Our next project will use an external 12-18V power supply. It will be again a Raspberry Pi powered device. Having an additional 5V/1A power supply in addition to the main 18V power supply is not really a nice solution. Therefore we want to create this 5V power supply from the 18V supply. As the Raspberry draws 500-1000mA current, a simple linear regulator is not an option. It has to be a switching regulator. The LMR12010 from Texas Instruments (formerly National Semiconductors) seems to be an interesting chip. It does not need many external components, but still has an acceptable efficiency. There are chips with better efficiency, however these usually need external switches. Today we tested the chip using the Evaluation kit from TI. Interestingly, the Eval kit still has the National Semiconductor logo on it. The result looks promising. The efficiency is good enough, no additional heat sinks or cooling for the switching regulator is needed.
Check out this 20V-powered Raspberry Pi: