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Author Topic: "RF and molecular bond breaking Kanzius style"  (Read 103468 times)

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I extensively tried severall output configurations for 13.56MHz, but none seems to be stable.
So there is something wrong in my setup, most probably the used shunt / output circuit capacitors.
I will redo my setup using ATC 100c series of RF capacitors (which are very hard to get) and use known workable MOSFET and drivers together with a new layout (input / output compartments with a grounded shield across the MOSFET input (gate) and output (drain)).

But this will take some time.

Regards Itsu
   

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Still trying to order some ATC 100C series RF capacitors, but either all sales reps are on vacation or they are not interested in me.


Meanwhile i was looking for a FG chip capable of 13.56MHz and found one in this Max038 chip.

It has 2 outputs, one, +/- but at only 2.3Vpp and two, a sync output with an all + signal at 4Vpp.
Unfortunately the sync output duty cycle cannot been changed and is about 64% which i guess is to much.

So need to find a way to amplify/modify the +/- signal.

Screenshot shows the 2 outputs,  yellow the +/- signal, blue the sync output

Video here: https://www.youtube.com/watch?v=-A9cm2M7-WA&feature=youtu.be


Regards Itsu   
   
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So need to find a way to amplify/modify the +/- signal.

Itsu, can you use a pot as a voltage divider and just level-shift this output on the ground/reference side?

It would be pretty close to 5Vpp.
   

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It has 2 outputs, one, +/- but at only 2.3Vpp and two, a sync output with an all + signal at 4Vpp.
Unfortunately the sync output duty cycle cannot been changed and is about 64% which i guess is to much.
Forget the sync output.
Amplify and DC level shift the ±2.3V square signal with an op-amp or if you do not have one - with a small MOSFET driver connected to the SG chip by a series capacitor to its input and a weak 2.5V voltage divider after the cap (for DC level shifting).  You just have to make sure that the VIN_H logic input threshold of this driver chip is not more than 2V (for example the UCC27321 we once used has this threshold).

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For your interest

http://www.israel21c.org/spilled-water-inspires-renewable-energy-startup/?utm_source=Israel21c+Weekly+Newsletter&utm_campaign=2a6f0de265-weekly_newsletter_5_8_15&utm_medium=email&utm_term=0_a2ed5ed71b-2a6f0de265-250415557

Itsu

I would not worry about using 13.56Mhz at the moment, go along with the 4.5Mhz+-  we will shield the reactor so as not to emit Rf to the world ;)

I have just been informed in the last week that someone in the USA is going to fire up in the near future my old system of RF splitting of H2O.

I think once it is realised what it is that causes the RF to split the molecule, it can be done quite a lot easier :)

regards

Mike 8)


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Thanks Matt,  thanks verpies,


i used a 2.2nF capacitor on the output of the max038 and used the suggested voltage divider (2x 1KOhm between point 1 REF (=2.5V) and ground) after the capacitor.
The signal can be seen in the first screenshot yellow trace, but.... i had to lower the frequency to around 10Mhz for the ucc37322 to show an output, see again first screenshot blue trace (ucc37322 is at 5V Vdd).


Adjusting the duty cycle and frequency to obtain a 50% duty cycle on the output of the ucc even lowered the frequency to about 9MHz, see screenshot 2.
So i guess the ucc37322 chip is not useable on 13.56MHz, right?

Looking at an ixdd414 driver (which i have) shows that the Vin_H is to high (3.5V), so not useable i guess, so need another fast low input driver





Mike, thanks for the info.

the 4.5MHz layout was not really stable as well, so i need to redesign the Amplifier setup and used RF capacitors.

It seems as if the ATC guys are reading this thread as a sales rep. contacted my yesterday and pointed me to how to order their 100C series of caps.  
Unfortunately they do not sell them in kits, nor do they have in stock many different values, just 27pF, 56pF and 100pF (2500V).



Regards Itsu
  
   
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I have a few Motorola MC1590G op-amps that I could donate, if that would help.


   

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Quote from: Itsu
So i guess the ucc37322 chip is not useable on 13.56MHz, right?

It could be if you were to operate your Power Amplifier stage
as a doubler or a tripler.  Those circuits were quite popular in the
early days of radio.

As a doubler, a drive signal of 6.78 MHz would produce the desired
13.56 MHz output.

Push-Push Doublers are sometimes used to advantage.
« Last Edit: 2015-08-08, 02:11:35 by muDped »


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So i guess the ucc37322 chip is not useable on 13.56MHz, right?
Looking at an ixdd414 driver (which i have) shows that the Vin_H is to high (3.5V), so not usable i guess, so need another fast low input driver
Right.  That other fast input driver/buffer does not need to be very strong as its only job will be to drive the IXDD power driver.  An op-amp would work, too.
Also, I would adjust the DC level shifting voltage divider after the cap so the lowest excursions of the waveform are closer to 0V (ground).
« Last Edit: 2016-02-05, 23:08:54 by verpies »
   

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Quote
I have a few Motorola MC1590G op-amps that I could donate, if that would help.

Thanks for the offer Tinsel, i keep that in mind, i still have some other drivers i could try like a ucc27511 (little bugger   :( ) which has better specs (3nS).


Quote
It could be if you were to operate your Power Amplifier stage as a doubler or a tripler.

Good suggestion muDped, if all fails i could try that.


Quote
Also, I would adjust the DC level shifting voltage divider after the cap so the lowest excursions of the waveform are closer to 0V (ground).

verpies,  ok, so use a potmeter instead of the fixed resistors



Thanks guys, i will get it to work this way.

Regards Itsu
   

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Why not. A multiturn pot would work well. Just don't use a 100ohm pot because such small resistance will attenuate the signal amplitude too much.
   

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Why not. A multiturn pot would work well. Just don't use a 100ohm pot because such small resistance will attenuate the signal amplitude too much.

Like this

regards

Mike 8)


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I used a 10K potmeter to DC shift the max038 output, and fed this into an ucc27511 MOSFET driver.

This seems to be able to handle the 13.56MHz ok, see screenshot.
Yellow is the voltage divider output, blue the ucc27511 driver output (5V Vdd).

I had to adjust the frequency, duty cycle AND the DC shift potmeter (slightly elevated from the zero line) to get to an acceptable 50% duty cycle on the ucc27511 output, see video:

https://www.youtube.com/watch?v=mNzlano5b00&feature=youtu.be  

Thanks,   regards Itsu
   

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I had to adjust the frequency, duty cycle AND the DC shift potmeter (slightly elevated from the zero line) to get to an acceptable 50% duty cycle on the ucc27511 output, see video:
https://www.youtube.com/watch?v=mNzlano5b00&feature=youtu.be  
Looks like you solved it without an op-amp.
Centralflow's method might work even better if you have a little signal transformer handy.

Now you can drive the big IXDD MOSFET driver with the signal coming out of the small UCC driver.
   

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Well, i still have the IXRFD630 driver in my setup which survived all the blowed MOSFETs.
I will start with that one and a fresh DE275X2-102N06A MOSFET, but need to rearrange the Amplifier layout.

http://www.rfmw.com/datasheets/ixysrf/IXRFD630.pdf
http://www.farnell.com/datasheets/1019384.pdf

Regards Itsu
   
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It's turtles all the way down
Since FET's usually only require a very small voltage change to go from full on to full off, the trick is biasing the gate into the conduction threshold and level shifting the signal with an ordinary capacitor. The normal output of the Max 038 should provide sufficient drive once level shifted, since you will be toggling +/- 2.3 V0lts right around the FET threshold voltage. Maybe you are already doing this. Best to adjust the pot so that the FET is "just off" with no signal, In this way, the pot does not attenuate the Max038 output and you get the full voltage swing at the gate. You can still use the UCC FET driver if inserted properly between the bias circuit and the gate.  Then you are level shifting to the required input of the UCC part instead of the FET gate. Values needed may differ slightly from those shown, but these should work.
« Last Edit: 2015-08-09, 14:22:15 by ION »


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The normal output of the Max 038 should provide sufficient drive once level shifted, since you will be toggling +/- 2.3 V0lts right around the FET threshold voltage. Maybe you are already
Yes, biasing just below the VGS(th) will save some energy, but not enough to operate at 13MHz ...and it will make the MOSFET susceptible to Miller turn-on if there are high dv/dt waveforms at the drain.
The turn on region is not a point.  Just to overcame the Miller plateau, which occurs above VGS(th), requires significant charge to be delivered to the gate that the MAX038 simply cannot deliver at the necessary rate.
   
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It's turtles all the way down
Yes, biasing just below the VGS(th) will save some energy, but not enough to operate at 13MHz ...and it will make the MOSFET susceptible to Miller turn-on if there are high dv/dt waveforms at the drain.
The turn on region is not a point.  Just to overcame the Miller plateau, which occurs above VGS(th), requires significant charge to be delivered to the gate that the MAX038 simply cannot deliver at the necessary rate.

I didn't look closely at the MAX038 data sheet and therefore you may be right, I was just trying to get some ideas across about level shifting as commonly used in industry. The driver chip is a better way to go with the capacitive level shifter.(second scheme).


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Besides enjoying the summertime and my free time, i was rebuilding my 13.56MHz amplifier.
The layout has been changed 90° and there is a grounded shield between the input and output compartments across the MOSFET, see picture.

Also the output circuit has been changed according to this design:   http://www.ixys.com/Documents/AppNotes/CO1.pdf

I have SMD multi layer RF capacitors (2Kv) and a 4 turn copper strip inductor around 2x T256 toroid's.

The output circuit sweeped with the FG attached to the MOSFET drain / source and the scope attached to the unconnected output plug (no dummy load attached).
shows a peak around 13.7MHz which is fine for me now (it will dampen down when the 50 Ohm dummy is attached) see screenshot.
(sweep is from 10.7Mhz to 16.7Mhz)

Presently i am still waiting for a new IXRFD630 driver as i don't trust the old one after blowing up many MOSFETs.

Hopefully this rebuild will be more stable as the old one, which i will let you know.


Regards Itsu
   

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Why was the Litz wire winding substituted with the copper tape ?
   

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Why was the Litz wire winding substituted with the copper tape ?

Nice as always Itsu, we will see how she runs

For me, using tape is far better as at these powers "1Kw" the possibilities of a wire break in the litz is high, this will change all the characteristics of the output "which is very sensitive in class E". Also you do not need to contend with the self capacitance of a litz wound coil which causes tuning problems "at these power levels". low power is another thing.

The SS is not showing the 13.56Mhz running frequency, or have I missed something :-\

regards

Mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
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As a general rule, the most successful person in life is the person that has the best information.
   

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Why was the Litz wire winding substituted with the copper tape ?

As i wanted to follow the output section as mentioned in the PDF design as close as possible.

Regards Itsu
   

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Nice as always Itsu, we will see how she runs

For me, using tape is far better as at these powers "1Kw" the possibilities of a wire break in the litz is high, this will change all the characteristics of the output "which is very sensitive in class E". Also you do not need to contend with the self capacitance of a litz wound coil which causes tuning problems "at these power levels". low power is another thing.

The SS is not showing the 13.56Mhz running frequency, or have I missed something :-\

regards

Mike 8)

Mike, i guess with SS you mean screenshot.

The screenshot shows the response of a continuous sweep from my FG of a sine wave signal running from 10.7Mhz till 16.7Mhz (center 13.7MHz).
The scopes frequency calculation is not accurate this way and i should had to remove that, so please ignore it.

The screenshot shows an unloaded bandpass around 13.7MHz of the output section, which is what we want.

Regards Itsu

 
   

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Mike, i guess with SS you mean screenshot.

The screenshot shows the response of a continuous sweep from my FG of a sine wave signal running from 10.7Mhz till 16.7Mhz (center 13.7MHz).
The scopes frequency calculation is not accurate this way and i should had to remove that, so please ignore it.

The screenshot shows an unloaded bandpass around 13.7MHz of the output section, which is what we want.

Regards Itsu

 


Ahh, thought I'd missed something, it was the frequency of CH1 @4.    Mhz that threw me off O0

regards

mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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For me, using tape is far better as at these powers "1Kw"
How can it be better when the 13.5MH RF current flows only in the upper 0.08mm layer of the copper tape before it gets attenuated by 98% ?
Compare the conductivity of a 100 strand Litz wire of the same cross sectional area as the copper tape and show me the quantitative comparison.

the possibilities of a wire break in the Litz is high, this will change all the characteristics of the output
The chances of a Litz strand breaking spontaneously are minuscule and even if that happened, the inductance of the coil would not be affected and 99% of it conductivity would remain.

Also you do not need to contend with the self capacitance of a litz wound coil which causes tuning problems "at these power levels". low power is another thing.
There is no self-capcitance between different strands of a Litz wire because they are at the same potential.  There is only the self-capacitance between turns of a winding, because different turns are at different potentials. Capacitance is proportional to the surface area of a conductor at different potentials and a tape has more surface area than a cylinder (round wire) of the same conductivity.

The turn spacing is another factor that affects the self-capacitance of a coil but I don't see how this spacing would be larger with a tape.
   
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