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Author Topic: Parametric Charging  (Read 38091 times)
Group: Experimentalist
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Well, negative input should not happen i guess.


Anyway, from 600KHz i went down in 10KHz steps and at 430KHz there is a sudden change, the voltage across
the load resistor jumps up to 14V, and the input power drops to -76mW, see screenshot 1.

So -76mW in, 6mW out.

When dropping frequency even more, a 2th jump happens at 370Khz where the voltage across the load resistor
jumps to 31.6V, and the input power is 331mW, see screenshot 2.

So 331mW in, 30mW out.

Finally continuing on down, max voltage across the load resistor is at 240Khz at 35.6V
But the input is 1.15W, see screenshot 3.

So 1.15W in, 39mW out.

By the way, my IXDN614 gets rather hot after some time.
Using 2PS's, one at 40V, one at 20V,  grounds connected together.

Itsu

Itsu,

OK, in your first scope pix or when you reach 430kHz, you have gone into a first unstable state.  You can tell this by looking at the current waveform symmetry.  Look carefully at the slope and magnitude of each current cycle and also notice the difference in the Math trace.  Also change your "CH4 rms" measurement to "CH4 mean" as it is more meaningful at this point to know the average offset cuurent.  You will want to raise the frequency until you come out of that state and lower back down to say 420kHz or just prior to being unstable and take measurements.

In your second scope pix, you have entered a second unstable mode which is OK but do the same thing as above- Raise the frequency until you are out of that mode and then lower to say to 360kHz or whatever frequency gets you as close as possible without "tripping" the circuit and then do your measurements.  I think this region will give you positive results from what I can tell but I'm not sure.

Everything else at 350kHz and below is essentially out of the optimum operational area for the device so that data can be discounted.

Don't be too surprised if you see negative inputs as we are dealing with highly non-linear functions in the circuits and therefore it may be possible IMO.

Pm
   
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Itsu,

I should have added that the Ixys drivers do not seem to like seeing negative current when the output pulse is high or near the supply voltage.  Their output device(s) do not handle reverse conduction so they will get hotter that normal under these conditions and if left on too long, they will short!

Pm
   

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PM,

ok,  i can't say i am with you right now, but this is what i did:

Green trace set to mean
From 600Khz lowered frequency in 10KHz steps until unstable state (430KHz).
Then in 10KHz steps up in frequency to get out of unstable state (540KHz).
Then in steps back to just before unstable state (440Khz), taking screenshot 1.
DDM across load resistor reads 2.4V = 0.175mW.

I cannot get out of 2th unstable mode as it goes right through the 1st unstable mode (to arrive at 540Khz again)

Itsu
   
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PM,

ok,  i can't say i am with you right now, but this is what i did:

Green trace set to mean
From 600Khz lowered frequency in 10KHz steps until unstable state (430KHz).
Then in 10KHz steps up in frequency to get out of unstable state (540KHz).
Then in steps back to just before unstable state (440Khz), taking screenshot 1.
DDM across load resistor reads 2.4V = 0.175mW.

I cannot get out of 2th unstable mode as it goes right through the 1st unstable mode (to arrive at 540Khz again)

Itsu

Itsu,

I think your negative input measurement is due to your -3.05ma mean current.  If you are using an amplifier with your probe, try to de-gauss or zero the amplifier just before taking any measurements.  You may not be able to get any closer to zero than this but zero would be the ideal value so the closer the better.  A positive offset would more than likely take the input into the positive range but you don't have enough output voltage across C1 to really matter at this point.

Maybe it would help the instability if you increased L1 to say something close to 500uh-1mh.  This will lower the the frequency before hitting instability and may allow a higher C1 voltage range with your mosfets.  I don't have anything else to suggest at this point but if I think of something I'll let you know.

Pm
   

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Quote from: PartzMan
...the Ixys drivers do not seem to like seeing negative current
when the output pulse is high or near the supply voltage.
Their output device(s) do not handle reverse conduction so
they will get hotter that normal under these conditions and if
left on too long, they will short!

Excellent observation.

MosFet Driver Chips are able to deliver an impressive high
current impulse into their normal load of Gate Capacitance
but cannot handle that high current for prolonged periods of
'on-time' without overheating or destruction.  They are rather
fragile.

Perhaps the driver for the circuit needs beefing up?
« Last Edit: 2018-09-07, 06:45:27 by muDped »


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Itsu,

I think your negative input measurement is due to your -3.05ma mean current.  If you are using an amplifier with your probe, try to de-gauss or zero the amplifier just before taking any measurements.  You may not be able to get any closer to zero than this but zero would be the ideal value so the closer the better.  A positive offset would more than likely take the input into the positive range but you don't have enough output voltage across C1 to really matter at this point.

Maybe it would help the instability if you increased L1 to say something close to 500uh-1mh.  This will lower the the frequency before hitting instability and may allow a higher C1 voltage range with your mosfets.  I don't have anything else to suggest at this point but if I think of something I'll let you know.

Pm

PM,

i use the AM 503B as amplifier for the probe, let it warm up at least one hour and normally i degauss before
every measurement.

I will try to increase L1 and/or use another current measurement method (differential or cvr).

Thanks,  itsu
   
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Excellent observation.

MosFet Driver Chips are able to deliver an impressive high
current impulse into their normal load of Gate Capacitance
but cannot handle that high current for prolonged periods of
'on-time' without overheating or destruction.  They are rather
fragile.

Perhaps the driver for the circuit needs beefing up?

Yes I think so too.  I was hoping to achieve a lower range of frequencies showing apparent OU which would open up more possibilities to do this, but no success thus far.

Pm
   

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Changed L1 from 330uH to 1mH.

Unstable mode happens now at 230Khz, so stopped at 240Khz.

Input current / power seems stable positive now, around 7mW
Power across the load resistor 2.61V (DMM) for a Pout of 0.2mW

Weather still humid allthough dry.

Itsu
   
Group: Experimentalist
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Changed L1 from 330uH to 1mH.

Unstable mode happens now at 230Khz, so stopped at 240Khz.

Input current / power seems stable positive now, around 7mW
Power across the load resistor 2.61V (DMM) for a Pout of 0.2mW

Weather still humid allthough dry.

Itsu
Itsu,

The current offset is much better now but the voltage across C1 is really low.  I think the problem is (if the device works) that since we do not the have a sweep of your circuit or a profile of your mosfets, your load resistance is not ideal and possibly L1.  You may also be affected by the weather but this circuit seemed to overcome that issue on my end as we still have rain and overcast with 95-100% humidity.

I need to spend more time trying to do a network analysis on one of these circuits so it would be a little easier to calculate component values for a given mosfet family.  I'm also working on other topologies that hopefully may yield a more replicable circuit.

Pm 
   

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No problem,  i have some RFD14N05L's on order, so will change to these MOSFETs when arrived.
Meanwhile i can change the load resistor to see if some other value will increase COP.

Itsu
   
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Itsu,

Just an update.  It is a sunny day in the morning here and while being very wet outside with dew all over everything, the OU has returned in the 14N05L test setup.  It seems to be related to the sunshine or perhaps cloud cover.  I thought I had run tests after dark but not sure now so will test for that later today.

Pm   
   

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PM,

thanks for the update, i cannot imagine that the OU noted could have anything to do with the type of weather.
But time (and further tests) will tell.

I lost my last IXDD driver, so need to search around on other PCB's for another one or wait for the slow
boat from China.

Regards Itsu
   

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Could it be an effect caused by the Earth's electric field.  This varies considerably and is influenced by the weather.  With charged clouds overhead the E field can drop to zero and even reverse polarity.  On a good clear day it is something like 300V/m pointing downwards (the Earth is charged negatively).
Smudge
   
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Could it be an effect caused by the Earth's electric field.  This varies considerably and is influenced by the weather.  With charged clouds overhead the E field can drop to zero and even reverse polarity.  On a good clear day it is something like 300V/m pointing downwards (the Earth is charged negatively).
Smudge

Smudge,

Now that's an idea!  How could I maybe confirm this?  Would a faraday shield or similar shielding work?

Pm
   
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  Suggest covering a large cardboard box with Aluminum foil, top and sides.  Then place this over  your device, and see what happens. 
  If it still gives ou, then you might put Al foil on the box top, sitting on the table (thinking of a Xerox-paper box or equivalent), put device on that - then the rest of the box over that.  Covering as much of your experiment as you can with the Faraday cage...

   This would be an interesting test...
   

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Hmmm,   the "Carnegie curve" comes in mind then for the daily fluctuations:


https://link.springer.com/article/10.1007/s10712-012-9210-2


Itsu
   

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Found some IXDN614PI's, so started testing again, now using severall load resistors in the 10K to 156K range.

Also added another 10uF in series with the 2 i already had lowering the C1 capacitance from 5 to 3.3uF again
in combination with severall resistors.

Staying just above "unstable mode" which is around 240KHz but the output is very low.

L1 still 1mH.

No sign of even a reasonable COP, let alone a COP > 1.

I notice some oscillations in the circuit when the FG drive is removed spanning a vast part (0 - 500Mhz) of
the frequency spectrum.


Itsu
   
   

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Buy me a beer
If you watch the sun series here https://www.youtube.com/user/Suspicious0bservers  You will see that each day is a different story as far as the energy around the earth which comes from the Sun.

I watch this guy every day, it will open your eyes.

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.
   
Group: Experimentalist
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  Suggest covering a large cardboard box with Aluminum foil, top and sides.  Then place this over  your device, and see what happens. 
  If it still gives ou, then you might put Al foil on the box top, sitting on the table (thinking of a Xerox-paper box or equivalent), put device on that - then the rest of the box over that.  Covering as much of your experiment as you can with the Faraday cage...

   This would be an interesting test...

Thanks, I'll give this a try.  I now think it is varying throughout the day but need more testing to confirm this.  I see there are other post relative to daily variations so will take a look at those links.

Pm
   
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Hmmm,   the "Carnegie curve" comes in mind then for the daily fluctuations:


https://link.springer.com/article/10.1007/s10712-012-9210-2


Itsu


Interesting link Itsu, thanks.  I'm more convinced than ever that the effect is diurnal.

Pm


   
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Found some IXDN614PI's, so started testing again, now using severall load resistors in the 10K to 156K range.

Also added another 10uF in series with the 2 i already had lowering the C1 capacitance from 5 to 3.3uF again
in combination with severall resistors.

Staying just above "unstable mode" which is around 240KHz but the output is very low.

L1 still 1mH.

No sign of even a reasonable COP, let alone a COP > 1.

Well, maybe go back try the full bridge configuration again as that is what I'm presently using ATM.  I have seen times thru the day where I may have COPs ranging from .6 to 3 or greater!?!  I'm also using a 1 ohm CSR instead of the current probe and all probes are de-skewed identically and set to full bandwidth.  Use the same tuning technique as you have been.

Quote
I notice some oscillations in the circuit when the FG drive is removed spanning a vast part (0 - 500Mhz) of
the frequency spectrum.


Now that is interesting!  I'll have to take some measurements for this.

Pm

Quote


Itsu
 
   
Group: Experimentalist
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If you watch the sun series here https://www.youtube.com/user/Suspicious0bservers  You will see that each day is a different story as far as the energy around the earth which comes from the Sun.

I watch this guy every day, it will open your eyes.

Regards

Mike 8)

Mike,

Thanks for the link, lots of info there.  I'm beginning to think that if the effect is due to potential variations in the atmosphere for whatever reason, it is interesting to study but not too useful for energy production on a practical scale at least with this circuitry.

Regards,
Pm
   
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Itsu and all,

Update- On this nice bright sunny morning with cloudless skies, the COPs are ~0.7!   ???

Pm
   
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Itsu and all,

For comparison, these are the data results from testing yesterday and today at approximately the same time with the identical circuit and layout.

Pm
   

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Buy me some coffee
Partzman do you have any energy saving lamps any where, I once had loads of problems measuring waveforms and the problem came and went, it turned out to be noisy energy saving spotlights.
   
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