Making symmetric full-wave rectifier by using two isolated secondary windings

[hkBattousai]

I have a transformer with the dot conventions given in the image blow. I design the full wave rectifier in the same image. However, I'm very confused and can't make it sure how to connect the transformer to the circuit.

Please help me by matching the SA1, SA2, SB1, SB2 pins to the UP, MID, DOWN nodes.

[Simon]

Connect SA2 and SB1 together, that is GND. the other two don't really matter, any way you fancy.

[hkBattousai]

Connect SA2 and SB1 together, that is GND. the other two don't really matter, any way you fancy.

Do you imply that I must use one of these four schemes?

Code: [Select]

UP    <--->  SA1
MID   <--->  SA2, SB1
DOWN  <--->  SB2

UP    <--->  SB2
MID   <--->  SA2, SB1
DOWN  <--->  SA1

UP    <--->  SA2
MID   <--->  SA1, SB2
DOWN  <--->  SB1

UP    <--->  SB1
MID   <--->  SA1, SB2
DOWN  <--->  SA2

A dotted pin from one winding must be connected to the non-dotted pin from the other one; they will together be connected to GND. The other pins will be connected to UP and DOWN interchangeably. Is this correct?

[Simon]

that is correct,

you could use any combination including dots together or non dots together as GND and it would seem to work but then you can end up with both side feeding the same cap in alternate half wave rectifier mode which is not really any good for a number of reasons for the transformer, efficiency or the load.

[DanielS]

You simply tie a dot to a no-dot end which becomes your center-tap/neutral-out and then put a full-wave rectifier across the remaining two outputs. That is the most common and usually preferable way to do symmetrical non-isolated output from two identical secondary windings.

[hkBattousai]

This is a different representation of the circuit. It may make it easier to see how the circuit works.