Patent ID: 6424798
Filing Date: 2002-07-23
Classification: B60L,H02P,Y02T

Abstract:
A device for controlling a sensorless brushless-DC-motor driven by a DC power source, the device comprising:an inverter for supplying a three-phase pulse width modulated motor voltage to the sensorless brushless-DC-motor, the motor voltage being formed from the DC power source; and a controller for controlling operation of the inverter, the controller including a rotational speed detector detecting a motor speed based on a rotor position determined from the motor voltage, the controller controlling a duty ratio of the three-phase pulse width modulated motor voltage to reduce a difference between a target motor speed and the detected motor speed, wherein, the controller modifies the duty ratio to eliminate influence of the voltage variation of the DC power source to an average level of the motor voltage, and wherein, the rotor position is determined based on the motor voltage controlled to eliminate variation of a voltage of the DC power source.