Lab Bench Power Supply
Lab PSU
2021
This is an new PSU I decided to build. I wanted this one to be an easier portable PSU with a large voltage range and current limiting. I ended up using a couple more LM317's for both the voltage regulation and current limiting. That knob thing with a ton of headers is a 10-step switch which allows me to connect a bunch of different resistors to the output of the first LM317, used for current limiting. This supply can go from ~1-20V at 2.5A max, with current limiting going to 1.2A. This was a good edition to my PSU's as current limiting comes in handy very often and it's mostly portable, given that I essentially threw it in a cardboard box.
The first stage is a current limiting LM317, with that 10-step switch switching in different value resistors to limit the current. I got this current limiting circuit from the LM317 datasheet, but could not get it working with a higher value potentiometer that I had on hand. This is why I opted for 8 set current limiting values, with one bypass step (the 10th step didn't function).
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The second stage is the actual voltage regulation, done again with the LM317. I edited this circuit from the datasheet and added a few things. I was considering adding a capacitor multiplier, but that seemed counterproductive as lower capacitance on the output of a constant current supply should be minimal, as the capacitors would fight this limiting.
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I stuck a large diode on the output to protect from reverse biasing and connected a voltage and current display I ordered for cheap. I was contemplating adding an extra overcurrent protection feature on the output in bypass mode, either with a FET or relay, but deemed it too much work because I wanted to be done with the project. This isn't a great idea as this could deliver a lot of power if connected wrongly, so I would recommend adding this protection to any sensitive projects.