Re: Voltage doubler (fwd)

To: tesla-at-pupman-dot-com
Subject: Re: Voltage doubler (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Fri, 16 Apr 1999 21:09:10 -0600 (MDT)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: Fri, 16 Apr 1999 09:35:25 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Voltage doubler

Hi Dave, all,

> Original Poster: David Trimmell <davidt-at-pond-dot-net> 
> 
> Hello, I was wondering if anyone on the list, who has a good understanding
> of what is actually going on within a voltage doubling circuit, could
> explain it to me. I am, at this time, using 3 uFd capacitance in my doubler
> to feed the plates on my 833A tube coil, and can range from 0-2890 VAC into
> the doubler (safely, keeping the tubes happy). I am very interested in
> finding the optimum capacitance value for a specific power and voltage
> value. I understand the principle of the halfwave voltage doubler circuit,
> but would like to know if the voltage is truly doubled, and how I can find
> the best value for the capacitance? I suspect that the higher the value for
> C, then the greater power available, but I need to find that optimum value ;-)
> 
> Thanks for any assistance,
> 
> David Trimmell

I have developed a simple way of analysing circuits. Start with a 
drawing of the circuit in black and two pens of different colours.
Now take a pen of one colour and draw a + at one end of the 
transformer winding and a - at the other. trace out the current flow 
that will occur and mark the voltage polarity that results across 
each circuit component. Then take the other pen and mark the reverse 
polarity across the transformer winding. Again trace out the current 
flow that will occcur. You will quickly see that in any multiplying 
circuit involving  capacitors, you end up with a charged capacitor in 
series with the transformer on a subsequent half cycle and if it is 
multistage, also in series with other charged capacitors. 

     In the case of analogue circuits generally, draw a small half 
sine at the input and at the terminals of each circuit device, draw a 
half sine of the correct polarity (e.g. for a transistor that has a 
signal fed into its base, a half sine of the same polarity appears at 
the emitter *if it is not tied to a voltage source or ground* and one 
of the opposite polarity appears at the collector. You will find it a 
breeze to get an intuitive picture of the way any circuit operates 
once you've had some practice. You can check your initial musings on 
low voltage circuitry with a dual beam scope.

Malcolm