| 摘要 |
PURPOSE:To drive a motor with optimal efficiency and good controllability over the entire operating frequency by employing only one second timer having reduced time lag thereby performing commutation control at an accurate timing. CONSTITUTION:Terminal voltage 43 of each phase of an armature winding is fed through a filter 2 in order to remove higher harmonics and outputs of two phases are compared through a comparator 3 to produce a position signal 11 for one remaining phase. Interval of the phase signal 11 is measured by means of a first timer 8 and a CPU 7 calculates a predetermined phase lead or lag, which is a characteristic value of the filter 2, according to a frequency represented by the measurement results. A second timer 9 then measures a predetermined time, corresponding to thus calculated phase lead or lag, starting from the nearest rising or falling of the position signal 11 fed from the comparator 3. Upon finish of time measurement, the CPU switches a transistor in an inverter circuit to a predetermined conducting state corresponding to the output from the comparator 3. |
