Patent ID: 6157151
Filing Date: 2000-12-05
Classification: H02P,Y02P

Abstract:
A motor drive circuit for supplying a motor drive current to first and second coils of a motor, comprising:first and second transistors for sequentially switching over the first and second coils to supply thereto drive currents which are complementarily to each other, based on a sine wave signal generated in accordance with a relative positional relationship between a stator and a rotor of a motor;a first drive off signal generation circuit for generating a sawtooth wave signal based on the sine wave signal for comparison with a predetermined reference voltage to generate a first drive off signal based on a comparison result near a changeover point of the motor drive current;a second drive off signal generation circuit for comparing a full wave signal and a sample hold signal to generate a second drive off signal near the changeover point of the motor drive current, the full wave signal being obtained through full wave conversion applied to the sine wave signal, the sample hold signal being obtained through sampling and holding an amplitude of an attenuated signal at a timing based on the first drive off signal, the attenuated signal being obtained by attenuating the full wave signal; anda third drive off signal generation circuit for adding the first drive off signal and the second drive off signal to generate a third drive off signal,whereinthe first and second transistors are simultaneously turned off in response to the third drive off signal.