Re: Please help to improve load regulation of flybuck SMPS power supply circuit
1. That schematic is a multi-output flyback, not a flybuck.
2. 48V 3.5A is pretty high power for a flyback, you may want to consider using another topology (forward, two switch flyback, etc).
3. Dropping from 48V to 32V at full load implies that some stage is saturating or hitting a hard limit. For example a peak current limit, a max duty cycle, transformer saturation, etc. Without more info it's impossible to say.
4. 0.05% is very tight, especially for a flyback. It will depend mostly on the DC gain of your feedback loop. First you should solve problem #3...
5. Load regulation and output ripple are two entirely different matters.