JPS55111661A - Conversion signal synchronizing device - Google Patents

Abstract

PURPOSE: To obtain a conversion signal the phase of which is synchronized with the power supply by correcting a phase lag, which is corresponding to the frequency produced in the filter that removes the distortion of waveform of the power supply, and by making it a phase lag at 180°.

CONSTITUTION: The phase lag θA₁ of a signal C detected by the zero detecting circuit 11 after frequency f₁ of the power supply with distortion is passed through the filter 10 is as follows. θA₁=2f₁.T.180° where T is the time constant of the filter 10. The dalta wave signal generator 13 of the frequency changing circuit 12 proeuces a dalta wave D with a maximum value V when the signal C shifts from a low level to a high level, the frequency voltage circuit 14 produces voltage of kf₁ and the subtraction circuit 15 does voltage of V-kf₁. Also the selecting circuit 16 provides the output kf₁ or V-kf₁ according to a high or low level of the signal C, the comparator 17 compares both output levels of the circuits 16, 13 with each other and provides a signal of a high or low level, the phase lag θB₁ becomes as follows. θB₁=180°-kf₁/V.180°. Accordingly, when the factor k is selected so that θA₁+ θB₁=180°, that is k=2TV, a conversion signal the phase of which is synchronized with the power supply can be obtained.

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