> 2kV * 4mA = 8W output!

    Yes, I realize that is quite drain from AA batteries. The duty cycle is
very low however. Just 2-3 sec every few minutes. So I don't think this will
be a big problem.

>  I'm guessing it's the transformer that's limiting you.
>  Either the magnetics can't handle that much power, or
>  the resistance of the transformer winding is killing you.

I agree.

>  also, your switching frequency will affect power handling
>  capability. higher frequency = more power through magnetics
>  of a given size, but parasitic capacitances & MOSFET gate drive
>  speed would become important...

Using the PIC I was easily able to determine the best freq and pulse width.
Only about 1200Hz. So the mosfet shouldn't have problems coping with that.

>  p.s. just curious: which diodes and caps are you using
>   on the output?

500 volt, .01uf caps
1N4007 1Amp, 1kV PIV diodes

>  > -----Original Message-----
>  > From: Matthew Ballinger [SMTP:MattBeck@AOL.COM]
>  > Sent: Monday, September 06, 1999 3:20 PM
>  > To:   PICLIST@MITVMA.MIT.EDU
>  > Subject:      OT 2kVolt from battery
>  >
>  >     I'm working on a little project right now that requires a 2kV source
>  > current limited to about 3-4 ma and powered from 4 AA batteries. At the
>  > moment I'm using a PIC for PWM to a logic level power mosfet which chops
>  > power to the secondary a mini audio z matching  1:12 xfrmr which then
>  > feeds 4
>  > stage cascading voltage multiplier. This setup is very compact (also
>  > required) and  gets me around 1.6kV, but current is much to low. Then I
>  > used
>  > 2 xfrmrs in parallel, but still to little current. I'm also using a 470uF
>  > cap
>  > to stiffen up the power supply some which helped somewhat. Anybody got
>  > ideas
>  > of a better way to do this? Any help would be greatly appriciated.
>  > Matt B
>