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Re: [Amps] High Voltage Switching Supply (Bob D.)

To: amps@contesting.com
Subject: Re: [Amps] High Voltage Switching Supply (Bob D.)
From: Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>
Date: Tue, 5 Mar 2024 19:20:02 +0200
List-post: <mailto:amps@contesting.com>
I don't know if it's been mentioned yet, but a 'feature' of any supply for a microwave oven is that it is designed for a short duty cycle. A "1500-watt" supply will not provide 1500 watts for amplifying compressed SSB, CW, or digital transmissions over a period of time of more than a few minutes. You would have to derate it and probably provide cooling.

73, Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco

On 05/03/2024 17:09, Bob D. wrote:
Hi Steve,

"Well, there's no free lunch... Although these inverters present an
interesting idea, this particular one uses a flyback transformer to
generate the HV, which is unregulated and so varies between 2200 and as
much as 6 kV, the youtube author said at one point in his first video."

The supplies are tightly regulated.They are regulated for power via current
sensing on the AC mains side of things. Something like 2% per one article.
It's what makes that type oven so nice in the kitchen. The one in my
kitchen can thaw from the freezer without cooking!
It will melt butter without popping. Best thing is the "sensor reheat"
mode, It steams vegetables perfectly.

I am not an EE and welcome any assistance in understanding this thing.

I think the small IGBT heatsink is possible because the flyback topology
allows for switching at zero current(voltage).

So far I've gathered that:
The cook power setting signal is PWM 220Hz(per the referenced videos) with
no indication as to delay or hysterisis, if any, in response;
220Hz will limit the minimum response time of any voltage regulation
feedback scheme.

My thoughts are: That a minimum load and enough capacitance will allow me
to repurpose the cook power setting and hopefully hold voltage to within
10%;
There is minimal filtering on DC feeding the inverter so 20 uFd should be
adequate for filtering the 120Hz feed through; If the power control
feedback response
is no more than a cycle or so at 220 Hz, the 20uf will be adequate; My
first task in learning if this will work is to measure the response time of
the power feedback loop;
If the existing control loop is too slow, an impractical amount of
capacitance may be required for ham amplifier regulation.


73, -bob ah7i


Not knowing specs for the black box regulator, I'm doubtful there us any
approach to learning if this will work aside from cut and try.
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