Hi,
I've come across a HV swithing problem, I wanna switch open and close two power rails, +400V and -400V simulataneously. Now i know the simplest solution would seem to be a DPST relay, but looking at the voltage/current requirements, they get very expensive. So seems the simplest way would be to switch some HV mosfets or IGBT's, but the problem seems to be the highside drivers for these guys all seem to use a bootstrapping method that won't allow them to have a 100% duty cycle and be continuously on. i came across this appnote from intnl rect:
http://www.irf.com/technical-info/designtp/dt92-4.pdf
and that seems to be the solution, adding a charge pump yourself using a 555 timer and some Rs, Cs, and diodes. Now I seemed confused on whether i can implement this on the negative rail as well, i want to basically mirror the circuit, but its that connection on the bottom of the load and the 555 circuit using a 100k that i'm not sure how to do on the negative rail? any help is greatly appreciated.
*http://www.irf.com/technical-info/designtp/dt92-4.pdf

 

Found this, easier then the 555 solution i think
http://www.supertex.com/pdf/datasheets/HT0440.pdf
app note: http://www.supertex.com/pdf/app_notes/AN-D26.pdf

Should work, 400VDC highside driver w/ charge pump for continous duty cycle . The datasheet dont say anything, but the support guy there says it only outputs a few microAmps, so fast switching is a problem, but for my application it should be fine, the app notes helped some too.