TDK-Lambda Americas Blog

Can an AC input filter be used with DC?

Thursday, May 29, 2025

Yes, a filter for AC power supply can be used with a DC input. Select an appropriate filter taking into consideration the rated current, rated voltage and characteristics. Depending upon the application, the attenuation performance may not be as effective as that shown in the datasheet. In addition, note the filter’s safety certification will apply to AC inputs only.

Surge current

Take into consideration any surge currents if the system has significant capacitive or inductive loads. Typically, the allowable levels are 50 times the filter’s rated current and the surge time remains within 1/4 cycle of the filter’s 50/60Hz (5ms) rating.

Grounding

When installing the filter in a DC system, ground the filter in the same manner as it would be with AC. Ensure any signal ground wires are insulated.

Applications

TDK-Lambda has a number of customers using AC filters to further reduce the noise on the output of an AC-DC power supply. If the output current is very high, 200 or 300A, it is easier to purchase a filter rather than design and manufacture an in-house solution.

Figure 1: RSHN high current AC filter

Power Guy