A flyback power supply protection circuit

Abstract

The present application discloses a flyback power supply protection circuit, including: a circuit protection module, two filter modules, an optocoupler, three resistors, two transistors and a unidirectional conducting element; when a short circuit occurs in the topological circuit where the flyback power supply is located, under the triggering action of the target control signal, the optocoupler is turned on and transmits the target control signal to the secondary side of the optocoupler, and at this time, the positive feedback circuit composed of the first transistor and the second transistor will pull down the COMP pin of the control chip of the flyback power supply to achieve the blocking output of the flyback power supply until the system is completely powered off. When the flyback power supply is powered off, the positive feedback circuit composed of the first transistor and the second transistor fails, and the flyback power supply will restart. Obviously, even if a short circuit occurs in the topological structure where the flyback power supply is located, the flyback power supply will not be burned, thereby improving the safety and reliability of the flyback power supply during operation.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a flyback power supply protection circuit. Background Art

[0002] Most of the current flyback power supply protection circuits limit the output power of the flyback power supply cycle by cycle through a current loop, and allow the output voltage of the flyback power supply to automatically drop below its minimum operating voltage, thereby achieving hiccup protection for the flyback power supply.

[0003] See also Figure 1 , Figure 1 This is the main topology diagram of the flyback power supply protection circuit in the prior art. Figure 1 In the high-power flyback power supply, since the transformer is an energy storage element, the energy stored in a single-cycle excitation will be close to the transformer's energy storage limit. When the transformer is short-circuited, the voltage of the transformer's secondary coil will be pulled down to close to zero. At this time, the energy stored in the transformer's secondary coil cannot be released, and the transformer is very likely to be saturated, and the flyback power supply protection circuit will be damaged. In this way, the safety and reliability of the flyback power supply during operation cannot be guaranteed. At present, there is no more effective solution to this technical problem. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a flyback power supply protection circuit to further improve the safety and reliability of the flyback power supply during operation. The specific scheme is as follows:

[0005] A flyback power supply protection circuit includes: a circuit protection module, a first filter module, a second filter module, an optical coupler, a first resistor, a second resistor, a third resistor, a first transistor, a second transistor, and a unidirectional conductive element;

[0006] Wherein, the first end of the circuit protection module is connected to the first end of the first filtering module, the second end of the circuit protection module and the second end of the first filtering module are both grounded, the first end and the second end of the first filtering module are respectively connected to the first end and the second end of the optocoupler, the third end of the optocoupler is respectively connected to the first end of the first resistor, the emitter of the first triode and the first end of the third resistor, the fourth end of the optocoupler is respectively connected to the collector of the first triode, the first end of the second resistor, the first end of the second filtering module and the base set of the second triode, the second end of the first resistor is connected to +5Vref, the base set of the first triode is respectively connected to the second end of the third resistor, the collector of the second triode and the output end of the unidirectional conductive element, and the emitter of the second triode is respectively connected to the second end of the second filtering module and the second end of the second resistor;

[0007] Correspondingly, the first end of the circuit protection module is used to receive a target control signal, the second end of the second resistor is connected to a target power line, and the input end of the unidirectional conductive element is connected to a control chip of a flyback power supply.

[0008] Preferably, the circuit protection module comprises: a fourth resistor, a fifth resistor, a first diode and a second diode;

[0009] The first end of the fourth resistor is connected to the first end of the fifth resistor, and the second end of the fourth resistor is connected to the second end of the fifth resistor, the cathode of the first diode, and the cathode of the second diode respectively;

[0010] Correspondingly, the first end of the fourth resistor is the first end of the circuit protection module, and the anode of the first diode and the anode of the second diode are both grounded.

[0011] Preferably, the first filtering module includes: a sixth resistor and a first capacitor;

[0012] Wherein, the first end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the sixth resistor is connected to the second end of the first capacitor;

[0013] Correspondingly, the first end of the sixth resistor is the first end of the first filtering module, and the second end of the sixth resistor is the second end of the first filtering module.

[0014] Preferably, the second filtering module is specifically a second capacitor.

[0015] Preferably, the unidirectional conducting element comprises: a third diode and a fourth diode;

[0016] Wherein, the anode of the third diode is connected to the anode of the fourth diode, and the cathode of the third diode is connected to the cathode of the fourth diode;

[0017] Correspondingly, the cathode of the third diode is the input end of the unidirectional conductive element, and the anode of the third diode is the output end of the unidirectional conductive element.

[0018] Preferably, the control chip of the flyback power supply is specifically UC2844.

[0019] It can be seen that in the present invention, when the topological circuit where the flyback power supply is located is short-circuited, under the triggering action of the target control signal, the optical coupler is turned on and transmits the target control signal to the secondary side of the optical coupler. At this time, the positive feedback circuit composed of the first transistor and the second transistor will pull down the COMP pin of the control chip of the flyback power supply to achieve the blocking output of the flyback power supply until the system is completely powered off. When the flyback power supply is powered off, the positive feedback circuit composed of the first transistor and the second transistor fails, and the flyback power supply will restart. If the short-circuit fault of the topological circuit where the flyback power supply is located is eliminated, the flyback power supply can still maintain a normal operating state. Obviously, through the flyback power supply protection circuit, even if the topological structure where the flyback power supply is located is short-circuited, the flyback power supply will not be burned, thereby further improving the safety and reliability of the flyback power supply during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0021] Figure 1 It is the main topology diagram of the flyback power supply protection circuit in the prior art;

[0022] Figure 2 A structural diagram of a flyback power supply protection circuit provided by an embodiment of the present invention;

[0023] Figure 3 It is a structural diagram of a flyback power supply control circuit in the prior art;

[0024] Figure 4 A structural diagram of another flyback power supply protection circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 2 , Figure 2A structural diagram of a flyback power supply protection circuit provided by an embodiment of the present invention, the flyback power supply protection circuit includes: a circuit protection module, a first filter module, a second filter module, an optical coupler U1, a first resistor R1, a second resistor R2, a third resistor R3, a first transistor Q1, a second transistor Q2, and a unidirectional conductive element;

[0027] Wherein, the first end of the circuit protection module is connected to the first end of the first filtering module, the second end of the circuit protection module and the second end of the first filtering module are both grounded, the first end and the second end of the first filtering module are respectively connected to the first end and the second end of the optocoupler U1, the third end of the optocoupler U1 is respectively connected to the first end of the first resistor R1, the emitter of the first transistor Q1 and the first end of the third resistor R3, the fourth end of the optocoupler U1 is respectively connected to the collector of the first transistor Q1, the first end of the second resistor R2, the first end of the second filtering module and the base set of the second transistor Q2, the second end of the first resistor R1 is connected to +5Vref, the base set of the first transistor Q1 is respectively connected to the second end of the third resistor R3, the collector of the second transistor Q2 and the output end of the unidirectional conductive element, and the emitter of the second transistor Q2 is respectively connected to the second end of the second filtering module and the second end of the second resistor R2;

[0028] Correspondingly, the first end of the circuit protection module is used to receive the target control signal COM, the second end of the second resistor R2 is connected to the target power line BUS_N, and the input end of the unidirectional conductive element is connected to the control chip of the flyback power supply.

[0029] In this embodiment, a novel flyback power supply protection circuit is provided, through which the safety and reliability of the flyback power supply during operation can be further ensured. Specifically, the flyback power supply protection circuit includes: an optocoupler, a circuit protection module for protecting the primary side of the optocoupler, a first filter module for filtering the target control signal, a positive feedback circuit composed of a first transistor Q1 and a second transistor Q2, and a unidirectional conduction element.

[0030] See also Figure 1 and Figure 2 In practical applications, Figure 1 COM and Figure 2 COM is connected to the COM in the output, and COM is used to output the target control signal. Figure 1 The voltage across resistors R17, R18 and R19 at the secondary output end of the transformer cannot Figure 2 The optocoupler in the flyback power supply is turned on, and the flyback power supply is in normal operation. Figure 1The capacitors C14 and C15 on the secondary side of the transformer no longer store energy. At this time, the current in the secondary coil of the transformer will directly flow through the resistors R17, R18 and R19, and will be much larger than the current during normal operation, thus Figure 2 The optocoupler in is turned on; when Figure 2 After the optocoupler in is turned on, the target control signal is transmitted to the secondary side of the optocoupler. After being amplified by the first transistor and the second transistor, the target control signal will pull down the COMP pin of the control chip of the flyback power supply, thereby blocking the output voltage of the flyback power supply until +5Vref is powered off.

[0031] See also Figure 3 , Figure 3 FIG. 1 is a structural diagram of a flyback power supply control circuit in the prior art. Figure 3 In the figure, U0 is the control chip of the flyback power supply (taking UC2844 as an example), and the COMP pin of the flyback power supply control chip U0 is Figure 2 COMP in, Figure 3 The BUS_N in the figure is the target power line. When the COMP pin of the flyback power supply control chip is pulled low, the flyback power supply will not output a drive signal. When the power supply voltage of the flyback power supply control chip drops below 10V, +5Vref loses power, and the positive feedback circuit composed of the first transistor and the second transistor fails. At this time, the flyback power supply will restart. If the short-circuit fault of the topology circuit where the flyback power supply is located is removed, the flyback power supply can still maintain normal operation. If the short-circuit fault of the flyback power supply is not removed, Figure 2 The optocoupler in Figure 1 The energy released by the secondary coil of the transformer is turned on again. Figure 2 Obviously, the flyback power supply protection circuit provided by this embodiment can further ensure the overall reliability of the flyback power supply during operation.

[0032] It can be seen that in the present embodiment, when the topological structure where the flyback power supply is located is short-circuited, under the triggering action of the target control signal, the optocoupler is turned on and transmits the target control signal to the secondary side of the optocoupler. At this time, the positive feedback circuit composed of the first transistor and the second transistor will pull down the COMP pin of the control chip of the flyback power supply to achieve the blocking output of the flyback power supply until the system is completely powered off. When the flyback power supply is powered off, the positive feedback circuit composed of the first transistor and the second transistor fails, and the flyback power supply will restart. If the short-circuit fault of the topological circuit where the flyback power supply is located is eliminated, the flyback power supply can still maintain a normal operating state. Obviously, through the flyback power supply protection circuit, even if the topological structure where the flyback power supply is located is short-circuited, the flyback power supply will not be burned, thereby further improving the safety and reliability of the flyback power supply during operation.

[0033] Based on the above embodiments, this embodiment further explains and optimizes the technical solution. Figure 4 , Figure 4 A structural diagram of another flyback power supply protection circuit provided by an embodiment of the present invention. As a preferred implementation, the circuit protection module includes: a fourth resistor R4, a fifth resistor R5, a first diode D1 and a second diode D2;

[0034] The first end of the fourth resistor R4 is connected to the first end of the fifth resistor R5, and the second end of the fourth resistor R4 is connected to the second end of the fifth resistor R5, the cathode of the first diode D1, and the cathode of the second diode D2 respectively;

[0035] Correspondingly, the first end of the fourth resistor R4 is the first end of the circuit protection module, and the anode of the first diode D1 and the anode of the second diode D2 are both grounded.

[0036] In this embodiment, a specific configuration of a circuit protection module is provided, that is, the circuit protection module composed of the fourth resistor R4, the fifth resistor R5, the first diode D1 and the second diode D2 is used to protect the primary side of the optocoupler, thereby preventing the optocoupler from burning due to excessive short-circuit current.

[0037] As a preferred implementation, the first filtering module includes: a sixth resistor R6 and a first capacitor C1;

[0038] Wherein, a first end of the sixth resistor R6 is connected to a first end of the first capacitor C1, and a second end of the sixth resistor R6 is connected to a second end of the first capacitor C1;

[0039] Correspondingly, the first end of the sixth resistor R6 is the first end of the first filter module, and the second end of the sixth resistor R6 is the second end of the first filter module.

[0040] As a preferred implementation, the second filtering module is specifically a second capacitor C2.

[0041] In this embodiment, the first filter module composed of the sixth resistor R6 and the first capacitor C1 is used to filter the target control signal received by the optical coupler, that is, the first filter module is used to remove the interference signal in the target control signal. At the same time, the second capacitor C2 is used to filter the output signal of the optical coupler, thereby further improving the working performance of the flyback power supply protection circuit.

[0042] As a preferred implementation, the unidirectional conducting element includes: a third diode D3 and a fourth diode D4;

[0043] The anode of the third diode D3 is connected to the anode of the fourth diode D4, and the cathode of the third diode D3 is connected to the cathode of the fourth diode D4;

[0044] Correspondingly, the cathode of the third diode D3 is the input end of the unidirectional conductive element, and the anode of the third diode D3 is the output end of the unidirectional conductive element.

[0045] In practical applications, a unidirectional conducting element composed of the third diode D3 and the fourth diode D4 is also used to protect the signal output by the flyback power supply, thereby further ensuring the safety of the flyback power supply during operation.

[0046] As a preferred implementation, the control chip of the flyback power supply is specifically UC2844.

[0047] Specifically, in practical applications, the control chip of the flyback power supply can be set to UC2844, because UC2844 adopts the current PWM (Pulse Width Modulation) control mode. In this setting mode, the duty cycle of the pulse can be quickly adjusted through the PWM modulator of the switching power supply, and the flyback power supply can have a faster dynamic response speed. Therefore, when the control chip of the flyback power supply is set to UC2844, the user experience of people when using the flyback power supply can be further improved.

[0048] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements that are not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements limited by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0049] The above is a detailed introduction to a flyback power supply protection circuit provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A flyback power supply protection circuit, characterized in that: include: Circuit protection module, first filter module, second filter module, optocoupler, first resistor, second resistor, third resistor, first transistor, second transistor, unidirectional conductive element; Wherein, the first end of the circuit protection module is connected to the first end of the first filtering module, the second end of the circuit protection module and the second end of the first filtering module are both grounded, the first end and the second end of the first filtering module are respectively connected to the first end and the second end of the optocoupler, the third end of the optocoupler is respectively connected to the first end of the first resistor, the emitter of the first triode and the first end of the third resistor, the fourth end of the optocoupler is respectively connected to the collector of the first triode, the first end of the second resistor, the first end of the second filtering module and the base set of the second triode, the second end of the first resistor is connected to +5Vref, the base set of the first triode is respectively connected to the second end of the third resistor, the collector of the second triode and the output end of the unidirectional conductive element, and the emitter of the second triode is respectively connected to the second end of the second filtering module and the second end of the second resistor; Correspondingly, the first end of the circuit protection module is used to receive the target control signal, the second end of the second resistor is connected to the target power line, and the input end of the unidirectional conductive element is connected to the control chip of the flyback power supply; When the flyback power supply is short-circuited, the optocoupler is turned on and transmits the target control signal to the secondary side of the optocoupler. After the target control signal is amplified by the first transistor and the second transistor, the COMP pin of the control chip of the flyback power supply is pulled down, thereby blocking the output voltage of the flyback power supply until +5Vref is powered off; When the flyback power supply loses power, the positive feedback circuit composed of the first transistor and the second transistor will fail, and the flyback power supply will restart. If the short-circuit fault of the topology circuit where the flyback power supply is located is removed, the flyback power supply will still maintain a normal operating state; The circuit protection module includes: a fourth resistor, a fifth resistor, a first diode and a second diode; The first end of the fourth resistor is connected to the first end of the fifth resistor, and the second end of the fourth resistor is connected to the second end of the fifth resistor, the cathode of the first diode, and the cathode of the second diode respectively; Correspondingly, the first end of the fourth resistor is the first end of the circuit protection module, and the anode of the first diode and the anode of the second diode are both grounded; The first filtering module includes: a sixth resistor and a first capacitor; Wherein, the first end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the sixth resistor is connected to the second end of the first capacitor; Correspondingly, the first end of the sixth resistor is the first end of the first filtering module, and the second end of the sixth resistor is the second end of the first filtering module; The second filtering module is specifically a second capacitor; The unidirectional conducting element comprises: a third diode and a fourth diode; Wherein, the anode of the third diode is connected to the anode of the fourth diode, and the cathode of the third diode is connected to the cathode of the fourth diode; Correspondingly, the cathode of the third diode is the input end of the unidirectional conductive element, and the anode of the third diode is the output end of the unidirectional conductive element; The control chip of the flyback power supply is specifically UC2844.

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