patent # 5,600,551

Isolated power/voltage multiplier apparatus and method  Patent on-line

This patent is for a switching power supply, utilizing capacitors instead of inductors to achieve ground isolation.

By selecting the number of 'stages' (of capacitor-diode pairs) the circuit can step up the supply volatage as well as provide simple output isolation. 

This patent grew out of a request from my employer to design a small (~ 1 sq. in), cheap (< $5), isolated supply to power an interface to customer owned PLC systems.  The existing interface did not use an isolated power supply and two instances occurred where attached PLC controllers (customer's equipment) with non-isolated interfaces were damaged when connected to the my employer's controller.