High power PSU have more extra transformers than the main one

[abdan]

Why most high power (at least 12A) AC-DC step-down (switching mode) PSU have many extra transformers instead of just one?

 

[Martaine2005]

I’m not really sure I understand the question.
But I’ll try. Many power supplies output different fixed voltages so there will be different types of internal transformers for each output.
And different power supplies also have circuitry that requires different voltages. This could be 12V, 5V, 3.3V or 1.8V etc.
And just to discombobulate, there are inductors and chokes that look like transformers. So you might be including these?.
But I’m just guessing that that’s your question.


Martin

 

[Harald Kapp]

As far as I know they don't. They usually have a single transformer, possibly with more than one winding for creating different voltages.
Show us examples (photos? Note: < 30 kB for uploading to avoid errors).
Could you possibly mistake the inductors on these PSUs for transformers? Lots of inductors are usually employed in addition to the transformer for filtering puproses.

 

[abdan]

I’m not really sure I understand the question.
But I’ll try. Many power supplies output different fixed voltages so there will be different types of internal transformers for each output.
And different power supplies also have circuitry that requires different voltages. This could be 12V, 5V, 3.3V or 1.8V etc.
And just to discombobulate, there are inductors and chokes that look like transformers. So you might be including these?.
But I’m just guessing that that’s your question.


Martin

Yes correct
this specs supply many V output so T are for each different output lines

 

[Martaine2005]

Yes correct
this specs supply many V output so T are for each different output lines

Is this a quiz?


Martin

 

[Harald Kapp]

Without a schematic we can only guess.

#1 could be an inductor for an active power factor correction (pfc).
#2 seems to be the main transformer, judging by the wide traces coming from it.
#3 could be an auxiliary transformer or a large inductor. Hard to decide without a schematic.

 

[kellys_eye]

Some PSU's have a 'standby' voltage that is also created in an SMPS-type of manner hence the 'extra' transformer. You might also find miniature versions used to isolate feedback signals and even used to drive switching transistors (driver transformers).

There is no 'standard' so each case has to be made on its merit.