# Transformerless high voltage from 120VAC

Discussion in 'Electronic Basics' started by noname, May 29, 2007.

1. ### nonameGuest

I need to build a compact transformerless high voltage supply that
will run off of 120VAC mains and produce at least 2000-4000 (AC or DC)
volts with very low current. I figure what would be best is the
"Walton-Cockroft voltage multiplier"

http://tinyurl.com/2vvnpz

How many capacitors (and what type, size, ect) would I have to use for
this to work?

TIA

2. ### John LarkinGuest

Roughly 60 capacitors, say 10 uF each, and 60 diodes... it sure won't
be "compact."

John

3. ### Homer J SimpsonGuest

Page 32 - Generates 7.5kV DC negative, 400uA.

5. ### defaultGuest

What size cap depends on how much power you want.

Capacitor voltage is established by the input voltage to the chain.

The URL you list, has the formula

Eout = 2n*Epk - VDrop .... VDrop=0 under no load

Voltage out, equals, 2 times the number of stages, and voltage peak of
the input. (sine wave 120 VAC, times 1.4142 equals 170 Volts peak)

You would need 12 stages to get 4 KV out and each stage consists of
two diodes and two capacitors.

The output of a Cockroft Walton is DC . . . always.

There are variations in the design to give full wave output with twice
the parts for twice the power.

The bigger the size of the caps, the more output power and current.

Ripple increases substantially when you try to pull off power, so CW
multipliers are used for low current applications, like ionizers,
loading the belts of Van De Graf machines with electrons, in TV sets
to provide acceleration voltage, bug zappers, charging up caps to high
voltages etc..

The higher the frequency the more power you can get out of a given
number of stages . . .

Charge a cap with one and you could conceivably electrocute yourself
with it. Connect the side shown grounded in the first schematic to
the AC hot wire and you could electrocute yourself with 120 volts.

An ionizing potential of ~10KV+ will charge objects near it with an
electrostatic charge - causes static shocks if you are insulated from
ground and near one spitting out ions, in a dry area.