Generic SMPS schematic

[ard]

Hello everyone,

Would anybody here have a circuit for one of those +5v 2A, +12v 2A generic brick supplies that usually come with USB to SATA/IDE cables? I eliminated the usual suspects, but still end up blowing the fuse at the input.

This kind has no controller IC, 1 mosfet, a pair of (npn, pnp) transistors at the input side of the transformer, one TL431 ref on the output side, and a PC 817 opto.

Any direction would be highly appreciated!

ARD

 

[BradtheRad]

It will be a challenge to construct your own commercial quality power supply, if you want to operate computer equipment from it.

It needs to be stable. It needs safeguards so there can be no overloads.

Are you sure you wouldn't rather make a simple everyday power supply?
The kind that contains a transformer, diode bridge, smoothing capacitor, and voltage regulator?

 

[ard]

Brad, I don't want to build these, just repair a couple that came my way, all defective, and mostly all in different ways.

 

[Kripton2035]

what "suspect" did you eliminate ?
a blowing fuse at startup is generally :
- one or more diode shorted in the primary side
- shorted mosfet primary side
- bad esr capacitor at the primary
- Shorted rectifier diodes in secondary circuits (which blown components in the primary then)
you must test every component in the primary side
if nothing is found, check the secondary side for short also