On Wed, 12 May 2004 20:34:48 +0200 "Thomas Hoeppe"
<thomas.hoeppe@asamnet.de> writes:
> Hello guys,
>
> I am new on this reflector, so may be I am asking a question whitch
> has been discussed before.
> I am looking for a simple design for the regulation of a screen
> supply. I need 800V and about 50 mA. I will have to take care of
> some negative current, so the supply has to be able to do that or I
> will use a 100mA supply and allow 50 mA of current through a
> resistor to ground. My anode voltage is 5 KV, so I don't want to get
> the G2 voltage from the anode voltage.
>
> I am looking for easy and rugged solutions. (KISS.......keep it
> simple and stupid!)
>
> Any ideas?
>
> Thanks in advance.......
>
> Tom, DJ5RE (DL0AO crew)
Hi Tom,
This is probably not the answer you seek but, I'm considering a
bidirectional Cuk converter for that spot in a project here.
I already have a switching supply for heaters, grid bias & control
power so, I can source the converter from the available 300 volts on the
switcher primary.
Running at 100 KHz, it only takes a small transformer, and a couple
each small chokes, capacitors, small FET's (IRF820's) plus a PWM control
IC (3525) to implement this scheme.
I'm using a 1:1 transformer in my application for a 375V Screen. A
2.5:1 part would better serve your 800 volt needs. You would also need
to use a 1KV FET on the Screen side of the converter.
The output is adjustable & regulated. The output FET of the converter
will have an additional gate R to clamp the Screen V to ground in the
event the PWM drive fails. I also have a separate SCR crowbar circuit
to protect the Screen... just in case.
This approach runs with 90% or so efficiency, requires no heatsinks on
the FET's, nor any bleed current.
73 & Good morning,
Marv WC6W
*
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