Figure 4This is a schematic diagram of another flyback power supply circuit provided in an embodiment of this disclosure. In some embodiments, such as Figure 4 As shown, the flyback primary-side circuit also includes a second switching circuit. The control terminal of the second switching circuit is connected to the power management chip, the first terminal of the second switching circuit is connected to the primary winding, and the second terminal of the second switching circuit is connected to the second ground terminal.

[0044] Please continue reading. Figure 4 The flyback primary-side circuit includes a second switching circuit that can be a MOSFET Q1. The first terminal of MOSFET Q1 is connected to the primary winding, and the second terminal is connected to the second ground terminal P1_DC_AL-. The primary winding is connected to a high-voltage power supply. The control terminal of MOSFET Q1 is connected to the MOS_G port of the power management chip, and is turned on or off under the drive of the power management chip.

[0045] When MOSFET Q1 is turned on according to the control signal at the control terminal, the flyback primary circuit stores energy from the high-voltage power supply. The high-voltage power supply flows into the primary winding, and the current in the primary winding continuously increases with the input of the high-voltage power supply, thus storing energy in the transformer. When MOSFET Q1 is turned off according to the control signal at the control terminal, the flyback primary circuit turns off, the flyback secondary circuit turns on, and outputs a low-voltage power supply at the power output terminal. The flyback secondary circuit also charges the energy buffer unit 220 according to the low-voltage power supply output. When MOSFET Q1 turns on again and the flyback secondary circuit turns off, the power output terminal can continue to supply power through the energy buffer unit 220.

[0046] Figure 5 This is a schematic diagram of a feedback circuit provided in an embodiment of this disclosure. In some embodiments, such as Figure 5 As shown, the flyback power supply circuit also includes a feedback circuit, which comprises an optocoupler primary circuit connected to the output of the flyback secondary circuit, and an optocoupler secondary circuit connected to the power management chip. The optocoupler primary circuit conducts when the output voltage of the flyback secondary circuit is greater than a preset voltage, so that the optocoupler secondary circuit sends a feedback signal to the power management chip when the optocoupler primary circuit is conducting.

[0047] The power management chip, as described in this embodiment, is used to manage the flyback power supply circuit. The second switching circuit of the flyback primary-side circuit is turned on according to the control signal output by the power management chip. Please refer to [link to relevant documentation]. Figure 5 In this embodiment of the application, the flyback power supply circuit provides feedback on the voltage at the power output terminal of the flyback power supply circuit through a feedback circuit. When the output voltage signal at the power output terminal is greater than a preset voltage, a feedback signal is sent to the power management chip so that the power management chip can adjust the control strategy in a timely manner according to the feedback signal.

[0048] In some embodiments, the primary-side circuit of the optocoupler includes a light-emitting element and a third switching circuit. The control terminal of the third switching circuit is used to connect to the power output terminal, the first terminal of the third switching circuit is connected to the light-emitting element, and the second terminal of the third switching circuit is connected to the first ground terminal.

[0049] Please continue reading. Figure 5 The feedback circuit is an optocoupler feedback circuit. The primary power supply of the optocoupler includes a light-emitting element, which is used to activate the photosensitive element of the secondary circuit of the optocoupler by emitting light. For example, the light-emitting element can be a light-emitting diode. The light-emitting element is connected to the first terminal of the third switching circuit, which is a precision switch. The control terminal of the third switching circuit is used to connect to the power output terminal, and the third switching circuit determines the conduction state according to the voltage output by the power output terminal.

[0050] For example, such as Figure 5 As shown, the third switching unit is TL431, denoted as U2. Pin 1 of the TL431 is connected to the light-emitting element, pin 3 is connected to the first ground terminal, and pin 2 is used to connect to the power output terminal KL30 Backup. Figure 5 As shown, pin 2 of the TL431 is connected to the power output terminal through a voltage divider circuit formed by resistors R6 and R7. When the voltage output from the power output terminal exceeds the preset voltage after being divided by R6 and R7, the voltage at pin 2 of the TL431 exceeds 2.5V, the TL431 conducts, and the LED emits light.

[0051] It should be noted that the power output terminal in this embodiment is represented as KL30 Backup in the circuit. The charging unit 230 is connected to the power output terminal KL30 Backup, which can be understood as being connected to the power output terminal of the flyback secondary circuit or the power output terminal of the optocoupler primary circuit. The two power output terminals are actually the same port.

[0052] In some embodiments, the optocoupler secondary circuit includes a photosensitive switch element, a first end of which is connected to a power management chip, and a second end of which is connected to a second ground terminal. The photosensitive switch element generates a feedback signal at the first end according to the conduction state of the light-emitting element.

[0053] Please continue reading. Figure 5 The optocoupler secondary circuit includes a photosensitive switch element. The first terminal of the photosensitive switch element is connected to the COMP port of the power management chip, and the second terminal is connected to the second ground terminal P1_DC_AL-. When the optocoupler primary circuit is turned on, causing the light-emitting element to emit light, the photosensitive switch element in the optocoupler secondary circuit also turns on along with the light-emitting element. As the photosensitive switch element turns on, the voltage at its first terminal decreases, and consequently, the voltage at the COMP port of the power management chip also decreases.

[0054] Figure 6 This is a connection diagram of a power management chip provided in an embodiment of this disclosure. Figure 6 As shown, port 1 of the power management chip is connected to the feedback signal COMP, and output port OUT6 is connected to the control terminal of the second switching circuit 110 of the flyback primary-side circuit, used to output the control signal MOS_G to control the conduction state of the second switching circuit 110. The power management chip outputs the gate control signal MOS_G according to the feedback signal COMP. When the feedback signal COMP decreases, the power management chip reduces the duty cycle of the gate control signal MOS_G, thereby reducing the voltage output at the power output terminal of the flyback power supply circuit, realizing feedback control of the flyback power supply circuit.

[0055] Please continue reading. Figure 5 When a negative voltage appears at the power output terminal of the flyback power supply circuit due to resonance or other reasons, the LED in the primary side of the optocoupler in the feedback circuit is cut off, and the secondary side of the optocoupler is not conducting. At this time, the instantaneous level of the feedback signal COMP is pulled up to 5V by the reference voltage of the primary side of the optocoupler. Since the feedback signal COMP is an adjustment signal, the higher the voltage of the feedback signal COMP, the larger the duty cycle of the primary side of the flyback circuit, and therefore the larger the current of the primary side of the flyback circuit. The current of the primary side of the flyback circuit induces a larger reverse voltage in the secondary side of the flyback circuit through the leakage inductance of the transformer, which leads to excessive reverse stress on the diode D1 in the switching unit 210. In this embodiment, a charging unit 230 is provided in the secondary side of the flyback circuit to charge the energy buffer unit 220 before the flyback power supply circuit starts, avoiding the negative voltage formed at the power output terminal at the moment of start-up of the flyback power supply circuit, reducing the negative voltage generated by harmonic oscillation in the secondary side of the flyback circuit, and improving the stability and reliability of the flyback power supply circuit.

[0056] The charging unit 230 in this embodiment can exit normally after the flyback power supply circuit outputs a stable voltage, without affecting the normal operation of the flyback power supply circuit, and will not generate additional power consumption during the operation of the flyback power supply circuit.

[0057] In this embodiment, a charging unit 230 can be set at the connection point between the power output terminal of the feedback power supply circuit and the energy buffer unit 220 to improve the stability and reliability of the flyback power supply circuit. This does not require changing the original structure of the flyback power supply circuit, is simple to operate, has low cost, and good applicability.

[0058] Secondly, embodiments of this application also provide a power supply, which includes a power management chip and a flyback power supply circuit as described in the above embodiments.

[0059] It should be understood that the above power supply is an embodiment corresponding to the above flyback power supply circuit. For a detailed description of the structure, operation mode and beneficial effects of each module in the power supply, please refer to the embodiment of the above flyback power supply circuit, which will not be repeated here.

[0060] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0061] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0062] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0063] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A flyback power supply circuit, characterized by comprising: include: The flyback primary-side circuit and the flyback secondary-side circuit, wherein: The flyback primary circuit includes a primary winding, which is connected to a high-voltage power supply. The flyback secondary circuit includes a secondary winding, a switching unit (210), an energy buffer unit (220), and a charging unit (230). The switching unit (210) is connected to the secondary winding. The energy buffer unit (220) is connected to the switching unit (210), the charging unit (230), and the power output terminal, respectively. The charging unit (230) is used to charge the energy buffer unit (220) before the flyback primary circuit is connected to the high-voltage power supply.

2. The circuit of claim 1, wherein, The charging unit (230) includes: Charging power supply; A voltage conversion circuit (231) is connected to the charging power supply. The voltage conversion circuit (231) receives the voltage signal output by the charging power supply and generates a converted voltage signal. The first switching circuit (232) is connected to the voltage conversion circuit (231) and the energy buffer unit (220) respectively. The first switching circuit (232) receives the conversion voltage signal and outputs the charging voltage signal. The energy buffer unit (220) charges when it receives the charging voltage signal.

3. The circuit according to claim 2, characterized in that, The charging voltage signal output by the charging unit (230) to the energy buffer unit (220) is related to the output voltage signal of the flyback power supply circuit at the power output terminal.

4. The circuit of claim 2 or 3, characterized in that, The first switching circuit (232) includes a first diode, the cathode of which is connected to the energy buffer unit (220), and the anode of which is connected to the voltage conversion circuit (231).

5. The circuit of claim 2, wherein, The voltage conversion circuit (231) includes: a first resistor and a second resistor, the first end of the first resistor is connected to the charging power supply, the second end of the first resistor is connected to the first switching circuit (232) and the first end of the second resistor respectively, and the second end of the second resistor is connected to the first ground terminal.

6. The circuit of claim 2, wherein, The voltage conversion circuit (231) includes a third resistor and a first Zener diode. The first end of the third resistor is connected to the charging power supply, and the second end of the third resistor is connected to the first switching circuit (232) and the cathode of the first Zener diode, respectively. The anode of the first Zener diode is connected to the first ground terminal.

7. The circuit of claim 1, wherein The switching unit (210) includes at least one diode, the cathode of which is connected to the secondary winding, and the anode of which is connected to the power output terminal and the energy buffer unit (220).

8. The circuit of claim 1, wherein, The flyback primary-side circuit also includes: The second switching circuit has a control terminal connected to the power management chip, a first terminal connected to the primary winding, and a second terminal connected to the second ground terminal.

9. The circuit of claim 8, wherein, The flyback power supply circuit further includes: a feedback circuit, the feedback circuit comprising an optocoupler primary circuit connected to the output terminal of the flyback secondary circuit, and an optocoupler secondary circuit connected to the power management chip, wherein: The primary-side circuit of the optocoupler is turned on when the voltage at the power output terminal is greater than a preset voltage, so that the secondary-side circuit of the optocoupler sends a feedback signal to the power management chip when the primary-side circuit of the optocoupler is turned on.

10. The circuit of claim 9, wherein, The optocoupler primary-side circuit includes: Light-emitting elements; The third switching circuit has a control terminal for connecting to the power output terminal, a first terminal for connecting to the light-emitting element, and a second terminal for connecting to the first ground terminal.

11. The circuit of claim 10, wherein, The optocoupler secondary circuit includes a photosensitive switch element, the first end of which is connected to the power management chip, and the second end of which is connected to a second ground terminal. The photosensitive switch element generates the feedback signal at the first end according to the conduction state of the light-emitting element.

12. A power supply, characterized in that, include: A power management chip, and a flyback power supply circuit as described in any one of claims 1 to 11.

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