| 摘要 |
PURPOSE:To switch current smoothly between respective driving coils while suppressing noise and vibration by providing a counter electromotive force detector for detecting counter electromotive force induced in a motor driving coil and shaping the counter electromotive force thus detected, and a mask signal generator generating a signal for partially masking the waveform of signal to be fed to the counter electromotive force detector. CONSTITUTION:Voltage waveforms U, V, W and output signals P1-P6 from a mask signal generator 12 are fed to a counter electromotive force generator 10 and counter electromotive force detection signals U1, V1, W1, from which spike noise is removed, are fed to a trapezoidal current synthesizing unit 11. The unit 11 produces current outputs IPL1-IPL3, IPU1-IPU3 and controls driving transistors 4-9 through a current distribution circuit 13 thus feeding driving coils 1, 2, 3 with driving current conduction waveform having gentle slopes at rising and falling thereof. Consequently, a driver for brushless motor, in which noise and vibration are suppressed at the time of rotation, can be configured without requiring any position detecting element or high capacity capacitor. |
