High Voltage Multiplier (Half Wave Villard Cascade) 28 STAGES!
By Radu Motisan Posted on October 29th, 2010 , 5430 Views (Rate 4.77)
Some time after I built my first Villard multiplier , it was time to re-make this device into a reliable, bullet-proof, high voltage source. I already had a pulsed high voltage supply, my 200.000 volt marx generator , but needed a continuous HV supply.
It's written in the schematics bottom note but I will say it again. This multiplier produces a positive high voltage. I've added an extra capacitor, identified by Cx, for the purpose of making this module...invertible. That's right, instead of connecting the high voltage supply (which can be a non-rectified flyback transformer) to terminals A,B (B is ground, A is the flyback output), you can connect it to C,D (C ground, D flyback non-rectified output), and you will have a Negative high voltage multiplier.
So you can easily do the switch according to your application .
I've used a Russian textolite board, it's a very good insulate used to manufacture PCB. Of course it is without the copper foil. You can use any insulating board like plastic, FB4, etc.
Drilled the holes for the components.
Between capacitors on the same line, I've allocated 1cm, and between the capacitor lines 1.5cm, for the diodes. I've used a marker to make signs, and after drilling the holes, I cleared the marker with some alcohol.
The first tests showed the device was producing heavy corona, so it was imperative to come with a design that would keep the components under mineral oil. The plastic tube in the second picture was the recipient for that. The unused textolit board was removed to save space.
Since the mineral oil that I have is quite old, I had to check its insulating properties with the flyback output. As you can see in the pictures, the arc is almost "rejected" by the oil surface. Good enough!
The entire multiplier board was submerged in oil. I've created 4 connectors, fixed with very tight screws to prevent oil leakage. A lot of hot glue secured the connectors against oil. Then I closed the plastic pipe recipient with some kind of lid and more hot glue and covered the module with black tape. The result:
For some tests I've used a simple 555 driven old Flyback (without rectifier), but for some reason it doesn't work good enough and I'll need to use a Feedback driven Flyback (yes, the simple 2n3055 schematics). I've added a 10KO resistor between the flyback and the multiplier, to protect the today's work. For the output, a TV High voltage resistor was added, so I could draw arcs in the air. Nothing spectacular, 2.5cm arcs only, as I said the Flyback supply is not good. Will test with another one and report back. Here are some pictures:
Just out of curiosity, I've inserted a DY86 tube (base pins connected to Multiplier Positive and the top connector to ground - reversed) and powered on the device (note: just 6Volts in to the 555 circuit/flyback), for a second then turned it off. My Radex 1706, placed at 3 cm from the tube, quickly jumped from 0.13uSv/h(background) to 23.6uSv/h and this was just a tiny fraction of what the multiplier+the DY86 can produce (not at full power).
So far no oil leakage, and I really like this multiplier, that can be used for as a Positive HV supply (+) and as a Negative HV supply (-) if connected the other way.
The Cx capacitor has another great advantage. You can use it to connect a TV Cascade , to this Multiplier's Output. I've tried it and it works. Basically you use the TV Cascade to add a few more stages to this multiplier.
To connect a TV Cascade to this multiplier, do the following:
1. On the TV Cascade, connect A and D together, let's call this terminal AD
2. Connect terminal C on the multiplier, to terminal ~ on the cascade
3. Connect terminal D on the multiplier to terminal AD on the cascade
Terminal HV on the cascade is now the new output of the combined multipliers.
Terminal B on the multiplier remains the Ground terminal.
Related: see my Marx Generator.
The multiplier has been packed into a nice box, with Flyback ZVS supply, limiting resistor so now I have a very high voltage supply ready to work using only 12V :
Unfortunately the multiplier soon failed because I was putting 10KV in while the capacitors were rated for 6KV only. One of the capacitors got conductive, short-circuiting the entire multiplier, so I had to dismantle it (including taking out the oil) and re-do everything properly. This was a good thing, since I had the chance to improve the design.