Power output of this PSU

[Oliver]

You are trying to choose an appropriate 12V DC adapter to supply your PW-200-M, right? I had a quick look at the manual. The DC-DC converter is pretty efficient at high load currents, so you should be able to select a supply rated at just a bit over the power requirements of the euipment you are driving. If you use a supply rated at say 1.2 times your load demands, then that should give you a bit of headroom for current draw.

The device is probably a combined switch mode regulator, and charge pump for the negative voltage. These things are pretty efficient, though they can add electrical noise into a system. It's not usually a problem though (depending on what is driven, and the type of bypassing used).

[Oliver]

motorollin wrote:
Now I just need to work out the power requirements of an EFIKA, a Radeon 9250, a CF card, an IDE -> USB adapter and a CD-ROM.

You could just play it safe, and use a 12V supply capable of driving the maximum load. Provided that your load does not exceed the max load for your DC-DC converter (I think this is unlikely), then you will have no problems.

You should keep in mind that your DC-DC converter efficiency is not so good under low loads. Because of this, if the converter is running on much less than max load, then you need to provide a greater excess of current beyond what is being delivered to your load, in order to supply the inefficiency of the converter.

I'm not sure, but I doubt you would save a lot of money by using a lower rated 12V supply anyway.

[Oliver]

Your calculation is right, and it is also true that you won't really need that much power. It is just an easy way to handle the calculations if you cover the worst case.

The reason I suggested a factor of 1.2, was that a lot of supplies don't really handle being driven close to their rated maximum.

Anyway, as you have a supply already, and you know what you will be driving, it would be worth looking a little closer.

I'll have a look into the requirements and get back to you.