| 摘要 |
PROBLEM TO BE SOLVED: To measure a charging voltage by a measuring means, when a flying capacitor is charged with a reverse polarity by a DC power supply insulated from a grounding potential part.SOLUTION: In the case where a potential VRL corresponding to a voltage division ratio between each ground fault resistance RLp2, RLn2 on the positive side and on the negative side on the secondary side exceeds a positive potential of a high-voltage DC power supply B on the primary side, when switches S1, S4 are switched on and switches S2, S3, S5, Sa are switched off by control of a microcomputer 15, a charging circuit is formed from the ground fault resistance RLn2 on the positive side on the secondary side to a positive electrode of the high-voltage DC power supply B via a resistance R4, the switch S4, another end and one end of the flying capacitor C1, a diode D1, a resistance R6 and the switch S1. When the flying capacitor C1 is charged with the reverse polarity by the charging circuit, a positive electrode (another end) of the flying capacitor C1 is connected to the microcomputer 15 by a negative potential measuring circuit 13, and a negative electrode (one end) is connected to the grounding potential part by a discharge circuit (the switch S5, a resistance R5). |
