| 摘要 |
PROBLEM TO BE SOLVED: To reduce vibration and noise of a motor by securing a specified time lag between an ON/OFF switching point of an upstream side switching element and that of a downstream side one. SOLUTION: A converter 8 voltage-compares a modulation signal and a chopping wave signal and then outputs driving signals to a driving circuit 10, which has a dead time setting section and secures a specified time lag between an ON/OFF switching point of an upstream side transistor and that of a downstream side one. The driving signals vary the ratio of a high level duration to a low level duration according to the level of the modulation signal while the frequency is kept the same. With the change in the duration rate of the driving signals, the ON-state duration rate of the upstream side transistor to the downstream side one changes and therefore the increase in the change of the duration ratio of the driving signals can be made as small as possible and thereby the deviation of the ON-state duration ratio of the transistors from the duration ratio of the driving signals can be lessened. By this method, the voltage distortion can be made as small as possible and vibration and noise of the motor can be reduced. |
