Two 24V PSUs in series + tap in the middle

[TeraHz]

Hi there,

I have a couple of 24V 6.5A switch mode PSUs (http://www.circuitspecialists.com/products/pdf/CSI-15024-1M.pdf) and I'd like to put them in series to get a 48V output but I have two questions:
The PSUs seem to have enough protection features (as per DS), should I add another set of diodes on the outputs?

And the main question, is it possible to tap one of the PSUs to get 24V out as well or will that cause issues?

The 48Vs will be loaded at 1.5A-2.2A and the 24V at 1.5A-1.75A.

[Classicmacintosh]

From my experimentation using a couple of old Toshiba laptop PSUs (15vDC at 3A), yes you can put them in series. I was using three in series (so producing 45vDC at 3A max) to blow up old PCI modems (not that I recommend using PSUs like this!) and tapped off the first PSU to run a 12v fan (at 15v) to remove the smoke.
I used no external circuitry as the PSUs seemed to be incredibly well protected. As I do not know if your PSUs are as well protected, I would play it cautious and use diodes.
If your PSUs are suitably protected, jut give it a shot as if they don't like it then the worst they can/will do is to go into protection mode.
Good luck!
-Ed

[Psi]

Just be careful that all of the power supplies are switched on before you apply a load.

[TeraHz]

I've actually tried them in series before and they worked just fine for the 1-2hrs I had them that way. I was only concerned about taping the 24V as well.

Psi, the supplies will be on pretty much 24/7, only the load will be turned on/off.

Thanks

[digsys]

This sort of thing is done all the time, so it's not scary. Maybe as a minimum extra protection, put fuses on the
+48V Tap and one on the +24V Tap. That way if anything goes wrong with either load, you're covered.

[ftransform]

Some people recommend adding diodes in between the power supplies in case one fails to turn on or a short occurs.
This website covers the issue briefly:
http://power-topics.blogspot.com/2009/07/operating-power-supplies-in-series.html