Protection circuit of switching power supply and electronic device

Abstract

The application relates to a protection circuit of a switching power supply and electronic equipment, which comprises a power supply circuit of a switching power supply, a short-circuit feedback circuit and / or an overvoltage feedback circuit. The short-circuit feedback circuit at least comprises an optical coupler and a switching component, and the overvoltage feedback circuit at least comprises a first stabilizing tube and a flip-flop. The feedback winding power supply of the power supply circuit is electrically connected with the control end of the switching component through the optical coupler, and the modulator of the power supply circuit is grounded through the switching component. In response to the short-circuit signal of the feedback winding power supply, the modulator is controlled to stop working through the optical coupler and the switching component. The auxiliary winding power supply loop of the power supply circuit is electrically connected with the control end of the flip-flop through the first stabilizing tube, and the modulator of the power supply circuit is grounded through the flip-flop. In response to the overvoltage signal of the auxiliary winding power supply loop, the modulator is controlled to stop working through the first stabilizing tube and the flip-flop. The application realizes the short-circuit protection and overvoltage protection of any one output, and improves the safety of the switching power supply.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to a protection circuit and electronic device for a switching power supply. Background Technology

[0002] A switching power supply is a high-frequency power conversion device. Its function is to convert a voltage at a certain level into the voltage or current required by the user through different architectures. The input of a switching power supply is mostly AC power (such as mains power) or DC power, while the output is mostly devices that require DC power. The switching power supply performs the voltage and current conversion between the two.

[0003] As Figure 1 The traditional switching power supply shown lacks corresponding short-circuit and overvoltage protection. When a short circuit or overvoltage occurs, the PWM control chip in the switching power supply is easily damaged, leading to the failure of the switching power supply.

[0004] Therefore, a short-circuit protection circuit has been proposed in the prior art, as detailed below. Figure 2 As shown, its short-circuit protection circuit structure has the following defects: When the +5V power supply is short-circuited, it only outputs a low voltage of about 2-3V, which is far from reaching the +5V feedback voltage. At this time, the PWM chip outputs at full duty cycle, and the input energy increases. Since the output voltage of this path is low, the turns ratio of the primary and secondary sides is far different. Although there is a short circuit, the energy consumed is less than the energy increased due to the full duty cycle of the PWM. As a result, the voltages of other paths rise, and the "hiccup" protection cannot be achieved. This will cause the rectifier diode to burn out, and the voltage of other windings to rise, causing the load chip to burn out, resulting in system failure. Summary of the Invention

[0005] Therefore, it is necessary to provide a protection circuit and electronic device for a switching power supply that can comprehensively protect the safe use of the switching power supply, addressing the aforementioned technical problems.

[0006] On the one hand, this application provides a protection circuit for a switching power supply, including the power supply circuit of the switching power supply, and further including: a short-circuit feedback circuit and / or an overvoltage feedback circuit, wherein the short-circuit feedback circuit includes at least an optocoupler and a switching component, and the overvoltage feedback circuit includes at least a first Zener diode and a trigger.

[0007] The power supply of the feedback winding of the power supply circuit is electrically connected to the control terminal of the switching assembly via an optocoupler. The modulator of the power supply circuit is grounded via the input and output terminals of the switching assembly. In the case of a short circuit in the power supply of the feedback winding, the short-circuit feedback circuit is configured to respond to the short-circuit signal of the power supply of the feedback winding and control the modulator to stop working via the optocoupler and the switching assembly.

[0008] The auxiliary winding power supply circuit of the power supply circuit is electrically connected to the control terminal of the trigger via the first Zener diode. The modulator of the power supply circuit is grounded via the input and output terminals of the trigger. In the case of overvoltage in the auxiliary winding power supply circuit, the overvoltage feedback circuit is configured to respond to the overvoltage signal of the auxiliary winding power supply circuit and control the modulator to stop working via the first Zener diode and the trigger.

[0009] Among them, the feedback winding power supply is the output power supply of the power supply circuit, and the auxiliary winding power supply circuit is the power supply circuit for the operation of the power supply circuit itself.

[0010] In one embodiment, the short-circuit signal is the voltage signal of the feedback winding power supply when it is short-circuited, and the overvoltage signal is the voltage signal of the auxiliary winding power supply circuit when it is over-voltaged.

[0011] In one embodiment, the switching assembly includes at least a first switch, a second switch, and a second Zener diode;

[0012] The input terminal of the optocoupler is electrically connected to the feedback winding power supply, and the output terminal of the optocoupler is electrically connected to the control terminal of the first switch. The auxiliary winding power supply output from the auxiliary winding power supply circuit is electrically connected to the control terminal of the second switch via the input and output terminals of the first switch and the second Zener diode. The modulator is grounded via the input and output terminals of the second switch.

[0013] In the event of a short circuit in the feedback winding power supply, the optocoupler is configured to disconnect its output in response to the short circuit signal in the feedback winding power supply. The first switch is configured to connect the auxiliary winding power supply and the second Zener diode in response to the disconnection of the optocoupler's output. The second switch is configured to connect the modulator and the ground wire in response to the saturation conduction of the second Zener diode, thereby stopping the modulator from operating.

[0014] In one embodiment, the short-circuit feedback circuit includes:

[0015] One input terminal of the optocoupler is grounded through a Zener diode ZD16, the other input terminal of the optocoupler is electrically connected to the power supply of the feedback winding through a resistor R286, one output terminal of the optocoupler is electrically connected to the power supply of the auxiliary winding, and the other output terminal of the optocoupler is grounded through a resistor R285.

[0016] One end of the input / output of the first switch is electrically connected to the auxiliary winding power supply and is electrically connected to the control terminal of the first switch via a resistor R281. The control terminal of the first switch is grounded via a resistor R282 and a resistor R285. The other end of the input / output of the first switch is electrically connected to the control terminal of the second switch via a resistor R283 and a second Zener diode and is grounded via a resistor R284.

[0017] One end of the second switch input / output is electrically connected to the cathode of a diode D33, and the anode of the diode D33 is electrically connected to the COM terminal of the modulator. The other end of the second switch input / output is grounded.

[0018] In one embodiment, the switching assembly further includes at least a startup capacitor, with one end of the first switch electrically connected to the second Zener diode electrically connected to one end of the startup capacitor, and the other end of the startup capacitor grounded.

[0019] In one embodiment, the short-circuit feedback circuit is also configured to control the modulator to resume normal operation in response to a normal signal from the feedback winding power supply via an optocoupler, a first switch, a start-up capacitor, a second Zener diode, and a second switch.

[0020] In one embodiment, the short-circuit feedback circuit further includes:

[0021] A resistor R287 and a capacitor C209 are connected in parallel between the two input terminals of the optocoupler.

[0022] One end of the second Zener diode is electrically connected to the second switch and is connected to a resistor R280 and a capacitor C207, while the other end of the resistor R280 and capacitor C207 is grounded.

[0023] In one embodiment, in the overvoltage feedback circuit, the cathode of the first Zener diode is electrically connected to the auxiliary winding power supply circuit, the anode of the first Zener diode is electrically connected to the control terminal of the trigger, the anode of the trigger is electrically connected to the modulator, and the cathode of the trigger is grounded.

[0024] In the event of an overvoltage in the auxiliary winding power supply circuit, the first Zener diode is configured to saturate and conduct in response to the overvoltage signal in the auxiliary winding power supply circuit. The trigger is configured to connect the modulator to ground in response to the saturation conduction of the first Zener diode, thereby causing the modulator to stop working.

[0025] In one embodiment, the overvoltage feedback circuit further includes:

[0026] The control terminal of the trigger is grounded via a capacitor C1;

[0027] The anode of the trigger is electrically connected to the COM terminal of the modulator via a diode D34, the cathode of the diode D34 is electrically connected to the anode of the trigger, and the anode of the diode D34 is electrically connected to the modulator.

[0028] On the other hand, this application also provides an electronic device, including: a protection circuit for a switching power supply as described in any of the above embodiments.

[0029] The aforementioned protection circuits and electronic devices of the switching power supply provide short-circuit and / or overvoltage protection through short-circuit feedback circuits and / or overvoltage feedback circuits. The short-circuit feedback circuit, based on an optocoupler and switching components, provides short-circuit protection. When the feedback winding power supply is short-circuited, it directly responds to the corresponding short-circuit signal to control the modulator to stop working. If a short circuit still exists in the next operating cycle of the switching power supply, the short-circuit feedback circuit will continue to provide short-circuit protection, thus forming a "hiccup" protection until the short circuit is eliminated and the short-circuit feedback circuit automatically recovers, allowing the switching power supply to return to normal operation, greatly increasing the safety of the switching power supply. The overvoltage feedback circuit, based on a first Zener diode and a trigger, provides overvoltage protection. When overvoltage occurs due to short circuits in other windings of the switching power supply or due to issues such as the number of transformer turns, it directly responds to the corresponding overvoltage signal to control the modulator to stop working. This achieves short-circuit protection for any output circuit and overvoltage protection for the power supply circuit, further increasing the safety of the switching power supply. Furthermore, the above eliminates the need for fuses and related complex circuits, significantly reducing costs. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a block diagram of a switching power supply in the prior art;

[0032] Figure 2 This is a schematic diagram of the circuit structure of a short-circuit protection circuit for a switching power supply in the prior art.

[0033] Figure 3 This is a block diagram of the protection circuit of a switching power supply in one embodiment;

[0034] Figure 4 This is a schematic diagram of the circuit structure of the protection circuit of the switching power supply in one embodiment.

[0035] Explanation of reference numerals in the attached figures:

[0036] 10. Short-circuit feedback circuit; 11. Optocoupler; 12. First switch; 13. Second Zener diode; 14. Second switch; 20. Overvoltage feedback circuit; 21. First Zener diode; 22. Trigger; 23. Auxiliary winding power supply circuit. Detailed Implementation

[0037] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0039] It is understood that the terms "first," "second," etc., used in this application may be configured herein to describe various components, but these components are not limited by these terms. These terms are only configured to distinguish one component from another. Similarly, the identifiers used in this application for electronic components, such as R286, R285, C209, C207, ZD13, ZD16, D33, D34, Q10, Q11, IC1, PC10, etc., do not represent specific component models, but are only used to distinguish electronic components of the same nature, and these components are not limited by these identifiers.

[0040] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. Furthermore, in the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if there is transmission of electrical signals or data between the connected objects.

[0041] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0042] As described in the background section, the short-circuit protection circuits of existing switching power supplies have problems such as incomplete protection, inability to achieve "hiccup" protection, and the potential for rectifier diodes and load chips to burn out. Therefore, this invention provides a solution for a short-circuit protection circuit and electronic device for switching power supplies.

[0043] In one embodiment, such as Figure 3 and Figure 4As shown, a protection circuit for a switching power supply is provided, including a power supply circuit for the switching power supply, a short-circuit feedback circuit 10 and / or an overvoltage feedback circuit 20. The short-circuit feedback circuit 10 includes at least an optocoupler 11 and a switching assembly, and the overvoltage feedback circuit 20 includes at least a first Zener diode 21 and a trigger 22.

[0044] The power supply of the feedback winding of the power supply circuit is electrically connected to the control terminal of the switching assembly via optocoupler 11. The modulator of the power supply circuit is grounded via the input and output terminals of the switching assembly. In the case of a short circuit in the power supply of the feedback winding, the short circuit feedback circuit 10 is configured to respond to the short circuit signal of the power supply of the feedback winding and control the modulator to stop working via optocoupler 11 and the switching assembly.

[0045] The auxiliary winding power supply circuit 23 of the power supply circuit is electrically connected to the control terminal of the trigger 22 via the first Zener diode 21. The modulator of the power supply circuit is grounded via the input and output terminals of the trigger 22. In the case of overvoltage in the auxiliary winding power supply circuit 23, the overvoltage feedback circuit 20 is configured to respond to the overvoltage signal of the auxiliary winding power supply circuit 23 and control the modulator to stop working via the first Zener diode 21 and the trigger 22.

[0046] Among them, the feedback winding power supply is the output power supply of the power supply circuit, and the auxiliary winding power supply circuit 23 is the power supply circuit for the operation of the power supply circuit itself.

[0047] This embodiment is applicable to the protection of power supply circuits in switching power supplies, especially for the protection of power supply circuits under abnormal conditions such as output short circuits and overvoltages, to prevent the power supply circuit from burning out due to short circuits and overvoltages. See below. Figure 3 As shown, a typical switching power supply generally includes a PWM modulator, a MOSFET power circuit, a mapped voltage absorption circuit, a rectifier and filter, and a voltage feedback circuit. The MOSFET power circuit is electrically connected to the PWM modulator, the mapped voltage absorption circuit, and the rectifier and filter. The rectifier and filter are electrically connected to the PWM modulator via the voltage feedback circuit. The PWM modulator controls the on / off time ratio of the semiconductor switches in the MOSFET power circuit, thereby regulating the voltage output from the transformer and rectifier circuits. It should be noted that this embodiment does not specifically limit the specific circuit of the switching power supply; more broadly, any switching power supply that meets the protection circuit connection relationships of this embodiment is acceptable.

[0048] Specifically, in this embodiment, the feedback winding power supply of the switching power supply is the power output from the secondary winding in the switching power supply, the modulator of the switching power supply is the chip in the switching power supply that controls the on / off time ratio of the semiconductor switch, and the auxiliary winding power supply circuit of the switching power supply is the auxiliary winding circuit in the switching power supply that supplies power to the modulator.

[0049] Specifically, in this embodiment, the short-circuit feedback circuit is electrically connected to the feedback winding power supply and the modulator of the switching power supply. The short-circuit feedback circuit receives a short-circuit signal from the feedback winding power supply and, in response to the short-circuit signal, controls the modulator to stop working, thereby causing the switching power supply to stop working and thus providing short-circuit protection. The short-circuit feedback circuit includes at least an optocoupler and a switching assembly. The optocoupler serves two purposes: firstly, it isolates the short-circuit feedback circuit from the feedback winding power supply, preventing mutual interference between the circuits; secondly, in response to the short-circuit signal, the optocoupler's output terminal is disconnected, i.e., the output terminal of the optocoupler is in an open-circuit state. The optocoupler further controls the switching assembly to connect the modulator to the ground wire, thereby causing the modulator to stop working and achieving short-circuit protection.

[0050] In this embodiment, the short-circuit signal of the feedback winding power supply is the output characteristic of the switching power supply itself when a short circuit occurs. For example, see... Figure 4 In this embodiment, when the +5V power supply of the feedback winding is short-circuited, the output voltage will change to 2-3V. This voltage change can serve as the short-circuit signal. Furthermore, the short-circuit signal can also be a specific identification signal, such as a high level representing a short circuit and a low level representing no short circuit. This specific identification signal can be obtained by monitoring the switching power supply through a detection circuit. This embodiment does not limit the specific detection circuit. Preferably, this embodiment directly uses the output characteristics of the switching power supply itself when a short circuit occurs as the short-circuit signal. The short-circuit feedback circuit directly performs feedback control of the modulator based on the output characteristics of the switching power supply itself when a short circuit occurs. That is, when a short circuit occurs in the switching power supply, the short-circuit feedback circuit directly controls the modulator to stop working in response to the corresponding circuit output characteristics. This avoids the cumbersome signal conversion in the intermediate stages and greatly improves the response speed of the switching power supply's short-circuit protection.

[0051] Specifically, in this embodiment, the overvoltage feedback circuit is electrically connected to the auxiliary winding power supply circuit and the modulator of the switching power supply. The overvoltage feedback circuit receives an overvoltage signal from the auxiliary winding power supply circuit. In response to the overvoltage signal, the overvoltage feedback circuit controls the modulator to stop working, thereby causing the switching power supply to stop working and thus forming overvoltage protection. The overvoltage feedback circuit includes at least a first Zener diode and a trigger. The first Zener diode responds to the overvoltage signal and becomes conductive, further enabling the input and output terminals of the trigger to conduct, i.e., connecting the modulator to ground, thereby causing the modulator to stop working and realizing overvoltage protection.

[0052] In this embodiment, the overvoltage signal of the auxiliary winding power supply circuit is the output characteristic of the switching power supply itself when an overvoltage occurs. For example, see... Figure 4In this embodiment, when other windings of the switching power supply are short-circuited or overvoltage occurs due to transformer turns issues, the voltage in the auxiliary winding power supply circuit rises. This voltage change can serve as the overvoltage signal. Furthermore, the overvoltage signal can also be a specific identification signal, such as a high level representing overvoltage and a low level representing no overvoltage. This specific identification signal can be obtained by monitoring the switching power supply through a detection circuit. This embodiment does not limit the specific detection circuit. Preferably, this embodiment directly uses the output characteristics of the switching power supply circuit itself when overvoltage occurs as the overvoltage signal. The overvoltage feedback circuit directly controls the modulator based on the output characteristics of the switching power supply circuit itself when overvoltage occurs. That is, when overvoltage occurs in the switching power supply, the overvoltage feedback circuit directly controls the modulator to stop working in response to the corresponding circuit output characteristics. This avoids cumbersome signal conversion in the intermediate stages and greatly improves the response speed of the switching power supply overvoltage protection.

[0053] Furthermore, the overvoltage signal when the auxiliary winding power supply circuit in this embodiment experiences overvoltage can include at least two parts: one part is the overvoltage caused by the power supply circuit due to issues such as the number of coil turns, and the other part is the overvoltage caused by the power supply circuit due to a short circuit in other windings besides the feedback winding power supply. Therefore, the overvoltage feedback circuit in this embodiment can not only provide overvoltage protection for the power supply circuit, but also, more importantly, provide short circuit protection for other winding power supplies, greatly increasing the safety of the switching power supply.

[0054] This embodiment provides short-circuit and / or overvoltage protection through short-circuit feedback circuits and / or overvoltage feedback circuits. The short-circuit feedback circuit, based on an optocoupler and switching components, provides short-circuit protection. When the feedback winding power supply is short-circuited, it directly responds to the corresponding short-circuit signal to control the modulator to stop working. If the short circuit persists in the next operating cycle of the switching power supply, the short-circuit feedback circuit continues to provide short-circuit protection, thus forming a "hiccup" protection until the short circuit is eliminated and the short-circuit feedback circuit automatically recovers, allowing the switching power supply to return to normal operation. This significantly increases the safety of the switching power supply. The overvoltage feedback circuit, based on a first Zener diode and a trigger, provides overvoltage protection. When overvoltage occurs due to short circuits in other windings of the switching power supply or due to issues such as the number of transformer turns, it directly responds to the corresponding overvoltage signal to control the modulator to stop working. This provides short-circuit protection for any output circuit and overvoltage protection for the power supply circuit, further increasing the safety of the switching power supply. Furthermore, the above eliminates the need for fuses and related complex circuits, greatly reducing costs.

[0055] In one embodiment, the short-circuit signal is the voltage signal of the feedback winding power supply when short-circuited, and the overvoltage signal is the voltage signal of the auxiliary winding power supply circuit when overvoltage occurs. Specifically, this embodiment uses the output characteristics of the feedback winding power supply circuit itself when a short circuit occurs as the short-circuit signal, and uses the output characteristics of the auxiliary winding power supply circuit itself when an overvoltage occurs as the overvoltage signal. This avoids cumbersome signal conversion in the intermediate links and greatly improves the response speed of the switching power supply's short-circuit protection and overvoltage protection.

[0056] In one embodiment, see Figure 4 The switching assembly includes at least a first switch 12, a second switch 14, and a second Zener diode 13; the input terminal of the optocoupler 11 is electrically connected to the feedback winding power supply, and the output terminal of the optocoupler 11 is electrically connected to the control terminal of the first switch 12; the auxiliary winding power supply output from the auxiliary winding power supply circuit 23 is electrically connected to the control terminal of the second switch 14 via the input / output terminals of the first switch 12 and the second Zener diode 13; the modulator is grounded via the input / output terminals of the second switch 14. Wherein, as Figure 4 As shown, in this embodiment, the auxiliary winding power supply is one end of the auxiliary winding power supply circuit output, which is V-16V.

[0057] Specifically, such as Figure 4 As shown, the input terminal of optocoupler PC10 is electrically connected to the +5V power supply of the feedback winding, and the output terminal of optocoupler PC10 is electrically connected to the control terminal of the first switch Q11. The auxiliary winding power supply V-16V output from the auxiliary winding power supply circuit is electrically connected to the control terminal of the second switch Q10 through the input / output terminals of the first switch Q11 and the second Zener diode ZD15. The modulator U4 is grounded through the input / output terminals of the second switch Q10. In this process, the optocoupler PC10 responds to a short-circuit signal of 2-3V from the +5V feedback winding power supply. That is, the feedback winding power supply changes from 5V to 2-3V due to the short-circuit voltage. The diode at the output terminal of the optocoupler PC10 is turned off. The first switch Q11 responds to the turn-off of the output terminal of the optocoupler PC10, and conducts the auxiliary winding power supply V-16V and the control terminal of the second switch Q10. The current flows through the second Zener diode ZD15, causing the second Zener diode ZD15 to conduct, thereby turning on the second switch Q10. At this time, the COM terminal of the modulator U4 is grounded, and the modulator U4 stops working, realizing short-circuit protection.

[0058] Furthermore, when the short-circuit signal 2-3V of the +5V power supply of the feedback winding is eliminated, that is, when the voltage of the +5V power supply of the feedback winding is restored to 5V, the modulator U4 restarts, the diode at the output terminal of the optocoupler PC10 is turned on, the first switch Q11 is turned off, and then the second switch Q10 is turned off, so that the COM terminal of the modulator U4 is disconnected from the ground wire, and the modulator resumes normal operation.

[0059] In one embodiment, such as Figure 4As shown, the short-circuit feedback circuit specifically includes: one input terminal of optocoupler PC10 is grounded through a Zener diode ZD16; the other input terminal of optocoupler PC10 is electrically connected to the +5V power supply of the feedback winding through a resistor R286; one output terminal of optocoupler PC10 is electrically connected to the -16V power supply of the auxiliary winding; and the other output terminal of optocoupler PC10 is grounded through a resistor R285; one input / output terminal of the first switch Q11 is electrically connected to the -16V power supply of the auxiliary winding and is connected to the first... The control terminal of switch Q11 is electrically connected. The control terminal of the first switch Q11 is grounded through resistors R282 and R285. The other end of the input / output of the first switch Q11 is electrically connected to the control terminal of the second switch Q10 through resistor R283 and the second Zener diode ZD15, and is grounded through resistor R284. One end of the input / output of the second switch Q10 is electrically connected to the cathode of a diode D33. The anode of the diode D33 is electrically connected to the COM terminal of the modulator U4. The other end of the input / output of the second switch Q10 is grounded.

[0060] In one embodiment, the switching assembly further includes at least a starting capacitor, with one end of the first switch electrically connected to the second Zener diode electrically connected to one end of the starting capacitor, and the other end of the starting capacitor grounded. Specifically, as shown... Figure 4 As shown, the switching assembly includes starting capacitors C208, C219, and C211. The three capacitors are connected in parallel to achieve the capacitance value required for the switching power supply to start. This embodiment does not impose specific limitations on the number and capacitance of the starting capacitors; they can be matched and set according to the actual circuit requirements. The starting capacitors in this embodiment provide a buffer period during the voltage rise phase of the feedback winding power supply and the auxiliary winding power supply when the power circuit is powered on or when the short circuit in the feedback winding power supply is cleared. This allows the voltages of the feedback winding power supply and the auxiliary winding power supply to reach a stable state, preventing erroneous short-circuit protection during the voltage rise phase. This ensures the power circuit can start normally upon power-on and can automatically start when the short circuit is cleared, greatly improving the accuracy and reliability of short-circuit protection and avoiding some manual starting operations, making it more user-friendly.

[0061] In one embodiment, the short-circuit feedback circuit is further configured to, in response to a normal signal from the feedback winding power supply, control the modulator to resume normal operation via an optocoupler, a first switch, a startup capacitor, a second Zener diode, and a second switch. Specifically, as shown... Figure 4As shown, when the short circuit in the feedback winding power supply is eliminated and the modulator restarts, the +5V of the feedback winding power supply rises from 0V to 2-3V in the short circuit signal state, and then rises back to the normal state of 5V. During this process, the output diode of the optocoupler PC10 will be cut off for a short period of time and then resume conduction. During the cut-off period of the output diode of the optocoupler PC10, the first switch Q11 is turned on. At this time, the current of the auxiliary winding power supply flows to the starting capacitor, which will charge the starting capacitor. When the charge in the starting capacitor accumulates to a certain level, the second Zener diode ZD15 will turn on. That is to say, during the cut-off period of the output diode of the optocoupler PC10, the second switch Q10 can be kept off by the time buffer of the starting capacitor, which ensures that the modulator U4 starts working normally. This realizes the self-starting of the switching power supply after the short circuit is eliminated.

[0062] Further, see Figure 4 During the power-on process of the switching power supply, there is also a voltage rise phase in both the auxiliary winding power supply and the feedback winding power supply. This will result in a sequential power-on relationship between the auxiliary winding power supply and the feedback winding power supply. Based on the same principle, the starting capacitor in this embodiment can act as a time buffer for the short-circuit feedback circuit, that is, delay the normal operation of the short-circuit feedback circuit, thereby realizing the power-on self-start of the switching power supply. The specific process is described above and will not be repeated here.

[0063] In one embodiment, see Figure 4 The short-circuit feedback circuit further includes: a resistor R287 and a capacitor C209 connected in parallel between the two input terminals of the optocoupler; a resistor R280 and a capacitor C207 connected to one end of the second Zener diode and the second switch, and the other end of the resistor R280 and capacitor C207 grounded. Specifically, in this embodiment, the above-mentioned resistors and capacitors perform filtering during signal transmission, avoiding the influence of interference signals on the short-circuit feedback circuit of this embodiment, and ensuring the reliability and accuracy of short-circuit protection.

[0064] In one embodiment, see Figure 4 In the overvoltage feedback circuit, the cathode of the first Zener diode 21 is electrically connected to the auxiliary winding power supply circuit 23, the anode of the first Zener diode 21 is electrically connected to the control terminal of the trigger 22, the anode of the trigger 22 is electrically connected to the modulator, and the cathode of the trigger 22 is grounded. For details, see [link to relevant documentation]. Figure 4 When the voltage of the auxiliary winding power supply circuit exceeds a certain threshold, the first Zener diode ZD13 is turned on, which further enables the input and output of the trigger IC1 to conduct, grounding the COM terminal of the modulator U4, stopping the modulator U4 from working, and realizing overvoltage protection.

[0065] Further, see Figure 4In this embodiment, once the trigger IC1 is turned on, the control terminal G will not function, that is, the trigger IC1 is locked. IC1 will only be turned off if the current flowing through the A and K terminals of the trigger IC1 is less than a certain value. This embodiment utilizes this function so that when the voltage of the auxiliary winding or the voltage of pin 7 of U4 rises to the set overvoltage threshold, the trigger IC1 is locked, the COM terminal of the modulator U4 is grounded, and the switching power supply stops working. After power-off and power-on, if there is still overvoltage after the switching power supply restarts, the above action is repeated to ensure the safety of the power supply circuit.

[0066] In one embodiment, see Figure 4 The overvoltage feedback circuit in this embodiment further includes: the control terminal of the trigger is grounded via a capacitor C1; the anode of the trigger is electrically connected to the COM terminal of the modulator via a diode D34, the cathode of the diode D34 is electrically connected to the anode of the trigger, and the anode of the diode D34 is electrically connected to the modulator. Specifically, the capacitor C1 in this embodiment plays a signal filtering role in the signal transmission process, filtering out interference signals in the signal and ensuring the reliability and accuracy of the overvoltage feedback circuit. Specifically, the diode D34 in this embodiment cooperates with the diode D33 in the short-circuit feedback circuit in the above embodiment to ensure that the short-circuit feedback circuit and the overvoltage feedback circuit do not interfere with each other, thereby improving the reliability of the short-circuit feedback circuit and the overvoltage feedback circuit.

[0067] Now combined Figure 4 The circuit diagram shown illustrates the working principle of the short-circuit feedback circuit and the overvoltage feedback circuit in this embodiment.

[0068] See Figure 4 In the short-circuit feedback circuit, when the +5V power supply of the feedback winding is short-circuited, the output voltage will change to 2-3V, causing the LED of the PC10 optocoupler to be cut off. Pins 3 and 4 of PC10 will be in an open-collector state (OC gate), causing the PNP transistor Q11 (first switch) to conduct linearly / saturately. After passing through R283 and C208, C219, and C211, current flows through the Zener diode ZD15 (second Zener diode). When the current reaches a certain level, the NPN transistor Q10 (second switch) will saturate and conduct, thereby pulling down the COM terminal of pin 1 of the modulator U4, turning off the MOSFET drive control in the switching power supply to achieve a protection function. When the short circuit of the +5V power supply of the feedback winding is eliminated, the modulator U4 chip restarts, and the switching power supply returns to normal operation.

[0069] See Figure 4In the overvoltage feedback circuit, when other winding power supplies (e.g., +24V) of the switching power supply are short-circuited or the voltage of the feedback winding V-16V rises due to transformer turns, when the voltage rises to the operating voltage of the ZD13 Zener diode (first Zener diode), the ZD13 Zener diode conducts, and current flows through it. This current is filtered by capacitor C1 and controls the control terminal G of the trigger IC1. The IC1 trigger is a current-type control device. When a certain current flows through it, the A and K terminals of the trigger IC1 conduct. Once it conducts, the control terminal G does not function unless the current flowing through the A and K terminals of the trigger IC1 is less than a certain value, at which point the trigger IC1 will turn off. Therefore, using this function, when the voltage of the auxiliary winding rises to the overvoltage threshold or the voltage at pin 7 of U4 rises to the overvoltage threshold, the trigger IC1 function locks up, causing pin 1 of the trigger U4 to pull low, and the switching power supply stops working. After power-off and power-on, the switching power supply restarts. If overvoltage still exists, the above actions are repeated.

[0070] In one embodiment, an electronic device is provided, including the protection circuit for the switching power supply in any of the above embodiments. Specific limitations of the electronic device can be found in the above description of the protection circuit for the switching power supply, and will not be repeated here.

[0071] Electronic devices based on the protection circuit of the switching power supply in any of the above embodiments provide short-circuit and / or overvoltage protection through short-circuit feedback circuits and / or overvoltage feedback circuits. The short-circuit feedback circuit provides short-circuit protection based on an optocoupler and switching components. When the feedback winding power supply is short-circuited, it directly responds to the corresponding short-circuit signal to control the modulator to stop working. If a short circuit still exists in the next operating cycle of the switching power supply, the short-circuit feedback circuit will continue to provide short-circuit protection, thus forming a "hiccup" protection until the short circuit is eliminated and the short-circuit feedback circuit automatically recovers, allowing the switching power supply to return to normal operation, greatly increasing the safety of the switching power supply. The overvoltage feedback circuit provides overvoltage protection based on a first Zener diode and a trigger. When overvoltage occurs due to a short circuit in other windings of the switching power supply or due to issues such as the number of transformer turns, it directly responds to the corresponding overvoltage signal to control the modulator to stop working. This achieves short-circuit protection for any output circuit and overvoltage protection for the power supply circuit, further increasing the safety of the switching power supply. Furthermore, the above eliminates the need for fuses and related complex circuits, significantly reducing costs.

[0072] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A protection circuit for a switching power supply, comprising the power supply circuit of the switching power supply, characterized in that, Also includes: A short-circuit feedback circuit and / or an overvoltage feedback circuit, wherein the short-circuit feedback circuit includes at least an optocoupler and a switching assembly, and the overvoltage feedback circuit includes at least a first Zener diode and a trigger. The feedback winding power supply of the power supply circuit is electrically connected to the control terminal of the switching assembly via the optocoupler. The modulator of the power supply circuit is grounded via the input / output terminals of the switching assembly. In the event of a short circuit in the feedback winding power supply, the short-circuit feedback circuit is configured to respond to a short-circuit signal in the feedback winding power supply and control the modulator to stop working via the optocoupler and the switching assembly. The switching assembly includes at least a first switch, a second switch, and a second Zener diode. The input terminal of the optocoupler is electrically connected to the feedback winding power supply, and the output terminal of the optocoupler is electrically connected to the control terminal of the first switch. The auxiliary winding power supply of the power supply circuit is fed back to the feedback winding power supply. The auxiliary winding power supply output from the circuit is electrically connected to the input / output terminals of the first switch, the second Zener diode, and the control terminal of the second switch. The modulator is grounded via the input / output terminals of the second switch. In the event of a short circuit in the feedback winding power supply, the optocoupler is configured to disconnect its output terminal in response to the short circuit signal of the feedback winding power supply. The first switch is configured to connect the auxiliary winding power supply and the second Zener diode in response to the disconnection of the optocoupler's output terminal. The second switch is configured to connect the modulator and ground in response to the saturation conduction of the second Zener diode, thereby stopping the modulator from operating. The auxiliary winding power supply circuit of the power supply circuit is electrically connected to the control terminal of the trigger via the first Zener diode. The modulator of the power supply circuit is grounded via the input and output terminals of the trigger. In the event of overvoltage in the auxiliary winding power supply circuit, the overvoltage feedback circuit is configured to respond to the overvoltage signal of the auxiliary winding power supply circuit by controlling the conduction of the modulator and the ground wire via the first Zener diode and the trigger, so that the modulator stops working. The feedback winding power supply is the output power supply of the power supply circuit, and the auxiliary winding power supply circuit is the power supply circuit for the operation of the power supply circuit itself.

2. The protection circuit for the switching power supply according to claim 1, characterized in that, The short-circuit signal is the voltage signal of the feedback winding power supply when it is short-circuited, and the overvoltage signal is the voltage signal of the auxiliary winding power supply circuit when it is over-voltage.

3. The protection circuit for the switching power supply according to claim 1, characterized in that, The short-circuit feedback circuit includes: One input terminal of the optocoupler is grounded via a Zener diode ZD16, the other input terminal of the optocoupler is electrically connected to the power supply of the feedback winding via a resistor R286, one output terminal of the optocoupler is electrically connected to the power supply of the auxiliary winding, and the other output terminal of the optocoupler is grounded via a resistor R285. One end of the first switch input / output is electrically connected to the auxiliary winding power supply and is electrically connected to the control terminal of the first switch via a resistor R281. The control terminal of the first switch is grounded via a resistor R282 and a resistor R285. The other end of the first switch input / output is electrically connected to the control terminal of the second switch via a resistor R283 and a second Zener diode and is grounded via a resistor R284. One end of the second switch input / output is electrically connected to the cathode of a diode D33, the anode of the diode D33 is electrically connected to the COM terminal of the modulator, and the other end of the second switch input / output is grounded.

4. The protection circuit for the switching power supply according to claim 1 or 3, characterized in that, The switching assembly further includes at least a starting capacitor, with one end of the first switch electrically connected to the second Zener diode electrically connected to one end of the starting capacitor, and the other end of the starting capacitor grounded.

5. The protection circuit for the switching power supply according to claim 4, characterized in that, The short-circuit feedback circuit is also configured to respond to a normal signal from the feedback winding power supply, and control the modulator to resume normal operation via the optocoupler, the first switch, the startup capacitor, the second Zener diode, and the second switch.

6. The protection circuit for the switching power supply according to claim 1 or 3, characterized in that, The short-circuit feedback circuit further includes: A resistor R287 and a capacitor C209 are connected in parallel between the two input terminals of the optocoupler. One end of the second Zener diode is electrically connected to the second switch and is connected to a resistor R280 and a capacitor C207, while the other end of the resistor R280 and the capacitor C207 is grounded.

7. The protection circuit for the switching power supply according to claim 1, characterized in that, In the overvoltage feedback circuit, the cathode of the first Zener diode is electrically connected to the auxiliary winding power supply circuit, the anode of the first Zener diode is electrically connected to the control terminal of the trigger, the anode of the trigger is electrically connected to the modulator, and the cathode of the trigger is grounded. In the event of an overvoltage in the auxiliary winding power supply circuit, the first Zener diode is configured to saturate and conduct in response to an overvoltage signal in the auxiliary winding power supply circuit, and the trigger is configured to connect the modulator to ground in response to the saturation conduction of the first Zener diode, thereby causing the modulator to stop operating.

8. The protection circuit for the switching power supply according to claim 7, characterized in that, The overvoltage feedback circuit also includes: The control terminal of the trigger is grounded via a capacitor C1; The anode of the trigger is electrically connected to the COM terminal of the modulator via a diode D34, the cathode of the diode D34 is electrically connected to the anode of the trigger, and the anode of the diode D34 is electrically connected to the modulator.

9. An electronic device, characterized in that, include: The protection circuit for the switching power supply as described in any one of claims 1 to 8.

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