| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC power source driven by various commercial AC power sources including a low voltage family of 100 V group. SOLUTION: Either one of 100 V group, 200 V group, 400 V group or 575 V group AC power source is supplied to input terminals 1a, 1b. A rectifier 3 is connected to the power input terminals 1a, 1b, and a step-down converter 4 is connected to the rectifier 3. A thyristor 10 is connected in between input and output of the step-down converter 4. Capacitors 8a, 8b are connected in series to the output side of the step- down converter 4, and a switching circuit 54 is connected in between a node of the capacitors 8a, 8b and an input side 31N2 to the rectifier 3. DC voltage between the capacitors 8a, 8b is converted by an inverter 14 to a high-frequency voltage, transformed by a transformer 18 and converted into a DC voltage by a high-frequency- DC converter 20. When the voltage at the power input terminals 1a, 1b is the 100 V group, the thyristor 10 is turned on, the step-down converter 4 is turned off and the switching circuit 54 is turned on. When the voltage at the power input terminals 1a, 1b is the AC voltage of the AC 200 V group, the thyristor 10 is turned on, step- down converter 4 is turned off and the switching circuit 54 is turned off. When the voltage at the power input terminals 1a, 1b is the voltage of the 400 V group or 575 V group, the thyristor 10 is turned off, the step-down converter 4 is turned on and the switching circuit 54 is turned off.
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