I'm designing a small programmable bench power supply (well, I say "small", but the AOT430 FETs will handle 10A+ in their linear region without thermal runaway so...).
A switching regulator provides coarse voltage stepdown (24Vdc to 0-20Vdc isolated) while a MOSFET based LDO handles the fine control, a small DSP oversees everything else.
I want to have both programmable current and voltage limits. As for the control loop, it's probably going to end up as a mix of analog and software controls. I can either regulate the voltage across the load with discretes and handle the current control in software or regulate the current through the load with discretes and handle the voltage regulation in software.
I would like to know what sort of advantages/disadvantages (if any) that either solution would have in the context of a variable bench supply. Or should I try something else altogether? (like all analog or all digital control loops)
At the moment I'm leaning more towards analog voltage control. I'm expecting that analog current control might result in bigger voltage spikes/sags when loads change while the DSP readjusts the current settings to bring the output voltage back under control. But at the same time, I'm thinking that the analog current version would have (much) faster current limiting and short-circuit protection.
(Note: These are only conceptual schematics and have been greatly simplified)