CN209929953U

CN209929953U - Overvoltage protection circuit

Info

Publication number: CN209929953U
Application number: CN201920991296.6U
Authority: CN
Inventors: 顾峥峣
Original assignee: Cambridge Industries Shanghai Co Ltd
Current assignee: CIG Shanghai Co Ltd; Cambridge Industries Shanghai Co Ltd
Priority date: 2019-06-27
Filing date: 2019-06-27
Publication date: 2020-01-10
Anticipated expiration: 2029-06-27

Abstract

The utility model discloses an overvoltage crowbar, it includes an input and an output to and: the circuit comprises a first triode, a second triode, a switching tube, a first resistor and a second resistor, wherein the first resistor and the second resistor are connected between the input end and the ground in series; the base electrode of the first triode is connected between the first resistor and the second resistor, the collector electrode of the first triode is connected with the input end and the base electrode of the second triode, and the emitting electrode of the first triode is grounded; the emitting electrode of the second triode is grounded, and the collector electrode of the second triode is connected with the grid electrode of the switching tube; the source electrode of the switch tube is connected to the input end, and the drain electrode of the switch tube is connected to the output end. The main control part only adopts two triodes and a switch tube, and is matched with a simple voltage division circuit, so that the overvoltage protection of the power supply end can be realized, the circuit design is simple, and the miniaturization of a system circuit is facilitated.

Description

Overvoltage protection circuit

Technical Field

The utility model relates to an overvoltage crowbar, in particular to overvoltage crowbar of power end.

Background

The power interface connectors of small electric appliances and electric control toys with different functions in daily life are basically the same in size, and other power adapters with the same specification can be used for supplying power to the equipment with the same voltage at any time. However, the output voltage of the conventional power adapter is divided into 5V, 9V, 12V and the like, and many times, a user often mistakenly takes the power adapter with the high voltage output to plug into a device with a low voltage, so that the device is damaged.

Certainly, some equipment can increase an overvoltage protection function at an input end, but for some small-sized and low-price electric appliances or electric control toys, the volume of the equipment is very small, and no space is left in the aspect of circuit layout for adding an overvoltage protection circuit; in terms of cost, the devices are originally sold at a low price, and overvoltage protection devices are undoubtedly added to the cost, so that most manufacturers of the small devices often omit the overvoltage protection function. Therefore, an overvoltage automatic power-off protection circuit with small volume and low cost is needed.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is to provide an overvoltage protection circuit that electronic components is less, simple structure, be fit for miniaturized equipment in order to overcome among the prior art's the miniaturized circuit design often to be difficult to increase overvoltage protection's function, current overvoltage protection circuit electronic components more, increase cost, increase system circuit volume's defect easily because of miniaturized circuit design.

The utility model discloses a solve above-mentioned technical problem through following technical scheme:

an overvoltage protection circuit comprising an input and an output, said overvoltage protection circuit further comprising: a first triode, a second triode, a switch tube, a first resistor and a second resistor,

wherein the first resistor and the second resistor are connected in series between the input terminal and ground; the base electrode of the first triode is connected between the first resistor and the second resistor, the collector electrode of the first triode is connected with the input end and the base electrode of the second triode, and the emitting electrode of the first triode is grounded; the emitting electrode of the second triode is grounded, and the collector electrode of the second triode is connected with the grid electrode of the switching tube; the source electrode of the switch tube is connected to the input end, and the drain electrode of the switch tube is connected to the output end.

Preferably, the switch tube is a PMOS (P-type metal oxide field effect transistor).

Preferably, the overvoltage protection circuit further comprises a third resistor connected between the base of the first triode and the first resistor and the second resistor.

Preferably, the collector of the first triode is connected to the input end through a fourth resistor.

Preferably, the base of the second triode is connected to the collector of the first triode through a fifth resistor.

Preferably, the base of the second triode is grounded through a sixth resistor and a first capacitor which are connected in parallel.

Preferably, a seventh resistor is connected between the source and the gate of the switching tube.

Preferably, the output terminal is grounded through a second capacitor.

Preferably, the output end is connected to the input end of the electrical appliance.

On the basis of the common knowledge in the field, the above preferred conditions can be combined at will to obtain the preferred embodiments of the present invention.

The utility model discloses an actively advance the effect and lie in: the main control part of the overvoltage protection circuit only adopts two triodes and a switching tube, and is matched with a simple voltage division circuit, so that overvoltage protection of a power supply end can be realized, the circuit design is simple, and miniaturization of a system circuit is facilitated.

Drawings

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

Detailed Description

The present invention is further illustrated by way of the following examples, which are not intended to limit the scope of the invention.

Referring to fig. 1, the overvoltage protection circuit of the present invention includes an input terminal X1 and an output terminal Vcc, and: the circuit comprises a first triode VT1, a second triode VT2, a switching tube VT3, a first resistor R1 and a second resistor R2, wherein the first resistor R1 and the second resistor R2 are connected in series between the input end and the ground; the base electrode of the first triode VT1 is connected between the first resistor R1 and the second resistor R2, the collector electrode of the first triode VT1 is connected with the input end and the base electrode of the second triode VT2, and the emitter electrode of the first triode VT1 is grounded; the emitter of the second triode VT2 is grounded, and the collector of the second triode VT2 is connected with the gate of the switching tube VT 3; the source of the switching transistor VT3 is connected to the input terminal, and the drain of the switching transistor VT3 is connected to the output terminal.

In this embodiment, the switch tube is PMOS. The overvoltage protection circuit also comprises a third resistor R3 connected between the base of the first transistor VT1 and the first resistor R1 and the second resistor R2.

More specifically, the collector of the first transistor VT1 is connected to the input terminal through a fourth resistor R4. The base of the second transistor VT2 is connected to the collector of the first transistor VT1 through a fifth resistor R5.

The base of the second transistor VT2 is grounded through the parallel connection of the sixth resistor R6 and the first capacitor C1. The fourth resistor R4, the fifth resistor R5 and the sixth resistor R6 are similar to the first resistor and the second resistor, and generate a voltage for controlling the base of the second transistor VT2 through voltage division. The fifth resistor R5 and the first capacitor C1 also form a low pass filter to filter the switching waveform generated by the first transistor VT1 in the critical state.

A seventh resistor R7 is connected between the source and the gate of the switching tube VT3, the seventh resistor R7 is used for controlling the switching tube VT3, and when the second triode VT2 is not turned on, the source and the gate voltages of the switching tube VT3 are the same, so that the switching tube VT3 is turned off.

The output end is grounded through a second capacitor C2, and the output end Vcc is connected to the input end of the electrical appliance.

The working principle of the overvoltage protection circuit is briefly described below by taking a common working voltage as 12V input and a misoperation voltage as 15V-18V as an example.

a. When the input end X1 is plugged into a normal power supply, the voltage of the point A is not enough to enable the first triode VT1 to be conducted, the voltage of the point B enables the second triode VT2 to be conducted, the voltage of the point C is low level, the source electrode and the drain electrode of the switching tube VT3 are conducted, the output end Vcc is equal to the input voltage, and the power can be normally supplied to an electric appliance;

b. when the input terminal X1 is plugged into a high voltage power supply (15-18V), the voltage at point a turns on the first transistor VT1, the voltage at point B is low, the second transistor VT2 is therefore turned off, and the voltage at point C is high, so that the switching tube VT3 is turned off, and at this time, the output terminal Vcc is not output, and the internal devices of the downstream equipment are not damaged.

The utility model discloses an overvoltage protection circuit produces different control voltage through divider resistance R1 and R2 with different input voltage to control first triode VT 1's state, and then control second triode VT2 and switch tube VT 3's state, thereby reach excessive pressure auto-power-off protect function.

Although particular embodiments of the present invention have been described above, it will be appreciated by those skilled in the art that these are examples only and that the scope of the present invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and the principles of the present invention, and these changes and modifications are all within the scope of the present invention.

Claims

1. An overvoltage protection circuit comprising an input and an output, said overvoltage protection circuit further comprising: a first triode, a second triode, a switch tube, a first resistor and a second resistor,

2. The overvoltage protection circuit of claim 1, wherein said switching transistor is PMOS.

3. The overvoltage protection circuit of claim 1, further comprising a third resistor coupled between the base of the first transistor and the first resistor and the second resistor.

4. The overvoltage protection circuit of claim 1, wherein a collector of the first transistor is coupled to the input terminal through a fourth resistor.

5. The overvoltage protection circuit of claim 1, wherein the base of the second transistor is coupled to the collector of the first transistor through a fifth resistor.

6. The overvoltage protection circuit of claim 1, wherein a base of the second transistor is coupled to ground through a sixth resistor and the first capacitor in parallel.

7. The overvoltage protection circuit of claim 1, wherein a seventh resistor is connected between the source and the gate of the switching tube.

8. The overvoltage protection circuit according to any one of claims 1-7, wherein said output terminal is connected to ground through a second capacitor.

9. The overvoltage protection circuit according to any one of claims 1-7, wherein the output terminal is connected to an input terminal of a consumer.