Patent ID: 8018189

Claim:
A motor drive apparatus for driving a 3-phase brushless motor without using a Hall sensor, comprising: a voltage comparison unit having a comparator which compares each of voltages of coil terminals of three phases with a voltage of a neutral point of 3-phase coils to determine which voltage is higher or lower; and a drive operation unit which calculates, based on a signal outputted from the voltage comparison unit, a zero cross point of a voltage of a position detection phase, of the voltages of the coil terminals of the respective phases by operation, and interrupts a current of the position detection phase by a first time from the zero cross point, wherein one interval is defined between the zero cross points at the phases for the coil terminal voltages, and wherein the drive operation unit performs the operation using time information measured based on the output signal from the voltage comparison unit at a previous interval and a present interval, and calculates the zero cross point at a next interval using the result of operation.