| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a switching device and a power system therewith which can keep a switching frequency nearer to an optimum value even during a synchronous operation.SOLUTION: A control circuit 50 includes a synchronization pulse input terminal 34 for external connection into which a synchronization pulse Vd is input, a reference frequency setting section 54 and a driving pulse generation section 56. The reference frequency setting section 54 has a time constant circuit 58 including a time constant setting resistor 58b, and specifies a reference frequency Vr depending on a time constant thereof. The driving pulse generation section 56 generates a driving pulse Vg at a frequency fr equal to the reference frequency Vr when no synchronization pulse Vd is detected, and otherwise generates the driving pulse Vg at a frequency equal to the higher of a frequency fd of the synchronization pulse Vd and the reference frequency fr. A variable time constant circuit 52 observes the synchronization pulse input terminal 34, and when detecting the synchronization pulse Vd, changes the time constant of the time constant circuit 58 such that the reference frequency fr becomes lower than the frequency fd.</p> |
