30V/10A Adjustable Desktop DC Regulated Power Supply

30V 10A Variable Table Power Supply

This section describes a circuit for a 30V 10A variable benchtop power supply, providing variable voltage and current regulation. The power supply is based on the LM723 voltage regulator chip and features current limiting. I frequently encounter short circuits in the power supply clips on my benchtop, but without any issues. I've used this circuit for over 20 years and it has never let me down; it's one of the most convenient tools I've ever built. The 2N3055 transistor is a proven high-current transistor. More 2N3055 transistors can be connected to achieve a larger output current. The transistors need to be mounted on a sufficiently large heatsink.

Bridge rectifiers can also be mounted on a heatsink. Therefore, I mounted them off-board and wired them. The input-side capacitor bank can be replaced with a single large capacitor if you have a suitable one. 5-watt resistors will run quite hot under high loads and need to be mounted in a well-ventilated area. I often solder them directly to the transistor pins, with the other leg connected and wired back to the board. When purchasing 2N3055 transistors, request they are all from the same batch number, as this helps eliminate internal variations. The potentiometer values ​​shown may need to be changed to allow adjustment within the desired voltage range and current limits. A test of shorting the output leads together will quickly reveal the maximum settable current range. A transformer suitable for the required amperage is required. This is a simple circuit with only a few components. Only a printed circuit board is needed for the LM723, 3 small resistors, and 2 capacitors. The rest is mounted on a heatsink or front panel and wired. The maximum input voltage is 40 volts. See the LM723 datasheet for more details.