A voltage regulator which controls the field coil current of an alternator in automobiles has been designed using proportional integral control scheme with pulse width modulation. The field coil current is controlled by a power MOSFET and the gate of the power MOSFET is controlled by the voltage regulator. The two gain parameters for PI controller have been chosen after measuring the transfer function of the alternator to reduce the steady state error and also to increase the overall system stability. The control scheme has been verified by an experiment which used commercial operational amplifier. The voltage regulator has been designed using CMOS integrated circuit technology.
This thesis reports only the pulse width control and bootstrap part. A companion thesis by Mr. Sang Gil Choi described the PI controller part of the voltage regulator. The proper operation of the designed CMOS circuit has been confirmed by SPICE simulation.
