Switching power supply and control method thereof

Abstract

The invention discloses a switching power supply and a control method thereof, the switching power supply comprises a primary winding, a secondary winding, a primary circuit and a secondary circuit, the primary circuit comprises a power switch tube and a first control circuit which are arranged on the primary side, and the secondary circuit comprises a synchronous rectifier tube and a second control circuit which are arranged on the secondary side; the first control circuit is configured to perform fault detection on the primary circuit in real time after normal power supply, control the power switch tube to stop switching action when detecting that the primary power supply has a fault, and restart the primary circuit when a restart condition corresponding to the fault is reached; and the second control circuit is configured to perform fault detection on the secondary circuit in real time after normal power supply, control the synchronous rectifier tube to stop the switching action when detecting that the secondary circuit has a fault, and restart the secondary circuit when a restart condition corresponding to the fault is reached, so that effective protection on the switching power supply is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a switching power supply and a control method thereof. Background Art

[0002] In a flyback switching power supply, the control module includes a primary controller for controlling a primary-side main power tube and a secondary controller for controlling a secondary-side synchronous rectifier tube, wherein one of the primary controller and the secondary controller is the main control of the control module.

[0003] In the secondary control architecture, after the system works normally, the on and off of the main power tube on the primary side is controlled by the secondary controller. After normal power supply, the primary controller needs to control the open-loop start-up of the main power tube on the primary side for a period of time. During the open-loop start-up time, as the output voltage on the secondary side is established, the secondary controller needs to take over the drive of the main power tube. When the switching power supply has faults such as overvoltage or overcurrent, the switching power supply needs to be protected. The secondary control architecture of the prior art only relies on the protection of the primary side when encountering a fault, which obviously cannot achieve effective protection of the switching power supply.

[0004] Therefore, a new switching power supply and a control method thereof need to be proposed to achieve effective protection of the switching power supply. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a switching power supply and a control method thereof, so as to achieve effective protection of the switching power supply.

[0006] According to one aspect of the present invention, a switching power supply is provided, the switching power supply comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the primary circuit comprises a power switch tube and a first control circuit arranged on the primary side, the first control circuit controls the on and off of the power switch tube; the secondary circuit comprises a synchronous rectifier tube and a second control circuit arranged on the secondary side, the second control circuit controls the on and off of the synchronous rectifier tube, wherein:

[0007] The first control circuit is configured to perform fault detection on the primary circuit in real time after normal power supply, and when a fault is detected in the primary circuit, control the power switch tube to stop switching, and restart the primary circuit when a restart condition corresponding to the fault is met;

[0008] The second control circuit is configured to perform fault detection on the secondary circuit in real time after normal power supply. When a fault is detected in the secondary circuit, the second control circuit controls the synchronous rectifier to stop switching, and restarts the secondary circuit when the restart condition corresponding to the fault is met.

[0009] Optionally, the faults existing in the primary circuit include a first fault and a second fault; the first fault includes a first sub-fault and a second sub-fault; when the first control circuit detects that there is a first sub-fault in the primary circuit, the first control circuit uses the primary circuit exiting the first sub-fault as a restart condition for the primary circuit; when the first control circuit detects that there is a second sub-fault or a second fault in the primary circuit, the first control circuit uses waiting for a first time as a restart condition for the primary circuit.

[0010] Optionally, the second fault includes that when the open-loop control of the power switch tube reaches a second time, the first control circuit has not received a handshake signal sent by the second control circuit.

[0011] Optionally, the first control circuit is used to perform a first fault detection on the primary circuit after normal power supply, and when the first fault is detected in the primary circuit, control the power switch tube to stop switching action, and restart the primary circuit when a restart condition corresponding to the fault is met;

[0012] The first control circuit is further used to perform open-loop control on the power switch tube when it is detected that the primary circuit does not have the first fault, and to perform first fault detection and second fault detection on the primary circuit during open-loop control, and to control the power switch tube to stop switching action when it is detected that the primary circuit has the first fault or the second fault, and to restart the primary circuit when a restart condition corresponding to the fault is met;

[0013] The first control circuit is also used to stop open-loop control of the power switch tube when receiving a handshake signal sent by the second control circuit during the open-loop control of the power switch tube, and control the switching action of the power switch tube according to the handshake signal sent by the second control circuit, and perform a first fault detection on the primary circuit, and when the first fault is detected in the primary circuit, control the power switch tube to stop the switching action, and restart the primary circuit when the restart condition corresponding to the fault is met.

[0014] Optionally, the first control circuit includes:

[0015] a first control unit, configured to perform open-loop control on the power switch tube, and after receiving a handshake signal sent by the second control circuit during the open-loop control process, stop the open-loop control on the power switch tube, and control the switching action of the power switch tube according to the handshake signal sent by the second control circuit;

[0016] A detection unit, configured to output a fault signal when a fault is detected in the switching power supply, and output a reset signal when a restart condition of the fault is met;

[0017] The first control unit is used to control the power switch tube to stop switching action according to the fault signal, and to control the primary circuit to reset according to the reset signal.

[0018] Optionally, the first control circuit further includes:

[0019] The judging unit is used to judge what kind of fault exists in the primary circuit and output a first trigger signal or a second trigger signal according to the judging result.

[0020] Optionally, the detection unit includes:

[0021] A first trigger, wherein a first input terminal receives a first trigger signal, and when the first trigger signal indicates that a first sub-fault occurs in the primary circuit, the trigger outputs a first fault signal to the first control unit, and a second input terminal receives a first start signal, and when the first start signal indicates that the primary circuit exits the first sub-fault, the trigger outputs a first reset signal to the first control unit;

[0022] a second trigger, wherein a first input terminal thereof receives a second trigger signal, and when the second trigger signal indicates that a second sub-fault or a second fault occurs in the primary circuit, the second trigger outputs a second fault signal to the first control unit, and a second input terminal thereof receives a second start signal, and when the second start signal indicates that a restart condition of the second sub-fault or the second fault is met, the second trigger outputs a second reset signal to the first control unit;

[0023] The first timing unit is used to start timing after receiving the second fault signal, and output a second start signal to control the primary circuit to restart after the timing time reaches the first time.

[0024] Optionally, when the second control circuit detects that the secondary circuit has a fault, waiting for a third time is used as a restart condition of the secondary circuit;

[0025] The faults existing in the secondary circuit include a third fault and a fourth fault; the fourth fault includes a handshake failure between the secondary circuit and the primary circuit.

[0026] Optionally, the second control circuit is used to perform a third fault detection on the secondary circuit after normal power supply, and when the third fault is detected in the secondary circuit, stop the switching action of the synchronous rectifier tube, start timing, and restart the secondary circuit after the timing time reaches a third time;

[0027] The second control circuit is also used to send a handshake signal to the primary circuit when it is detected that there is no fault in the secondary circuit, and perform a fourth fault detection on the secondary circuit, and after detecting that the fourth fault exists in the secondary circuit, stop the switching action of the synchronous rectifier tube and start timing, and after the timing time reaches the third time, restart the secondary circuit, and after detecting that the fourth fault exists in the secondary circuit, continue to send a handshake signal to control the switching action of the power switch tube.

[0028] Optionally, the second control circuit includes:

[0029] A second control unit is used to control the synchronous rectifier to conduct to output a handshake signal, and control the switching action of the power switch tube through the handshake signal after the handshake is successful;

[0030] a third trigger, wherein a first input terminal of the third trigger receives a third trigger signal, and when the third trigger signal indicates that the secondary circuit has a fault, the third trigger outputs a third fault signal to the second control unit, and a second input terminal of the third trigger receives a third start signal, and when the third start signal indicates that a fault restart condition is met, the third trigger outputs a third reset signal;

[0031] The second timing unit is used to start timing after receiving the third fault signal, and output the third start signal after the timing time reaches a third time.

[0032] The second control unit is further configured to stop the switching action of the synchronous rectifier tube after receiving the third fault signal, and to control the secondary circuit to reset after receiving the third reset signal.

[0033] Optionally, the second time is shorter than the third time, and the third time is shorter than the first time.

[0034] The present invention also provides a control method for a switching power supply, the switching power supply comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the primary circuit comprises a power switch tube arranged on the primary side and a first control circuit, the first control circuit controls the on and off of the power switch tube; the control method is applied to the primary circuit, and the control method comprises:

[0035] After the first control circuit supplies power normally, it is determined whether the primary circuit has a first fault, and when the primary circuit has the first fault, the switching action of the power switch tube is stopped, and after a fault restart condition of the fault is met, the primary circuit is restarted;

[0036] When the primary circuit does not have the first fault, open-loop control is performed on the power switch tube, and it is determined whether the primary circuit has the first fault or the second fault. When the primary circuit has the first fault or the second fault, the switching action of the power switch tube is stopped, and the primary circuit is restarted after the fault restart condition of the fault is met, and

[0037] When the primary circuit does not have the first fault or the second fault, it is determined whether the primary circuit receives a handshake signal sent by the secondary circuit, and when the primary circuit receives the handshake signal sent by the secondary circuit, the open-loop control of the power switch tube is stopped, and the switching action of the power switch tube is controlled according to the handshake signal.

[0038] When controlling the switching action of the power switch tube according to the handshake signal, determine whether the primary circuit has a first fault, and when the primary circuit has the first fault, stop the switching action of the power switch tube, and restart the primary circuit after the fault restart condition of the fault is met.

[0039] Optionally, the faults existing in the primary circuit include a first fault and a second fault; the first fault includes a first sub-fault and a second sub-fault; when it is detected that the primary circuit has a first sub-fault, the primary circuit exiting the first sub-fault is used as a restart condition for the primary circuit; when it is detected that the primary circuit has a second sub-fault or a second fault, waiting for a first time is used as a restart condition for the primary circuit.

[0040] Optionally, the second fault includes that when the open-loop control of the power switch tube reaches a second time, the first control circuit has not received a handshake signal sent by the secondary circuit.

[0041] The present invention also provides a control method for a switching power supply, the switching power supply comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the secondary circuit comprises a synchronous rectifier tube arranged on the secondary side and a second control circuit, the second control circuit controls the conduction and shutdown of the synchronous rectifier tube; the control method is applied to the secondary circuit, and the control method comprises:

[0042] After the second control circuit is powered normally, it is determined whether the secondary circuit has a third fault, and when the secondary circuit has the third fault, the switching action of the synchronous rectifier is stopped, and the secondary circuit is restarted after a third time;

[0043] When the secondary circuit does not have the third fault, a handshake signal is sent to the primary circuit, and it is determined whether the secondary circuit has a fourth fault. If the secondary circuit has the fourth fault, the switching action of the synchronous rectifier is stopped, and the secondary circuit is restarted after the third time.

[0044] If the secondary circuit does not have the fourth fault, the switching action of the power switch tube and the synchronous rectifier tube is controlled according to the output voltage of the switching power supply, and at the same time, it is determined whether the secondary circuit has the third fault. When the secondary circuit has the third fault, the switching action of the synchronous rectifier tube is stopped, and the secondary circuit is restarted after the third time.

[0045] Optionally, the fourth fault includes a handshake failure between the secondary circuit and the primary circuit.

[0046] In the switching power supply and control method thereof provided by the embodiment of the present invention, the first control circuit performs fault detection on the primary circuit in real time after normal power supply, and controls the power switch tube to stop switching action after detecting a fault in the primary circuit at any time, and restarts the primary circuit after the fault restart condition of the fault is met; the second control circuit performs fault detection on the secondary circuit in real time after normal power supply, and controls the synchronous rectifier tube to stop switching action after detecting a fault in the secondary circuit at any time, and restarts the secondary circuit after the fault restart condition of the fault is met, so that effective protection of the switching power supply can be achieved regardless of whether a fault occurs in the primary circuit or the secondary circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0048] Figure 1 A schematic diagram of the structure of a switching power supply according to an embodiment of the present invention is shown;

[0049] Figure 2 shows a circuit schematic diagram of a first control circuit according to an embodiment of the present invention;

[0050] Figure 3 shows a circuit schematic diagram of a second control circuit according to an embodiment of the present invention;

[0051] Figure 4 A flow chart showing a control method for primary circuit protection applied to the implementation of the present invention is shown;

[0052] Figure 5 A flow chart of a control method for secondary circuit protection applied to the present invention is shown. DETAILED DESCRIPTION

[0053] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements or modules are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0054] It should be understood that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by programmable circuits. When an element or circuit is said to be "connected to" another element or an element or circuit is said to be "connected between" two nodes, it may be directly coupled or connected to another element or there may be an intermediate element, and the connection between the elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0055] At the same time, certain words are used in this patent specification and claims to refer to specific components. It should be understood by those skilled in the art that hardware manufacturers may use different terms to refer to the same component. This patent specification and claims do not use differences in names as a way to distinguish components, but rather use differences in components' functions as the criteria for distinction.

[0056] In addition, it should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the statement "comprise one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0057] Figure 1 A schematic structural diagram of a switching power supply according to an embodiment of the present invention is shown.

[0058] See also Figure 1 The switching power supply provided in the embodiment of the present invention is a flyback switching power supply. The switching power supply includes a transformer 100, and the transformer 100 includes a primary winding N P and the secondary winding N S The switching power supply further includes a voltage input circuit 200, a voltage output circuit 300, a primary circuit located on the primary side, and a secondary circuit located on the secondary side.

[0059] The voltage input circuit 200 includes a rectifier unit 210 and an input capacitor Ci. The rectifier unit 210 can be connected to an external power source through an AC input port to facilitate the external power source to provide electrical energy to the switching power supply. The first end of the input capacitor Ci is connected to the output end of the rectifier unit 210, and the second end of the input capacitor Ci is connected to the reference ground. The first end of the input capacitor Ci also provides an input voltage VIN. The external power source may include, but is not limited to, a power grid, a generator, a transformer, a battery, a solar panel, a wind turbine, a regenerative braking system, a hydraulic or wind generator, or any other form of device capable of providing electrical energy to the switching power supply.

[0060] The voltage output circuit 300 includes an output capacitor Co, which is connected between the output terminal of the switching power supply and the ground terminal (ie, connected to the secondary winding N S The output terminal of the switching power supply provides an output voltage Vout, and the output capacitor Co is used to stabilize the output voltage Vout. The voltage output circuit 300 supplies power to the load through the output voltage Vout. In some instances, the power of the switching power supply also passes through a filter before reaching the load. In some instances, the filter is a subcomponent of the switching power supply, an external component of the switching power supply, and / or a subcomponent of the load. In any case, the load can use filtered or unfiltered power from the switching power supply to perform a function. Figure 1 In the figure, the load is equivalently represented by the load resistance RL.

[0061] Furthermore, the switching power supply further comprises a peak absorption circuit 600, which is used to absorb the peak P The peak absorption circuit 600 includes a resistor R1, a capacitor C1 and a diode D1, wherein the resistor R1 and the capacitor C1 are connected in parallel to the primary winding N P The first end of the diode D1 is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the primary winding N P The second end of the connection. Figure 1 The figure only illustrates an example of a peak absorption circuit. Of course, other circuit structures can also be used to achieve this function.

[0062] The primary circuit includes a power switch tube Q1, a sampling resistor Rs and a first control circuit 400 (primary control circuit). The first terminal of the power switch tube Q1 is connected to the primary winding N PThe second end of the power switch tube Q1 is connected to the reference ground via the sampling resistor Rs. In a possible embodiment, the power switch tube Q1 adopts an NMOS field effect transistor, for example, a first end thereof is the drain of the NMOS field effect transistor, a second end thereof is the source of the NMOS field effect transistor, and a control end thereof is the gate of the NMOS field effect transistor. The first control circuit 400 at least includes a driving end GT1 and a sampling end CS, wherein the driving end GT1 is connected to the control end of the power switch tube Q1, and the sampling end CS is connected to the second end of the power switch tube Q1. The first control circuit 400 also includes an input end VIN and a power supply end VCC1, wherein the input end VIN is used to receive an input voltage VIN, and the power supply end VCC1 is used to power the first control circuit 400, and the power supply end VCC1 is connected to the reference ground via a capacitor C2.

[0063] The secondary circuit includes a synchronous rectifier SR and a second control circuit 500 (secondary control circuit). The first terminal of the synchronous rectifier SR is connected to the secondary winding N S The second end of the synchronous rectifier SR is connected to the ground. Here, only one connection method of the synchronous rectifier is shown, and the present application is not limited thereto. Other connection methods may also be used. The second control circuit 500 includes at least a driving terminal GT2 and a power supply terminal VCC2, wherein the power supply terminal VCC2 is connected to the output terminal of the switching power supply, that is, the secondary winding N S The first end of the synchronous rectifier SR is connected to the control end of the synchronous rectifier SR, and the driving end GT2 thereof is connected to the control end of the synchronous rectifier SR. In a possible embodiment, the synchronous rectifier SR is, for example, an NMOS field effect transistor, the first end of which is the drain of the NMOS field effect transistor, the second end of which is the source of the NMOS field effect transistor, and the control end of which is the gate of the NMOS field effect transistor.

[0064] It should be noted that Figure 1 The circuit structure in the present application is only an example, and the present application is not limited to Figure 1 The circuit structure shown in the figure may of course also include other functions in the prior art.

[0065] When the switching power supply is powered on, the first control circuit 400 charges the power supply terminal VCC1 to the first power supply voltage VCC1_ON by the input voltage VIN. The present application does not specifically limit the voltage value of the first power supply voltage VCC1_ON, for example, 9.5V. The first control circuit 400 is used to perform fault detection on the primary circuit in real time after normal power supply, that is, normal power supply of the power supply terminal VCC1. When a fault is detected in the primary circuit at any time, the power switch tube Q1 is controlled to stop the switching action, and the primary circuit is restarted when the restart condition corresponding to the fault is reached. Among them, in the present invention, the normal power supply of the first control circuit 400 refers to that the voltage of its power supply terminal VCC1 reaches the first power supply voltage VCC1_ON, and the power supply terminal VCC1 is powered normally. The power switch tube Q1 stops switching action means that the driving end GT1 of the first control circuit 400 stops outputting control signals to the power switch tube Q1.

[0066] Specifically, the first control circuit 400 is used to perform a first fault detection on the primary circuit after normal power supply. When the first fault is detected in the primary circuit, the power switch tube Q1 is controlled to stop the switching action, and the primary circuit is restarted when the restart condition corresponding to the fault is met.

[0067] The first control circuit 400 is also used to perform open-loop control on the power switch tube Q1 when it is detected that the primary circuit does not have the first fault, and to perform fault detection on the primary circuit during open-loop control, and to control the power switch tube Q1 to stop switching action when it is detected that the primary circuit has the first fault or the second fault, and to restart the primary circuit when the restart condition corresponding to the fault is met.

[0068] Among them, the first fault refers to a fault that can be identified by the primary circuit, for example, including a fault in the primary circuit itself. The second fault includes that when the power switch tube Q1 is open-loop controlled, the time of the open-loop control reaches the second time T2, and the first control circuit 400 has not received the handshake signal sent by the secondary circuit (the second control circuit 500). The second fault may be caused by secondary circuit faults, transformer faults, etc. The first fault includes a first sub-fault and a second sub-fault. When the primary circuit is in the first type of protection state, it indicates that the primary circuit has a first sub-fault, and when the primary circuit is in the second protection state, it indicates that the primary circuit has a second sub-fault. The first protection state may include one or more of the protections of short circuit protection SCP, power management protection brown-in / out, overvoltage protection OVP, undervoltage protection UVP, inductor (CS) open circuit protection, overtemperature protection OTP, etc. The second protection state includes other protection states except the first protection state.

[0069] The first control circuit 400 is also used to stop the open-loop control of the power switch tube Q1 when receiving the handshake signal sent by the secondary circuit during the open-loop control of the power switch tube Q1, and control the switching action of the power switch tube Q1 according to the handshake signal sent by the secondary circuit.

[0070] The first control circuit 400 is also used to perform a first fault detection on the primary circuit during the process of controlling the switching action of the power switch tube Q1 according to the handshake signal sent by the secondary circuit, and when the first fault is detected in the primary circuit, control the power switch tube Q1 to stop the switching action, and restart the primary circuit when the restart condition corresponding to the fault is met.

[0071] Furthermore, the first control circuit 400 is further configured to restart the primary circuit when it is detected that the primary circuit has a first sub-fault and when it is detected that the primary circuit exits the first sub-fault.

[0072] The first control circuit 400 is further configured to restart the primary circuit after timing a first time T1 when a second sub-fault or a second fault is detected in the primary circuit.

[0073] Figure 2 A circuit diagram of a first control circuit according to an embodiment of the present invention is shown.

[0074] See also Figure 2 The first control circuit 400 includes a power supply unit 410 , a first control unit 420 and a detection unit 430 .

[0075] The power supply unit 410 charges the power supply terminal VCC1 to the first power supply voltage VCC1_ON through the input voltage VIN to supply power to the first control unit 420 and the detection unit 430. The present invention does not specifically limit the structure of the power supply unit 410, which can be selected according to actual needs. The power supply unit 410 can be implemented by a low-dropout linear regulator (Low-Dropout Regulator, LDO), or by other circuit structures.

[0076] The first control unit 420 is used to perform open-loop control on the power switch tube Q1 after the power supply terminal VCC1 supplies power normally, and after receiving a handshake signal sent by the secondary circuit (the second control circuit 500) during the open-loop control process, stop the open-loop control of the power switch tube Q1 (i.e., stop the switching action of the power switch tube Q1), and control the switching action of the power switch tube Q1 according to the handshake signal, that is, the secondary circuit controls the primary circuit.

[0077] Optionally, the switching power supply provided by the embodiment of the present invention may further include an isolation communication module, which is used to convert the handshake signal sent by the secondary circuit into a signal that can be received by the first control circuit 400 after certain modulation and / or demodulation, and transmit the converted signal to the first control circuit 400. The isolation communication module can be implemented by an isolation method such as capacitive isolation or magnetic isolation.

[0078] Optionally, the switching power supply provided in the embodiment of the present invention may also not need an isolation communication module, and by comparing the voltage of the second sampling terminal CS with the threshold voltage, it can be determined whether the first control circuit 400 has received the handshake signal sent by the secondary circuit. Specifically, for example, when the voltage of the second sampling terminal CS is less than the threshold voltage, it can be considered that the first control circuit 400 has received the handshake signal sent by the secondary circuit. The threshold voltage is close to 0V, and can be slightly less than 0V, for example, it can be set to any voltage between -100mV and 0V.

[0079] The detection unit 430 is used to output a fault signal Fault_P when a fault is detected in the primary circuit, and output a reset signal RST when a restart condition corresponding to the fault is met. The fault signal Fault_P includes a first fault signal Fault1_P and a second fault signal Fault2_P. The reset signal RST includes a first reset signal RST1 and a second reset signal RST2.

[0080] The first control unit 420 is further configured to control the power switch tube Q1 to stop switching after receiving the fault signal Fault_P, and to control the primary circuit to restart after receiving the reset signal RST.

[0081] The detection unit 430 includes a first trigger 431, a second trigger 432, and a first timing unit 433. The first input terminal of the first trigger 431 receives a first trigger signal, and when the first trigger signal indicates that the primary circuit has a first sub-fault, the first output terminal thereof outputs a first fault signal Fault1_P to the first control unit 420. The second input terminal of the first trigger 431 receives a first start signal, and when the first start signal indicates that the primary circuit has exited the first sub-fault, the first output terminal thereof outputs a first reset signal RST1 to the first control unit 420. The first input terminal of the second trigger 432 receives a second trigger signal, and when the second trigger signal indicates that the primary circuit has a second sub-fault or a second fault, the first output terminal thereof outputs a second fault signal Fault2_P to the first control unit 420. The second input terminal of the second trigger 432 receives a second start signal, and when the second start signal indicates that the restart condition of the second sub-fault or the second fault has been reached, the second output terminal thereof outputs a second reset signal RST2 to the first control unit 420. In this embodiment, the first or second trigger can be an RS trigger, the first input terminal is the set terminal S, the second input terminal is the reset terminal R, the first output terminal is the output terminal Q, and the second output terminal is the output terminal QN; of course, other circuits or variations can also be used to implement this function. The first timing unit 433 is used to start timing after receiving the second fault signal Fault2_P, and after the timing time reaches the first time T1, output the second start signal to control the restart of the primary circuit. Among them, Figure 2 The circuit structure in is only an example of the present application, and it can also be transformed to achieve the same function.

[0082] Furthermore, the first control circuit 400 further includes a judgment unit (not shown in the figure), which is used to judge what kind of fault the switching power supply has, and output a first trigger signal or a second trigger signal according to the judgment result. Specifically, the judgment unit outputs the first trigger signal when the primary circuit is in the first protection state, and outputs the second trigger signal when the primary circuit is in the second protection state or the open-loop control time of the primary circuit on the power switch tube Q1 reaches the second time T2.

[0083] After the output end of the switching power supply generates an output voltage Vout, the output voltage Vout is provided to the power supply end VCC2 of the second control circuit 500. When the output voltage Vout, i.e., the voltage of the power supply end VCC2 reaches the second power supply voltage VCC2_ON and the power supply end VCC2 is normally powered, it can be considered that the second control circuit 500 is normally powered.

[0084] The second control circuit 500 is used to perform real-time fault detection on the secondary circuit after normal power supply. When a fault is detected in the secondary circuit at any time, the synchronous rectifier SR is controlled to stop switching, and the secondary circuit is restarted when the restart condition corresponding to the fault is met.

[0085] Specifically, the second control circuit 500 is used to perform a third fault detection on the secondary circuit after normal power supply, and when the third fault is detected in the secondary circuit, control the synchronous rectifier SR to stop the switching action and start timing, and restart the secondary circuit after the timing time reaches the third time T3.

[0086] The second control circuit 500 is also used to send a handshake signal to the primary circuit (first control circuit 400) when it detects that the secondary circuit does not have the third fault, and detects whether the secondary circuit has the fourth fault. When it is detected that the secondary current does not have the fourth fault, it continues to send a handshake signal to control the switching action of the power switch tube Q1. The handshake signal at this time can be understood as a signal transmitted from the secondary to the primary, and when it is detected that the secondary circuit has the fourth fault, it starts timing, and after the timing time reaches the third time T3, the secondary circuit is restarted.

[0087] The fourth fault includes a handshake failure between the primary circuit and the secondary circuit. The fourth fault may be caused by a primary circuit fault and a transformer 100 fault.

[0088] The switching frequency fsw of the power switch tube Q1 and the synchronous rectifier tube SR may be determined by the output voltage Vout, specifically, by an error signal between the output voltage Vout and a reference voltage.

[0089] In the present invention, stopping the switching action of the synchronous rectifier SR means that the driving terminal GT2 of the second control circuit 500 stops outputting the control signal to the synchronous rectifier SR.

[0090] Figure 3 FIG. 4 shows a circuit diagram of a second control circuit according to an embodiment of the present invention.

[0091] See also Figure 3 The second control circuit 500 includes a second control unit 510, a third trigger 520 and a second timing unit 530. As an example of the present application, the second control unit 510 is used to control the synchronous rectifier tube SR to be turned on after normal power supply to output a handshake signal, and control the switching action of the power switch tube Q1 through the handshake signal after the handshake is successful.

[0092] The first input terminal of the third trigger 520 receives the third trigger signal, and when the third trigger signal indicates that a fault (third fault or fourth fault) occurs in the secondary circuit, the first output terminal thereof outputs the third fault signal Fault_S to the second control unit 510 and the second timing unit 530. The second input terminal of the third trigger 520 receives the third start signal, and when the third start signal indicates that the fault restart condition of the secondary circuit is met, the second output terminal thereof outputs the third reset signal RST3. Similarly, in this embodiment, the third trigger may be an RS trigger, the first input terminal being the first input terminal S, the second input terminal being the second input terminal R, the first output terminal being the output terminal Q, and the second output terminal being the output terminal QN; of course, other circuits may also be used to implement this function. The second timing unit 530 starts timing after receiving the third fault signal Fault_S, and outputs the third start signal to control the reset of the secondary circuit after the timing time reaches the third time T3. The second control unit 510 is also used to stop the switching action of the synchronous rectifier SR after receiving the third fault signal Fault_S, and to control the reset of the secondary circuit after receiving the third reset signal RST3. Among them, Figure 3 The circuit structure in is only an example of the present application, and it can also be transformed to achieve the same function.

[0093] In the embodiment of the present invention, further, the second time T2 is less than the third time T3, and the third time T3 is less than the first time T1, wherein the second time T2 is less than the third time T3 to ensure that the open-loop control of the primary circuit on the power switch tube Q1 is also terminated after the secondary circuit is reset. The first time T1 is set to be larger, or the ratio of the second time T2 to the first time T1 is set to be smaller to avoid the primary circuit and the secondary circuit from being subjected to a larger power in a fault state, resulting in damage to the circuit.

[0094] The present invention also provides a control method for a switching power supply, which is applied to a primary circuit to protect the primary circuit. Figure 4 A flow chart of a control method for primary circuit protection applied to an embodiment of the present invention is shown.

[0095] See also Figure 4 , the control method specifically comprises the following steps:

[0096] S1: The first control circuit is powered normally.

[0097] S2: Determine whether there is a first fault in the primary circuit. When there is a first fault in the primary circuit, execute step S3; when there is no first fault in the primary circuit, execute step S4.

[0098] Step S3: Stop the switching action of the power switch tube, and restart the primary circuit after the fault restart condition is met.

[0099] Step S4: performing open-loop control on the power switch tube.

[0100] Step S5: Determine whether the primary circuit has the first fault or the second fault. When the primary circuit has the first fault or the second fault, execute step S3; when the primary circuit does not have the first fault or the second fault, execute step S6.

[0101] Step S6: Determine whether the primary circuit receives the handshake signal sent by the secondary circuit. When the primary circuit receives the handshake signal sent by the secondary circuit, execute step S7; when the primary circuit does not receive the handshake signal sent by the secondary circuit, execute step S4.

[0102] Step S7: stop the open-loop control of the power switch tube.

[0103] Step S8: Control the switching action of the power switch tube according to the handshake signal.

[0104] Step S9: Determine whether the primary circuit has a first fault. When the primary circuit has a first fault, execute step S3; when the primary circuit does not have the first fault, execute step S8.

[0105] The present invention also provides a control method for a switching power supply, which is applied to a secondary circuit to protect the secondary circuit. Figure 5 A flow chart of a control method for secondary circuit protection applied to the present invention is shown.

[0106] See also Figure 5 , the control method specifically comprises the following steps:

[0107] Step S11: The second control circuit is powered normally.

[0108] Step S12: Determine whether the secondary circuit has the third fault. When the secondary circuit has the third fault, execute step S13; when the secondary circuit does not have the third fault, execute step S14.

[0109] Step S13: stop the switching action of the synchronous rectifier tube, and restart the secondary circuit after a third time.

[0110] Step S14: the secondary circuit sends a handshake signal to the primary circuit.

[0111] Step S15: Determine whether the secondary circuit has the fourth fault. If the secondary circuit does not have the fourth fault, execute step S16; if the secondary circuit has the fourth fault, execute step S13.

[0112] Step S16: Controlling the switching actions of the power switch tube and the synchronous rectifier tube according to the output voltage of the switching power supply.

[0113] Step S17: Determine whether the secondary circuit has the third fault. When the secondary circuit has the third fault, execute step S13; when the secondary circuit does not have the third fault, execute step S16.

[0114] In the switching power supply and control method thereof provided by the embodiment of the present invention, the first control circuit performs fault detection on the primary circuit in real time after normal power supply, and controls the power switch tube to stop switching action after detecting a fault in the primary circuit at any time, and restarts the primary circuit after the fault restart condition of the fault is met; the second control circuit performs fault detection on the secondary circuit in real time after normal power supply, and controls the synchronous rectifier tube to stop switching action after detecting a fault in the secondary circuit at any time, and restarts the secondary circuit after the fault restart condition of the fault is met, so that effective protection of the switching power supply can be achieved regardless of whether a fault occurs in the primary circuit or the secondary circuit.

[0115] According to the embodiments of the present invention, as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the only specific embodiments. Obviously, according to the above description, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention and their equivalents.

Claims

1. A switching power supply, comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the primary circuit comprises a power switch tube and a first control circuit arranged on the primary side, the first control circuit controls the on and off of the power switch tube; the secondary circuit comprises a synchronous rectifier tube and a second control circuit arranged on the secondary side, the second control circuit controls the on and off of the synchronous rectifier tube, wherein: The first control circuit is configured to perform fault detection on the primary circuit in real time after normal power supply, and when a fault is detected in the primary circuit, control the power switch tube to stop switching, and restart the primary circuit when a restart condition corresponding to the fault is met; The second control circuit is configured to perform fault detection on the secondary circuit in real time after normal power supply. When a fault is detected in the secondary circuit, the second control circuit controls the synchronous rectifier to stop switching, and restarts the secondary circuit when the restart condition corresponding to the fault is met.

2. The switching power supply according to claim 1, wherein: The faults existing in the primary circuit include a first fault and a second fault; the first fault includes a first sub-fault and a second sub-fault; when the first control circuit detects that the primary circuit has a first sub-fault, the first control circuit uses the primary circuit exiting the first sub-fault as a restart condition for the primary circuit; when the first control circuit detects that the primary circuit has a second sub-fault or a second fault, the first control circuit uses waiting for a first time as a restart condition for the primary circuit.

3. The switching power supply according to claim 2, wherein: The second fault includes that when the open-loop control is performed on the power switch tube, the open-loop control time reaches a second time, and the first control circuit has not received a handshake signal sent by the second control circuit.

4. The switching power supply according to claim 3, wherein: The first control circuit is used to perform a first fault detection on the primary circuit after normal power supply, and when the first fault is detected in the primary circuit, control the power switch tube to stop the switching action, and restart the primary circuit when the restart condition corresponding to the fault is met; The first control circuit is further used to perform open-loop control on the power switch tube when it is detected that the primary circuit does not have the first fault, and to perform first fault detection and second fault detection on the primary circuit during open-loop control, and to control the power switch tube to stop switching action when it is detected that the primary circuit has the first fault or the second fault, and to restart the primary circuit when a restart condition corresponding to the fault is met; The first control circuit is also used to stop open-loop control of the power switch tube when receiving a handshake signal sent by the second control circuit during the open-loop control of the power switch tube, and control the switching action of the power switch tube according to the handshake signal sent by the second control circuit, and perform a first fault detection on the primary circuit, and when the first fault is detected in the primary circuit, control the power switch tube to stop the switching action, and restart the primary circuit when the restart condition corresponding to the fault is met.

5. The switching power supply according to claim 4, wherein: The first control circuit comprises: a first control unit, configured to perform open-loop control on the power switch tube, and after receiving a handshake signal sent by the second control circuit during the open-loop control process, stop the open-loop control on the power switch tube, and control the switching action of the power switch tube according to the handshake signal sent by the second control circuit; A detection unit, configured to output a fault signal when a fault is detected in the switching power supply, and output a reset signal when a restart condition of the fault is met; The first control unit is further used to control the power switch tube to stop switching action according to the fault signal, and to control the primary circuit to reset according to the reset signal.

6. The switching power supply according to claim 5, wherein: The first control circuit further includes: The judging unit is used to judge what kind of fault exists in the primary circuit and output a first trigger signal or a second trigger signal according to the judging result.

7. The switching power supply according to claim 6, wherein: The detection unit comprises: A first trigger, wherein a first input terminal receives a first trigger signal, and when the first trigger signal indicates that a first sub-fault occurs in the primary circuit, the trigger outputs a first fault signal to the first control unit, and a second input terminal receives a first start signal, and when the first start signal indicates that the primary circuit exits the first sub-fault, the trigger outputs a first reset signal to the first control unit; a second trigger, wherein a first input terminal thereof receives a second trigger signal, and when the second trigger signal indicates that a second sub-fault or a second fault occurs in the primary circuit, the second trigger outputs a second fault signal to the first control unit, and a second input terminal thereof receives a second start signal, and when the second start signal indicates that a restart condition of the second sub-fault or the second fault is met, the second trigger outputs a second reset signal to the first control unit; The first timing unit is used to start timing after receiving the second fault signal, and output a second start signal to control the primary circuit to restart after the timing time reaches the first time.

8. The switching power supply according to claim 3, wherein: When the second control circuit detects that the secondary circuit has a fault, waiting for a third time is used as a restart condition of the secondary circuit; The faults existing in the secondary circuit include a third fault and a fourth fault; the fourth fault includes a handshake failure between the secondary circuit and the primary circuit.

9. The switching power supply according to claim 8, wherein: The second control circuit is used to perform a third fault detection on the secondary circuit after normal power supply, and when the third fault is detected in the secondary circuit, stop the switching action of the synchronous rectifier tube, start timing, and restart the secondary circuit after the timing time reaches a third time; The second control circuit is also used to send a handshake signal to the primary circuit when it is detected that there is no fault in the secondary circuit, and perform a fourth fault detection on the secondary circuit, and after detecting that the fourth fault exists in the secondary circuit, stop the switching action of the synchronous rectifier tube and start timing, and after the timing time reaches the third time, restart the secondary circuit, and after detecting that the fourth fault exists in the secondary circuit, continue to send a handshake signal to control the switching action of the power switch tube.

10. The switching power supply according to claim 9, wherein: The second control circuit comprises: A second control unit is used to control the synchronous rectifier to conduct to output a handshake signal, and control the switching action of the power switch tube through the handshake signal after the handshake is successful; a third trigger, wherein a first input terminal of the third trigger receives a third trigger signal, and when the third trigger signal indicates that the secondary circuit has a fault, the third trigger outputs a third fault signal to the second control unit, and a second input terminal of the third trigger receives a third start signal, and when the third start signal indicates that a fault restart condition is met, the third trigger outputs a third reset signal; The second timing unit is used to start timing after receiving the third fault signal, and output the third start signal after the timing time reaches a third time. The second control unit is further configured to stop the switching action of the synchronous rectifier tube after receiving the third fault signal, and to control the secondary circuit to reset after receiving the third reset signal.

11. The switching power supply according to claim 8, wherein: The second time is shorter than the third time, and the third time is shorter than the first time.

12. A control method for a switching power supply, the switching power supply comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the primary circuit comprises a power switch tube arranged on the primary side and a first control circuit, the first control circuit controls the on and off of the power switch tube; the control method is applied to the primary circuit, the control method comprises: After the first control circuit supplies power normally, it is determined whether the primary circuit has a first fault, and when the primary circuit has the first fault, the switching action of the power switch tube is stopped, and after a fault restart condition of the fault is met, the primary circuit is restarted; When the primary circuit does not have the first fault, open-loop control is performed on the power switch tube, and it is determined whether the primary circuit has the first fault or the second fault. When the primary circuit has the first fault or the second fault, the switching action of the power switch tube is stopped, and the primary circuit is restarted after the fault restart condition of the fault is met, and When the primary circuit does not have the first fault or the second fault, it is determined whether the primary circuit receives a handshake signal sent by the secondary circuit, and when the primary circuit receives the handshake signal sent by the secondary circuit, the open-loop control of the power switch tube is stopped, and the switching action of the power switch tube is controlled according to the handshake signal. When controlling the switching action of the power switch tube according to the handshake signal, determine whether the primary circuit has a first fault, and when the primary circuit has the first fault, stop the switching action of the power switch tube, and restart the primary circuit after the fault restart condition of the fault is met.

13. The control method according to claim 12, wherein: The faults existing in the primary circuit include a first fault and a second fault; the first fault includes a first sub-fault and a second sub-fault; when it is detected that the primary circuit has a first sub-fault, the primary circuit exiting the first sub-fault is used as a restart condition for the primary circuit; when it is detected that the primary circuit has a second sub-fault or a second fault, waiting for a first time is used as a restart condition for the primary circuit.

14. The control method according to claim 13, wherein: The second fault includes that when the open-loop control is performed on the power switch tube, the open-loop control time reaches a second time, and the first control circuit has not received a handshake signal sent by the secondary circuit.

15. A control method for a switching power supply, the switching power supply comprising a primary winding, a secondary winding, a primary circuit and a secondary circuit; the secondary circuit comprising a synchronous rectifier tube arranged on the secondary side and a second control circuit, the second control circuit controlling the conduction and the shutoff of the synchronous rectifier tube; the control method is applied to the secondary circuit, the control method comprising: After the second control circuit is powered normally, it is determined whether the secondary circuit has a third fault, and when the secondary circuit has the third fault, the switching action of the synchronous rectifier is stopped, and the secondary circuit is restarted after a third time; When the secondary circuit does not have the third fault, a handshake signal is sent to the primary circuit, and it is determined whether the secondary circuit has a fourth fault. If the secondary circuit has the fourth fault, the switching action of the synchronous rectifier is stopped, and the secondary circuit is restarted after the third time. If the secondary circuit does not have the fourth fault, the switching action of the power switch tube and the synchronous rectifier tube is controlled according to the output voltage of the switching power supply, and at the same time, it is determined whether the secondary circuit has the third fault. When the secondary circuit has the third fault, the switching action of the synchronous rectifier tube is stopped, and the secondary circuit is restarted after the third time.

16. The control method according to claim 15, wherein: The fourth fault includes a handshake failure between the secondary circuit and the primary circuit.

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