Reversible speed control system with additional current limiting circuit

The reversible speed control circuit of the micro
DC motor is directly driven by pins 12 and 13 of SG17 31 . The tachogenerator signal
is connected to the non-inverting input pin 3 of the error amplifier through the attenuation network and RC' low-pass filter. The circuit on the right is added to consider
adding current limiting protection. Pin 14 and pins 10 and 11 of the chip were originally connected to the power
supply ±15V respectively, but are now connected to two designated points of the circuit. When the motor suddenly reverses , an overcurrent
occurs , and the voltage signal generated by the sampling resistor 4fl controls the state of the two transistors to achieve current limiting to protect the chip. When the current exceeds 200~250mA, the circuit is shut down.