For a standalone project with a small case I was in need of an small dual voltage PSU. I can't find a dual voltage wall wart, but I had an external AC Power Adapter from Yamaha the PA-30. The PA-30 has a 2x18V AC output with a three pole connector. So I decided to build a small PSU with the LM317L and LM337L. The design is straight forward. It is easy to expand for more current and other voltages if you need to. If you don't want to use a external AC Power Adapter you can use a center tapped transformer.
Specs and features
- Input: Select 3 pole AC power adapter like Yamaha PA-30 or center tapped transformer according to your needs
- Output: +/-xV; Voltage depends on the voltage divider around LM317 and LM337. Values given here are for +/-15V.
- Download docs
Nothing special. Just refer to the data sheet of the LM317L/LM337L. Calculate R1/R2 and R3/R4 to your needs. The given values here are for +/-15V. Input is from a center tapped transformer or external AC Power Adapter like the Yamaha PA-30. For more current replace the LM317L/LM337L Version with the TO220 version. You'll need to redesign the PCB then.