1. The operation in DC input voltage

In input circuit of switch mode power suppies, basically once AC input voltage is rectified and is converted to DC voltage. Therefore, they could be operated with DC voltage. However input voltage selector type 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 they are 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.
When DC input is applied to AC-DC power supplies, please put DC rated fuse on the input line for protection at the power supplies failure.

2.3 Internal fuse

The most of all power supplies have AC rated fuse. Please add DC rated fuse on the input line, because AC rated fuse wouldn't work safely with DC input at abnormal condition.

2.4 Condition of acceptability for safety approval

Most of Universal input type AC-DC power supplies are certified under the input voltage condition of "100VAC-240VAC(50/60Hz)".
Please see instruction manual of each product for details.
Therefore, safety approvals are not applied to DC input condition except some products certified with DC input.