| 摘要 |
PURPOSE:To decrease the number of times of switching of a switching means and the generation of heat and electromagnetic noise by synchronizing the rise of a PWM(pulse width modulation) signal with that of ON control signal and by setting the period of said PWM signal as the minimum ON period more than 1. CONSTITUTION:Outputs UL, VL, WL of a coil-ON logical circuit 2 is supplied to a rising pulse generator 11 to generate an output pulse synchronized with the rise of said outputs UL, VL, WL. The output pulse from said rising pulse generator 11A is supplied as reset pulse to a PWM signal generator 10. In this case, a rising pulse is outputted for every period twice as long as the minimum ON period by the output of said coil-ON logical circuit 2 and at every 120 of an electrical angle, and said PWM signal has a period twice as long as the minimum ON period by the output of said coil-ON logical circuit 2. Thus, even if switching characteristics of diodes D1-D3, D11-D13 are poor, it is possible to reduce the number of times of switching, a heat generation because of no through current flowing, and also the generation of electromagnetic noise. |
