| 摘要 |
PROBLEM TO BE SOLVED: To suppress the peak value of a current (iA+iB) flowing from an operating power supply to the exciting coils 4A and 4B of an electromagnet apparatus being closed simultaneously upon turning a breaker contact 1 on with the closing currents being controlled constantly by PWM control through current mode PWM control ICs 11A and 11B, main FETs 17A and 17B, and the like. SOLUTION: In the closing signal output interval where a closing signal V3 is H and an auxiliary FET 20A is turned on, the IC 11A turns the main FET 17A on at every moment in time when the voltage of the capacitor 16 in an oscillator oscillating at a period dependent on a resistor 15, and the capacitor 16 reaches a specified upper limit level, and turns the main FET 17A off when the voltage Vcs of resistors 18 and 19 for detecting a current iA rises up to a specified level. Since the IC 11B turns the main FET 17B on in synchronism with a sync signal V4 rising upon turning the main FET 17A off when the closing signal V3 is H and turns the main FET 17B off when the detection voltage Vcs of a current iB rises up to a specified level, the currents iA and iB flow alternately without overlapping for a long period of time. COPYRIGHT: (C)2004,JPO
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