[Amps] HV Switch Mode Power Supplies

[Bill Fuqua]

     You can go to wallmart and get a Panasonic "Inverter" microwave oven 
for about $60. It contains a 1500 watt SMP. But there are  a few problems:
1.  The output is negative around 4 or 5 Kv and very unregulated. With out 
load it will go up to 8 or 10Kv.
2.  Control is done thru a optical coupler and you need to figure that out.
3.  It will not drive a full gallon amplifier.
4.   It is designed so that it produces HV output pulsed at 2x line 
frequency. That is intentional so that data packets from wireless phones 
and routers can get thru during the off interval but at a slower rate. A 
microwave oven near a wireless device at 2400 MHz has a tendency to 
overload the receiver.
5.   The output is a full wave voltage doubler. If you want lower voltage 
you need to use a full wave bridge rectifier and which requires two more HV 
fast switching rectifiers.

The microwave ovens are easy to identify due to their light weight. The 
power supply is about 1.5 lbs. The oven itself weighs about the same as the 
box, glass tray and packing materials. It is very light.  I have taken one 
apart and done some experiments but it is very hazardous work. It will kill 
you in a split second if you are not paying attention to what you are 
doing.  It is small but deadly. There is no information on the controller 
IC at all and the circuitry is very complex.
     I don't think these were available in the 1990's it is a recent 
development that allows them to provide lower power settings with out  the 
very slow cycling used in standard microwave ovens. Also, it reduces the 
shipping cost from China by quite a bit.

73
Bill wa4lav





At 04:37 PM 6/21/2005 -0700, John Irwin wrote:
>Hi
>Be advised that some Panasonic microwave in the late 90' used switch mode 
>power supplies and were light as a feather.  Find one in the junk and 
>check it out.  They are at about 2300vdc give or take a little.
>
>john kb9tc
>
>"DUGAS, JASON A. (JSC-EP) (NASA)" <jason.a.dugas at nasa.gov> wrote:
>I have seen very little discussion in the amateur community for HV Switch
>Mode Power supplies in conjunction with RF amplifiers. With the increased
>difficulty of finding 60Hz 2400VAC transformers as well as the light-weight
>advantages of using switch mode power supplies, I'm surprised there has been
>no discussion thus far for homebrewing these for amateur use.
>
>Jason
>KB5URQ
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