I'm in the early planning phase of a new project: A variable output buck converter. I've done some research and lots of reading, but several questions remain. For now I'm researching the power section (shown below), to drive this I plan for an AVR, running at 5V, the precise chip is not yet determined.
I've tried to find examples on the web, but most of them are geared to a fixed voltage on the output, I'd like it to be variable an controlled by the AVR.
For now I have two applications in mind: One as a variable output lab power supply, the other as a freely programmable battery charger. The basic schematic and layout PCB should go to 50V/10Amps (not necessarily at the same time). I think that ripple may be a problem for the lab supply application, but in many cases it is not a problem.
For now I plan for a synchronous buck converter, I plan for synchronous because I think it gives me some more flexibility. I may replace the lower transistor with a diode in the beginning, to simplify things. If I use a 20Mhz AVR and plan for 10bit resolution my PWM will run at 20kHz, I'd like it higher, but thinks I need the 10 bit too.
Initially I'll supply power from a 20V Laptop power brick (20V, 4Amps), but I'd like to be able to make versions with higher voltage or current. This using the same PCB, just with some variations in components.
I'm interested in discussion and critique, I'd like to start with the least amount of smoke possible :-).