[Amps] Rectifier equilization?

[Ian White]

It is NOT necessary to use "equalizing" resistors or capacitors across
rectifier diodes in the 1N400x and 1N540x series... or any other
rectifier diode manufactured in the last 30 years. 

That advice has been in the Power Supplies chapter of the ARRL Handbook
since 1995. The chapter author was a professional power supply designer
for a well known US company, and he confirmed that the information had
come directly from major diode manufacturers.

Also, the economics have changed. Today, the cheapest way to double the
reverse surge handling capacity of a HV rectifier stack is simply to
double the number of diodes in each string. To update an existing PC
board, strip out the old "equalizing" Rs and Cs, and then double the
number of diodes by standing them vertically in the existing holes and
connecting the pairs in series. 



73 from Ian GM3SEK


>-----Original Message-----
>From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Carl
>Sent: 14 September 2013 14:42
>To: Alex Eban; 'Vic K2VCO'; amps at contesting.com
>Subject: Re: [Amps] Rectifier equilization?
>
>Ive measured the beginning of breakdown on a large number of diodes and
>the
>1N5408 PIV always falls in the 1300-1600V range. Its also a good reason
>why marginal PS designs survive.
>
>Carl
>KM1H
>
>
>
>----- Original Message -----
>From: "Alex Eban" <alexeban at gmail.com>
>To: "'Vic K2VCO'" <k2vco.vic at gmail.com>; <amps at contesting.com>
>Sent: Saturday, September 14, 2013 5:56 AM
>Subject: Re: [Amps] Rectifier equilization?
>
>
>> Neither are needed any longer.
>> The capacitors were required because the recovery time of old
rectifiers
>> was
>> soo bad, that you could hear the noise generated in any close by
>> amplifier.
>> This is no longer the case thanks to much improved manufacturing
>processes
>> now in use.
>> The resistors were needed because the junction capacitances were so
>> different from diode to diode, that simply by voltage divider action
the
>> voltage spread across the diodes could cause some t exceed the PIV
rating
>> (the ones with lower junction capacitances). I remember measuring
>junction
>> capacitance spreads of over 10 to one on diodes FROM THE SAME BATCH!
>It's
>> no
>> longer the case today.
>> Alex 4Z5KS
>>
>> -----Original Message-----
>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Vic
>K2VCO
>> Sent: Friday, September 13, 2013 7:54 PM
>> To: amps at contesting.com
>> Subject: Re: [Amps] Rectifier equilization?
>>
>> The resistors are definitely not needed. I used capacitors in my
recent
>> project in order to eliminate switching noise which might appear in
my
>> receiver -- I don't know if this was needed, since I didn't try it
without
>> the capacitors first!
>>
>> They should also provide some protection against transients, although
I
>> also
>> have MOVs in the primary.
>>
>> On 9/13/2013 9:28 AM, Hardy Landskov wrote:
>>> I have just rejoined the amp list after a few years and am wondering
>>> if the diode equalization question was ever resolved. I am building
a
>>> new bridge HV PS and it uses
>>> 12 diodes per leg. Rich Measures says using a .01 & 470K across each
>>> diode is no longer needed due to improvements in semiconductor manf.
>>> processes. I have 100 1N5408's that came off the same reel so I feel
>>> they should be matched fairly close. I would like to hear a few
>>> opinions. Thanks 73 Hardy N7RT
>>> _______________________________________________ Amps mailing
>list
>>> Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>> --
>> Vic, K2VCO
>> Fresno CA
>> http://www.qsl.net/k2vco/
>> _______________________________________________