MOTOR DRIVE CIRCUIT, METHOD, AND DISC DEVICE USING THE SAME

摘要

A motor drive circuit compares a back electromotive voltage generated in a coil of the motor with a middle point voltage of the coil to detect a zero cross point and outputs a back electromotive detection signal. According to the back electromotive detection signal, the motor drive circuit controls ON/OFF of a plurality of switching elements so as to adjust current flowing into the coil of the motor. Prior to the detection of the zero cross point, a window signal which is outputted for a period of the back electromotive detection signal multiplied by a predetermined coefficient sets the switching circuit to a high-impedance state. With this configuration, it is possible to adaptively set the length and the timing of the non-drive period of the switching circuit according to the motor rotation state.