UCC28063: PMP11064 current sharing control circuit

Hallo Aneesh,

Please see the attachment that describes the theyretical circuit operation.

Regards,

Mike

Hello Aneesh.pdf

Hello Mike,

Thanks for sharing the document.

I have some more doubt,

If the current amplifier U505 is not present, then also 20V output will regulate through the opto coupler and TL431 circuit encircled in 1. Then what is the use of that current amplifier circuit?

Regards
Aneesh

Hello Aneesh,

If circuit 3 is removed you are correct the 20V will be regulator through feedback circuitry 2 and the 12V output will be regulated with feedback circuitry 1.  Please note that these two feedback circuircuits are trying to ajust the frequency of the UCC25600 to control both output voltages.

Once circtry three is added it will sense the current load on the 20V output and will adjust feedback circuitry 1.  As the current increasees on the 20V output the voltage on U506 reference is pulled high.  This will cause more current to go through U503 causing the UCC25600 to operate at higher freqeuncy decreasing the LLC gain.

These three feedback paths are trying to modify the oscillator freqency to control the output.  This is a complicated control scheme and the three could fight each other if not designed correctly.

Regards,

Mike