Senior systems engineer Toby Chui has designed a handy portable benchtop power supply driven using USB Power Delivery (PD) — built with just $10 in parts.
“I did [see] a few great [USB] Type-C powered PD power supply [designs] out there, but most of them use fancy buttons and a MCU [Microcontroller Unit] to control the output voltage,” Chui explains. “I really like their concept of having a fancy display to show real-time power usage statistic, but when I think about it, when I want to adjust the voltage or current output, instead of a fancy multi-layer menu, what I prefer is a much more simple options of knobs and buttons (lets call it the ‘Classic” type of power supply).”
Chui’s custom power supply is an attempt to bridge the world of classic and clever power supplies: it uses the USB Power Delivery standard to negotiate voltages and current limits from a connected phone charger or other compatible power brick, complete with a screen confirming the negotiated power, but is controlled as simply as twiddling a couple of knobs. Better yet: it fits in your pocket, and cost just $10 in parts.
The custom PCB inside the power supply is controlled by a low-cost WCH Electronics CH552G microcontroller, which implements Intel’s vintage MCS-51/8051 architecture, and the company’s CH224k USB Power Delivery “trigger” chip — the part actually responsible for communicating with the connected USB charger. There’s an Allegro MicroSystems ACS712-05B current sensor, and XLSemi XL4015E buck converter, and a tiny 0.91″ OLED display for visual feedback — plus the adjustment knobs, of course, for control.
Designed for portability, the power supply comes in at just 70g (around 2.5oz) in weight. (📷: Toby Chui)
Chui’s supply can negotiate 20V at 3A from a compatible USB Power Delivery charger, and output between 2V and 20V at up to 4A. Its measurement accuracy is claimed at ±0.02V and ±0.05A for voltage and amperage respectively, and measurements are output via a USB serial connection as comma-separated values for graphing or later analysis.
Chui has published a guide to building your own power supply on Instructables, with source code, PCB design files, and a 3D-printable case available on GitHub under the permissive MIT license.
