JPS5586379A - Control circuit for semiconductor device - Google Patents

Abstract

PURPOSE: To obtain a control circuit which can adapt to voltage fluctuation without using a filter, by controlling the generation of a turn-on signal by a signal obtained by averaging the output of a semiconductor device throughout the generation term of the turn-on signal.

CONSTITUTION: When the output level of a flip-flop circuit 9 is high, integrators 71, 72 integrate a signal produced by voltage-dividing the output of a semiconductor device and other integrators 73, 74 integrate a constant DC voltage. A divider 75 divides the outputs of the integrators 71 and 73 or 72 and 74. When the output level of the flip-flop circuit 9 is high, sample/hold circuits 716, 726 perform sampling. Values, which are sampled when the output level of the flip-flop circuit has turned low, are held by the sample/hold circuits until the output level of the flip-flop circuit turns high. The output of a switching circuit 717 or 727, which is open when the output level of the flip-flop circuit 9 is high and which is closed when the output level is low, is compared with an output set signal at 78 to apply a comparison value to a turn-on signal generation circuit 8. As a result, an average voltage determined throughout a thyristor turn-on signal can be used for control and voltage fluctuation can be adapted without using a filter.

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