Re: DC Supplies for SSTC Coils ? ? ?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 14:17 26/05/03 -0600, you wrote:
>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><dhmccauley-at-spacecatlighting-dot-com>
>
>Just curious to see what you guys were using for DC supplies when running DC
>to your SSTC coils.
>I'm revisiting audio modulation with mine and I tried running full-bridge
>rectified with smoothing capacitors of up to 21,000uF (450VDC capacitors) to
>get 170VDC output of the
>circuit, but the peak DC currents are just killing my controller and
>everything else.  I try lowering the capacitance, but i still get too much
>120Hz ripple.
>
>I wonder what Richie and Alan were using . . .

I've never seen more than 1,000uF used. You might like to try a pi-section 
filter, that is, a rectifier feeding a capacitor of about 470uf, which 
feeds into a big iron cored choke, then another capacitor which can be as 
big as you like. This is what is used in tube hi-fi and musical instrument 
amps. The choke is typically between 1 and 10H but you may want to use less 
so you can have a low DCR in an acceptable size/weight of package.

If you don't like chokes there are also capacitance multiplier circuits 
using a power MOSFET as a source follower. You basically put the 
unregulated supply into the drain, put a well smoothed 150VDC reference 
(this might come from the unregulated supply through a 100K:1M potential 
divider bypassed to ground with a several uF plastic film cap) onto the 
gate, and take the output from the source.

Steve C.