I have been reading up on switch mode power supplies, and one that has peaked my interest is the attached schematic from the datasheet of a TOP249Y.
If you look at the bottom right of the schematic you will see three zeners, along with R6 create a voltage reference of +/-48V (the desired output).
When the zeners forward bias, it turns on the opto which allows current to flow into the SMPS Chip U1, which controls the switching.
I was wondering if I just vary that combined zener voltage, do I now have a variable power supply (0-48VDC)? I am pretty sure it is not that simple because all the examples in the datasheet are fixed voltage outputs.
The only reason I can think of why it wouldnt work is because that high frequency transformer is set up for certain conditions that only "work" for 48V.
Can anyone see any limiting factors as to why one couldnt simply change that supply to be a variable one?
Thanks for any insight!