Tweakers' Asylum

Can I put 5 Switching Mode PS in serial for 200V

218.186.8.248

wlee

I had a great idea of getting a few of higher voltage SMPS in serial so I could use them as B+ for tube amp.
But just put the output in serial cause one of them to have a loud pop and smoke, even before loading them.
Since the transformers inside are isolation transformers, so any reason why they may interfere with each other?
Also what is the highest output voltage SMPS you have seen?

Follow Ups:

Your SMPS units may not be isolating. - Al Sekela 10:42:23 12/17/10 (3)
There may be a direct connection of the output negative terminal to the AC input ground, so that connecting two SMPS' in series shorts one output and burns up the unit.

You can determine this with a simple ohm-meter.

If this is the case, then you need a separate AC isolation transformer for each SMPS (except the one at the bottom of the chain, if having the negative terminal grounded is not a problem).
- RE: Your SMPS units may not be isolating. - wlee 12:02:00 12/18/10 (2)
  ok tks! I got a bit chicken after 2 went smoked up!
  The one with metal casing I could see the TO220 type transistor inside broke up. Hope I still could ID the transistor type to repair it...
  Btw is there any standard schematic for SMPS? I know some most used MOSFET, but the plastic casing type could not adjust the voltage.
  - There are many designs. - Al Sekela 12:57:24 12/18/10 (1)
    Here is a link to a list of basic topologies. There may be dozens of circuit designs using each topology. Some have the ground connected through from input to output (which I suspect is the case with yours) and some don't.
    
    You would have to find a schematic from the manufacturer or generate your own.
    - SMPS Topologies (Open in New Window)
    - RE: There are many designs. - wlee 23:49:13 12/18/10 (0)
      Wow, tks a lot! I just need them for the repair, also, use them for hifi by changing to better cap!
      I have never seen a full bridge SMPS, wonder for those single output type if bridge rectifying is ok... once I tried to crease a negative output from a half wave, and the MOSFET burnt. I repair the Mosfet and found that I need to add 300 ohm at the gate as it broke down again a month later, but never dare to get a -ve supply again!!.
RE: Can I put 5 Switching Mode PS in serial for 200V - djk 20:58:07 12/16/10 (0)
Swithmode supplies generally will not run properly without a minimum load.

There are small capacitors from the seconday to the primary, this may be your problem.

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