All,
I use the fast-recovery version of the 1N5408, called the UF5408,
originally intended for fast switching in switched-mode PSUs in my
bigh HT supplies.
You need no capacitors or resistors - just diodes - and I use 12
in each leg in for a 3900V 1.4A supply for my 8877 6m amp and
GS35b 2m amp. This ensures that they are run consertively and
they've never been a problem...
Mike G8TIC/M0VHF
>Richard escribió:
>>
>> >Conrad, why not use the Motorola MR-760 diodes. They
>> >are 1000 volts at 6
>> >amps. They mainly high pot around 1.5KV They sell for
>> >around .75 at Digikey.
>> >Put some matched resistors and matched capacitors and it
>> >will be bomb proof
>> >for everything but HV to gnd short.
>>
>
>> ? Put "equalizer" resistors/capacitors on a string of same-type Si
>> rectifiers and one increases the chance of failure.
>
>Please, can you tell why?
? Because diodes ordinarily have differing Peak Inverse Voltages, if the
equalizer resistors try to force the same V across each diode, the lowest
PIV diode can be subjected to more PIV than it can safely handle. For
example, two diodes rated at 1000PIV are connected in series. An
equalizer resistor is connected in parallel with each diode. The
measured PIV (avalanche V) of one diode is 1000V and the other is 1600V.
An inverse voltage transient of 2400V comes along. Each diode receives
c. 1200V due to the equalizers. The 1000PIV diode will fail/short, which
in turn puts 2400V on the 1600V diode, which then shorts, much like
dominoes falling. However, without the equalizer resistors, because the
currents in a series circuit are always (=), the PIV will divide
according to the avalanche V of each diode. Thus, the V on the 1000V
diode will limit at c. 1000V and the remaining 1400V will appear across
the 1600V diode. So, neither diode is torpedoed by the 2400V transient.
cheers, Guillermo.
>
>> >
>> >Denis Ve6AQ
>> >
>> >Conrad G0RUZ wrote:
>> >
>> >> Has anyone ever used the P600M diode in an HT supply, it looks like a
good
>> >> choice, twice the current rating of the 1N5408. Any other
recommendations
>> >> for a bomb proof rectifier stack? I was thinking of using 8 per leg in
my
>> >> test supply which can do 5kV @ 1.75 amps.
>> >>
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