CN217508270U

CN217508270U - Undervoltage and short-circuit protection circuit

Info

Publication number: CN217508270U
Application number: CN202122868113.1U
Authority: CN
Inventors: 王刚志; 廖胜灵
Original assignee: Hangzhou Zhishan Intelligent Control Technology Co ltd
Current assignee: Hangzhou Zhishan Intelligent Control Technology Co ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-09-27
Anticipated expiration: 2031-11-22

Abstract

The utility model provides an under-voltage, short-circuit protection circuit, including power chip and the protection circuit who is connected with power chip circuit, protection circuit includes line connection's electric capacity CA2 and triode QA1, triode QA 1's base is connected to electric capacity CA2, PWM signal's power chip can be controlled in triode QA 1's collecting electrode access, power chip passes through resistance RA3 and connects electric capacity CA2 and charges to electric capacity CA 2. The utility model relates to an under-voltage, short-circuit protection circuit passes through power chip and protection circuit and can carry out under-voltage, short-circuit protection to switching power supply, and circuit structure is simple, and the lower easy realization of cost.

Description

Undervoltage and short-circuit protection circuit

Technical Field

The utility model belongs to the technical field of switching power supply protection, concretely relates to undervoltage, short-circuit protection circuit.

Background

With the rapid development of power electronic technology, the power electronic equipment has increasingly close relationship with the work and life of people, and the electronic equipment can not be connected with a reliable power supply, so that the switching power supply is widely used in various fields, and the rapid development of the switching power supply technology is promoted. And the development and the application of the switching power supply have important significance in the aspects of security monitoring, energy conservation, resource conservation and environmental protection.

The switching power supply must have the protection functions of overcurrent, overheat, short circuit and the like in the design, so a switching power supply module with complete protection functions is preferred in the design, and the technical parameters of a protection circuit of the switching power supply module are matched with the working characteristics of electric equipment so as to avoid damaging the electric equipment or the switching power supply.

The switching power supply undervoltage and short-circuit protection scheme used in the current market mostly adopts chip control, but the used chip is high in price and not beneficial to reducing cost, and part of related chips are low in price but do not have the function of short-circuit protection.

Disclosure of Invention

The utility model aims at the above-mentioned problem, provide an under-voltage, short-circuit protection circuit, can carry out under-voltage, short-circuit protection to the switching power supply, the lower easy realization of cost.

In order to achieve the above purpose, the utility model adopts the following technical proposal:

a kind of undervoltage, short-circuit protective circuit, including power chip and protective circuit in circuit connection with power chip, the said protective circuit includes capacitor CA2 and triode QA1 of line connection, the said capacitor CA2 connects the base of triode QA1, the collector of the said triode QA1 inserts the power chip that can control PWM signal, the said power chip connects the capacitor CA2 and charges to the capacitor CA2 through the resistance RA 3. The utility model discloses a power chip connects protection circuit, can be applicable to more power chips and carry out undervoltage, short-circuit protection to switching power supply, and the cost is lower.

Further, the capacitor CA2 is a polar capacitor, the anode of the capacitor CA2 is connected to the base of the transistor QA1, and the cathode of the capacitor CA2 is grounded.

Further, the power supply chip includes a UC3485 chip; the UC3845 chip has low price and can realize low-cost under-voltage and short-circuit protection of the switching power supply by being connected with a protection circuit.

Further, the collector of the transistor QA1 is connected to the RT/CT pin of the power chip via a resistor.

Further, the Comp pin of the power chip is connected to the positive electrode of the capacitor CA2 through the resistor RA3 to charge the capacitor CA 2.

Further, a Comp pin and a Vfb pin of the power chip are respectively connected to two ends of the capacitor C201, and the resistor RA3 is connected in parallel with the capacitor C201.

Further, an OUT pin of the power supply chip outputs a PWM signal and is connected to a frequency converter M1 through a resistor.

Furthermore, a linear optocoupler PC817B is connected to two ends of the resistor RA3, and an emitter of the linear optocoupler PC817B is connected to the anode of the capacitor CA 2. The linear optocoupler PC817B can isolate the upper and lower stage circuits, and can avoid mutual influence.

Further, the emitter of the transistor QA1 is connected to a reference voltage VREF 1.

Compared with the prior art, the utility model has the advantages of:

the utility model relates to an under-voltage, short-circuit protection circuit passes through power chip and protection circuit and can carry out under-voltage, short-circuit protection to switching power supply, and circuit structure is simple, and the lower easy realization of cost.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

Fig. 1 is a circuit schematic diagram of an under-voltage and short-circuit protection circuit of the present invention.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

As shown in fig. 1, the undervoltage and short-circuit protection circuit of this embodiment includes a power chip and a protection circuit connected to the power chip, where the protection circuit includes a capacitor CA2 and a transistor QA1 connected by a line, the capacitor CA2 is connected to a base of the transistor QA1, a collector of the transistor QA1 is connected to the power chip capable of controlling a PWM signal, and the power chip is connected to a capacitor CA2 through a connection resistor RA3 and charges the capacitor CA 2.

The capacitor CA2 of the present embodiment is a polar capacitor, the positive electrode of the capacitor CA2 is connected to the base of the transistor QA1, and the negative electrode of the capacitor CA2 is grounded.

The power supply chip of the embodiment preferably adopts a UC3485 chip; the UC3845 chip has low price and can realize low-cost under-voltage and short-circuit protection of the switching power supply by being connected with a protection circuit.

The collector of the triode QA1 is connected to the RT/CT pin of the power chip through a resistor; the Comp pin of the power chip is connected with the positive electrode of the capacitor CA2 through a resistor RA3 to charge the capacitor CA 2; the OUT pin of the power supply chip outputs a PWM signal and is connected with a frequency converter M1 through a resistor. The Comp pin and the Vfb pin of the power chip are connected to both ends of the capacitor C201, respectively, and the resistor RA3 is connected in parallel to the capacitor C201.

In this embodiment, a linear optocoupler PC817B is connected to both ends of the resistor RA3, and an emitter of the linear optocoupler PC817B is connected to the anode of the capacitor CA 2. The linear optocoupler PC817B can isolate the upper and lower-stage circuits, and can avoid mutual influence.

The emitter of the transistor QA1 of this embodiment is connected to the reference voltage VREF 1.

The utility model relates to an under-voltage, short-circuit protection circuit's principle does: when the power is on, the positive electrode of the capacitor CA2 is at a low level, the triode QA1 is switched on, the RT/CT pin of the power chip UC3845 starts to vibrate, the power chip UC3845 works normally, the Comp pin of the power chip UC3845 charges the capacitor CA2 through the resistor RA3, and the dynamic level on the capacitor CA2 can still enable the triode QA1 to keep a conducting state; when short circuit or under-voltage occurs, the potential of the Comp pin of the power chip UC3845 rises, the potential of the capacitor CA2 rises, the triode QA1 is cut off, the RT/CT pin of the power chip UC3845 stops working, and the OUT pin of the power chip UC3845 stops outputting a PWM signal, so that the purpose of under-voltage and short circuit protection can be achieved.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Claims

1. The undervoltage and short-circuit protection circuit comprises a power chip and a protection circuit connected with the power chip, and is characterized in that the protection circuit comprises a capacitor CA2 and a triode QA1 which are connected through a circuit, the capacitor CA2 is connected with the base electrode of the triode QA1, the collector electrode of the triode QA1 is connected with the power chip capable of controlling PWM signals, and the power chip is connected with a capacitor CA2 through a resistor RA3 and charges the capacitor CA 2.

2. The under-voltage and short-circuit protection circuit of claim 1, wherein the capacitor CA2 is a polar capacitor, the anode of the capacitor CA2 is connected to the base of the transistor QA1, and the cathode of the capacitor CA2 is grounded.

3. The under-voltage and short-circuit protection circuit of claim 2, wherein the power chip comprises a UC3485 chip.

4. The undervoltage and short-circuit protection circuit according to claim 3, wherein the collector of said triode QA1 is connected to the RT/CT pin of the power chip through a resistor.

5. The under-voltage short-circuit protection circuit of claim 3, wherein the Comp pin of the power chip is connected to the positive electrode of the capacitor CA2 through a resistor RA3 to charge the capacitor CA 2.

6. The under-voltage and short-circuit protection circuit according to claim 5, wherein the Comp pin and the Vfb pin of the power chip are respectively connected to two ends of the capacitor C201, and the resistor RA3 is connected in parallel with the capacitor C201.

7. The undervoltage and short-circuit protection circuit as claimed in claim 3, wherein the OUT pin of the power chip outputs PWM signal and is connected with a frequency converter M1 through a resistor.

8. The undervoltage and short-circuit protection circuit according to claim 1, wherein a linear optocoupler PC817B is connected to two ends of the resistor RA3, and an emitter of the linear optocoupler PC817B is connected to an anode of the capacitor CA 2.

9. The undervoltage and short-circuit protection circuit as claimed in claim 1, wherein an emitter of said transistor QA1 is connected to a reference voltage VREF 1.