In the design of DC motor drive circuit, we mainly consider the following: 1. Function: unidirectional or bidirectional motor is rotating? Or need speed? For one-way motor drive, as long as a power transistor or FET or relay can be directly driven by the motor when the motor needs bidirectional rotation, you can use the H-bridge circuit consists of four components consisting of power or the use of a double-pole double throw relays. If you do not control, you can just use a relay; but if you need speed, you can use the transistor, FET switches and other components to achieve PWM (pulse width modulation) speed. 2. Performance: For PWM speed motor drive circuit, mainly in the following performance indicators: (1) the output current and voltage range, which determines the circuit can drive more powerful motors. (2) efficiency, high efficiency not only means saving power, will reduce the heat driving circuit. To improve the efficiency of the circuit, switching state can guarantee power devices and prevent common conduction (an H-bridge or push-pull circuit problems that may arise, that is, two power devices are turned on simultaneously making power short circuit) from the start. (3) Effects of the control input. Power input of the circuit due to its good signal isolation to prevent high voltage and high current into the control circuit, which can be used with high input impedance or optocoupler isolation. (4) on the power supply. Common conduction can cause the power supply voltage drop caused by the high-frequency power supply transient contamination; large current may cause a floating ground potential. (5) reliability. Motor drive circuit should be possible to do, no matter what kind of control signals plus, what passive load, the circuit is safe. Understanding of the above design on DC motor drive circuit during operation, it can be more handy. Reference article from: http: //www.zbxinlian.com