Automobile electronic high-current over-current protection circuit

[0012] Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0013] Embodiments of the present invention relate to a large current overcurrent protection circuit for automotive electronics, such as figure 1 As shown, it includes a MOS tube drive circuit, the input terminal of the MOS tube drive circuit is connected to the output of the drive control module, the output terminal is connected to the load module, and an operational amplifier circuit and a protection circuit are also included. The input terminal of the operational amplifier circuit It is connected with the output end of the MOS transistor drive circuit, the output end is connected with the input end of the protection circuit, and the output end of the protection circuit is connected with the input end of the MOS transistor drive circuit. When working normally, the MOS tube drive circuit works normally, and the operational amplifier circuit and protection circuit do not work; when an overcurrent abnormality occurs, the operational amplifier circuit and protection circuit work, and simultaneously disconnect the MOS tube drive circuit .

[0014] Wherein, the MOS transistor drive circuit includes an N-MOS transistor Q1, a second resistor R2 and a fifth resistor R5, the gate of the N-MOS transistor Q1 is connected to the output of the drive control module through the second resistor R2, the drain is grounded, The source is connected to the load module; one end of the fifth resistor R5 is connected to the output of the drive control module, and the other end is connected to the drain of the N-MOS transistor Q1.

[0015] The operational amplifier circuit includes an operational amplifier U1, a first resistor R1, a sixth resistor R6, an eighth resistor R8, and a capacitor C1; the non-inverting input terminal of the operational amplifier U1 connects with the N-MOS transistor Q1 through the first resistor R1 The source is connected, the inverting input terminal is connected to the drain of the N-MOS transistor Q1 through the sixth resistor R6, and the output terminal is connected to the input terminal of the protection circuit; the non-inverting input terminal of the operational amplifier U1 and the inverting A capacitor C1 is also connected between the phase input ends; one end of the eighth resistor R8 is connected to the output end of the operational amplifier U1, and the other end is connected to the inverting input end of the operational amplifier U1.

[0016] The protection circuit includes an NPN transistor Q2, a third resistor R3, a fourth resistor R4 and a seventh resistor R7; one end of the fourth resistor R4 is connected to the output end of the operational amplifier circuit, and the other end is connected to the output end of the NPN transistor Q2. The base is connected, one end of the seventh resistor R7 is connected to the other end of the fourth resistor R4, and the other end is grounded; the emitter of the NPN transistor Q2 is grounded, and the collector is connected to the MOS tube drive circuit through the third resistor R3 connected to the input.

[0017] The load module in this embodiment can be a high-power device such as a loading motor or a heating wire. When the system is working normally, the drive control module outputs a high level to turn on the N-MOS transistor Q1, and the turned-on N-MOS transistor Q1 The drain of the N-MOS transistor is at a low level, and there is basically no voltage difference between the drain and the source of the N-MOS transistor. The differential voltage between the drain and the source enters the operational amplifier through the input resistors R1 and R6, and the drain-source differential voltage is amplified. The amplified voltage Input to the NPN transistor Q2 through the voltage divider circuit composed of the fourth resistor and the seventh resistor. Since there is basically no voltage difference between the drain and the source, the amplified driving voltage is low level (less than 0.3V) and cannot make the transistor Q2 When it is turned on, the collector of transistor Q2 is still at high level, and the system works normally without abnormality.

[0018] When the system is working, when the port of the load module fails and short-circuits to the power supply, the voltage between the drain and the source of the N-MOS transistor Q1 rises rapidly due to the existence of the Rds resistance of the N-MOS transistor Q1. After the drain-source voltage is amplified by the operational amplifier, it is input to the base of the transistor Q2, the transistor Q2 is quickly turned on, the collector of the transistor Q2 is pulled down to a low level, and the driving N-MOS tube is cut off, thereby realizing a large current overcurrent Protective function.

[0019] In this embodiment, the amplification factor of the operational amplifier circuit can be set by adjusting the resistance values ​​of the first resistor R1 , the sixth resistor R6 and the eighth resistor R8 . The adjustment of the operating voltage threshold of the transistor Q2 can be realized by adjusting the voltage division ratio of the fourth resistor R4 and the seventh resistor R7.

[0020] The main parameters of the overcurrent protection circuit in this embodiment are shown in Table 1:

[0021] Characteristic parameters

[0022] Table 1

[0023] It is not difficult to find that the present invention uses discrete devices to realize the large current overcurrent protection function of the power circuit, reduces the cost of the controller, and at the same time, the protection measure is hardware protection without software intervention, and has the advantage of fast response time.