Abstract: In circuitry for driving a motor 9 by PWM (Pulse Width Modulation) control. a pulse sequence Spwm is generated on the basis of a triangular wave TR that is control led by a capacitor. The pulses of the pulse sequence Spwm are counted in synchronism with position signals U1, V1 and W1 output from position sensing means, which is responsive to the angular positions of the motor 9, so that a duty modulation signal Sduty-b is generated for reducing noise ascribable to the rotation of the motor 9. An exciting pulse generating circuit 8 switches a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) circuit 11 with gate signals Q1P through Q3P and Q1N through Q3N.

Abstract: In circuitry for driving a motor 9 by PWM (Pulse Width Modulation) control, a pulse sequence Spwm is generated on the basis of a triangular wave TR that is controlled by a capacitor. The pulses of the pulse sequence Spwm are counted in synchronism with position signals U1, V1 and W1 output from position sensing means, which is responsive to the angular positions of the motor 9, so that a duty modulation signal Sduty-b is generated for reducing noise ascribable to the rotation of the motor 9. An exciting pulse generating circuit 8 switches a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) circuit 11 with gate signals Q1P through Q3P and Q1N through Q3N.