Power supply [Intro]

This is the update to the teaser posted a while back. I finally got the boards back from China via snailmail. This is a long-term project that I started in college. An earlier incarnation of it was used in my Masters dissertation.

It’s a modular power supply with a capacitive touch keypad/front panel. The idea is to have up to 4 channels in one unit with 0-20V and 0-4A and no fans. I don’t know about you but there are few things more annoying to me than the hum of a chinesium grade bearing in a fan.

To kick off this series of posts I’ll list some of the features that I wanted for this thing. Over time I’ll explain each section of it and the design decisions that went into it and at the end of the series I’ll post the full schematic file (for Kicad) so you can do the layout and fabricate it yourself.

Onward with the features/design constraints:

  1. No fans and smallest heat sinks possible
  2. Get the cheapest/simplest transformer for it (it shouldn’t need more than one winding per channel)
  3. Get the highest resolution/read-back accuracy from the cheapest DAC/ADC combo (ended up using an XMEGA)
  4. Have current limiting and over-voltage protection
  5. Get up to 4 channels per unit (the theoretical limit is 127)
  6. Have a simple interface (went with capacitive touch pad built into the front panel)
  7. Layout should fit into 100x100mm and 2 layers
  8. Have as little output capacitance as humanly possible (better current limiting)
  9. Relatively low noise output
  10. Have a relay to disconnect the load from the unit

Next up I have to assemble the new boards and clean up the firmware. The first few posts will probably cover this process and then I’ll get into the theoretical part of the schematic and system.

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