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Re: [Amps] GPT-750 power supply

Subject: Re: [Amps] GPT-750 power supply
From: "Dave" <>
Date: Fri, 10 Feb 2012 12:57:51 -0000
List-post: <">>
Re the smart bleeder.

Cascode two or more HV Power Fet modules, Drain to Source etc, and use 
resistors to set the individual gate voltages for the upper FET's so they 
(more or less) share the load.   Top most resistor to the top most FET 
Drain..  Then the lower end of the lowest resistor to Negative (the 
Source of the lower "controled" FET)   Then, taps in the chain, to set 
the gate voltage of the middle and top FET, spreading the applied voltage 
across them more or less evenly.   Even FET's have safe operating areas, 
not as square as you might like either, when the disipation limit line 
intersects the graph.

Or..  SSR in/out series resistors in the transformer primary, much like 
the "Step Start" scheme, to prevent the unloaded HV from wandering up too 
much.  In conjunciton with a low disipation bleader.

Or..  A regulated HT supply, much like the G4FRX (I think) design a while 
back.  (Phase controled Thyristors in the primary, I can't find the 
article at the moment)  Should be easier now perhaps, with more modern 
and capable power semiconductors.

QRM from the Thyristors shouldn't be much of a problem, as you're not 
receiving when you're "using" them.   Good filters on the AC input 
though, with short wires to the transfomer, and the whole HT supply in a 
screened enclosure.

Then you can dial up whatever volts you want, and they'll be stable with 
it.  Mostly.

Just musing.


Dave G0WBX.

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