smps for rf power unit , scr freq and measuring rf voltage w

[nanotech1]

i have a question to ask about switching mode power supply ,scr switching
frequency and measuring rf voltage with digital multimeter

1) i want to use an old smps for making a fix freq rf power unit

is it possible to used the smps transformer output tap as a rf power source

leaving only the converter portion of the ps intact

most of these smps have a optocoupler for circuit isolation

i am going to use the optocoupler circuit for controling the ouput power

and a matching inductor at the transformer output tap for protection before
the load

i plan to used an old pc power supply for rf source and a rf air coil for
load

i want to use it for small induction heating system

can it be done with a minimum of circuit modification to a stock pc smps


2) what maximum switching frequency can i expect form a generic type
standard switching speed SCR

3) can it be possible to do a rf voltage reading with a standard digital
multimeter if so what kind of circuit do i need between the dmm and the rf
voltage source

any help appreciated

 

[nanotech1]

i know that high speed scr can be drive to 10khz but for low speed one i
guees thats above 60hz
may be somewhere in the 400 hz i am not an expert in electronic


for my rf power unit i only need rf freq in the 100 to 200khz and rf output
of 100w to 200w range

the 13mhz induction heating band is used for labotary equipment most of the
time

 

[nanotech1]

it is possible to make a scr oscillate at 200khz !

so do you know any schematic that do so please give me a lead to where
i can get it a web site would be great

i want to build a high power SCR oscillator ( it simplyfied the circuit
without having any amplification stage to bather with)
but i dont think that scr can oscillate at 200khz unless it is a really
specific expensive device

as for the smps especially the ones for pc computer they have high power
transistor oscillator circuit in them that could be salvage i want to use
sutch a circuit to drive a small coil with it

 

[mike]

nanotech1 wrote:

i have a question to ask about switching mode power supply ,scr switching
frequency and measuring rf voltage with digital multimeter

1) i want to use an old smps for making a fix freq rf power unit

is it possible to used the smps transformer output tap as a rf power source

leaving only the converter portion of the ps intact

most of these smps have a optocoupler for circuit isolation

i am going to use the optocoupler circuit for controling the ouput power

and a matching inductor at the transformer output tap for protection before
the load

i plan to used an old pc power supply for rf source and a rf air coil for
load

i want to use it for small induction heating system

can it be done with a minimum of circuit modification to a stock pc smps


2) what maximum switching frequency can i expect form a generic type
standard switching speed SCR

3) can it be possible to do a rf voltage reading with a standard digital
multimeter if so what kind of circuit do i need between the dmm and the rf
voltage source

any help appreciated


If you really have an SCR switcher, it's probably switching at 60

Hz...at least
where I live. That's all the faster it can go. Now if you don't really
have a SCR switcher, we can't help 'till we figger out what you do have.

FWIW, isn't induction heating done at 13 MHz? Probably ain't gonna get
there with ANY commercial switching supply.
mike


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[mike]

nanotech1 wrote:

i know that high speed scr can be drive to 10khz but for low speed one i
guees thats above 60hz
may be somewhere in the 400 hz i am not an expert in electronic

You need to be VERY MUCH more specific.

It's likely that you can build an SCR switcher that runs at 200 KHz.
Not at all clear why you'd do this when a simple oscillator can easily
do this.
Your original post related to an "old" whateverthatis "smps" whateverthatis.
It's likely that an "old" scr smps swtiches at line frequency. The way
to convert it to 200 KHz. is to take out all the parts, lay them out on
the table, replace the scrs with MUCH faster units, design a circuit
using them, throw away any existing parts that don't fit, buy new parts,
put them all back in the box.

Or you could wire up one or two transistors as a Colpitts or Hartley
oscillator at any frequency you want and be done with it.

First thing I'd do is borrow a ham radio transmitter, couple it to the
load and make sure the thing works. But probably can't get below 1 MHz.
that way.

mike

for my rf power unit i only need rf freq in the 100 to 200khz and rf output
of 100w to 200w range

the 13mhz induction heating band is used for labotary equipment most of the
time

--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/