Tag Archives: circuits

An AP3003-based Switching Power Supply

In most of my past projects, I’ve been using basic linear regulator circuits for voltage regulation. That has worked fine up to this point, but now a couple of my projects are needing to use higher voltages for some components. A good example is my CNC machine, which uses 24v for the stepper motors. I had designed my own AVR-based controller board (running GRBL), but after running it for a while I realized that the linear regulator was getting too hot for my tastes. I could increase the pad size on the regulator a little, which would have provided better thermal dissipation, but I decided it was time to try a different approach. Everybody likes to play with new hardware, right?

I started searching for buck regulators and ran across the Diodes Inc. AP3003S switching regulator. After reading through the datasheet, I decided this part would cover my needs. For the 5v output version, the input voltage range was 7-32v and the current capacity(2A) was well over what I needed. I set out to build an initial circuit around that part, basically using the reference design from the datasheet. After a few minutes of layout time in gschem and playing with various part placements in PCB, I ended up with the schematic and PCB layout shown below.

Initial AP3003S 5v switching supply schematic
Initial AP3003S 5v switching supply schematic

 

AP3003S 5v switching supply board layout
AP3003S 5v switching supply board layout

 

A fair amount of copper was placed on the board to provide heat dissipation for the AP3003S, even thought I don’t expect to push too much current through it. Once the boards come back from the fab house and are assembled, I plan to run the board through it’s paces on the test bench.