The circuit is based around a cheap CCFL inverter module and the common LM2576 3 Amp Adjustable Switchmode Regulator which can be bought over the counter at many electronics stores. The output of the inverter is rectified and filtered and and then feed back into the feedback of pin 4 on the LM2576 through a voltage divider. The output of the LM2576 is then used to supply of the inverter.
The LM2576 maybe seem like over-kill but my aim is to be both accessible and cost effective, and although there are better chips available unless your building a few hundred of these, it would be harder to choose a cheaper and more accessible alternative.
Hi HC I've used this design for over 10 years on many project, most were built from junk box parts on vero board, it's low noise and quite stable. Its to power high impedance loads such as Geiger, proportional or photomultiplier tubes e.g. #Cosmic Ray (Muon) 81 (9x9) Pixel Hodoscope. No doubt it could be improved, please feel free to redesign it as well as my other projects are open source and build for recreation, not production. More details are on my website http://www.hardhack.org.au/hv_reg_power