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I have an application where I need a 24V DC Power source at approximately 5 Amps (so approx 120 Watts). I've also got a shed load of old computers which all have 12V power supplies rated at up to 300W. Is it safe/okay to connect two ATX power-supplies in series to achieve what I'd like to do (which is a 24V DC Power Supply on the cheap).

Thanks in Advance, Patrick

Patrick Rynhart
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    Possible duplicate of [24V 3A from ATX power supply?](https://electronics.stackexchange.com/questions/7657/24v-3a-from-atx-power-supply) – winny Sep 01 '19 at 07:43
  • Most ATX style power supplies regulate primarily on the 5V rail so unless this is significantly loaded regulation may be poor. – Warren Hill Sep 01 '19 at 10:18

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Its possible, but less safe, as these supplies are ground referenced, it means you have to deliberately disconnect 1 power supply PCB from mains ground (leave the enclosure grounded!)

This will then make that supply floating, and able to be used in series with another supply, again, it makes it more dangerous for yourself, so set things up so you don't have to touch it before powering it on.

And to catch it before it gets asked, some ATX power supplies still have a -12V supply, however it is extremely low current and easy to damage, avoid using this.

Reroute
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40VA thermostat transformers ($10) are common and cheap. Three paralleled will give 24VAC at 5 amps. Rectify and regulate (if your application even needs that).. you're all set.

Harper - Reinstate Monica
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