| 摘要 |
PURPOSE:To detect an open phase precisely by few circuit components by detecting the spreading of the duty of an output waveform from a supply-voltage phase detecting circuit. CONSTITUTION:An open-phase detecting circuit 9' consists of duty detecting sections 96, 96', diodes 97, 97', a reference setter 94' and a comparator 95'. Phase detecting signals 7A, 7D and 7B, 7E for a supply-voltage phase detecting circuit are inputted to the open-phase detecting circuit 9'. The phase detecting signals 7A, 7D and 7B, 7E are 120 deg. wide on the normality of a power supply, but width thereof is changed into 180 deg. on an open phase, and the width is detected by the open-phase detecting circuit 9' and an open-phase detecting signal 9A' is outputted.
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