Short circuit protection electronic circuit diagram

In the process of debugging the smart car, because the circuit board is a homemade PCB circuit board, there is a problem of low reliability. At the same time, human operating errors inevitably occur during the debugging process, resulting in the risk of short circuiting the output terminal of the BTS7960. Since the current of the 540 motor that drives the smart car is relatively large, if it is short-circuited, it will be harmful to both the motor and the drive circuit. In order to protect the circuit and motor to the greatest extent, a short-circuit automatic power-off protection circuit is added. The schematic diagram is shown in Figure 5. OL1 in Figure 5 is connected to the signal output terminal of the BTS7960 drive circuit motor when it rotates forward. The signal output terminal OL2 when it rotates reversely is also connected to the same overcurrent protection circuit. Here, one channel is taken as an example. The output terminal marked OUT in the circuit Connect the motor.

The working principle of the circuit is: when the circuit is working normally, switch S1 is set to position 1, the driving current of OL1 passes through resistor R1, passes through point b, and then flows through relay K1, with the contact at position A. At this time, point b is high level, transistor Q1 is cut off and does not conduct, and no current flows through the relay. If there is a short circuit at the OUT terminal at this time, it is equivalent to point b being connected to the ground of the circuit. The potential is reduced, the transistor Q1 is turned on, and a current flows out of the c terminal. After being divided by the resistors R2 and R3, the voltage at the a terminal of R3 causes the thyristor Q2 to When it is turned on, the current flows through the relay coil to make the relay close the contact. The contact is connected to point B so that D1 is turned on and lights up the alarm. At the same time, point A is disconnected so that the output current of the circuit is zero, which plays a protective role. If the circuit wants to return to normal, the start S1 needs to be set to position 2 to cut off the power to the entire circuit. After the relay contact returns to point A, turn switch S1 to position 1, and the circuit can output normally again.