Dual feedback loops for split rail outputs?

[cupoftea]

Hi,
Doing an LLC with +/-180V output.....the transformer is split sec.....one coil for each "half" output.
Can i use two TL431/Opto feedback loops, one on on each output...and just parallel the optos' collectors and emitters , as they connect back to the primary side controller?

 

[crutschow]

How do you expect to control two outputs with one controller?
The controller only has one output.

 

[FvM]

You can do it but it doesn't constitute a dual feedback loop. Just a single loop controlling max(V1,V2).

 

[cupoftea]

ou can do it but it doesn't constitute a dual feedback loop. Just a single loop controlling max(V1,V2).

..Thanks.....that indeed is our intended desire.
There's a bit of worry that if somehow the "halves" get differently loaded, then one will go overvoltage...so just want two feedback loops in there to stop that......basically a safety measure.

 

[crutschow]

one will go overvoltage...so just want two feedback loops in there to stop that.

So you would need a circuit to pick the maximum of the two voltages for feedback to the regulator.
That may be more than just paralleling the optos' outputs.
What does the feedback circuit look like?

 

[cupoftea]

Feedback circuit would be a typical TL431/opto type (x2).

Opto collectors pull down on the single controller chip feedback pin.

Its an ICE3H LLC controller

 

[crutschow]

Opto collectors pull down on the single controller chip feedback pin.

Does pulling down the voltage increase or decrease the output voltage?

Its an ICE3H LLC controller

I could find no info on the ICE3H controller.

 

[cupoftea]

Sorry, my apologies, its ICE2HS01G...

ICE2HS01G - Infineon Technologies

www.infineon.com

...Pulling down the FB pin brakes the converter.