Power supply circuit and switching power supply

Abstract

The utility model discloses a power supply circuit and a switching power supply, and relates to the technical field of switching power supplies. The power supply circuit comprises a PFC power supply circuit, an LLC power supply circuit and a switching circuit. The PFC power supply circuit is used for outputting a first power supply, and the LLC power supply circuit is controlled by the control circuit of the switching power supply to output / stop outputting a second power supply. And when the LLC chip triggers protection to be locked, the LLC power supply circuit stops outputting the second power supply. The switching circuit detects that the LLC power supply circuit does not output power and controls the circuit between the PFC power supply circuit and the LLC chip to be conducted, the LLC chip can receive the first power supply and recover the starting state, and the LLC power supply circuit outputs the second power supply again. The switching circuit detects power output and controls the circuit between the PFC power supply circuit and the LLC chip to be switched off. According to the utility model, the problem that the LLC chip cannot be self-recovered after the trigger protection is locked is solved.

Description

Technical Field

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

[0002] In current switching power supply designs, the combination of PFC (Power Factor Correction) chips and LLC (Resonant Converter Circuit) chips is widely used in applications with high power density requirements. PFC chips improve the power factor by refining the input current waveform, while LLC chips achieve efficient DC-DC conversion and reduce switching losses.

[0003] However, LLC chips trigger a protection mechanism and lock up when encountering abnormal conditions such as short circuits, overcurrent, or overvoltage. In this case, the LLC chip can only resume normal operation after power is restored or the supply voltage drops to a preset threshold. While this protection mechanism effectively prevents circuit damage, in special applications such as uninterruptible power supplies (UPS) and communication base stations, the locking up of the LLC chip may lead to system interruption, resulting in economic losses and safety risks. Utility Model Content

[0004] The main purpose of this utility model is to provide a power supply circuit that aims to solve the problem that LLC chips in existing switching power supplies cannot automatically resume normal operation after the protection lock-up mechanism is triggered.

[0005] To achieve the above objectives, the power supply circuit proposed in this utility model is applied to a switching power supply. The switching power supply includes a PFC chip, an LLC chip, and a control circuit. The control circuit is connected to the LLC chip and is used to output corresponding power control signals according to the startup state of the LLC chip. The power supply circuit includes:

[0006] The PFC power supply circuit has its power output terminal connected to the power supply terminal of the PFC chip, and the PFC power supply circuit is used to output the first power supply.

[0007] LLC power supply circuit, wherein the power output terminal of the LLC power supply circuit is connected to the power supply terminal of the LLC chip, and the controlled terminal of the LLC power supply circuit is connected to the control terminal of the control circuit, and the LLC power supply circuit is used to output / stop outputting a second power supply according to the power control signal;

[0008] A switching circuit, wherein the power detection terminal of the switching circuit is connected to the LLC power supply circuit, the first terminal of the switching circuit is connected to the power output terminal of the PFC power supply circuit, and the second terminal of the switching circuit is connected to the power supply terminal of the LLC chip.

[0009] The switching circuit is used to control the circuit between the power output terminal of the PFC power circuit and the power terminal of the LLC chip to be turned off when the LLC power circuit outputs the second power supply, and to control the circuit between the power output terminal of the PFC power circuit and the power terminal of the LLC chip to be turned on when the LLC power circuit stops outputting the second power supply.

[0010] In one embodiment, the switching circuit includes a first capacitor, a first switching transistor, a second switching transistor, and a first resistor. The positive terminal of the first capacitor, the controlled terminal of the first switching transistor, and one end of the first resistor are connected to the power detection terminal of the switching circuit. The negative terminal of the first capacitor, the first terminal of the first switching transistor, and the other end of the first resistor are grounded. The second terminal of the first switching transistor, the controlled terminal of the second switching transistor, and the first terminal of the second switching transistor are connected to the power output terminal of the PFC power supply circuit. The second terminal of the second switching transistor is connected to the power supply terminal of the LLC chip.

[0011] In one embodiment, the switching circuit further includes a second resistor and a Zener diode. One end of the second resistor is connected to a first end of the second switching diode, and the other end of the second resistor, the controlled end of the second switching diode, and the second end of the first switching diode are connected to the cathode of the Zener diode. The anode of the Zener diode is grounded.

[0012] In one embodiment, the switching circuit further includes a first diode and a third resistor. One end of the third resistor is connected to the controlled terminal of the first switching transistor, and the other end of the third resistor, the positive terminal of the first capacitor, and the negative terminal of the first diode are connected. The positive terminal of the first diode is connected to the power detection terminal of the switching circuit.

[0013] In one embodiment, the first switching transistor is an NPN transistor, the base of the NPN transistor is the controlled terminal of the first switching transistor, the emitter of the NPN transistor is the first terminal of the first switching transistor, and the collector of the NPN transistor is the second terminal of the first switching transistor.

[0014] In one embodiment, the second switching transistor is an NPN transistor, the base of the NPN transistor is the controlled terminal of the second switching transistor, the collector of the NPN transistor is the first terminal of the second switching transistor, and the emitter of the NPN transistor is the second terminal of the second switching transistor.

[0015] In one embodiment, the switching circuit further includes a second diode, the anode of which is connected to the second terminal of the second switching transistor, and the cathode of which is connected to the power supply terminal of the LLC chip.

[0016] In one embodiment, the PFC power supply circuit includes a first transformer, a third diode, a second capacitor, and a third capacitor. The first end of the auxiliary winding of the first transformer is connected to the positive terminal of the third diode. The negative terminal of the third diode, one end of the second capacitor, and the positive terminal of the third capacitor are connected to the power output terminal of the PFC power supply circuit. The second end of the auxiliary winding of the first transformer, the other end of the second capacitor, and the negative terminal of the third capacitor are grounded.

[0017] In one embodiment, the LLC power supply circuit includes a second transformer, a fourth diode, a fourth capacitor, and a fifth capacitor; the adjustment terminal of the second transformer is connected to the control terminal of the control circuit; the first terminal of the auxiliary winding of the second transformer and the positive terminal of the fourth diode are connected to the power detection terminal of the switching circuit; the negative terminal of the fourth diode, one end of the fourth capacitor, and the positive terminal of the fifth capacitor are connected to the power output terminal of the LLC power supply circuit; the second terminal of the auxiliary winding of the second transformer and the other end of the fourth capacitor are grounded to the negative terminal of the fifth capacitor.

[0018] This utility model also proposes a switching power supply, including the power supply circuit described above.

[0019] This utility model provides a power supply circuit for a switching power supply, which includes a PFC chip, an LLC chip, and a control circuit. The control circuit is connected to the LLC chip and outputs corresponding power control signals based on the LLC chip's startup state. The power supply circuit comprises a PFC power circuit, an LLC power circuit, and a switching circuit. The PFC power circuit outputs a first power supply to the PFC chip. If the control circuit detects that the LLC chip is in a normal startup state, it outputs a corresponding power control signal to control the LLC power circuit to output a second power supply to the LLC chip. When the LLC chip experiences a short circuit, overcurrent, or overvoltage and becomes locked (i.e., in a locked-up protection state), the control circuit detects that the LLC chip is in an abnormal startup state and outputs a corresponding power control signal to control the LLC power circuit to stop outputting the second power supply. At this time, the switching circuit detects that the LLC power circuit has stopped outputting the second power supply and controls the circuit between the power output terminal of the PFC power circuit and the power supply terminal of the LLC chip to conduct, allowing the LLC chip to receive the first power supply output from the PFC power circuit, thus regaining power and restoring normal startup. At this time, the control circuit detects that the LLC chip is in a normal startup state and outputs a corresponding power control signal to control the LLC power supply circuit to output a second power supply to power the LLC chip again. Simultaneously, the switching circuit detects that the LLC power supply circuit is outputting the second power supply and controls the circuit between the power output terminal of the PFC power supply circuit and the power supply terminal of the LLC chip to be turned off. The LLC chip is then powered again through the second power supply of the LLC power supply circuit. Thus, this invention allows the LLC chip to regain power and automatically resume normal operation after the LLC chip triggers the protection lock-up mechanism, solving the problem in existing switching power supplies where the LLC chip cannot automatically resume normal operation after the protection lock-up mechanism is triggered. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 A schematic diagram of an embodiment of the power supply circuit provided by this utility model;

[0022] Figure 2 An electronic circuit diagram of an embodiment of the power supply circuit provided by this utility model.

[0023] Explanation of icon numbers:

[0024]

[0025] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0028] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0029] In existing technologies, LLC chips trigger a protection mechanism and lock up when encountering abnormal conditions such as short circuits, overcurrent, or overvoltage. At this point, the LLC chip can only resume normal operation after power is restored or the supply voltage drops to a preset threshold. While this protection mechanism effectively prevents circuit damage, in special applications such as uninterruptible power supplies (UPS) and communication base stations, the locking up of the LLC chip may lead to system interruptions, resulting in economic losses and safety risks.

[0030] This utility model proposes a power supply circuit.

[0031] Please see Figure 1 In one embodiment of this utility model, the power supply circuit is applied to a switching power supply, which includes a PFC chip, an LLC chip, and a control circuit. The control circuit is connected to the LLC chip and is used to output corresponding power control signals according to the startup state of the LLC chip.

[0032] The power supply circuit includes:

[0033] PFC power supply circuit 01, the power output terminal of PFC power supply circuit 01 is connected to the power supply terminal of PFC chip, PFC power supply circuit 01 is used to output the first power supply.

[0034] It should be noted that the PFC power supply circuit 01 may include a power input circuit and a rectification and filtering circuit. The power input circuit can input a first power supply, which is then rectified and filtered by the rectification and filtering circuit before being output. It should also be noted that the transformer of the switching power supply may include a main winding, a secondary winding, and an auxiliary winding. When the high-frequency switch is turned on, the current in the main winding establishes a magnetic field in the transformer core, storing energy. When the switch is turned off, the energy stored in the magnetic field is released through the secondary winding to supply the load. The auxiliary winding can utilize the magnetic flux generated by the main winding to generate an induced voltage to power the control system. In this embodiment, the power input circuit may include a first transformer T1, from which the first power supply is induced. The rectification and filtering circuit may include components such as diodes and capacitors to rectify and filter the power supply before output. In this embodiment, the PFC power supply circuit 01 can output the first power supply to power the PFC chip.

[0035] LLC power supply circuit 02: The power output terminal of LLC power supply circuit 02 is connected to the power supply terminal of LLC chip, and the controlled terminal of LLC power supply circuit 02 is connected to the control terminal of control circuit. LLC power supply circuit 02 is used to output / stop outputting a second power supply according to the power control signal.

[0036] It should be noted that in a switching power supply, the coordinated operation of the PFC chip and LLC chip is crucial to ensuring stable power output. The PFC chip is responsible for power factor correction of the input power supply before outputting the power to the LLC chip. The LLC chip performs voltage transformation and other processing on the received power before outputting it to the load. The output voltage Vbulk of the PFC chip has a certain rise delay during startup. Therefore, in this embodiment, the control circuit can also be connected to the controlled terminal of the PFC power circuit 01. It can first control the PFC power circuit 01 to output the first power supply. After a preset time, i.e., after the PFC chip's output voltage Vbulk increases to the preset required voltage and remains stable, it then outputs a power control signal to control the LLC power circuit 02 to output the second power supply.

[0037] It should be noted that the LLC power supply circuit 02 may include components such as transformers for power transformation and output, as well as components such as diodes and capacitors for power rectification and filtering. In this embodiment, after the PFC chip starts up and outputs a stable output voltage Vbulk, the control circuit controls the LLC power supply circuit 02 to output a second power supply to power the LLC chip. The power output can be set to be provided by the LLC power supply circuit 02 after a preset time since the PFC chip starts up. When the LLC chip experiences a short circuit, overcurrent, or overvoltage and locks up, the startup state becomes abnormal. The control circuit can detect this abnormality and output a corresponding power control signal to stop the LLC power supply circuit 02 from outputting the second power supply. At this time, the LLC chip is in a locked-up protection state. Only when the LLC chip is re-energized and the startup state returns to normal will the control circuit control the LLC power supply circuit 02 to resume outputting the second power supply to power the LLC chip.

[0038] Switching circuit 03, the power detection terminal of switching circuit 03 is connected to LLC power circuit 02, the first terminal of switching circuit 03 is connected to the power output terminal of PFC power circuit 01, and the second terminal of switching circuit 03 is connected to the power terminal of LLC chip.

[0039] The switching circuit 03 is used to control the circuit between the power output terminal of the PFC power circuit 01 and the power terminal of the LLC chip to turn off when the LLC power circuit 02 outputs the second power supply, and to control the circuit between the power output terminal of the PFC power circuit 01 and the power terminal of the LLC chip to turn on when the LLC power circuit 02 stops outputting the second power supply.

[0040] It should be noted that in high-power switching power supplies, the PFC chip and LLC chip need to be powered independently, for example through their respective transformers, to ensure their independence and stability.

[0041] It should be noted that the switching circuit 03 may include a capacitor and a switching transistor. Based on the charging and discharging characteristics of the capacitor, the controlled terminal voltage of the switching transistor is adjusted to control the switching transistor's on / off state, thereby controlling the conduction state of the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip.

[0042] In this embodiment, the PFC power supply circuit 01 outputs a first power supply to power the PFC chip. After the PFC chip stabilizes its output voltage, if the control circuit detects that the LLC chip is in a normal startup state, it outputs a corresponding power control signal to control the LLC power supply circuit 02 to output a second power supply to power the LLC chip. When the LLC chip experiences a short circuit, overcurrent, or overvoltage and becomes locked (i.e., in a locked-up protection state), the control circuit can detect that the LLC chip is in an abnormal startup state and outputs a corresponding power control signal to control the LLC power supply circuit 02 to stop outputting the second power supply. At this time, the switching circuit 03 detects that the LLC power supply circuit 02 has stopped outputting the second power supply and controls the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip to be connected. The LLC chip can then receive the first power supply output by the PFC power supply circuit 01, i.e., it is re-energized, and the startup state returns to normal. At this time, the control circuit detects that the LLC chip is in a normal startup state and outputs a corresponding power control signal to control the LLC power supply circuit 02 to re-output the second power supply to power the LLC chip. At this time, the switching circuit 03 detects that the LLC power supply circuit 02 is outputting a second power supply, and then controls the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip to be turned off. The LLC chip is then powered again by the second power supply output by the LLC power supply circuit 02. Thus, in this embodiment, after the LLC chip triggers the protection lock-up mechanism, the LLC chip can be powered back up and automatically resume normal operation, solving the problem in existing switching power supplies where the LLC chip cannot automatically resume normal operation after the protection lock-up mechanism is triggered.

[0043] In this invention, the PFC power supply circuit 01 outputs a first power supply to power the PFC chip. If the control circuit detects that the LLC chip is in a normal startup state, it outputs a corresponding power control signal to control the LLC power supply circuit 02 to output a second power supply to power the LLC chip. When the LLC chip experiences a short circuit, overcurrent, or overvoltage and becomes locked (i.e., in a locked-up protection state), the control circuit can detect that the LLC chip is in an abnormal startup state and outputs a corresponding power control signal to control the LLC power supply circuit 02 to stop outputting the second power supply. At this time, the switching circuit 03 detects that the LLC power supply circuit 02 has stopped outputting the second power supply and controls the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip to be connected. The LLC chip can then receive the first power supply output by the PFC power supply circuit 01, i.e., it is re-energized, and the startup state returns to normal. At this time, the control circuit detects that the LLC chip is in a normal startup state and outputs a corresponding power control signal to control the LLC power supply circuit 02 to re-output the second power supply to power the LLC chip. At this time, the switching circuit 03 detects that the LLC power supply circuit 02 is outputting a second power supply, and then controls the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip to be turned off. The LLC chip is then powered again by the second power supply output by the LLC power supply circuit 02. Thus, this invention allows the LLC chip to regain power and automatically resume normal operation after the protection lock-up mechanism is triggered, solving the problem in existing switching power supplies where the LLC chip cannot automatically resume normal operation after the protection lock-up mechanism is triggered.

[0044] Please see Figure 2 In one embodiment of this utility model, the switching circuit 03 includes a first capacitor C1, a first switching transistor Q1, a second switching transistor Q2, and a first resistor R1. The positive terminal of the first capacitor C1, the controlled terminal of the first switching transistor Q1, and one end of the first resistor R1 are connected to the power detection terminal of the switching circuit 03. The negative terminal of the first capacitor C1, the first terminal of the first switching transistor Q1, and the other end of the first resistor R1 are grounded. The second terminal of the first switching transistor Q1, the controlled terminal of the second switching transistor Q2, and the first terminal of the second switching transistor Q2 are connected to the power output terminal of the PFC power circuit 01. The second terminal of the second switching transistor Q2 is connected to the power supply terminal of the LLC chip.

[0045] In this embodiment, the first capacitor C1 can specifically be an electrolytic capacitor. When the LLC power supply circuit 02 outputs the second power supply, the first capacitor C1 charges, and the voltage at the controlled terminal of the first switch Q1 increases. When the voltage at the controlled terminal of the first switch Q1 is higher than its turn-on voltage, the controlled terminal of the second switch Q2 receives a low level, and the second switch Q2 is turned off. At this time, the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip is turned off. When the LLC power supply circuit 02 stops outputting the second power supply, the first capacitor C1 discharges, and the voltage at the controlled terminal of the first switch Q1 decreases. When the voltage at the controlled terminal of the first switch Q1 is lower than the cutoff voltage of the first switch Q1, the controlled terminal of the first switch Q1 receives a low level, and the controlled terminal of the second switch Q2 receives a high level, and the second switch Q2 is turned on, controlling the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip to be connected. Thus, this embodiment allows the LLC chip to receive the first power supply output from the PFC power circuit 01 to regain power and automatically resume normal operation after the protection lock-up mechanism is triggered. Furthermore, the capacitance value of the first capacitor C1 can be set according to specific needs to control the time it takes for the first capacitor C1 to discharge and drop to the cutoff voltage of the first switching transistor Q1, thereby adjusting the self-recovery startup time of the LLC chip after the protection lock-up mechanism is triggered, providing high flexibility in circuit configuration.

[0046] Please see Figure 2 In one embodiment of this utility model, the switching circuit 03 further includes a second resistor R2 and a Zener diode DW. One end of the second resistor R2 is connected to the first end of the second switching transistor Q2, and the other end of the second resistor R2, the controlled end of the second switching transistor Q2, and the second end of the first switching transistor Q1 are connected to the cathode of the Zener diode DW. The anode of the Zener diode DW is grounded.

[0047] In this embodiment, the circuit structure of the second resistor R2 and the Zener diode DW can improve the safety and stability of the circuit. The second resistor R2 can be used for current limiting, helping to protect the safe operation of the second switch Q2. The Zener diode DW can provide a stable reference voltage. When the voltage in the circuit exceeds the breakdown voltage of the Zener diode DW, the Zener diode DW conducts, releasing the excess voltage and thus protecting the circuit's switching transistors and other components from damage due to excessive voltage. Therefore, this embodiment improves the safety and stability of the switching circuit 03.

[0048] Please see Figure 2In one embodiment of this utility model, the switching circuit 03 further includes a first diode D1 and a third resistor R3. One end of the third resistor R3 and one end of the first resistor R1 are connected to the controlled terminal of the first switching transistor Q1. The other end of the third resistor R3 and the positive terminal of the first capacitor C1 are connected to the negative terminal of the first diode D1. The positive terminal of the first diode D1 is connected to the power detection terminal of the switching circuit 03.

[0049] In this embodiment, the first diode D1 rectifies the input voltage to prevent interference from reverse voltage, and the third resistor R3 limits the current to protect the safe operation of the first switching transistor Q1. Thus, this embodiment improves the safety and stability of the switching circuit 03.

[0050] Please see Figure 2 In one embodiment of this utility model, the first switching transistor Q1 is an NPN transistor, the base of the NPN transistor is the controlled terminal of the first switching transistor Q1, the emitter of the NPN transistor is the first terminal of the first switching transistor Q1, and the collector of the NPN transistor is the second terminal of the first switching transistor Q1.

[0051] Please see Figure 2 In one embodiment of this utility model, the second switch Q2 is an NPN transistor, the base of the NPN transistor is the controlled terminal of the second switch Q2, the collector of the NPN transistor is the first terminal of the second switch Q2, and the emitter of the NPN transistor is the second terminal of the second switch Q2.

[0052] It should be noted that, in one feasible embodiment of this utility model, the first switching transistor Q1 and the second switching transistor Q2 can also be transistors such as MOSFETs and IGBTs. In this embodiment, the first switching transistor Q1 and the second switching transistor Q2 are NPN transistors, which have a low base-emitter turn-on voltage (approximately 0.6V to 0.7V). This means that a smaller control signal is sufficient to turn on the transistor, reducing power loss. Moreover, NPN transistors exhibit good stability under temperature variations, with relatively small parameter changes. This allows the circuit to maintain stable performance under different environmental conditions.

[0053] Please see Figure 2 In one embodiment of this utility model, the switching circuit 03 further includes a second diode D2. The positive terminal of the second diode D2 is connected to the second terminal of the second switching transistor Q2, and the negative terminal of the second diode D2 is connected to the power supply terminal of the LLC chip.

[0054] In this embodiment, the second diode D2 can rectify the first power supply to prevent interference from reverse voltage and improve the stability of the first power supply.

[0055] Please see Figure 2In one embodiment of this utility model, the PFC power supply circuit 01 includes a first transformer T1, a third diode D3, a second capacitor C2, and a third capacitor C3. The first end of the auxiliary winding of the first transformer T1 is connected to the positive terminal of the third diode D3. The negative terminal of the third diode D3, one end of the second capacitor C2, and the positive terminal of the third capacitor C3 are connected to the power output terminal of the PFC power supply circuit 01. The second end of the auxiliary winding of the first transformer T1, the other end of the second capacitor C2, and the negative terminal of the third capacitor C3 are grounded.

[0056] In this embodiment, the third capacitor C3 can specifically be an electrolytic capacitor. The auxiliary winding of the first transformer T1 outputs the first power supply, which is rectified by the third diode D3 and filtered by the second capacitor C2 and the third capacitor C3 before being output.

[0057] Please see Figure 2 In one embodiment of this utility model, the LLC power supply circuit 02 includes a second transformer T2, a fourth diode D4, a fourth capacitor C4, and a fifth capacitor C5; the adjustment terminal (not shown in the figure) of the second transformer T2 is connected to the control terminal of the control circuit; the first end of the auxiliary winding of the second transformer T2 and the positive terminal of the fourth diode D4 are connected to the power detection terminal of the switching circuit 03; the negative terminal of the fourth diode D4, one end of the fourth capacitor C4, and the positive terminal of the fifth capacitor C5 are connected to the power output terminal of the LLC power supply circuit 02; the second end of the auxiliary winding of the second transformer T2, the other end of the fourth capacitor C4, and the negative terminal of the fifth capacitor C5 are grounded.

[0058] In this embodiment, the fifth capacitor C5 can be an electrolytic capacitor. The auxiliary winding of the second transformer T2 outputs the second power supply, which is rectified by the fourth diode D4 and filtered by the fourth capacitor C4 and the fifth capacitor C5 before being output.

[0059] To facilitate understanding of the circuit principle of this utility model, please refer to [link / reference]. Figure 2 In one embodiment of this utility model, the auxiliary winding of the first transformer T1 outputs a first power supply, which is rectified and filtered by a circuit consisting of a third diode D3, a second capacitor C2, and a third capacitor C3, and then outputs the first power supply to the PFC chip via the VCC1 terminal. After the PFC chip starts working and the output stabilizes, the auxiliary winding of the second transformer T2 outputs a second power supply, which is rectified and filtered by a circuit consisting of a fourth diode D4, a fourth capacitor C4, and a fifth capacitor C5, and then outputs the second power supply to the LLC chip via the VCC2 terminal.

[0060] When an output fault occurs, such as a short circuit, overcurrent, overvoltage, or overtemperature, the LLC chip is in a protection lockout state. At this time, the auxiliary winding of the second transformer T2 has no voltage output, and the first capacitor C1 begins to discharge through the first resistor R1 and the third resistor R3. When the voltage is less than the cutoff voltage of the first transistor, the base of the second transistor is at a high level, and the second transistor is turned on. At this time, the circuit between the power output terminal of the PFC power supply circuit 01 and the power supply terminal of the LLC chip is connected, and the LLC chip resumes startup.

[0061] After the LLC chip starts up, the auxiliary winding of the second transformer T2 outputs the second power supply normally. This second power supply is rectified and filtered by the circuit consisting of the fourth diode D4, the fourth capacitor C4, and the fifth capacitor C5, and then output to the LLC chip via VCC2. Simultaneously, the second power supply begins charging the first capacitor C1 via the first diode D1. When the voltage exceeds the turn-on voltage of the first transistor, the base of the second transistor is at a low level, and the second transistor is cut off.

[0062] Thus, the power supply circuit provided in this embodiment can realize the self-recovery function of LLC chip power supply based on the charging and discharging characteristics of capacitor, solving the problem that LLC chip in existing switching power supplies cannot automatically resume normal operation after triggering the protection lock-up mechanism.

[0063] This utility model also proposes a switching power supply, which includes a power supply circuit. The specific structure of the power supply circuit is as described in the above embodiments. Since this switching power supply adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0064] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A power supply circuit, characterized in that, This is applied to a switching power supply, which includes a PFC chip, an LLC chip, and a control circuit. The control circuit is connected to the LLC chip and is used to output a corresponding power control signal according to the startup state of the LLC chip. The power supply circuit includes: The PFC power supply circuit has its power output terminal connected to the power supply terminal of the PFC chip, and the PFC power supply circuit is used to output the first power supply. LLC power supply circuit, wherein the power output terminal of the LLC power supply circuit is connected to the power supply terminal of the LLC chip, and the controlled terminal of the LLC power supply circuit is connected to the control terminal of the control circuit, and the LLC power supply circuit is used to output / stop outputting a second power supply according to the power control signal; A switching circuit, wherein the power detection terminal of the switching circuit is connected to the LLC power supply circuit, the first terminal of the switching circuit is connected to the power output terminal of the PFC power supply circuit, and the second terminal of the switching circuit is connected to the power supply terminal of the LLC chip. The switching circuit is used to control the circuit between the power output terminal of the PFC power circuit and the power terminal of the LLC chip to be turned off when the LLC power circuit outputs the second power supply, and to control the circuit between the power output terminal of the PFC power circuit and the power terminal of the LLC chip to be turned on when the LLC power circuit stops outputting the second power supply.

2. The power supply circuit as described in claim 1, characterized in that, The switching circuit includes a first capacitor, a first switching transistor, a second switching transistor, and a first resistor. The positive terminal of the first capacitor, the controlled terminal of the first switching transistor, and one end of the first resistor are connected to the power detection terminal of the switching circuit. The negative terminal of the first capacitor, the first terminal of the first switching transistor, and the other end of the first resistor are grounded. The second terminal of the first switching transistor, the controlled terminal of the second switching transistor, and the first terminal of the second switching transistor are connected to the power output terminal of the PFC power supply circuit. The second terminal of the second switching transistor is connected to the power supply terminal of the LLC chip.

3. The power supply circuit as described in claim 2, characterized in that, The switching circuit further includes a second resistor and a Zener diode. One end of the second resistor is connected to the first end of the second switching diode, and the other end of the second resistor, the controlled end of the second switching diode, and the second end of the first switching diode are connected to the cathode of the Zener diode. The anode of the Zener diode is grounded.

4. The power supply circuit as described in claim 2, characterized in that, The switching circuit further includes a first diode and a third resistor. One end of the third resistor and one end of the first resistor are connected to the controlled terminal of the first switching transistor. The other end of the third resistor, the positive terminal of the first capacitor, and the negative terminal of the first diode are connected. The positive terminal of the first diode is connected to the power detection terminal of the switching circuit.

5. The power supply circuit as described in claim 2, characterized in that, The first switching transistor is an NPN transistor, the base of the NPN transistor is the controlled terminal of the first switching transistor, the emitter of the NPN transistor is the first terminal of the first switching transistor, and the collector of the NPN transistor is the second terminal of the first switching transistor.

6. The power supply circuit as described in claim 2, characterized in that, The second switching transistor is an NPN transistor, the base of which is the controlled terminal of the second switching transistor, the collector of which is the first terminal of the second switching transistor, and the emitter of which is the second terminal of the second switching transistor.

7. The power supply circuit as described in claim 2, characterized in that, The switching circuit further includes a second diode, the anode of which is connected to the second terminal of the second switching transistor, and the cathode of which is connected to the power supply terminal of the LLC chip.

8. The power supply circuit as described in claim 1, characterized in that, The PFC power supply circuit includes a first transformer, a third diode, a second capacitor, and a third capacitor. The first end of the auxiliary winding of the first transformer is connected to the positive terminal of the third diode. The negative terminal of the third diode, one end of the second capacitor, and the positive terminal of the third capacitor are connected to the power output terminal of the PFC power supply circuit. The second end of the auxiliary winding of the first transformer, the other end of the second capacitor, and the negative terminal of the third capacitor are grounded.

9. The power supply circuit as described in claim 1, characterized in that, The LLC power supply circuit includes a second transformer, a fourth diode, a fourth capacitor, and a fifth capacitor. The adjustment terminal of the second transformer is connected to the control terminal of the control circuit. The first terminal of the auxiliary winding of the second transformer and the positive terminal of the fourth diode are connected to the power detection terminal of the switching circuit. The negative terminal of the fourth diode, one end of the fourth capacitor, and the positive terminal of the fifth capacitor are connected to the power output terminal of the LLC power supply circuit. The second terminal of the auxiliary winding of the second transformer and the other end of the fourth capacitor are grounded to the negative terminal of the fifth capacitor.

10. A switching power supply, characterized in that, Includes the power supply circuit as described in any one of claims 1 to 9.

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