A variable power supply is one of the most important pieces of equipment to have on the electronics workbench. Inexpensive Bench-top variable power supplies available today are typically transformer-fed linear voltage regulators which are both simple and inexpensive to manufacture. They are also large, heavy, and inefficient for most of their output voltage range. Most cannot operate anywhere near their rated output current when large Vo-Vi is required, but for low power applications they provide stable and noise free output.
The Switched-mode power supply covered in this project is more than 90% efficient through almost the entire output voltage and current range, requires much less space for heat sinks and transformer cores (90% less in medium to high current designs), and is as much as 5 times lighter than an equivalent linear power supply. The output ripple of this switch-mode supply is slightly higher than a linear supply, but is still low enough to power the vast majority of analog and digital projects without a hitch.