Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!oliveb!amdahl!pacbell!osc!jgk
From: jgk@osc.COM (Joe Keane)
Newsgroups: sci.electronics
Subject: Re: Design wanted !
Keywords: battery power
Message-ID: <1765@osc.COM>
Date: 23 Dec 89 14:24:21 GMT
References: <1269@maestro.htsa.aha.nl> <1989Dec20.184339.21760@deimos.cis.ksu.edu>
Distribution: usa
Organization: Object Sciences Corp., Menlo Park, CA
Lines: 50

In article <1269@maestro.htsa.aha.nl> paulf@solist.htsa.aha.nl (Paul Ferron) writes:
>I'm looking for a design to convert a 9V DC to 1800V.

>It is for a Neontube  of about 500 mm long.

>The design has to be with  an oscilator.
>
>thanks in advance.


In article <1989Dec20.184339.21760@deimos.cis.ksu.edu> mac@harris.cis.ksu.edu (Myron A. Calhoun) writes:
>I hope you aren't trying to start with a 9-volt "transistor" battery!
>
>I don't know how much current a Ne tube will need, but let's assume
>one milliampere (that's about what I put through an Ne-2 pilot lamp);
>let's also assume a 50 percent efficiency in the conversion:
>
>0.001 amp x 1800 volts = 1.8 watts.
>1.8 watts x 2 = 3.6 watts when allowing for conversion inefficiency.
>3.6 watts / 9 volts = 0.4 amps = 400 milliamperes,
>
>which is about 10 times the maximum practical current drain on a
>little "transistor" battery.  Of course, several of my assumptions
>may be wrong.

Hmm, what is a good drain on a transistor battery?  All i know is that i have
run small HeNe tubes from them and a wimpy switching power supply.

The power output of batteries can be impressive, especially for short surges.
The short-circuit current of a good D cell is something like 20 amperes, and a
car battery can put out up to 500 amperes to cold-crank the starter motor.

Anyway, back to the original question.  There are a bunch of ways to do it,
but they all come down to rapidly changing the current in a coil to induce a
voltage, in that coil or a different one.

Here's a circuit description off the top of my head.  Run a 555 from the
battery to make a 20KHz or so signal, which gates some power FETs.  These
switch a capacitor forwards and backwards into the primary of a step-up
transformer, which has diodes clamping it to prevent having hundreds of volts
across the FETs.  This capacitor is recharged from the battery through a small
resistance, the idea being to supply current spikes from the capacitor rather
than the battery.  On the transformer secondary you may have a couple stages
of a voltage multiplier ladder, then a final capacitor to dump into.

That's the general idea.  To make it specific you need to know the output
current needed and the allowable drain on the battery.  You have to find an
available transformer, and get its turns ratio and magnetizing inductance.
Then you can figure out what the FETs have to be rated for, what sort of
ladder (if any) you want, and a whole slew of appropriate capacitor values.