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Electronics Forum / Basics / May 2007Transformerless high voltage from 120VAC
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 >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) [quoted text clipped - 7 lines] > >TIA Roughly 60 capacitors, say 10 uF each, and 60 diodes... it sure won't be "compact." John > 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" See http://www.ramseyelectronics.com/downloads/catalog/Rmz2007W-4.pdf Page 32 - Generates 7.5kV DC negative, 400uA. > > 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" > > Seehttp://www.ramseyelectronics.com/downloads/catalog/Rmz2007W-4.pdf EXCELLENT link Homer. Thanks. > Page 32 - Generates 7.5kV DC negative, 400uA. >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) [quoted text clipped - 7 lines] > >TIA 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. |
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