| 摘要 |
PURPOSE:To improve the control resolution by shifting successively by the specific value between the phase of a waveform of the power supply voltage and the phase set at the start of energization of a control cycle so that the time of energization is changed for a bidirectional semiconductor switch. CONSTITUTION:A cycle control device 6 selects an optional integer (n) via an input means 13 and supplies it to an m-arithmetic means 14. The means 14 decides an integer (m) from the value of the integer (n) and the time (t) of a single cycle of a power supply waveform. Both integers (m) and (n) are supplied to a control cycle arithmetic means 15 for decision of a control cycle T via an equation. Thus the phase of the waveform of the power supply voltage is successively shifted by t/n from the phase set at the start of energization of the cycle T. As a result, the time of energization of a bidirectional semiconductor switch 2 is changed in each cycle T by a zero cross trigger circuit 3 and therefore the average energization factor of n-frequency control cycles can be optionally set. Thus, the accuracy of the average energization factor and the control resolution can be improved and therefore the load is controlled with high accuracy.
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