psu 800vdc

hi,
i am looking for schematic to build a inverter to provide around
800Vdc few mA from 9-12V batteries.
Any info will be wlecome.
Thanks
cs

 

If a "few mA" means something like 5mA then your power output is fairly
small. As such probably the simplest solution (in the sense it wouldn't
require custom transformers) would be a discontinuous conduction mode boost
converter. Normally boost converters aren't very well suited to very high
voltage step up ratios (since the loop gain goes to near infinity for very
large duty cycles in continuous conduction mode), but for low power output
levels a large step up voltage can still be accommodated in discontinuous
conduction mode.

You will need a high voltage MOSFET (800V+) and a good diode. The UF4007
would likely be appropriate. The boost inductor would need to have
insulation capable of withstanding greater than 800V.

What kind of battery are we talking about here? If by "9V" you mean "9V"
alkaline battery, then the problem gets a whole lot more complicated since
4W + inefficiency or so would be a rather large load for such a pitiful
battery. What kind of output regulation and efficiency do you need? If you
don't need good regulation, and can tolerate some power loss perhaps you
could just use an 800V MOSFET and let it avalanche to perform the "voltage
regulation" function (the MOSFET would need a small heatsink to dissipate
the extra power). As such the problem becomes much simpler since it could
operate without closed loop control. All you would need is a fixed
frequency fixed duty cycle oscillator driving your gate.