Currently I’m working on my first electrical project and having a few issues with the negative side of the supply, it is not adjusting the same as my positive side, and I think the LM337 is blown?
I’ve attached a photo of the circuit, which consists of an LM317/337 with 2 PNP/NPN's in parallel for boosted current.
There is no capacitor on the adj pin, and no output capacitors currently so there are no bypass diodes in place as recommended from the 317/337 datasheet. Although I do plan to add them in the future.
EDIT: I’ve tested the npn transistors on the negative side and they are good. R5 and R6 also have a potentiometer following them to limit the minimum voltage to 24 volts with the maximum at 49 volts.
If there are any recommendations to improve this circuit in any way I'd love to hear them. I’ve seen so many different LM317 current boosted circuits that I decided to try and design my own instead.
EDIT 2: After doing a bit of research I was able to find another person referencing issues with a current boosted LM337.
Using a low-esr, 220µ cap at the output solved the problem completely. But their solution was adding a 12uh inductor in series with a 2.7 Ω resistor on the emitter of the NPN.
Apparently ouput/adj pin capacitors are critical in a current boosted lm337 circuit.