Patent ID: 9401672
Filing Date: 2016-07-26
CPC Classification: H02P

Claim Text:
1. A brushless motor driving system, comprising: a brushless motor; a power device that is connected between a power supply voltage and a ground, and supplies the power supply voltage to the brushless motor in the form of a sinusoidal wave signal; a brushless motor driving circuit that controls the power device; and a detecting resistor to which a motor current flowing through the brushless motor flows via the power device, wherein the brushless motor driving circuit comprises: a peak hold circuit that outputs a second voltage obtained by holding a peak of a first voltage that is based on a detected voltage responsive to a voltage drop in the detecting resistor; a filter circuit that outputs a third voltage, which is a direct-current component of the second voltage; a differential voltage detecting circuit that outputs a first differential voltage between the second voltage and the third voltage; an integrating amplifier circuit that converts a speed instruction pulse signal that is a pulse wave responsive to a rotational speed of the brushless motor into an analog voltage; a computing circuit that calculates a second differential voltage between the analog voltage and a fourth voltage responsive to the first differential voltage, and outputs a speed control signal responsive to the second differential voltage; and an output waveform generating circuit that generates a driving signal for driving the brushless motor based on an energization timing and the speed control signal.