| 摘要 |
PROBLEM TO BE SOLVED: To prevent short circuit (reverse connection) of a power supply due to polarity automatic setting, regardless of the electrical contact state of the wiring to which a DC voltage is applied, and a DC power supply device outputting the DC voltage, and to speed up the rising of the system by eliminating the need for the polarity determination processing which is performed when AC power is turned on.SOLUTION: When an AC power supply 20 is turned on, a control unit 14 confirms a voltage polarity signal if the polarity data does not exist in a storage section 13. If a voltage has been applied between the wiring 8a and wiring 8b, a polarity instruction signal is outputted to a polarity switching section 17 according to the polarity of the voltage thus applied, otherwise the polarity instruction signal is outputted to a polarity switching section 17 according to a previously defined polarity, and the polarity data corresponding to the voltage polarity of the polarity instruction signal thus instructed is stored in the storage section 13. If the polarity data exists in the storage section 13, a polarity instruction signal corresponding to the polarity data is outputted to the polarity switching section 17. |
