Application brief: Linear versus switching power supplies

-- Control Engineering, 6/5/2008

Storteboom says, “We have applications, in our validation lab, that seem more suited for a linear power supply. We test flashers that drive as many as 18 automotive bulbs at a time. The in-rush current, with the bulbs at -40 °C, is in the neighborhood of 170 A for the first flash and drops off, in a logarithmic fashion, to ~20 A per flash after 5 to 7 flashes.

“There may be switching power supplies out there that can handle this type of dynamic load. I'm much more comfortable, however, using my very old Sorensen DCR40-250A when this test comes into the lab. We also have 'Cold Cranking' tests that we have to run that require relatively fast voltage transitions based on an analog input signal from a PLC.

“We use the older HP6267B supplies for these types of tests. I have avoided the move to the switching supplies as long as I can; but, my antiquated power supplies are starting to let the smoke out, and they need to be replaced. The challenge is finding power supplies that meet our dynamic load requirements and budget constraints,” Storeteboom concludes.

For research, more comments, and new products on this topic, watch for the June 2008 Control Engineering Product Research article and report on dc power supplies at www.controleng.com/archive.

– Mark T. Hoske, editor in chief

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