For those interested in looking at low power switchers take a look at what National Semiconductor has to offer. They have the LM2594 chip which is quite well suited to the 50V to 5V buck regulator problem for currents up to 0.5A. Take a look here:

http://www.national.com/pf/LM/LM2...#Datasheet

National also has now on their Web site a tool that lets you basically design and evaluate small switcher designs to see what is available and how suitable it may be to a project you are working on.

Buck regulator designs basically have Vin voltage switched directly to the input side of the inductor. Use care in building and using designs such as these because if the switch transistor ever fails shorted you can see the full input voltage at the output!!
The use of the highly integrated switcher ICs of manufacturers such as National or Linear Technology beings a batch of safety features that make buck regulators feasible in product design. These include thermally stable references, overload detection, and output overvoltage detection. All of these are integrated into the design of the chip to keep the switch component held OFF when it is unsafe for it to be ON.

I did not see any of these features in the romanblack circuit.

Michael Karas