[sdiy] how to double Si diode voltage rating

[Bob Weigel]

Firstly, dont' forget that 300VAC is rms.  Peak voltages, which are what 
will contribute to breakdown of a diode are1.4x that amount so add 120V 
=420Vpeaks and of course it does that above and below ground being AC.   
ie. from the point where it's dumping charge from one wire onto the plus 
side of the capacitor, that point sinks in 1/120th of a second in the US 
to double the peak below that.  The rating recommendation is usually 
2.82 x the RMS voltage output of the transformer I think.  So you'd want 
1KV diodes in this application to keep the peak unloaded accumulation on 
the capacitor from overstressing the diode that is blocking flow of 
current when the voltage sinks all the way to the bottom on that line 
and visa versa on the negative side. -. -Bob



anthony wrote:

> If I wanted to use some Si diodes in a bridge to increase their 
> voltage, like say I wanted to use 200V BY251's in a bridge with a 
> 300VAC secondary, would putting 2 in series suffice to double the 
> voltage they can handle? That is, would I use 8 diodes, 2 in series in 
> each part of the bridge? Or would using these diodes in a bridge, 
> singley give a bridge that can handle 300VAC? When in doubt, is it 
> better just to use more?
>
> If I wanted to increase current carrying capability would I put the 
> diodes in parallel? Like if I wanted to use 1N4007's (since I have a 
> ton) and I needed 2Amps?
>
>
> Anthony
>
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