13.8V, 40A Switching Power Supply

This power supply project describes the construction of a switching power supply designed to power a complete ham station, with several radios and accessories. This power supply produces 13.8V regulated to better than 1%, at a continuous load current of up to 40A.

This switching power supply circuit has current limiting, making it appropriate for direct connection to a 12V backup battery. If the current limit potentiometer is turned up, the power supply can deliver up to 60A on an intermittent basis, while maintaining regulation. No minimum load is required. The ripple on the output is about 20mV, and the efficiency is 88%.

A power supply cooling fan operates depending on the average current drawn, and a tricolor LED tells you if the voltage is normal, too high or too low. It produces no detectable RF noise at any frequency higher than the main switching frequency of 50kHz (I checked it with an antenna wire looped around the operating power supply, tuning my TS450 from 30kHz to 40MHz).

13.8V, 40A Switching Power Supply in detail

This article was originally published (in a slightly modified form) in the QST magazine, December 1998 and January 1999, and in the Radio Amateur's Handbook, 1999.
Visit the American Radio Relay League for information on these publications.

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