ka4inm at gmail.com
Wed Feb 29 07:56:02 PST 2012
Alf OH2QM Pousar wrote:
> Why not skip the bleeder entirely, and make a current discharge circuitry when the session is over.
> If the anode voltage is very high then stack some thyristors and fire them with opto couplers.
> So when you hit the big switch it turns off all power to the power supply, except for the auxillary
> circuit that keeps the draining alive and then shut off .
> Not very complicated to do and you get rid of the bleeder heat.
This idea is along the lines of what has been used in many high power broadcast amplifiers for
over 50 years. (guillotine style)
Except they use/d a solenoid to wind up a spring that hit a micro-switch (at it's completion) that
"allowed" the supply to be powered, when the power was de-energized a clockwork mechanism slowly
lowered a shorting bar with the six* second mechanical delay. If the solenoid failed the power
would be de-energized way before the shorting bar would reach the two fixed contacts.
(* in RCA transmitters)
We would never open an interlocked door until the mechanism completely wound down, by the sound.
There were still bleeder strings across the filter capacitors.
If you use thyristors in place of the guillotine, without the bleeders and the delay you will
injure the capacitors with the extremely high discharge current, in a short while.
73 Ron KA4INM - All E-mail sent to this address shall linger in the Google cloud forever!
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