DRIVING DEVICE OF SENSORLESS BRUSHLESS MOTOR

PROBLEM TO BE SOLVED: To provide a driving device of a sensorless brushless motor, capable of surely detecting the rotational position of a rotor even during low speed rotation to allow lower rotational driving than before.SOLUTION: A driving motor 1 of a sensorless brushless motor 9 includes an inverter circuit 2 which supplies a power supply voltage Vcc of which duty ratio is variable by a PWM method, to terminals 95U, 95V, and 95W in three phases of an armature winding, A PWM generating circuit 3 which generates a PWM signal SP, a position detection circuit 3 which detects a rotational position based on the induction voltage induced at the terminal by operation in specific phase of the PWM signal SP, and an inverter control circuit 4 which controls timing in an electrification time zone based on the rotational position. It further includes a PWM delay circuit 6 for generating a position detecting PWM signal PSD in which the PWM signal SP is delayed according to a transmission delay time in the inverter control circuit 4 and the inverter circuit 2. The position detection circuit 3 operates in a specific phase of the position detecting PWM signal PSD.