Patent ID: 7847498

Claim:
A driving device for a brushless motor, comprising: an energization pattern determining device that, during startup of the brushless motor, energizes the brushless motor with an excitation pattern in accordance with a stop position of a rotor of the brushless motor for an initial energization time and then stops the energization to cause the rotor of the brushless motor to coast; an excitation switch timing calculating device that determines an excitation timing by detecting the rotor position from an induced voltage that is generated at the motor terminals during coasting of the rotor, wherein the excitation switch timing calculating device calculates the excitation timing from a time interval between the second and subsequent induced voltage signals generated at the motor terminals during coasting of the rotor; an excitation voltage output device that selects a plurality of excitation patterns that are capable of driving the brushless motor and energize with each excitation pattern in turn within a time range in which the rotor does not rotate; a square-wave pulse voltage width detecting device that detects the pulse widths of a square-wave pulse voltage generated in a coil of the brushless motor when the excitation patterns are switched; and a rotor position estimating device that obtains the minimum value or the maximum value from the pulse widths of each of the square-wave pulse voltages in the plurality of excitation patterns and determines the stop position of the rotor from the excitation pattern of the minimum value or maximum value; wherein the driving device is constituted so as to output an energization pattern that leads or lags by a predetermined electrical angle from the stop position of the rotor determined by the rotor position estimating device as a start-up excitation pattern.