Russian voltage multiplier stacking

Thread Starter

Nikša

Joined Mar 26, 2018
72
I been watching EEV's video on Cockcroft Voltage Multiplier again.

It's a great vid and among other things he makes clear upper side is pulsating voltage and bottom side is steady dc. He explains why in the beginning of the vid.


And then i stumbled on this russian craziness.


So they used this 3 stage multipliers from old TVs. You can see in the diagram is missing first top capacitor, but i guess that's a mistake.

What i find strange is how they connected them.

To stack them they drilled a hole marked A in diagram, which is presumably the top part of the last stage, and they connected it to "ground" of the next multiplier.

They also connected bottom side of the last stage marked + to top side of next multiplier.

I made a diagram to compare normal 4 stages to how they connected them. I used 2 and 2 instead of 3 and 3 but same thing.

I find it strange and it sure does not look like the same circuit like normal 4 stages.

It obviously works, but why does it work connected like this?

Anyone?
 

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SamR

Joined Mar 19, 2019
2,121
The Russians probably didn't have any capacitors available to link the modules together so used a "workaround".
 

MisterBill2

Joined Jan 23, 2018
6,058
I been watching EEV's video on Cockcroft Voltage Multiplier again.

It's a great vid and among other things he makes clear upper side is pulsating voltage and bottom side is steady dc. He explains why in the beginning of the vid.


And then i stumbled on this russian craziness.


So they used this 3 stage multipliers from old TVs. You can see in the diagram is missing first top capacitor, but i guess that's a mistake.

What i find strange is how they connected them.

To stack them they drilled a hole marked A in diagram, which is presumably the top part of the last stage, and they connected it to "ground" of the next multiplier.

They also connected bottom side of the last stage marked + to top side of next multiplier.

I made a diagram to compare normal 4 stages to how they connected them. I used 2 and 2 instead of 3 and 3 but same thing.

I find it strange and it sure does not look like the same circuit like normal 4 stages.

It obviously works, but why does it work connected like this?

Anyone?
It works because when putting voltage sources IN SERIES to ADD voltages the positive output of the one must connect to the negative output of the next. Think about a series stack of 1.5 volt AA batteries to visualize what I am saying. Looking at the circuit drawing makes it very clear.
 

Bordodynov

Joined May 20, 2015
2,603
Note that the last diode of the first multiplier and the first diode of the second multiplier are switched on in parallel and work as one diode. Indeed, the Russians took advantage of what they had.
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
It works because when putting voltage sources IN SERIES to ADD voltages the positive output of the one must connect to the negative output of the next. Think about a series stack of 1.5 volt AA batteries to visualize what I am saying. Looking at the circuit drawing makes it very clear.
That was my first thought but still that is no answer to the question. For this to work circuit must be equivalent of normal stages.
 
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Thread Starter

Nikša

Joined Mar 26, 2018
72
Note that the last diode of the first multiplier and the first diode of the second multiplier are switched on in parallel and work as one diode. Indeed, the Russians took advantage of what they had.
Yes, they are in parallel with cap inbetween i forgot in upper diagram.

Basically, they turned the second multiplier upside down.

Looks weird as if it should not work.

3.jpg
 
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Thread Starter

Nikša

Joined Mar 26, 2018
72
Here is a good video on voltage multiplier, i asked the kid if he understands this russian connection. I doubt he will.

 

Tonyr1084

Joined Sep 24, 2015
4,521
This is what I got out of the first set of drawings. All I did was flip the second set upside down and placed the two diodes in parallel. Does it work? I don't know.

1588606865434.png
Looking at post #7 you've added in a cap. Not sure why (or why not). These circuits are a mystery to me. I know they add their voltage with each cycle but it still boggles the mind.

Was once (more than once) busted on for my smooth scalp. I replied "Grass doesn't grow on a busy street." I was promptly reminded "It doesn't grow on concrete either!".
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
This is what I got out of the first set of drawings. All I did was flip the second set upside down and placed the two diodes in parallel. Does it work? I don't know.

View attachment 206228
Looking at post #7 you've added in a cap. Not sure why (or why not). These circuits are a mystery to me. I know they add their voltage with each cycle but it still boggles the mind.

Was once (more than once) busted on for my smooth scalp. I replied "Grass doesn't grow on a busy street." I was promptly reminded "It doesn't grow on concrete either!".
Russian diagram shows no first cap but that must be a mistake as i said. So i left it out by mistake in first diagram.

I already did what you did in diagram above with cap and 6 stages. (or rather 5 stages now that last 3 are flipped?)

Basic multistage voltage multiplier is quite simple to understand, it's just first cap + input voltage on positive halfcycle charging second cap to 2Vp and so on for next stages.

But i don't see why this works the way Russians connected them.

I hope there is someone on this forum who really knows this stuff, the answer must be a simple one.
 
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Tonyr1084

Joined Sep 24, 2015
4,521
Well, I'm currently enjoying the first video. Will check out the second after. But now I'm starting to get an understanding.

Thanks.
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
Well, I'm currently enjoying the first video. Will check out the second after. But now I'm starting to get an understanding.

Thanks.
You're welcome. The first video doesn't explain how capacitor gets charged and i think he got the cap polarity wrong. Second video goes in detail.
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
I take back that it is easy to understad, it is very very complex, even this simple doubler. Just the basic principle of input voltage + cap voltage adding up is easy to understand. Nothing else is easy.
 

Beau Schwabe

Joined Nov 7, 2019
51
If you look at image in post in #7 and imagine pulling the diodes on each end until they form a straight line ( a missing diode or extra diode in the chain shuch as the Russians did is neglagible to the overall performance, notice the missing cap at that location also ) , the capacitors can be stacked and compressed flat .... Here is a video of such a design I was playing with a few years ago using a 12V to CFL bulb driver (about 450VAC) for the input...

7kV Output (16 Stage)

21kV Output (48 stage)
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
To simplify

1. only first diode conducts, first cap gets charged
2. only second diode conducts, now input voltage + cap1 voltage charge cap2 to 2Vp
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
If you look at image in post in #7 and imagine pulling the diodes on each end until they form a straight line ( a missing diode or extra diode in the chain shuch as the Russians did is neglagible to the overall performance, notice the missing cap at that location also ) , the capacitors can be stacked and compressed flat .... Here is a video of such a design I was playing with a few years ago using a 12V to CFL bulb driver (about 450VAC) for the input...

7kV Output (16 Stage)

21kV Output (48 stage)
You did not explain WHY missing diode and cap or extra diode and cap (whichever way you see it) do not affect performance.
 

Beau Schwabe

Joined Nov 7, 2019
51
The diodes in parallel can be treated as a single diode... flipping the stage only serves to correctly align the diode polarity in the diode chain. The stage itself is AC in nature at the input and doesn't care if it is flipped or not as long as you give it AC or pulsed DC.
 

Thread Starter

Nikša

Joined Mar 26, 2018
72
The diodes in parallel can be treated as a single diode... flipping the stage only serves to correctly align the diode polarity in the diode chain. The stage itself is AC in nature at the input and doesn't care if it is flipped or not as long as you give it AC or pulsed DC.
That's better.
 
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