[AMPS] Diodes

[Ian White, G3SEK]

Rich Measures wrote:
>>
>>measures wrote:
>>
>>I wrote:
>>>>Therefore in his professional view and that of the diode manufacturers
>>>>he consulted, it is not necessary to use equalization components - so
>>>>that's what the Handbooks now say.
>>
>>>hardly
>>
>>Erm, don't you mean "amen"?
>
>no.  My position is that "not necessary" is not The compelling reason to 
>avoid equalization.  

Ah, I see... sorry, that was a bit too cryptic for me.

>
>>> -  page 11-9 of the Handbook:
>>>"In fact shunt resistors produce a low impedance source of damaging 
>>>current to any diode that may have reached avalanche potential."  
>>
>>>It seems a bit curious that you missed the statement about damaging 
>>>current.


>Your position appears to be 
>'not necessary.    The p.11-9 Handbook statement goes one step beyond 
>saying not necessary".  It  says "damaging current".  In other words, if 
>the diodes are perfectly matched, equalizers are not necessary.  However, 
>if the diodes are not perfectly matched in piv, 

  AND IF there are too few diodes in the string (a design fault) 
  AND IF (in spite of the equalization of inverse voltages) one diode is 
         still pushed into breakdown
THEN

>"damaging current" can be 
>produced by the equalizer itself. .  

That's a lot of IFs, so I don't think the case against equalizers is
totally damning. That's why I stick at "not necessary."

I don't use equalizers in any new power supply, but I do take care to
use more and better matched diodes - so we agree on that much, Rich. 
On the other hand, I won't tear the equalizers out of existing power
supplies that have proved reliable.


73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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