Digitally Controlled Bench Power Supply, 0-30VDC, 0-5A, Current Limiting

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Joined Jul 23, 2012
Before I start, I know I can purchase a power supply for [substantially] less than it would take to design and build one. But I'm doing this in the spirit of extending my knowledge and making myself a better designer. I've designed/built several fixed voltage buck switching power supplies over the years for various products that I have worked on, though none of them were digitally controllable, or had a current limiting option, or could be used as a constant voltage/current source.

I'm mostly looking for ideas, things to avoid, suggestions, app notes, and general advice as power supplies are outside of my day to day expertise. I would like my power supply to be digitally controlled, primarily through a digital encoder (Call me olde fashioned, but I love turning dials), though one day I'd like to connect a Bluetooth module for remote control. Regardless the controls and interface circuitry are closer to what I am familiar with and not what I need help with. I want to operate the power supply as either a constant voltage or constant current supply, but be fully adjustable. I don't like noisy fans, so I am hoping to use large heatsinks if required. Luckily heatsinking is part of my skillset.

As for the main portion of the project, I was contemplating using an isolated transformer that is connected to mains voltage (110VAC 60Hz up here in Canada), that drops the voltage down to 30-50VAC (Yet to be determined). I don't like the option of accidentally killing myself with this thing, or worse accidentally connecting ground up backwards and destroying a piece of equipment that is independently connected to it. This would then be fed into a full wave rectifier. The next part is where I need some guidance, as I was thinking of instead of using a dedicated module, I would put a dedicated microcontroller complete with control systems to regulate the voltage/current. I am very familiar with PICs from Microchip and was planning on using one of their dsPIC33... or similar chips. The inductor, control switch, balancing caps, and feedback would all be laid out separately. Finding a MOSFET and a current sense resistor should be easy, though I don't know how I would go about selecting inductors or capacitors (in the past I used what the the TI Webench suggested).