rsdio tipped us to an app note on isolated power-supply circuits:
Wow! It’s quite interesting to see how to substitute capacitors for a transformer. Without digging deeper, though, it’s not clear whether voltage boost can be achieved.
An integrated H-bridge driver for isolated power-supply circuits (MAX256) usually drives the primary of a transformer, but it can also drive a pair of capacitors that substitute for the transformer in providing isolation and power transfer.
Thanks rsdio!
“Without digging deeper, though, it’s not clear whether voltage boost can be achieved”
Why not feed diode/capacitor voltage multiplier stages instead of the bridge rectifier. Voltage multipliers are used to boost an AC signal to a higher DC voltage. Getting high-current might be a bit of a design challenge. Plus I would need to look at the way the H-bridge drives the multipliers through the caps with no common DC ground point – but off the top of my head, I think it would work.
http://en.wikipedia.org/wiki/Voltage_multiplier
Rgds, David
Also keep in-mind, this cap-coupled circuit doesn’t not provide code-compliant isolation. Unwanted transients appearing on the caps will cross the caps.
Rgds agn, David