Re: Need a calculator that knows about coulombs
On Wed, 23 Dec 2015 05:09:18 -0500
Gene Heskett <gheskett@shentel.net> wrote:
> On Tuesday 22 December 2015 21:02:31 John Hasler wrote:
>
> > Gene Heskett writes:
> > > In this case, the size of a capacitor hooked to a square wave
> > > source, and I want to know how much charge is transfered for every
> > > full cycle of the input square wave.
> >
> > Zero assuming linear source and load impedence.
>
> Ahh, but its being fed to a voltage-doubler with schottky diodes, so
> there should be a calculatable amount of charge delivered to the
> output capacitor Cf, by the pump capacitor Cp, per cycle. With Cp
> being of a capacity such that with the usual logic circuits output
> impedance, capable of delivering 10 to 20 milliamps into a resistive
> load, IOW not a zero impedance source. Cf would be sized such as to
> be about 50x Cp, and will be driving an enhancement mode fet which
> will turn on a 40 amp SSR once the charge has built up on Cf to make
> the fet conduct.
>
>
Do it numerically with a spreadsheet.
It takes a while with any reasonably-sized spreadsheet, but you can
trust the result, you can see every stage and can spot anything
obviously wrong.
I once needed to analyse the start-up surge into a large capacitance
using a toroidal mains transformer, and given the non-linearity of the
rectifiers, I could see no other way. When results can reach hundreds of
amps for a millisecond or so, you don't want large piecewise-linear
approximations.
--
Joe
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