| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem of a sensorless system brushless motor drive circuit that it is susceptible to noise generated especially from a motor itself or from a peripheral IC operating through a feeder line of the same system as that of a drive circuit when an amplifier for detecting the phase of counter- electromotive force is employed. SOLUTION: The brushless motor drive circuit comprises an initial setting section 11 for setting the initial frequency in initial operation mode, an oscillating section 12 generating an initial frequency set at the initial setting section 11, and a frequency control section 13 for varying the oscillation frequency at the oscillating section 12 from the initial frequency toward a constant rate frequency. Since a synchronous waveform generating circuit 38 generates drive pulses UP, VP, WP, UN, VN and WN based on the oscillation frequency at the oscillating section 12 and three-phase coils U, V and W are driven through the drive section 15 based on these drive pulses, a phase detecting amplifier is eliminated. |
