Rich,
I would think it would be easy as some of the large commercial switch mode
supplies work with feedback regulation. It would be just a form of a voltage
regulation circuit like used on everything else I would think. Adding a bleeder
resistor to drag it down would be prett wasteful after I looked into it. A 4000
ohm 250 watt resistor would do it to get 250 mA.. Only thing is this wastes
power just to get it down some. Here the problem is that by viewing the curve,
at 250 mA, there's a 500 Vdc swing. For say a 300 volt swing equivelant to
about 13% transformer regulation, there would need to be a 400 mA draw from a
bleeder. That's a bunch! I'm not sure how accurate this curve they have
published is though.
Best,
Will
>
> The switch mode 5V PS in this computer delivers constant V when
> additional USB devices are plugged in because there is a feedback
> loop that changes the pulse width of the switch to maintain
> constant DC output. Why can't this be done at 3000V?
>
> On Jun 25, 2005, at 1:43 PM, Will Matney wrote:
>
> > Harry,
> >
> > That much of a voltage drop is ok (3.4 kV to 3 kV), but what were
> > mentioning is the chart on their website which shows it having a
> > 1000 Vdc swing from 0 to 1 ampere. From the knee, it's kind of
> > steep at first, then if I remember from 1/2 ampere on or so, the
> > voltage stayed around 2800-2500 Vdc from a 3500 Vdc open voltage.
> > I would think that one might need to fix that graph if it isn't
> > correct.
> >
> >
> > Best,
> >
> > Will
> >
> > ----- Original Message -----
> > From: "Harry Brown" <harryhbrown@earthlink.net>
> > To: "David Kirkby" <david.kirkby@onetel.net>,
> > "amps@contesting.com" <amps@contesting.com>
> > Subject: Re: [Amps] HV Switch Mode Power Supplies
> > Date: Sat, 25 Jun 2005 07:34:30 -0400
> >
> >>
> >> Here's some more info on a "real" application of the Watts
> >> Unlimited power supply.
> >>
> >> At the VHF Dinner at Dayton this year, K5AND gave a talk on a 6
> >> Meter amp he designed using an 8877 for DXpedition purposes.
> >>
> >> It uses a switching supply from Watts Unlimited and the total
> >> weight of the amp including power supply is 20 pounds.
> >>
> >> His amp idles at 175 ma. with the plate voltage at 3.4 Kv. At full
> >> output, 1.5 KW, the palate current is 3 Kv and the plate current is
> >> 850 ma. So the voltage swing is not all that terrible when compared
> >> to conventional power supplies. When the amp is not on, the power
> >> supply is keyed off.
> >>
> >> 73, Harry, W3IIT
> >>
> >> I
> >> At 01:16 AM 6/25/2005 +0100, David Kirkby wrote:
> >>
> >>> Will Matney wrote:
> >>>> David,
> >>>>
> >>>> You are correct on the regulation. A regular transformer type
> >>> power supply when designed right will have a regulation
> >>> somewherre around 11-14%. In the case of the switching supply, it
> >>> looks like 30-35%. 1000 kV drop over 1 amp is a good bit of sag.
> >>>>
> >>>> Best,
> >>>>
> >>>> Will
> >>>
> >>> I would have thought that cause serious non-linearity problems on SSB.
> >>>
> >>>
> >>> Having gone to a switch mode design, I would have thought they used some
> >>> feedback to keep the voltage constant. But it seems not. Given the line
> >>> voltage will probably sag too at 2.5kV, you can rekon on over a kV drop
> >>> in practice.
> >>>
> >>> I assume you mean 1kV sag, or 1000V, and not 1000kV !! Reminds me of a
> >>> lecturer I know who got fed up with the cleaners moving his equipment
> >>> that worked from 12V. So he decided to put a sign on it
> >>>
> >>> "Danger, 1200000 uV"
> >>>
> >>> Apparently nobody touched it any more.
> >>>
> >>>>
> >>>> ----- Original Message -----
> >>>> From: "David Kirkby" <david.kirkby@onetel.net>
> >>>> To: "amps@contesting.com" <amps@contesting.com>
> >>>> Subject: Re: [Amps] HV Switch Mode Power Supplies
> >>>> Date: Fri, 24 Jun 2005 00:39:13 +0100
> >>>>
> >>>>
> >>>>> Steve Thompson wrote:
> >>>>>
> >>>>>> Winfried Kriegl wrote:
> >>>>>>
> >>>>>>
> >>>>>>> http://www.wattsunlimited.com
> >>>>>>> have a 2500W SMPS. Works fine.
> >>>>>>
> >>>>>> Looks very nice.
> >>>>>
> >>>>> But look at the regulation (or lack of).
> >>>>>
> >>>>> http://wattsunlimited.com/_wsn/page3.html
> >>>>>
> >>>>>
> >>>>> --
> >>>>> David Kirkby,
> >>>>> G8WRB
> >>>>>
> >>>>> Please check out http://www.g8wrb.org/
> >>>>> of if you live in Essex http://www.southminster-branch-line.org.uk/
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> Amps mailing list
> >>>>> Amps@contesting.com
> >>>>> http://lists.contesting.com/mailman/listinfo/amps
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>> --
> >>> David Kirkby,
> >>> G8WRB
> >>>
> >>> Please check out http://www.g8wrb.org/
> >>> of if you live in Essex http://www.southminster-branch-line.org.uk/
> >>>
> >>>
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>>
> >>>
> >>> --
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> >
> >>
> >>
> >>
> >>
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> >>
> >>
> >> _______________________________________________
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> >
> >
> > -- ___________________________________________________________
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> >
>
> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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