| 摘要 |
PROBLEM TO BE SOLVED: To compute the phase of a gate signal so as not to receive the effect of a disturbance due to noise, an instantaneous service interruption, or the like, and to control on-off of a thyristor. SOLUTION: A controller 3 detects a zero-cross and generates a zero-cross detecting signal in the case of operation-off, and computes an input-voltage period and sets a period lower-limit value and a period upper-limit value. The controller 3 generates a model phase inside in a model-phase zero-cross detector 24 in case of operation-on, inputs the zero-cross detecting signal, and resets the model phase and generates a model-phase zero-cross detecting signal when the input-voltage period is larger than the period lower-limit value or when the zero-cross detecting signal is not input and when the model phase is larger than the period upper-limit value. The controller 3 computes the mean value of model-phase periods in a model-phase period computing section 25, and generates the gate signal for controlling on-off of the thyristor for a power element 4. COPYRIGHT: (C)2011,JPO&INPIT
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