Patent ID: 8610386

Claim:
A brushless motor drive circuit driving a three-phase brushless motor with sine wave signals, the brushless motor drive circuit comprising: a first AD converter which converts a voltage value depending upon a power supply voltage supplied from a power supply to drive a three-phase brushless motor, to a digital signal and outputs the digital signal; an energization timing adjustment circuit which outputs an adjustment signal for adjusting a lead angle value or a lag angle value of energization timing of the three-phase brushless motor, in response to the digital signal which is output by the first AD converter; and an energization timing setting circuit which sets the energization timing of the three-phase brushless motor, wherein if a regenerated voltage is generated by decelerating the three-phase brushless motor with sine wave signals and the power supply voltage rises, then the energization timing setting circuit sets energization timing changed by the lead angle value or the lag angle value on the basis of the adjustment signal to further decelerate the three-phase brushless motor, wherein if the power supply voltage is at least a preset threshold, then the first AD converter outputs a digital signal, and wherein if the power supply voltage is at least a first threshold, then the first AD converter outputs a first digital signal corresponding to a first lead angle value or a first lag angle value, and if the power supply voltage is at least a second threshold which is higher than the first threshold, then the first AD converter outputs a second digital signal corresponding to a second lead angle value which leads the first lead angle value or a second lag angle value which lags behind the first lag angle value.