Patent ID: 7106013

Claim:
A motor drive apparatus driving a 3-phase brushless motor without using a Hall sensor, comprising an output circuit applying 3-phase PWM voltages out of phase with each other to 3-phase coil terminals of said 3-phase brushless motor in response to a PWM signal, a comparison circuit comparing each voltage of said 3-phase coil terminals and a voltage of a neutral point of 3-phase coils to determine which voltage is higher/lower, a current detection circuit detecting, based on a comparison result by said comparison circuit, that a coil current of a position detection phase becomes 0 A, a position detection circuit detecting a zero cross point of a voltage of said position detection phase based on the comparison result by said comparison circuit in response to the fact that said current detection circuit detects that the coil current of said position detection phase becomes 0 A, a current interruption circuit interrupting the current flowing into a next position detection phase after a lapse of a predetermined time period since the zero cross point was detected by said position detection circuit, and a signal generation circuit generating said PWM signal based on a detection result by said position detection circuit.