| 摘要 |
PURPOSE:To simplify circuits and enhance reliability, by frequency-modulating a triangular wave signal with a sine wave to obtain a pulse-width-modulated signal approximating the sine wave. CONSTITUTION:A pulse width modulation circuit is composed of the detecting circuit 30 of the output voltage/current of an inverter, an oscillating circuit 31, a first-a second divider circuits 32-33, a triangular wave generating circuit 34, a sine wave generating circuit 40, and a modulation circuit 41. In a comparator 42, the signal detected by the voltage/current detecting circuit 30 is compared with the frequency-modulated triangular wave signal generated from the triangular wave generating circuit 34, and the output of a square-wave pulse train having pulse widths according to the respective widths is generated as pulse width modulation output. Besides, the output as ON/OFF controlling signal is properly applied to the transistor element of the inverter via a logical circuit 37 and an amplifier circuit 38.
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