Q&A(FAQ)
Is it allowed to apply DC voltage to AC-DC unit?

1. The operation in DC input voltage

In input circuit of switch mode power supply, basically once AC input voltage is rectified and is converted to DC voltage. Therefore, power supply could be operated with DC voltage. However power supply which has input voltage selector is not allowed to be operated with DC voltage.

Since the rectified voltage is smoothed by capacitor, it is required to apply DC voltage in which value is equal to the crest value of AC voltage. Therefore, when the power supply is operated with DC voltage, the rated AC voltage times the square root of two (= AC voltage x √2) needs to be applied. Please refer to the DC input voltage range in COSEL catalog.

2. The wiring for DC input

2.1 The outline

Because there is the full-wave rectifier circuit, the positive / negative voltage can be applied to either terminal of the input.

2.2 The recommended wiring

The positive voltage can be applied to either terminal of the input, but COSEL recommend that the positive voltage is applied to the terminal AC(L) which has fuse. Please refer to Fig. 2.1.

Fig. 2.1 The recommended wiring for DC input

Fig. 2.1 The recommended wiring for DC input

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