Can I Operate my AC-DC Power Supply with a DC Input?

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The reply is sure, typically.

Many commonplace AC-DC swap mode power provides (most of Lambda’s merchandise) specify a high voltage DC enter vary along with the extra frequent AC enter vary of 90-264VAC. We obtain many questions on how and the place to attach the DC enter to an AC-DC provide that’s spec’d to function off of DC in addition to an AC inputs.

The place and why is high voltage DC power used? It seems that many power technology amenities present a high voltage DC to power the plant’s tools relatively than the common 115VAC or 208VAC power grid. This high voltage DC (sometimes 120 or 130-330VDC) could be simply used with batteries to offer a safe source of power relatively than utilizing costly centralized or native UPS programs.

Now again to the topic. The topology of many switch-mode power provides really lends itself to operation from both AC or DC enter. Vital Be aware: All the time test your power provide’s Operations Guide or spec sheet to verify that it’s designed to function from both an AC or DC enter.

Referring to the simplified power provide schematic under:


When powered by an AC sine wave, throughout the first half cycle the present flows from the Line terminal by way of the enter filter and expenses capacitor C1 by way of diodes D1 and D3. Throughout the second (destructive) cycle, present flows from the Impartial terminal and capacitor C1 is charged by way of diodes D2 and D4.

When powered from a high voltage DC source, the polarity of the connection isn’t essential so far as the operation of the power provide is worried. If the optimistic connection is made to the Line terminal, C1 is charged by way of diodes D1 and D3. If the optimistic connection is made to the Impartial terminal, then C1 is charged by way of diodes D2 and D4.
An vital note of warning to insert right here is in regards to the protecting fusing of the power provide. Internally most power provides have a quick appearing AC rated fuse in collection with the Line terminal. It’s endorsed that a DC rated fuse be put in external to the power provide. If one aspect of the high voltage DC buss is linked to floor, then the fuse is often positioned in collection with the “sizzling” aspect (the ungrounded aspect). It’s endorsed that you just seek the advice of with your native security engineer to make sure.