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Re: switchers -- input range

In another group; there's a discussion about PC switcher inputs ranges. This came up after a poster suffered from an open neutral, and lost a lot of equipment.

A) Are there any switchers that automagicly sense the input and change ranges? Some older Mac's are labeled "110-130 or 220-250" vice the "110-250" of newer ones. Note I am NOT talking about units with a {manual} voltage selector switch.

B) What's the gotcha on having a wider input range: More design effort, to be sure, but do you also lose in efficiency, watts/cc^3, power factor, etc? I've only read a little on switcher design & never soldered on one. I'd assume you need to worry about the ratings on the input L, C and other items, and the one limit is high-input voltage, low load, [vs low, high...] cases. Other things?

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Reply to
David Lesher
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I have seen some designs that basically had two windings in the primary on the input transformer, and either put them in series or parallel depending on the voltage.

If the load isn't too high, you just design in a regulator that can take twice the input voltage and still give the right output. It usually isn't as efficient, but works well enough... 8-)

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Charlie
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Reply to
Charles Edmondson

The selection between 110V & 220V operation is usually a single connection somewhere in the rectifier which selects between full wave or half wave. This link can easely be replaced by a triac and a simple control circuit. Keep in mind though that the PSU from the average PC is still quite similar to the PSU fitted in the original XT PC.

Nowadays it is more economic to make a wide range PSU than having to set all kind of switches (a switch needs to be mounted & wired) or implement auto sensing schemes.

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Reply to
Nico Coesel

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