Why Buy a Commercial Power Supply When You Can Build This 1 kW Beast?

Powering electronics projects shouldn't be harder than building them, but it can be when you're relying on a random collection of wall adapters. Finding one with the right voltage is only half the battle. It also needs to supply enough current, and many inexpensive adapters fall short of their advertised specifications, leading to unstable operation.

That's why a bench power supply is considered an essential piece of equipment for anyone serious about electronics. It provides precise, adjustable voltage and current, making it much easier to prototype, test, and troubleshoot circuits. Commercial units can be expensive, but there's another option: build your own. A DIY bench power supply can deliver the same core functionality at a fraction of the cost, while giving you the flexibility to tailor it to your own needs.

These units are usually pretty simple, but GitHub user Luq1308 took DIY bench power supplies to another level with his recent build. He engineered an entirely custom 1 kW switched-mode power supply from the ground up. The result, called the Forwarder 1kW, is an open source design that combines high output power, configurable voltage and current, and an accessible construction process for experienced builders.

The power supply has a half-bridge topology and is built around an SG3525 PWM controller and LM324 op-amps for constant-voltage and constant-current regulation. Depending on how it is configured, the design can deliver outputs ranging from 40 V at 25 A up to 400 V at 2.5 A at the high end. It also includes analog interfaces for external voltage and current control, monitoring outputs, dedicated fan control, adjustable switching frequency and dead time, and a power stage enable input for integration into more advanced bench power supply designs.

The PCB contains fewer than 130 components, with most being through-hole parts that are easy to source and solder. Builders do need to wind several magnetic components themselves, including the main ETD49 transformer, output inductor, and gate-drive transformer, but the documentation walks through the entire process in detail. Along with the hardware, Luq1308 has published the KiCad project files, schematics, Gerber files, transformer calculations, and supporting spreadsheets so others can reproduce or modify the design.

To validate the build, Luq1308 subjected the Forwarder 1kW to extensive testing using a custom load setup capable of drawing the full kilowatt continuously. After an hour at maximum output, the hottest MOSFET reached 75°C, while the transformer stabilized at 55°C and the output inductor stayed at just 44°C. Efficiency exceeded 89% across most of the operating range, peaking at just over 90%, while output ripple remained below 100 mV peak-to-peak even at full load.

There are still a few areas where Luq1308 is working to make improvements. The current limiting reacts more slowly than desired, the compensation network can oscillate during certain operating conditions, and the output diodes could be easier to replace. Even so, the project is a good demonstration of how much a hardware hacker can achieve in their own home lab.