Motivation
This PSU is build around the well known LM317 and follows mostly a straight forward design as in the data sheet. To mention is an additional filter before the LM317 to lower the ripple. With this filter the ripple is down in the noise floor. I have tested this design with a current load of 1.2A for some hours. No problems whatsoever. Because the heat sink is not that big I recommend keeping the load below 1A. It is getting quite hot though. For a +/- PSU you need two of those. You can daisy chain them and use the connection as ground
Specs and features
Implementation
Schematic
Low ripple PSU with LM317. Schematic
Description:
This design is straight forward like in the data sheet of the LM317. The led indicates the presence of the unregulated voltage before the LM317. R2, R5 and C5 builds a RC input filter between the reservoir capacitor and the regulator. The resistors should kept low and the capacitance high. The filter sinks the ripple below the noise level of the regulator. You have some loss of efficiency due to the voltage drop across the series resistor. All protection features of the LM317 regulator are preserved.
Calibration
- Adjust the output with TR2 to 15V
Special parts
- R2 and R5 should be 2W types
