CN204190352U - Automatically controlled output short circuit protection circuit - Google Patents

Abstract

The utility model relates to an electric control output short circuit protection circuit. The utility model aims at that in the prior art, the driving of peripheral devices such as LEDs, fans, and motors requires a triode drive circuit, and this kind of drive circuit is prone to triode breakdown when short-circuited, and will damage the hardware during the production assembly process and fault status. The problem is to provide a control module input terminal, a power supply input terminal, an output terminal, a drive circuit, a protection circuit and a current limiting circuit. The input terminal of the control module is connected to the protection circuit, and the protection circuit is respectively connected to the drive circuit, the current limiting circuit and the The output end is connected, and the drive circuit is respectively connected with the current input end and the current limiting circuit. Compared with the traditional current-limiting scheme using resistors, only low-power resistors are needed, and the output will be automatically turned off after a short circuit. The circuit can be protected no matter whether it is a repeated short circuit or a long-term short circuit. There is no heating problem, and the implementation is simple, low-cost, and fast. Greatly improve the reliability and safety of the electric control board. Suitable for road protection circuits.

Description

Electric control output short circuit protection circuit

technical field

The utility model relates to the field of electronic circuits, in particular to a short circuit protection circuit.

Background technique

With the development of refrigerator and air conditioner technology and the improvement of people's living standards, refrigerators and air conditioners have become popular in people's daily life. At present, the electronically controlled refrigerators on the market can detect the temperature of each storage room through the MCU The air conditioner can receive the information sent by the remote control through the MCU, detect the ambient temperature, and Control compressors, four-way valves, air deflectors and other peripherals to realize functions such as heating and direct cooling. The driving of peripherals such as LEDs, fans, and motors requires a triode drive circuit, and this kind of drive circuit is prone to triode breakdown when short-circuited, which will damage the hardware during the production assembly process and fault status, and affect the reliability of the whole machine.

Utility model content

The technical problem to be solved by the utility model is to provide an electronically controlled output short-circuit protection circuit to achieve short-circuit protection. At the same time, the current-limiting resistor can also use low-power resistors to avoid hardware damage caused by repeated short-circuits and long-term short-circuits.

The utility model solves the technical problem. The technical solution adopted is to include a control module input terminal, a power supply input terminal, an output terminal, a drive circuit, a protection circuit and a current limiting circuit. The control module input terminal is connected to the protection circuit to protect the The circuit is respectively connected with the driving circuit, the current limiting circuit and the output terminal, and the driving circuit is respectively connected with the current input terminal and the current limiting circuit.

Further, the protection circuit includes a resistor 5 and a diode 1, the input terminal of the control module is connected to one end of the resistor 5, the other end of the resistor 5 is respectively connected to the drive circuit and the anode of the diode 1, and the cathode of the diode 1 is respectively connected to the limiter. Flow circuit and output connection.

Further, the drive circuit includes resistor one, resistor two, resistor three, resistor four, transistor two and transistor one, one end of the resistor three is connected to the other end of the resistor five, and the other end of the resistor three is respectively connected to the resistor four One end is connected to the base of transistor two, the other end of resistor four and the emitter of transistor two are grounded, the collector of transistor two is connected to one end of resistor two, and the other end of resistor two is connected to one end of resistor one and the base of transistor one respectively. The emitter of the transistor 1 and the other end of the resistor 1 are respectively connected to the input terminal of the power supply, and the collector of the transistor 1 is connected to the current limiting circuit.

Further, the current limiting circuit is a resistor six, one end of the resistor six is connected to the collector of the transistor one, and the other end of the resistor six is connected to the output terminal and the cathode of the diode one, respectively.

Still further, the resistor six is a current limiting resistor.

The beneficial effect of the utility model is that short-circuit protection can be realized only by adding a resistor and a diode, and when the output is short-circuited to the ground, the driving voltage of the triode is clamped, thereby realizing the shutdown of the triode, protecting the triode and avoiding limiting The flow resistor is damaged by heat;

Compared with the traditional resistor current limiting scheme, it only needs to use low-power resistors, and the output will be automatically turned off after a short circuit. It can protect the circuit no matter whether it is repeated short circuit or long-term short circuit. There is no problem of heat generation. It has simple implementation, low cost, and fast response. The advantages greatly improve the reliability and safety of the electric control board.

Description of drawings

Fig. 1 is the structural diagram of the electric control output short-circuit protection circuit of the utility model;

Fig. 2 is the circuit diagram of the embodiment of the electric control output short-circuit protection circuit of the present invention;

Among them, R1 is resistor one, R2 is resistor two, R3 is resistor three, R4 is resistor four, R5 is resistor five, R6 is resistor six, D1 is diode one, Q1 is transistor one, and Q2 is transistor two.

Detailed ways

Describe the technical scheme of the utility model in detail below in conjunction with accompanying drawing and embodiment:

The utility model aims at that in the prior art, a triode drive circuit is needed to drive peripherals such as LEDs, fans, motors, etc., and this kind of drive circuit is prone to triode breakdown when short-circuited, and will damage the hardware during the production assembly process and fault status. Affect the reliability of the whole machine, provide an electric control output short circuit protection circuit, as shown in Figure 1, including control module input, power supply input, output, drive circuit, protection circuit and current limiting circuit, the described The input terminal of the control module is connected with the protection circuit, the protection circuit is respectively connected with the driving circuit, the current limiting circuit and the output terminal, and the driving circuit is respectively connected with the current input terminal and the current limiting circuit. Short-circuit protection can be realized only by adding a resistor and a diode. When the output is short-circuited to ground, the drive voltage of the transistor will be clamped, so as to realize the shutdown of the transistor, protect the transistor and avoid heat damage of the current-limiting resistor; Compared with the current limiting scheme of resistors, only low-power resistors need to be used, and the output will be automatically turned off after a short circuit. The circuit can be protected no matter whether it is repeated short circuit or long-term short circuit. There is no problem of heat generation, and it has the advantages of simple implementation, low cost, and fast response. Greatly improve the reliability and safety of the electric control board.

Example

The electric control output short-circuit protection circuit in this example, as shown in Figure 2, includes the control module input terminal, power supply input terminal, output terminal, resistor one R1, resistor two R2, resistor three R3, resistor four R4, resistor five R5, resistor Six R6, transistor one Q1, transistor two Q2 and diode one D1, the input terminal of the control module is connected to one end of resistor five R5, and the other end of resistor five R5 is respectively connected to one end of resistor three R3 and the anode of diode one D1, The other end of resistor 3 R3 is respectively connected to one end of resistor 4 R4 and the base of transistor 2 Q2, the other end of resistor 4 R4 and the emitter of transistor 2 Q2 are grounded, and the collector of transistor 2 Q2 is connected to one end of resistor 2 R2 , the other end of resistor two R2 is respectively connected to one end of resistor one R1 and the base of transistor one Q1, the emitter of transistor one Q1 and the other end of resistor one R1 are respectively connected to the power input terminal, the collector of transistor one Q1 is connected to One end of the resistor six R6 is connected, and the other end of the resistor six R6 is respectively connected to the output terminal and the cathode of the diode D1.

Resistor 1 R1, resistor 2 R2, resistor 3 R3, resistor 4 R4 and transistor 2 Q2 form the driving circuit of transistor 1 Q1; resistor 6 R6 is a current limiting resistor, forming a current limiting circuit; resistor 5 R5 and diode 1 D1 form a protection circuit , when a short circuit occurs, the resistor five R5 limits the current flowing through the diode one D1.

When the output is normal, the single chip microcomputer sends a high level, and the transistor 2 Q2 is driven to be turned on through the voltage division of the resistor 3 R3, the resistor 4 R4, and the resistor 5 R5. At this time, the Vbe of the transistor 2 Q2 is 0.7V. After the transistor 2 Q2 is turned on, Resistor 1 R1 and resistor 2 R2 form a loop to the ground. At this time, the Vbe of triode 1 Q1 is -0.7V, and triode 1 Q1 is turned on. At this time, 12V is output to the output terminal through resistor 6 R6 current limiting resistor. Resistor 6 R6 should be based on The size of the output current is selected so that the voltage drop on the resistor six R6 is small to avoid affecting the output voltage.

When the output is short-circuited to ground, the current increases instantaneously. Since it takes time for the transistor Q2 to turn off, the resistor R6 can limit the current in a short time.

After the short circuit, the MCU drives through the resistor 5 R5 and the diode D1 to form a loop to the ground, the voltage of the resistor 3 R3 and the resistor 4 R4 is clamped at 0.7V, and the Vbe voltage of the transistor 2 Q2 is lower than 0.7V, the transistor 2 Q2 is turned off. Since the transistor 2 Q2 is turned off, the 12V circuit to the ground through the resistor 1 R1 and the resistor 2 R2 is disconnected, the Vbe voltage of the transistor 1 Q1 is 0V, the transistor 1 Q1 is turned off, and the output is turned off to realize the function of short circuit protection. No current flows through the current-limiting resistor R6, and if the short-circuit fault is not released, the transistor-Q1 will always be in the off state.

Claims (5)

1. The electronically controlled output short-circuit protection circuit is characterized in that it includes a control module input terminal, a power supply input terminal, an output terminal, a drive circuit, a protection circuit and a current limiting circuit, the control module input terminal is connected to the protection circuit, and the protection circuits are respectively It is connected with the driving circuit, the current limiting circuit and the output terminal, and the driving circuit is respectively connected with the current input terminal and the current limiting circuit. 2. The electronically controlled output short-circuit protection circuit according to claim 1, wherein the protection circuit comprises a resistor five and a diode one, the input terminal of the control module is connected to one end of the resistor five, and the other ends of the resistor five are respectively It is connected with the driving circuit and the anode of the diode one, and the cathode of the diode one is respectively connected with the current limiting circuit and the output end. 3. The electronically controlled output short-circuit protection circuit according to claim 2, wherein the drive circuit includes resistor one, resistor two, resistor three, resistor four, transistor two and transistor one, and one end of the resistor three is connected to The other end of resistor five is connected, the other end of resistor three is connected to one end of resistor four and the base of transistor two, the other end of resistor four and the emitter of transistor two are grounded, and the collector of transistor two is connected to one end of resistor two , the other end of the resistor two is respectively connected with one end of the resistor one and the base of the triode one, the emitter of the triode one and the other end of the resistor one are respectively connected with the power input end, and the collector of the triode one is connected with the current limiting circuit. 4. The electric control output short-circuit protection circuit according to claim 3, characterized in that, the current limiting circuit is a resistor six, one end of the resistor six is connected to the collector of the triode one, and the other end of the resistor six is connected to the collector of the triode one, respectively. The output terminal is connected to the cathode of diode one. 5. The electric control output short-circuit protection circuit according to claim 4, characterized in that the resistor 6 is a current-limiting resistor.