I was looking for a dual voltage power supply initially to power an old HDD with 12V and 5V. I wanted to build a home server based on the Raspberry Pi. I later realized that I had a newer hard-drive that needed only 5V. By then I had already designed and built this one. This power supply has a typical efficiency of 85%+ under real-world conditions and is based on TI’s TPS54383 DC-DC converter chip which operates at 300 KHz. A 600 KHz version is also available and is a drop-in replacement for TPS54383.
Edit @08 Feb 2014: Pictures of the new revision added. Also the board shows reverse polarity for Vout-II. This is what happens when you create boards at 1 AM. The ‘+’ and ‘-‘ should be switched. You’d see a negative supply on Vout-II with the way the board is as of now.
Edit @25 Dec 2013: Attached are Gerbers and PDFs for a board with USB female connectors should you want to use this power supply to connect to devices such as the RPI or standalone MCU systems. Remember that USB connectors support a maximum of 1A current through its pins.
A piece of advice and a warning of sorts: We are dealing with high currents and voltages here (especially if you use transformers to step down voltages to power this system). Please be careful and I’d hate to see you get zapped. If you are not sure about certain connections, DO NOT make them. Read and research about it. Ask questions! Disconnect all power to the board before assembly. Understand what outputs you’ll expect to read and where. Even though the output voltages may seem low they are high-current outputs that can still give you nasty jolts if you touch them and act as the load. Do not short the outputs. Even though this device has some protection built it in it, its never a good to test and see if it works. I’m not responsible for your actions with this project that may land you in the ER.
This particular chip was selected because of its high efficiency. This plays a critical role when the system needs to be always on. This also is very useful when the whole system is powered through a battery. The TPS54383 also features an over-current protection (hard-wired at 3.5A here for Output 2 and 4.5A for Output 1), a soft-start where Output 2 starts after Output 1 has reached full regulation.
Step 1: Design Stage
An important note: This is a switching power supply. Your computer SMPS is a switching power supply. Though the chip its based on isn’t very expensive, it is not very cheap either. The total project cost me roughly $50. Here is a Digikey link where its priced at $6.22 per piece. The datasheet is available here. If you do not want to go through the entire datasheet and just adjust the voltages you will need to refer to the “design example” section.
For more detail: High efficiency Dual Voltage 3A power supply