Hi,
Anyone got any pointers for the conversion of a switching power supply designed for 110v to 220v?.
The PS uses a Fairchild Semi IC (5M02659R).
Would it be too difficult to turn this PS into one taking 220v as source?.
Thanks in advance
FC
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The IC has little to do with your question. You have to look at the way the mains is rectified, so the DC voltage that powers the IC. If that voltage is below 200VDC you have bad luck. It means that the transformer has been made for that voltage and modifiing it will be hardly possible. On the other hand, if the voltage is above 300VDC, the mains rectifier uses a voltage doubler. See a more or less standard mains rectifier schematic below. If you are very lucky you'll find a bridge rectifier and you'll only have to look for the switch. Which may not be a real switch but only a piece of wire. Otherwise you'll have to replace two mains rectifier diodes by a mains bridge rectifier *and* disconnect the mains wire from capacitors.
+----+-----------+------- | | | - - --- ^ ^ --- | | | | | , | ------------+ +--+-o´ o---+ | | | switch | mains | | | | - - | --- 220Vac switch open ^ ^ | --- | | | | 110Vac switch closed| | | | +----+--|--------+------- | --------------------+ (created by AACircuit v1.28 beta 10/06/04petrus bitbyter
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If it's a wire link then check the voltage rating on those caps as well.
They work well. Just be sure to get one designed for the power you need. Many of those sold at airports are small low power devices only suitable for mobile phones etc. If you need 400W to power a big PC then you may have to hunt around a bit.
I originally asked the question of the switching PS modification specifically to avoid having to add a bulky external step-down transformer. Even the small ones are an annoyance. :)
FC
Most of the above is questionable advice.
The lightweight "transformers" often sold at airports are only diodes or SCRs that chop half the supply and are hence not too good for anything other than heating devices.
Changing anything within the power supply will void the HIPOT test done by the manufacturer and thereby void the UL/CSA or whatever approval was appropriate.
Then a fire or electrocution would be on your head.
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