| 摘要 |
PURPOSE:To reduce the noise of a motor rotating with a low revolution and suppress the loss of a controller. CONSTITUTION:A rotor 21 is linked with an air-conditioner fan. A logic signal generating circuit 12 generates selective logic signals in accordance with the output signals of Hall elements 23A-23C which detect passing of rotor poles. The selective logic signals are chopped by a chopping pulse with a predetermined duty and a predetermined frequency and inputted to switching transistors 11A-11F which apply currents to respective stator coils 22A-22C. If a revolution instruction signal N is increased, the duty of the chopping pulse is increased and, at the same time, the frequency of the chopping pulse is reduced. Therefore, as the chopping frequency is high when the fan revolution is low, a chopping noise is not created. If the fan revolution is high, the chopping frequency is low and the increase of the loss of a controller can be suppressed. In the high revolution region of the fan, the chopping noise is masked in the fan noise. |
