| 摘要 |
PURPOSE:To reduce acoustic noise and improve motor efficiency by forming a driving voltage on the basis of an inclined waveform of output signal of a magnetically susceptible element and by determining the relation between a voltage at the point, where inclined waveforms cross each other, and a peak value of a driving waveform appropriately. CONSTITUTION:Respective output signals of Hall elements 1a-1c are outputted as detection signals through a differential amplifier of a current control circuit 29. Said detection signals have trapezoidal waveforms with phases differing from each other at an electrical angle of 120 deg.. A driving voltage is formed on the basis of said trapezoidal waveforms and supplied to a stator coil. On the other hand, output signals of Hall elements 1a-1c are gain controlled by a gain control circuit; and a voltage at the point, where said trapezoidal waveforms cross each other, is controlled so as to be about 70% of a peak of said driving waveform. |
