I’m going to try to design an open source programmable precision bench power supply. There are plenty of power supply designs floating around (see my recent link roundup), however, I’m not aware of any designs that compare with even low-end professional grade power supplies. I’m going to loosely base my target specs on the $409 Rigol 832 (without the precision upgrade):
- 0-30V and 0-3A adjustable.
- 10mV and 1mA resolution.
- The usual over current, over voltage and thermal protections.
- Quantified regulation accuracy, transient and programming response, and thermal and temporal drift, again, initially aiming for something like the Rigol 832.
I would like the design to be modular in the sense that the above specs could be improved by choosing higher precision components, larger heat sinks, etc. I’m going to aim for a single channel to start but, again, I’d like a modular design that makes it relatively easy to support other channel configurations.
I will aim to produce the following:
- A discussion of the design (as a series of blog posts to start), including background theory and trade-offs. This should make it easy for others to modify the design for different goals.
- A complete set of design files, firmware and instructions so anyone can build a power supply for themselves. There may be a few versions of this (TH vs SMT, multiple channels, higher precision, etc.)
Depending on how successful the design is, interest, etc., I might try to sell bare PCBs, kits, or maybe even a finished product. That’s still a long way off.
I plan to break the design process into several stages. To begin, in order to avoid the complexity of working with mains power, I plan to start with unregulated DC input. This can either be provided by a wall wort, step-down transformer, rectifier and filter, or, in my case, a switching ATX power supply I have lying around. To avoid a huge transformer and minimize the need for heat management in the final design, I plan to use a design which cascades a switching pre-regulator with a linear regulator. This is the design I have been prototyping. Pictured is prototypes of a microcontroller controlled non-inverting buck-boost converter, linear regulator and programmable dummy load. I realize it might be prohibitive to filter the switching noise to achieve high accuracy regulation, in which case I will modify the design when I get more experience. I will describe the circuits in more detail in coming posts as I continue to flesh out the design.
Thoughts? Let me know!