Can two ATX SMPS be connected in series to get +10 and +24V DC (from 5V and 12DC output of each SMPS)
Needing lots of current at 24V with atleast 5A so cannot use -5V or -12V inside SMPS as negative voltage have less than 1A rating
I know transformer based PSU can be uses this way, but professor telling that SMPS cannot be connected in series the same way.
He not tell me reason as he says I will understand better next year when SMPS in course offering.
If he correct, then why not SMPS work like transformer based PSU?
Best Answer
No, you can't connect two ATX supplies in series and get double the voltage. There are many issues to consider, and most of them require detailed knowledge about the insides of each power supply.
One issue to consider is what happens when one supply is turned on, while the other is off? This can happen for many reasons, but #1 reason is that both power supplies will never come up at exactly the same time even if you use the same power switch for both. When one is on, and the other is off, the off supply will be subjected to -5 & -12v on it's outputs. This is a case that the supply was never designed to handle. Odds are that you'll blow up the caps on the output, and maybe a diode or MOSFET as well.
There are ways to protect against this sort of fault, but why bother? You will be much better off getting a supply that does what you want-- and the risk of burning down your house is much less.