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Parallel Bridge Rectifiers. .

cjdelphi

Oct 26, 2011
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My bridge rectifier died, but i have several 2amp rectifiers doing nothing, AC side it can supply 5amps at 13v (AC) to 19v when rectified..

Can i just parallel them? Otherwise i'll dump these and use 4 regular 1 amp diodes..
 

(*steve*)

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In general it's a bad idea to parallel semiconductors in this manner.

However if you connect three of these 2A rectifiers in parallel and place a 0.1 ohm resistor in series with each AC input they will share current reasonably well.

1A diodes are not a better solution :)
 

(*steve*)

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Oh, I'm assuming the 2A rectifiers are bridge rectifiers. Is that correct?
 

cjdelphi

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Yup i got 4 unused (2amp / 240vac) but i got a feeling i might need to use like a 0.1ohm out on each to load balance?
 

cjdelphi

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4 diodes (each carry 1amp max)

In a bridge rectifier combo, what is wrong with doing that? (They won't be in parallel)
 

davenn

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In a bridge rectifier combo, what is wrong with doing that? (They won't be in parallel)

what is wrong is that you haven't specifically told us what current you are likely to be drawing from the PSU ??
or what the current rating of the original diodes was ?
 

cjdelphi

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I did... (5amp/13v multiply it for VA) but that's not the point

The point is, i can't use them in parallel without balance loading, so i'll use 4 diodes as i normally do without using these all in 1 bridge rectifiers ...

But Steve, in every bridge rectifier circuit i've ever built, i always used 4 diodes, that's how it's done, did you think i refered to parallel loading of the diodes? (In which case no)
 

(*steve*)

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OK, let's go back to basics.

What is the load current?

If it's up to 1A you can use either the 2A bridge or 4 x 1A diodes.

If it's up to 2A you can use the 2A bridge

If it's above 2A you can use a pair of 2A bridge rectifiers, each with a pair of 0.1 ohm resistors on each of either the AC inputs or the DC outputs (that's 4 resistors for 2 bridge rectifiers).

4 x 1A diodes will make a single 1A bridge rectifier.

OK I read (now I'm awake) what I missed before that the transformer is rated at 5A AC. That's only 3.5A DC, so a pair of 2A bridge rectifiers will be fine.

Likewise 4 regular 4A diodes would be fine (actually, probably better).
 

cjdelphi

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Alrighty then, 4 x 2 amp .6v diodes it is!

Shame, i wanted to use these useless 2 amp rectifiers, all sorted, cheers
 

(*steve*)

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4 x 2A diodes is *exactly* the same as your 2A bridge.

Did you mean 4 x 4A diodes?
 

cjdelphi

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Alright, ok i'm with it now and why i got confused...

All sorted, 4* 4amp diodes on the way :)

Thanks!
 
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