Motor drive circuit, fan motor, electronic device, and notebook personal computer

摘要

A motor drive circuit comprising: first and second transistors connected in series, a voltage of a connection-point therebetween being a drive-voltage applied to one end of a motor coil; an operational amplifier for controlling the transistors such that the drive-voltage is a voltage according to a difference between first and second control voltages; a switch circuit for driving the transistors such that the motor coil is in an undriven state regardless of control by the operational amplifier when a pulse-signal is at one logic level, and driving the transistors based on the control when the pulse-signal is at the other logic level; and an auxiliary drive circuit for driving the transistors to increase the drive-voltage for a predetermined time period shorter than a time period of the pulse signal being at the other level regardless of the control, when the pulse-signal changes from the one level to the other.