Using an ATX transformer "backwards" to get high voltage?

[daviddeakin]

I have a hankering to make a high-voltage SMPS, but I want to avoid having to wind my own transformer.

I have been looking at some old off-line ATX power supplies, and they all seem to use a half-bridge to step down half the supply voltage (about 300Vdc where I live) to +/-12V etc. I think the supplies I have are similar to this circuit: http://www.eejournal.org/wp-content/uploads/2010/10/PC-SMPS-2003-schematic1.gif

Therefore, can I simply use the same transformer, but backwards, driving the 12-0-12V winding with a push-pull switcher to get about 150V on the 'secondary'? Bascially, can I use something like this, but substituting an ATX transformer instead of a hand-wound one? (I'm an EE, but I know very little about SMPUs, so be gentle with me! ((@ )

 

[Redwire]

Yes, the ATX PSU transformers will work backwards. I've also used junk AC inverter (i.e. 12V to 240VAC) transformers. It depends on the voltage and power you are wanting.
Looking at your design, R10 and R11 are too small; R10 will dissipate a lot of heat. L1 might make stressful spikes on the rectifiers, I'd use an RC snubber on the secondary.