Electronics - Running HID lights from PC power supply

Most PC power supplies rely on recieving a "Power Good" signal back from the processor or they shut down. A PC powersupply does not make a good bench supply. If you want 12v on the bench you should get a proper power supply. Maybe a battery charger will do what you want.

The issue is that HID's draw a lot of current on start up. Each 55w globe will draw up to about 20 Amps for up to about 20 seconds. 2 of them is about 40 Amps or 480 Watts.

What you are seeing is exactly what will happen if they don't get enough start up current when they change from start up to constant mode.

First try just one at a time, that *may* work. Otherwise you could put say a 7AH battery in parallel to act as a large current source at start up.

Thanks for the replies !
I just checked it with one 55W on & it's doing the same thing. there is a surge at startup but not as high as 20amp (only 7amp). These are new so technology may have improved in the surge part. But it dies out after about 20 -30 seconds.

I then got out my CTEK charger & it doing the job just fine without any cutout, however I can only run one light as it's a 7amp charger.. Think your right John it's something to do with these PC power supplies.

thxs Don

As has been said for a number of reasons computer power supplies unmodified do not make good bench supplies, particularly the later ones.

PC supplies have very little surge capacity and they are designed to run lots of little loads.

Additionally many switchmode power supplies do not like running with outputs unloaded

Also I would have thaught to have any hope of sucess you would be better off looking at AT supplies with a mechanical power switch rather than ATX supplies with a fly by wire power switching system.
BUT....then ya looking as uncommon high power supples, some of the early At supplies where only 150 watts all up.

If ya trying to run HIDs of 240v mains, what ya doing is a round about way of getting the result...reinventing the wheel so to speak.

ya probably beter off doing some homework and getting an archtrual or projection balast to do the job.

what are you trying to achieve?

cheers

I'm not sure if it still holds true with PC power supplies, but they originally required a 5v load and a 'power good' signal back from the motherboard before the other outputs would even light up. They are primarily designed to provide 5v power as that is what most of the load runs on, the 12v is normally an ancillary supply.