Closed Loop PWM Motor Control Circuit Schematic Diagram
semiconductor application notes April 7th, 2010Servo control, or also often called closed loop control, is useful to make a constant speed motor control. Which means the speed will stay constant despite of load and electric voltage change. The following circuit maintain the speed at constant value by sensing the actual speed with the help of a tachometer. If the speed is slowing down, the circuit will increase the power transfer automatically by increasing the duty cycle of the motor drive until no reference speed difference sensed by the tachometer.
You cannot change the motor direction by the control signal, on in other word, unipolar. This switched mode motor drive (SMMD) uses NE5560 as the core of the circuit, which is suitable for small DC motor. A single Phillips BUK456-100A Power MOSFET is used as the power switching component. The handling capability over 30 A, and 100V voltage rating of VDS, and 0.057 ohms RDS-On. Even though the nominal frequency of the PowerMotor Control is 10 KHZ, much higher frequency is also possible and can be applied. To avoid audible interference, setting the frequency over 20kHz also a good idea. To ensure the power loss in the power MOS switch is minimum, the peak gate voltage is kept at 15V.
A current sense resistor is included in this circuit. It is placed in the source lead to monitor motor drive current on a cycle-by-cycle basis. To produce the error amplifier treshold voltage at the desired maximum current, the current sense resistor values is set. NE5560 will automatically limit the duty cycle of the PWM output when the threshold is exceeded. This can also be called a torque limiter feature which is actually an unavoidable effect of the switching device protection by limiting the current.
To avoid power surge, a slow start network (Pin 2,5,6) gradually ramps up the duty cycle at power on. A fixed duty cycle brake can be produced by forcing the input of the error amplifier by K1B. The over-current circuit will still be working during braking. [Source : Phillips Semiconductor Power Semiconductor Applications]
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July 21st, 2010 at 4:15 am
Thank to u,
Its working properly my friend