An adjustable power supply with configurable output voltage and current limiting is an essential tool in any electronics lab. Yet, the perceived complexity of a switch-mode design often discourages many enthusiasts from attempting to build one. In reality, constructing such a power supply is quite manageable when leveraging a thoughtful blend of established technologies. The bench supply circuit presented here from 2010 offers a practical solution for creating either a single or dual power supply.

Bench Supply Circuit

Refer to the power supply schematic diagram. A negative auxiliary voltage allows the output voltage to be adjusted down to 0 V.
 
Power supply schematic diagram
According to the designers, Sebastian Richter and Stephan Pohl, the bench supply is based on an integrated switching regulator to keep the component count within reasonable limits. "The functional units of this IC include voltage regulation, switching signal generation, and integrated power switch. This means that only a few external components are necessary," the explained. "Thanks to the compact construction, it is easy to build a dual power supply in a single enclosure. A dual power supply is especially handy when you need more than one supply voltage. Naturally, both supplies are galvanically isolated, so they can also be connected in series to achieve higher voltages or used in parallel (connected via diodes) to provide more current."

The double-sided circuit board allows very compact bench supply construction.
Double-sided PCB for the bench supply project
The bench supply design has the following features:
 
  • Adjustable secondary-side switch-mode power supply (buck converter)
  • Output voltage 0–30 V (typical) (25 V minimum)
  • Adjustable current limiting up to 3 A
  • Maximum output power 90 W
  • Compact PCB layout
  • Switching frequency 52 kHz
Two views of the project.

The Original Project

The article, “UniLab: A switch-mode 0–30 V / 3 A bench supply,” appeared in Elektor April 2010. You can download the article for free during the two weeks following the publication of this post. Enjoy the article and let us know if you build something of your own!
Editor's Note: The article was first published in a 2010 edition of ElektorMag. Some of the components, products, printed circuit boards, and/or links may no longer be available. Yet, we feel the educational content is valuable, and we think it will inspire you to start new projects of your own.

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