Computer SMPS DC-DC converter type ?

Thread Starter

DarthVolta

Joined Jan 27, 2015
150
I'm watching a video talking about a basic flyback converter, and he says you don't need an inductor on the output, unlike in a forward converter. In most every ATX SMPS I've seen and taken apart, there are always lots of output inductors spread around the rails.


I know in a flyback converter the current rises in 1 inductor, building a B field in the core, and only after the switch is off, does the current in the secondary side start.

So in a Forward converter, the current flows on both sides when the mosfet is on.

Well what type is in 90% of computer ATX PSU's ? Are they FLY's using output inductors too? Some PCB's label the main "transformer" as FLY

Or are they usually DC-DC forward converter's ?

I have differential probes, so I can probe both sides of 1 of these things and see what the voltage is doing at least, I guess if I looked at the Vf of an output diode I'd know if that side was conducting.
 

Thread Starter

DarthVolta

Joined Jan 27, 2015
150
Hmm , so many of these use dual diodes with 1 side sitting on ground looks more like a forward converter, where the output inductor can run like a flywheel. Ok that makes a lot more sense.

 

Dodgydave

Joined Jun 22, 2012
8,465
I'm watching a video talking about a basic flyback converter, and he says you don't need an inductor on the output, unlike in a forward converter. In most every ATX SMPS I've seen and taken apart, there are always lots of output inductors spread around the rails.


I know in a flyback converter the current rises in 1 inductor, building a B field in the core, and only after the switch is off, does the current in the secondary side start.

So in a Forward converter, the current flows on both sides when the mosfet is on.

Well what type is in 90% of computer ATX PSU's ? Are they FLY's using output inductors too? Some PCB's label the main "transformer" as FLY

Or are they usually DC-DC forward converter's ?

I have differential probes, so I can probe both sides of 1 of these things and see what the voltage is doing at least, I guess if I looked at the Vf of an output diode I'd know if that side was conducting.
Most Atx psus are push pull outputs with a Full or Half bridge mosfet.

They have a startup Standby oscillator that then feeds the main chip usually a TL494,, or SG6105,,, and it Syncs with the oscillator when running.

Plenty of circuits here....

http://danyk.cz/s_atx_en.html
 
Top