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Old 18th September 2004, 10:41 PM   #1
Prune is offline Prune  Canada
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Default Mixing diodes in a bridge

I have three HVR-1X 4 and one HVR-1X 3 (they are 9 kV rectifiers). Will I have a problem if I make a bridge rectifier out of these? The difference is that the forward drop on the 4 is 9 V, whereas on the 3 it is 14 V.
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Old 19th September 2004, 06:52 PM   #2
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What are you going to use these diodes for? If doing a HV (> 1 kV) supply, consider using a diode-capacitor ladder configuration instead.

/Magnus
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Old 19th September 2004, 07:14 PM   #3
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As long as you use them symetrically it should be okay... i.e., have the opposite legs of the FWB conduct so there's a 9V and 14V in series. Then do the same on the other half wave.

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Old 19th September 2004, 07:50 PM   #4
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That's what I thought. Unfortunately I have three of one kind, and one of the other, so it's impossible to get symmetry. I guess I'll stick with the 1N4007 chains; they can handle more current anyway (the HV diodes are only rated to 350 mA).

Swedish Chef, paralleling capacitors/resistors is not necessary for diodes produced recently, as now most manufacturers design them so that they can be put in series without other components. I read somewhere this, where as the diode begins to be overvoltaged and before it avalanches, its leakage increases, equalizing the chain. Capacitors/resistors may actually worsen the setup.
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Old 20th September 2004, 12:17 AM   #5
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Prune,

I was not talking about stringing diodes in series and then compensate the voltage on each diode, but rather to just make an diode/capacitor voltage multiplier to reach high voltages (in your case up to 30-35 kV). But I still don't have a clue of what you are trying to build or if it is for audio or anything else.

/Magnus
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Old 20th September 2004, 06:58 AM   #6
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It's described in these threads:
Plasma/ionic
Transformer question
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Old 20th September 2004, 11:19 PM   #7
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D'oh! With 5V more voltage drop in one leg, you'll get slightly more voltage on one half cycle. If there's like 100V of ripple, you won't notice it, but if it's as low as 2V at the rectifiers, it'll be entirely through one pair of diodes (half wave).
You could use a 5V zener backwards in the string to increase Vf. When the string is off, the zener would be forward so it doesn't change PIV or anything.

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