Short-circuit protection control device based on TL431 and application

Abstract

The invention provides a switching power supply protection control device and application. The switching power supply protection control device comprises a fault signal voltage sampling circuit, a short-circuit protection circuit based on a pulse width modulator and a soft start circuit. One end of the fault signal voltage sampling circuit is connected with an output voltage Vo of the switching power supply, the other end of the fault signal voltage sampling circuit is connected with a COMP end of a pulse width modulator in the short-circuit protection circuit based on the pulse width modulator, and the other end of the short-circuit protection circuit based on the pulse width modulator is connected with one end of the soft start circuit; the other end of the soft start circuit is connected with the SS end of the pulse width modulator in the short-circuit protection circuit based on the pulse width modulator; the short-circuit protection control device based on the TL431 remarkably improves the stability, reliability and safety of a switching power supply system, has wide application prospects and practical value, and solves the problems that a traditional switching power supply protection circuit is poor in protection precision, complex in circuit and single in function.

Description

Technical Field

[0001] The invention belongs to the technical field of short-circuit protection circuits of switching power supplies, and relates to a short-circuit protection control device based on TL431 and an application thereof. Background Art

[0002] Switching power supplies are widely used in the fields of industry and national defense, in electronic systems such as aerospace, aviation, weapons, medical electronics, and industrial automation equipment. When a switching power supply fails or shorts out during use or debugging, a protection circuit is an essential safeguard. The protection circuit can greatly reduce damage to the switching power supply and ensure the normal operation of the equipment in the electronic system.

[0003] Many pulse width modulators, the core electronic devices of switching power supplies, still do not have short-circuit protection functions. In order to ensure the reliability of switching power supplies, it is still necessary to build short-circuit protection circuits around the pulse width modulators. The basic principle of output short-circuit protection is: when a fault (short circuit) occurs, the fault signal triggers the protection device after a certain time delay, and controls the shutdown of the power unit; after a certain time delay, the power unit is released and the fault state is detected again. If the fault still exists, the above process is repeated. Many current short-circuit protection methods use voltage comparators as core devices to build peripheral circuits. These methods have various problems in application.

[0004] (1) Invention patent "Low power consumption short circuit protection circuit and DC / DC converter" CN202797901U The device is composed of a comparator, a reference voltage, and a diode. The specific implementation circuit is as follows Figure 1As shown. The specific working principle is that when the DC / DC converter outputs the circuit, the voltage of the compensation comparison pin 1 (COMP) of the PWM control chip U1 is higher than the first reference voltage (REF), the first comparator IC1 outputs a high level, the diode D1 is turned on, the positive input terminal of the second comparator IC2 is lower than the negative input terminal and outputs a low level, and after the diode D2 is turned on, the level of the comparison pin 1 (COMP) of the PWM controller U1 is pulled down to stop the PWM control chip from working, and short circuit protection is achieved. When the DC / DC converter resumes normal working state, the voltage of the compensation comparison pin 1 of the PWM control chip U1 is lower than the first reference voltage (2.5V), the first comparison IC1 outputs a low level, the diode D1 is in the cut-off state, the energy storage capacitor C1 discharges through the voltage divider resistor R8, the positive input terminal of the second comparator IC2 is higher than the reverse input terminal voltage and outputs a high level, the diodes D2 and D3 are cut off, and the PWM control chip resumes normal working. The scheme uses two comparators and three diodes to form a comparison circuit, which is the key to implementing protection. Since the short-circuit protection circuit is composed of two-stage comparators, the circuit structure is relatively complex. The on-off characteristics of three diodes are used to realize the comparison signal input and clamping effect. The diodes are composed of ordinary pn structures, and their accuracy and temperature coefficient are poor, which affects the short-circuit protection effect. The above circuit has a complex circuit structure and a large number of components, resulting in a high probability of failure of the short-circuit protection circuit and a relatively expensive price.

[0005] Invention patent "A short-circuit protection circuit and soft-start circuit based on pulse width modulator" CN209913488U The device includes a current sampling circuit, a soft start circuit, and a comparison circuit. The specific circuits are as follows Figure 2 As shown. The specific working principle is that when the output is short-circuited, the current of the COMP pin begins to increase, and the primary current becomes very large, that is, the current of the transformer T1 becomes very large. Most of the current passes through the resistor R11, and part of the current charges the capacitor C2 through the resistor R3. The voltage of the capacitor C2 rises rapidly and is higher than the positive input terminal of the voltage comparator U1A. The voltage follower U1A quickly outputs a low level, and releases the capacitor C3 voltage through the resistor R5 and the diode D2. The voltage of the COMP pin also drops, and the switching power supply stops working and enters the protection state. The output of the voltage comparator U1A becomes a low level, so the voltage of the positive input terminal of the voltage comparator U1A decreases, and the capacitor C2 is slowly released through the resistor R4. When the voltage of the reverse input terminal drops to less than the voltage of the forward input terminal, the voltage comparator U1A outputs a high level again, and charges the soft start circuit 3, and the power supply starts.

[0006] This method uses a current transformer to detect the output fault state. Due to the influence of the coupling degree of the two windings of the transformer and the load adjustment degree, there is a large signal acquisition error. At the same time, the protection triggering process requires the fault signal to trigger the voltage comparator to flip the output level and then pull down the COMP terminal voltage to achieve short-circuit protection. The complex line structure makes it difficult to accurately control the protection trigger time and the locking time after protection, which greatly affects the protection effect.

[0007] In summary, the traditional switching power supply protection circuit has the problems of poor protection accuracy, complex circuit and single function. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention proposes a switching power supply protection control device and application, which can realize the short-circuit protection function of the switching power supply output. It has the characteristics of simple circuit structure and low cost, and solves the problems of poor protection accuracy, complex circuit and single function in traditional switching power supply protection circuit.

[0009] The present invention is achieved through the following technical solutions: A short circuit protection control device based on TL431, comprising: Fault signal voltage sampling circuit, short circuit protection circuit based on pulse width modulator and soft start circuit; One end of the fault signal voltage sampling circuit is connected to the output voltage Vo of the switching power supply, the other end of the fault signal voltage sampling circuit is connected to the COMP end of the pulse width modulator in the short-circuit protection circuit based on the pulse width modulator, the other end of the short-circuit protection circuit based on the pulse width modulator is connected to one end of the soft start circuit, and the other end of the soft start circuit is connected to the SS end of the pulse width modulator in the short-circuit protection circuit based on the pulse width modulator.

[0010] Preferably, the fault signal voltage sampling circuit includes a first reference source IC1, an optocoupler device IC2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a first capacitor C1; The output voltage Vo of the switching power supply is connected to one end of the first resistor R1 and the fifth resistor R5, the other end of the first resistor R1, one end of the first capacitor C1 and one end of the second resistor R2 are commonly connected to the R end of the first reference source IC1, the A end of the first reference source IC1 and the other end of the second resistor R2 are commonly connected to the ground, the K end of the first reference source IC1 is connected to one end of the third resistor R3 and one end of the fourth resistor R4, and are commonly connected to the K end of the optocoupler IC2; the other end of the fourth resistor R4 and the other end of the fifth resistor R5 are connected to the A end of the optocoupler IC2, the E end of the optocoupler IC2 is grounded, and the C end of the optocoupler IC2 is output to the short-circuit protection circuit based on the pulse width modulator and is connected to the COMP end of the pulse width modulator.

[0011] Preferably, the specific working process of the fault signal voltage sampling circuit is: When the output of the switching power supply is short-circuited, the output voltage Vo drops. After being sampled by the first resistor R1 and the second resistor R2, it is lower than the internal reference voltage of the first reference source IC1. The K-level voltage of the first reference source IC1 increases, and the current flowing from the A terminal to the K terminal of the optocoupler IC2 increases accordingly, further causing the current from the C terminal of the optocoupler to the ground to increase, causing the COMP terminal voltage of the pulse width modulator to increase.

[0012] Preferably, the internal reference voltage of the first reference source IC1 is 2.5V.

[0013] Preferably, the short-circuit protection circuit based on the pulse width modulator includes a second reference source IC3, a transistor P1, a second capacitor C2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9; One end of the sixth resistor R6, one end of the seventh resistor R7 and one end of the second capacitor C2 are commonly connected to the R end of the second reference source IC3, the other end of the seventh resistor R7, the other end of the second capacitor C2 and the A end of TL431 are commonly grounded, the K end of the second reference source IC3 is connected to the eighth resistor R8, one end of the ninth resistor R9, the other end of the eighth resistor R8 is connected to the base of the transistor P1, and the other end of the ninth resistor R9 is connected to the emitter of the transistor P1 and is commonly connected to the Vcc end of the pulse width modulator.

[0014] Preferably, the transistor P1 is a P-type transistor.

[0015] Preferably, the specific working process of the short-circuit protection circuit based on the pulse width modulator is: When the output of the switching power supply is short-circuited, the COMP voltage of the pulse width modulator increases. After sampling by the first resistor R1 and the second resistor R2, when the voltage at the R terminal of the second reference source IC3 is higher than the internal reference voltage of the second reference source IC3, the K terminal of the second reference source IC3 flips and outputs a low voltage. The voltage through the eighth resistor R8 and the base of the transistor P1 decreases accordingly, and the transistor P1 turns on the Vcc terminal voltage of the pulse width modulator and outputs a low level.

[0016] Preferably, the soft start circuit includes a MOS tube Q1, a tenth resistor R10 and a third capacitor C3; The collector of the transistor P1 of the short-circuit protection circuit based on the pulse width modulator is connected to one end of the tenth resistor R10, one end of the third capacitor C3 and the base of the MOS tube Q1, the other end of the tenth resistor R10, the other end of the third capacitor C3 and the source of the MOS tube Q1 are connected to the ground, and the drain of the MOS tube Q1 is connected to the SS end of the pulse width modulator.

[0017] Preferably, the specific working process of the soft start circuit is: When the output of the switching power supply is short-circuited, the voltage at the K terminal of the second reference source IC3 flips and outputs a low level, and the base voltage of the transistor P1 decreases accordingly. After the transistor P1 is turned on, the third capacitor C3 is quickly charged, and the voltage of the third capacitor C3 increases. When it exceeds the gate threshold voltage of the MOS tube Q1, the MOS tube Q1 is turned on and the pulse width modulator SS terminal outputs a low level.

[0018] Application of a short-circuit protection control device based on TL431 in switching power supply, The short-circuit protection control device based on TL431 is applied to a single-ended flyback switching power supply, a single-ended forward switching power supply, a push-pull switching power supply, a half-bridge switching power supply and a full-bridge switching power supply.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a switching power supply protection control device and application, including a fault signal voltage sampling circuit, a short circuit protection circuit based on a pulse width modulator, and a soft start circuit; the output voltage Vo of the switching power supply is monitored in real time by the fault signal voltage sampling circuit, and once an abnormality (such as a voltage drop or disappearance caused by a short circuit) is detected, the protection mechanism can be quickly triggered; this instant response can prevent potential dangers such as overcurrent and overheating caused by a short circuit, and effectively protect the power supply and load equipment from damage. Using a pulse width modulator (PWM) as a core control element, the width of the output pulse can be accurately adjusted according to the fault signal provided by the sampling circuit, thereby realizing fine control of the power supply output. This control method not only improves the accuracy of protection, but also can quickly resume normal operation after the fault is removed, reducing unnecessary downtime. The design of the soft start circuit enables the power supply to increase the output voltage smoothly during the startup process, avoiding damage to the power supply and load caused by instantaneous large current impact; this not only prolongs the service life of the equipment, but also improves the stability and reliability of the system. The short-circuit protection control device based on TL431 significantly improves the stability, reliability and safety of the switching power supply system through precise control, effective protection and convenient soft start function. It has broad application prospects and practical value, and solves the problems of poor protection accuracy, complex circuits and single functions in traditional switching power supply protection circuits.

[0020] Furthermore, the device integrates fault detection, protection control and soft start functions, simplifies the circuit structure, reduces the use of external components, thereby reducing costs and improving system integration. This compact design makes the device easier to install and maintain.

[0021] Furthermore, through effective short-circuit protection and soft-start mechanisms, the device significantly improves the safety of the entire power system. Whether in normal operation or fault conditions, it can ensure the safety of power and load equipment and reduce the risk of equipment damage or casualties caused by power problems.

[0022] Furthermore, since the device is based on the universal TL431 chip and pulse width modulation technology, it has strong adaptability and scalability; it can be applied to various types of switching power supplies to meet the protection and control needs in different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an existing short-circuit protection circuit based on a comparator; Figure 2 Provide an existing current detection short-circuit protection circuit; Figure 3 The switch power supply protection control circuit of the present invention; Figure 4 This is an application example of the switching power supply protection control circuit of the present invention; Figure 5 Waveform diagram of key nodes of short-circuit protection in application example. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0026] The present invention is a switching power supply protection control method and device, which can realize the switching power supply output short circuit protection and soft start function. The specific circuit is as follows Figure 3 shown.

[0027] The protection control circuit includes three units: unit circuit 1 is a fault signal voltage sampling circuit; unit circuit 2 is a short circuit protection circuit based on a pulse width modulator; and unit circuit 3 is a soft start circuit.

[0028] Unit circuit 1, fault signal voltage sampling circuit unit The circuit of the unit circuit 1 is as follows Figure 3 As shown, the fault signal voltage sampling circuit includes a first reference source IC1, an optocoupler device IC2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a first capacitor C1; The output voltage Vo of the switching power supply is connected to one end of the first resistor R1 and the fifth resistor R5, the other end of the first resistor R1, one end of the first capacitor C1 and one end of the second resistor R2 are commonly connected to the R end of the first reference source IC1, the A end of the first reference source IC1 and the other end of the second resistor R2 are commonly connected to the ground, the K end of the first reference source IC1 is connected to one end of the third resistor R3 and one end of the fourth resistor R4, and are commonly connected to the K end of the optocoupler IC2; the other end of the fourth resistor R4 and the other end of the fifth resistor R5 are connected to the A end of the optocoupler IC2, the E end of the optocoupler IC2 is grounded, and the C end of the optocoupler IC2 is output to the short-circuit protection circuit based on the pulse width modulator and is connected to the COMP end of the pulse width modulator.

[0029] The specific working process of the fault signal voltage sampling circuit is as follows: When the output of the switching power supply is short-circuited, the output voltage Vo drops, and after being sampled by the first resistor R1 and the second resistor R2, it is lower than the internal reference voltage of the first reference source IC1. The K-level voltage of the first reference source IC1 increases, and the current flowing from the A terminal to the K terminal of the optocoupler IC2 increases accordingly, further increasing the current from the C terminal of the optocoupler to the ground, causing the voltage at the COMP terminal of the pulse width modulator to increase. The internal reference voltage of the first reference source IC1 is 2.5V.

[0030] The working mechanism of the fault signal voltage sampling circuit embodies the keen monitoring and rapid response to the output state of the switching power supply, and its beneficial effect is remarkable. When the output of the switching power supply is short-circuited, causing the output voltage Vo to drop, the circuit accurately samples the voltage through the first resistor R1 and the second resistor R2, and compares it with the internal reference voltage (2.5V) of the first reference source IC1. Once the sampled voltage is lower than the reference voltage, the K-level voltage of IC1 will increase, and this change is quickly transmitted to the optocoupler IC2, increasing the current from its A terminal to its K terminal. Furthermore, the current from the C terminal of the optocoupler to the ground also increases, eventually causing the COMP terminal voltage of the pulse width modulator to increase. This series of chain reactions constitutes a rapid identification and response mechanism for short-circuit faults.

[0031] The beneficial effects of this circuit design are: first, through precise voltage sampling and comparison, it can promptly detect and respond to faults such as output short circuits, effectively protecting the power supply and load equipment; second, the use of optocouplers to achieve electrical isolation improves the safety and stability of the circuit; finally, the circuit has a simple structure, fast response, and is easy to integrate with various pulse width modulators, providing an efficient and reliable short-circuit protection solution for the switching power supply, which helps to improve the performance and reliability of the entire power system.

[0032] Unit circuit 2, short circuit protection circuit unit based on pulse width modulator The unit circuit is as follows Figure 3 As shown, the short-circuit protection circuit based on the pulse width modulator includes a second reference source IC3, a transistor P1, a second capacitor C2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9; One end of the sixth resistor R6, one end of the seventh resistor R7 and one end of the second capacitor C2 are commonly connected to the R end of the second reference source IC3, the other end of the seventh resistor R7, the other end of the second capacitor C2 and the A end of TL431 are commonly grounded, the K end of the second reference source IC3 is connected to the eighth resistor R8, one end of the ninth resistor R9, the other end of the eighth resistor R8 is connected to the base of the transistor P1, the other end of the ninth resistor R9 is connected to the emitter of the transistor P1 and is commonly connected to the Vcc end of the pulse width modulator; the transistor P1 is a P-type transistor.

[0033] The specific working process of the short-circuit protection circuit based on the pulse width modulator is as follows: When the output of the switching power supply is short-circuited, the COMP voltage of the pulse width modulator increases. After sampling by the first resistor R1 and the second resistor R2, when the voltage at the R terminal of the second reference source IC3 is higher than the internal reference voltage of the second reference source IC3, the K terminal of the second reference source IC3 flips and outputs a low voltage. The voltage through the eighth resistor R8 and the base of the transistor P1 decreases accordingly, and the transistor P1 turns on the Vcc terminal voltage of the pulse width modulator and outputs a low level.

[0034] The short-circuit protection circuit based on the pulse width modulator exhibits efficient and accurate protection characteristics during its working process, which is of great significance to the safe operation of the switching power supply. When a short circuit occurs at the output of the switching power supply, the voltage at the COMP terminal of the pulse width modulator will increase abnormally, and this change will be accurately sampled by the first resistor R1 and the second resistor R2. Once the sampled voltage causes the voltage at the R terminal of the second reference source IC3 to exceed its internal reference voltage, the K terminal of IC3 will quickly flip and output a low voltage. This low voltage signal is transmitted to the base of the transistor P1 through the eighth resistor R8, causing the transistor P1 to turn on quickly. The conduction of the transistor P1 further causes the Vcc terminal voltage of the pulse width modulator to output a low level, thereby effectively cutting off the output of the power supply and achieving instant protection of the circuit.

[0035] The beneficial effects of this protection circuit are mainly reflected in the following aspects: first, through precise voltage sampling and comparison, it can quickly identify short-circuit faults and respond to them, protecting the power supply and load equipment from damage; second, the design of the protection circuit is simple and reliable, low-cost, and easy to be widely used in various types of switching power supplies; finally, the implementation of this protection mechanism does not rely on external complex control logic, which improves the stability and reliability of the power supply system and provides users with a safer and more reliable power supply solution.

[0036] Unit circuit 3, soft start circuit The soft start circuit includes a MOS tube Q1, a tenth resistor R10 and a third capacitor C3; The collector of the transistor P1 of the short-circuit protection circuit based on the pulse width modulator is connected to one end of the tenth resistor R10, one end of the third capacitor C3 and the base of the MOS tube Q1, the other end of the tenth resistor R10, the other end of the third capacitor C3 and the source of the MOS tube Q1 are connected to the ground, and the drain of the MOS tube Q1 is connected to the SS end of the pulse width modulator.

[0037] The specific working process of the soft start circuit is: When the output of the switching power supply is short-circuited, the voltage at the K terminal of the second reference source IC3 flips and outputs a low level, and the base voltage of the transistor P1 decreases accordingly. After the transistor P1 is turned on, the third capacitor C3 is quickly charged, and the voltage of the third capacitor C3 increases. When it exceeds the gate threshold voltage of the MOS tube Q1, the MOS tube Q1 is turned on and the pulse width modulator SS terminal outputs a low level.

[0038] When the output of the switching power supply is short-circuited, the protection mechanism responds quickly, and the voltage at the K terminal of the second reference source IC3 is flipped to output a low level. This change directly affects the base voltage of the transistor P1, causing it to turn on. Subsequently, the rapid conduction of the transistor P1 provides a rapid charging path for the third capacitor C3, causing the voltage of C3 to rise rapidly. When the voltage of C3 exceeds the gate threshold voltage of the MOS tube Q1, the MOS tube Q1 is immediately turned on, thereby causing the SS terminal of the pulse width modulator to output a low level, effectively cutting off the power output and achieving short-circuit protection for the circuit.

[0039] The beneficial effects of this mechanism are its fast response and efficient protection. Through precise voltage monitoring and fast circuit control, this protection mechanism can cut off the power supply instantly when a short circuit occurs, preventing potential dangers such as overcurrent and overheating caused by the short circuit, and effectively protecting the safety of the power supply and load equipment. At the same time, the implementation of this mechanism is simple and reliable, low-cost, and easy to promote and apply in various switching power supplies, which is of great significance to improving the stability and safety of the power supply system.

[0040] The protection control circuit proposed in the present invention is described by taking the single-ended flyback switching power supply as an example, but is not limited to the single-ended flyback power supply, and can also be applied to other power topologies such as single-ended forward switching power supply, push-pull switching power supply, half-bridge switching power supply, full-bridge switching power supply, etc. Figure 4 shown.

[0041] like Figure 4 As shown, the working principle of short-circuit protection is: When the output of the switching power supply is short-circuited, the output voltage Vo decreases, the current from the C terminal of the optocoupler IC2 to the ground increases, and the voltage at the COMP terminal of the pulse width modulator increases; like Figure 5As shown, when the COMP terminal voltage of the pulse width modulator is greater than 3.75V, the K terminal of the second reference source TL431 (IC3) flips to output a low voltage, and the base voltage of the transistor P1 decreases accordingly. After the transistor P1 is turned on, the third capacitor C3 is quickly charged. When the voltage of the third capacitor C3 exceeds the gate threshold voltage of the MOS tube Q1, the MOS tube Q1 is turned on, the SS terminal of the pulse width modulator is pulled low, and the pulse width modulator stops working; after the pulse width modulator stops working, the COMP terminal voltage of the pulse width modulator decreases. At this time, the K terminal of the second reference source TL431 (IC3) outputs a high voltage, and the base voltage of the transistor P1 increases accordingly. After the transistor P1 is turned off, the third capacitor C3 is slowly discharged through the tenth resistor R10. When the voltage of the third capacitor C3 is lower than the gate threshold voltage of the MOS tube Q1, after the MOS tube Q1 is turned off, the SS terminal of the pulse width modulator is restarted, and a short-circuit protection cycle ends; After the SS end of the pulse width modulator is soft-started again, when the output voltage is still short-circuited, the short-circuit circuit enters the next cycle, and when the output load is normal, the circuit exits the short-circuit protection mechanism.

[0042] TL431 is an adjustable precision shunt regulator, also known as a programmable precision reference voltage source. It is a very common electronic component used to stabilize power supply voltage, current, and perform tasks such as comparison and feedback control.

[0043] The protection control circuit proposed in the present invention has a wide range of applicability, which enables the protection control circuit to meet the needs of different power topologies, providing power supply designers with more choices and flexibility, and helping to reduce design costs and improve design efficiency. Secondly, the stable performance of the circuit in different power topologies verifies its reliability and robustness, and provides a strong guarantee for the safe operation of the power supply system. Finally, by applying the protection control circuit in different types of switching power supplies, comprehensive monitoring and rapid response to the power supply output status can be achieved, and the occurrence of short circuits, overcurrents and other faults can be effectively prevented, thereby extending the service life of the power supply and load equipment, and improving the stability and reliability of the entire power supply system. Therefore, the protection control circuit proposed in the present invention has significant technical advantages and application value.

[0044] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0047] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A short circuit protection control device based on TL431, characterized in that: include, Fault signal voltage sampling circuit, short circuit protection circuit based on pulse width modulator and soft start circuit; One end of the fault signal voltage sampling circuit is connected to the output voltage Vo of the switching power supply, the other end of the fault signal voltage sampling circuit is connected to the COMP end of the pulse width modulator in the short-circuit protection circuit based on the pulse width modulator, the other end of the short-circuit protection circuit based on the pulse width modulator is connected to one end of the soft start circuit, and the other end of the soft start circuit is connected to the SS end of the pulse width modulator in the short-circuit protection circuit based on the pulse width modulator.

2. A short circuit protection control device based on TL431 according to claim 1, characterized in that: The fault signal voltage sampling circuit includes a first reference source IC1, an optocoupler device IC2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a first capacitor C1; The output voltage Vo of the switching power supply is connected to one end of the first resistor R1 and the fifth resistor R5, the other end of the first resistor R1, one end of the first capacitor C1 and one end of the second resistor R2 are commonly connected to the R end of the first reference source IC1, the A end of the first reference source IC1 and the other end of the second resistor R2 are commonly connected to the ground, the K end of the first reference source IC1 is connected to one end of the third resistor R3 and one end of the fourth resistor R4, and are commonly connected to the K end of the optocoupler IC2; the other end of the fourth resistor R4 and the other end of the fifth resistor R5 are connected to the A end of the optocoupler IC2, the E end of the optocoupler IC2 is grounded, and the C end of the optocoupler IC2 is output to the short-circuit protection circuit based on the pulse width modulator and is connected to the COMP end of the pulse width modulator.

3. A short circuit protection control device based on TL431 according to claim 2, characterized in that: The specific working process of the fault signal voltage sampling circuit is as follows: When the output of the switching power supply is short-circuited, the output voltage Vo drops. After being sampled by the first resistor R1 and the second resistor R2, it is lower than the internal reference voltage of the first reference source IC1. The K-level voltage of the first reference source IC1 increases, and the current flowing from the A terminal to the K terminal of the optocoupler IC2 increases accordingly, further causing the current from the C terminal of the optocoupler to the ground to increase, causing the COMP terminal voltage of the pulse width modulator to increase.

4. A short circuit protection control device based on TL431 according to claim 3, characterized in that: The internal reference voltage of the first reference source IC1 is 2.5V.

5. A short circuit protection control device based on TL431 according to claim 1, characterized in that: The pulse width modulator-based short-circuit protection circuit includes a second reference source IC3, a transistor P1, a second capacitor C2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9; One end of the sixth resistor R6, one end of the seventh resistor R7 and one end of the second capacitor C2 are commonly connected to the R end of the second reference source IC3, the other end of the seventh resistor R7, the other end of the second capacitor C2 and the A end of TL431 are commonly grounded, the K end of the second reference source IC3 is connected to the eighth resistor R8, one end of the ninth resistor R9, the other end of the eighth resistor R8 is connected to the base of the transistor P1, and the other end of the ninth resistor R9 is connected to the emitter of the transistor P1 and is commonly connected to the Vcc end of the pulse width modulator.

6. A short circuit protection control device based on TL431 according to claim 5, characterized in that: The transistor P1 is a P-type transistor.

7. A short circuit protection control device based on TL431 according to claim 5, characterized in that: The specific working process of the short-circuit protection circuit based on the pulse width modulator is as follows: When the output of the switching power supply is short-circuited, the COMP voltage of the pulse width modulator increases. After sampling by the first resistor R1 and the second resistor R2, when the voltage at the R terminal of the second reference source IC3 is higher than the internal reference voltage of the second reference source IC3, the K terminal of the second reference source IC3 flips and outputs a low voltage. The voltage through the eighth resistor R8 and the base of the transistor P1 decreases accordingly, and the transistor P1 turns on the Vcc terminal voltage of the pulse width modulator and outputs a low level.

8. A short circuit protection control device based on TL431 according to claim 1, characterized in that: The soft start circuit includes a MOS tube Q1, a tenth resistor R10 and a third capacitor C3; The collector of the transistor P1 of the short-circuit protection circuit based on the pulse width modulator is connected to one end of the tenth resistor R10, one end of the third capacitor C3 and the base of the MOS tube Q1, the other end of the tenth resistor R10, the other end of the third capacitor C3 and the source of the MOS tube Q1 are connected to the ground, and the drain of the MOS tube Q1 is connected to the SS end of the pulse width modulator.

9. A short circuit protection control device based on TL431 according to claim 8, characterized in that: The specific working process of the soft start circuit is: When the output of the switching power supply is short-circuited, the voltage at the K terminal of the second reference source IC3 flips and outputs a low level, and the base voltage of the transistor P1 decreases accordingly. After the transistor P1 is turned on, the third capacitor C3 is quickly charged, and the voltage of the third capacitor C3 increases. When it exceeds the gate threshold voltage of the MOS tube Q1, the MOS tube Q1 is turned on and the pulse width modulator SS terminal outputs a low level.

10. Application of a short-circuit protection control device based on TL431 in a switching power supply according to any one of claims 1 to 9, characterized in that: The short-circuit protection control device based on TL431 is applied to a single-ended flyback switching power supply, a single-ended forward switching power supply, a push-pull switching power supply, a half-bridge switching power supply and a full-bridge switching power supply.

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