CN213693127U

CN213693127U - Short-circuit protection circuit of switching power supply

Info

Publication number: CN213693127U
Application number: CN202022667191.0U
Authority: CN
Inventors: 印宗杰
Original assignee: Zhengzhou Jiachen Electric Co ltd
Current assignee: Henan Jiachen Intelligent Control Co Ltd
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2021-07-13
Anticipated expiration: 2030-11-17

Abstract

The utility model discloses a switching power supply short-circuit protection circuit, including resistance R1, resistance R2, transistor Q1, resistance R3, electric capacity C1 and transistor Q2, the utility model discloses simple structure, components and parts are few, and through R3 and C1's filtering time delay, can prevent the mistake protection that the chronogenesis leads to of starting, also can prevent the mistake protection that the fluctuation of output voltage brought, have the function of protection time delay, can prevent the mistake protection, have short-circuit protection self-locking function, even the short circuit resumes can not continue the start power yet.

Description

Short-circuit protection circuit of switching power supply

Technical Field

The utility model relates to a switching power supply technical field, concretely relates to switching power supply short-circuit protection circuit.

Background

The switching power supply is widely applied to the fields of industry and national defense, is widely applied to military and civil electronic systems such as aerospace, aviation, ships, weapons, railways, communication, medical electronics, industrial automation equipment and the like, and can cause heating and even burning of power devices and power chips when the switching power supply is overloaded or short-circuited in the use or debugging process. Therefore, the switching power supply is generally designed with a short-circuit protection scheme. The short-circuit protection circuit can greatly reduce the damage to the switching power supply, ensure the normal operation of machine equipment and the personal safety, and is widely used in various switching power supplies; a control loop consisting of the current transformer, the comparator and the NPN triode can realize the short-circuit protection function. For example, chinese patent publication No. CN110021916A discloses "a switching power supply short-circuit protection circuit and a protection method thereof", which proposes a short-circuit protection scheme for a switching power supply, and adopts a mode of sampling input-side current to design the short-circuit protection scheme, when an intermittent large current occurs on a load side, the short-circuit protection scheme is easily interfered by the input-side large current to cause error protection, a protection signal cannot be locked, an intermittent output hiccup can be caused, and devices are still damaged with probability; and the existing switching power supply short-circuit protection circuit has more components and parts and higher cost.

Therefore, it is a problem to be studied to provide a short-circuit protection circuit for a switching power supply, which can cut off the output of a power supply chip when a load side of the switching power supply is short-circuited, has a protection delay, and can prevent an erroneous protection.

Disclosure of Invention

The utility model aims at providing a switching power supply short-circuit protection circuit that cuts off power chip output, has the protection time delay when switching power supply load side short circuit, can prevent the mistake protection.

The purpose of the utility model is realized like this:

a short-circuit protection circuit of a switching power supply comprises a resistor R1, a resistor R2, a transistor Q1, a resistor R3, a capacitor C1 and a transistor Q2, wherein one end of the resistor R1 is connected with a power supply output Vout, and the other end of the resistor R1 is connected with the resistor R2 and the base of the transistor Q1; the other end of the resistor R2 is grounded; the base electrode of the transistor Q1 is respectively connected with the resistor R1 and the resistor R2, the collector electrode of the transistor Q1 is respectively connected with the resistor R3, the capacitor C1 and the base electrode of the transistor Q2, and the emitter electrode of the transistor Q1 is connected with the ground; the other end of the resistor R3 is connected with a reference voltage Vref; the other end of the capacitor C1 is grounded; the base electrode of the transistor Q2 is connected with the capacitor C1, the resistor R3 and the collector electrode of the transistor Q1, the collector electrode of the transistor Q2 is connected with a pin COMP of a power supply chip, and the emitter electrode of the transistor Q2 is grounded.

The resistor R1 and the resistor R2 are voltage dividing resistors, and the resistor R3 is a current limiting resistor.

The capacitor C1 is a filter delay capacitor.

Has the positive and beneficial effects that: the utility model discloses simple structure, components and parts are few, and through the filtering time delay of R3 and C1, can prevent the mistake protection that the machine time sequence leads to of opening, also can prevent the mistake protection that the fluctuation of output voltage brought, have the function of protection time delay, can prevent the mistake protection, have short-circuit protection self-locking function, even the short circuit resumes can not continue the starting power yet.

Drawings

Fig. 1 is a circuit diagram of the present invention.

Detailed Description

The present invention will be further explained with reference to the accompanying drawings.

As shown in fig. 1, a switching power supply short-circuit protection circuit includes a resistor R1, a resistor R2, a transistor Q1, a resistor R3, a capacitor C1 and a transistor Q2, wherein one end of the resistor R1 is connected to a power output Vout, and the other end of the resistor R1 is connected to the resistor R2 and a base of the transistor Q1; the other end of the resistor R2 is grounded; the base electrode of the transistor Q1 is respectively connected with the resistor R1 and the resistor R2, the collector electrode of the transistor Q1 is respectively connected with the resistor R3, the capacitor C1 and the base electrode of the transistor Q2, and the emitter electrode of the transistor Q1 is connected with the ground; the other end of the resistor R3 is connected with a reference voltage Vref; the other end of the capacitor C1 is grounded; the base electrode of the transistor Q2 is connected with a capacitor C1, a resistor R3 and a collector electrode of the transistor Q1, the collector electrode of the transistor Q2 is connected with a COMP pin of a power chip, an emitter electrode of the transistor Q2 is grounded, the resistor R1 and the resistor R2 are voltage dividing resistors, the resistor R3 is a current limiting resistor, and the capacitor C1 is a filtering delay capacitor.

The using process is as follows: 1. the resistor R1 and the resistor R2 are voltage dividing resistors, Vout voltage gradually rises during startup, when the grid voltage of the transistor Q1 reaches 2.5V, the transistor Q1 is conducted, the grid of the transistor Q2 is connected to a GND end through the transistor Q1, and the transistor Q2 is cut off; 2. in the starting process, the reference voltage Vref is earlier than the establishment time of the power output Vout, and in order to prevent the starting error protection, a filtering delay circuit is formed by a resistor R3 and a capacitor C1 to prevent the error protection caused by the starting time sequence problem; 3. when the load side is short-circuited, the power output Vout is reduced, the voltage of the grid electrode of the transistor Q1 is reduced to be lower than 1V after the resistor R1 and the resistor R2 divide the voltage of the resistor, and the transistor Q1 is cut off. After filtering delay of the resistor R3 and the capacitor C1, the voltage of the transistor Q2 is increased to the reference voltage Vref, the transistor Q2 is conducted, and the pin COMP of the power chip is grounded through the transistor Q2, so that short-circuit protection is realized; 4. the voltage value of the reference voltage Vref is constant, the transistor Q2 is always in a conducting state, the voltage of the pin end of the power chip COMP is 0, therefore, protection locking can be realized after short circuit, and the power supply can not be restarted after the load side recovers from the short circuit state. By means of the filtering time delay of R3 and C1, error protection caused by starting time sequence can be prevented, error protection caused by output voltage fluctuation can also be prevented, a short-circuit signal self-locking function is achieved, even if a short circuit is recovered, a power supply cannot be started continuously, short-circuit protection and self-locking functions are achieved by means of two-stage transistor, and error protection is prevented by means of a filter capacitor.

The utility model discloses simple structure, components and parts are few, and through the filtering time delay of R3 and C1, can prevent the mistake protection that the machine time sequence leads to of opening, also can prevent the mistake protection that the fluctuation of output voltage brought, have the function of protection time delay, can prevent the mistake protection, have short-circuit protection self-locking function, even the short circuit resumes can not continue the starting power yet.

Claims

1. A short-circuit protection circuit of a switching power supply is characterized in that: the power supply comprises a resistor R1, a resistor R2, a transistor Q1, a resistor R3, a capacitor C1 and a transistor Q2, wherein one end of the resistor R1 is connected with a power output Vout, and the other end of the resistor R1 is connected with the resistor R2 and the base of the transistor Q1; the other end of the resistor R2 is grounded; the base electrode of the transistor Q1 is respectively connected with the resistor R1 and the resistor R2, the collector electrode of the transistor Q1 is respectively connected with the resistor R3, the capacitor C1 and the base electrode of the transistor Q2, and the emitter electrode of the transistor Q1 is connected with the ground; the other end of the resistor R3 is connected with a reference voltage Vref; the other end of the capacitor C1 is grounded; the base electrode of the transistor Q2 is connected with the capacitor C1, the resistor R3 and the collector electrode of the transistor Q1, the collector electrode of the transistor Q2 is connected with a pin COMP of a power supply chip, and the emitting electrode of the transistor Q2 is grounded.

2. The switching power supply short-circuit protection circuit according to claim 1, wherein: the resistor R1 and the resistor R2 are voltage dividing resistors, and the resistor R3 is a current limiting resistor.

3. The switching power supply short-circuit protection circuit according to claim 1, wherein: the capacitor C1 is a filter delay capacitor.