Patent ID: 7830104

Claim:
A brushless motor comprising: a coil array having a plurality of magnet coils; a magnet array having a plurality of permanent magnets; a magnetic sensor for detecting a relative position of the magnet array and the coil array; a drive control circuit for utilizing an output of the magnetic sensor and driving the coil array using a driving element; and a temperature sensor for detecting a detection target temperature associated with either a coil temperature of the coil array or a temperature of the driving element, wherein the drive control circuit reduces an effective value of a driving voltage supplied to the coil array to be a non-zero value when the detection target temperature detected by the temperature sensor has exceeded a prescribed first threshold value, wherein the drive control circuit reduces the effective value of the driving voltage with a reduction step such that the reduction step of the effective value becomes greater as the detection target temperature becomes higher, wherein the drive control circuit includes: a driver circuit including a plurality of drive transistors for supplying electrical current to the coil array; and a drive signal generating circuit for generating a drive signal that controls the plurality of drive transistors of the driver circuit; wherein the drive signal generating circuit includes: a temperature monitoring circuit for generating, based on the output of the temperature sensor, a temperature monitoring signal whose signal level changes depending on the detection target temperature; a waveform signal generator for generating, based on at least the temperature monitoring signal and the output of the magnetic sensor, a waveform signal that exhibits change identical to analog change in the output of the magnetic sensor, and having amplitude proportional to a signal level of the temperature monitoring signal; and a PWM control circuit for executing PWM control utilizing the waveform signal, and generating the drive signal which exhibits change in effective voltage identical to change in the waveform signal, and wherein the waveform signal generator sets an amplitude of the waveform signal based not only on the temperature monitoring signal, but also on an externally provided control value of operating voltage of the brushless motor.