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Author Topic: The Rosemary Ainslie Circuit  (Read 429830 times)

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It's not as complicated as it may seem...
As an alternative to replacing the MOSFET Rose, you can solder in a diode with high VBr (reverse breakdown voltage) across the Source and Drain leads.

This will tell you right away if the internal body diode is faulty or not. If the wave forms change significantly, then the body diode is damaged. If there is no change, then the diode is ok, and  I am wrong.

Pay attention to the diode polarity if you try this.

.99

EDIT: However, the preference is and always shall be to replace the existing MOSFET with a known good unit.
« Last Edit: 2011-02-19, 17:36:29 by poynt99 »
   
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As an alternative to replacing the MOSFET Rose, you can solder in a diode with high VBr (reverse breakdown voltage) across the Source and Drain leads.

This will tell you right away if the internal body diode is faulty or not. If the wave forms change significantly, then the body diode is damaged. If there is no change, then the diode is ok, and  I am wrong.

Pay attention to the diode polarity if you try this.

.99

I'm going to take the 10% bet on this, Poynt.  You're 90% sure it's the body diode.  I'm not at all convinced.  Your challenge, above, is a tiny bit of a heads-I-win, tails-you-lose situation.  If the body diode is good and she adds another diode in parallel with different recovery characteristics and added capacitance, there will surely be some change in the waveform, however small, and possibly significant change.  

If it's bad, and she puts a weak little diode across there, it could pop open (rare, but your theory says highly possible) quickly and she'd see no change after the first few moments of operation.

I just finished doing your no-Mosfet sim, exactly as you showed yours, with the switch and all the latest inductance changes, etc.
With the diode gone, the oscillation still dies out rather quickly...quicker than my MOSFETwith diode intact sim with the quite reasonable and highly possible gate drive impedance mismatch.  Yes, it gets absolutely whacked down with the diode in place in your switch circuit, for sure.  No argument there.

Why doesn't it get equally quickly whacked down with my MOSFET-installed model?  My theory is because the circuit is operating under normal Nyquist feedback common source mode.  Gate and drain are already 180 degrees out of phase;  add another 90 and you have the verge of instability.

The switch (non-Mosfet) model has no gate to accept feedback, no parasitic Crss or Ciss capacitances, source lead inductance, etc.  That's why the ringing tank dies out pretty quick (due to Rload losses) even without the diode and really quick with it.  There is no possible gain/feedback mechanism with the switch simulation.

As far as the proof being in the pudding, I don't see where you have posted any continuous oscillating circuit at any time, switch or MOSFET.  I looked, but did not find.  Did I miss it?  At least I did post one configuration (with impractically large gate inductance added) that rang on at a non-decaying level.

Finally, I am still at a loss to understand why you say that unless the diode is open, the Vbatt (at the point you suggest probing) can't ever go below the nominal DC battery voltage.  The only thing the diode clamps is when the actual drain itself tries to go south of the source.  Between the actual positive battery terminal and the drain itself, there are two inductors (2.5nH and 10nH) plus the load resistance.  Those nodes are relatively free to go anywhere between the peak of the first flyback spike all the way to the source voltage and a volt or two below (source "ground").  Of course they will swing below the battery positive node during the oscillations.  The body diode doesn't turn on until drain is south of source.  Nothing to do with battery positive voltage.

That's my position and I'm taking the 10% odds against your 90% confidence level the other way.  Until I'm re-educated, which is entirely possible.   ;)  Unless my position is so unreasonable or poorly stated or so hopelessly stupidly flawed that it deserves to be dismissed with appropriate ridicule, I await your corrections to my thinking at your leisure, Sir!   O0

Humbugger

   

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It's not as complicated as it may seem...
OK, I agree, bad idea.

Scrap that suggestion Rose. Just replace the MOSFET please.

Hum,

Still, you need to show your wave forms that match those of Rose. I've not seen anything close yet.

The wave forms I posted so far are quite close, and exhibit similar characteristics. More tweaking will be required to perfect them though. I'll see what I can do.

.99
   
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Poynt me to the post in question...I genuinely looked for a real good one that rang on and on, but didn't find it.  Thanks,

Homboger
   

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@Dumped:

That link is poor in terms of his description of the MOSFET internal body diode and his description of a free-wheeling (flyback) diode. He claims that the MOSFET body diode is a free-wheeling diode "built-in" for free. INCORRECT. They are not the same and do not perform the same function. A MOSFET driving an inductive load without a flyback diode across the inductor, will be hit by huge voltage spikes on its Drain pin. The body diode ONLY conducts under two conditions; 1) if VD goes negative wrt the Source, and 2) if VD exceeds the body diode (really a NPN transistor) avalanche voltage. In that latter sense, it performs a similar job to what a fb diode would do, but it clamps the voltage at the avalanche voltage (very high) vs. at a few volts higher than V+ as a fb diode would.

.99




Granted, his "practical" explanations do have some
shortcomings.  But, the body diode does in certain
switching applications tend to function as a "free
wheeling" diode.

This tendency has resulted in the re-engineering of
the body diode characteristics to achieve fast recovery
in order to enhance the reliability of the devices.

The low side MOSFET in the synchronous buck converter
is subjected to those conditions just before it is turned on
to divert the reverse current away from the body diode.

Your points are well taken.  Both conditions (reverse
body diode current and avalanche) can cause MOSFET
failure when excessive.  Particularly when the body diode
is slow recovery.


---------------------------
For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open.
   
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Granted, his "practical" explanations do have some
shortcomings.  But, the body diode does in certain
switching applications tend to function as a "free
wheeling" diode.

This tendency has resulted in the re-engineering of
the body diode characteristics to achieve fast recovery
in order to enhance the reliability of the devices.

The low side MOSFET in the synchronous buck converter
is subjected to those conditions just before it is turned on
to divert the reverse current away from the body diode.

Your points are well taken.  Both conditions (reverse
body diode current and avalanche) can cause MOSFET
failure when excessive.  Particularly when the body diode
is slow recovery.

Intelligent and well-informed points, as you well know.  This is part of why I doubt Poynt's theory about the Ainslie body diode being ruptured open.  There just isn't any opposing active device nipping at the heels a nanosecond away from total destruction in a single-MOSFET flyback/boost type circuit.  None of the scary mechanisms that synchronous and resonant switchers have to wreak havoc on body diodes that get stuck.

By the way, Dumped, you asked they key question on this matter a few posts back:  Can the body diode be thrashed yet the part still function without problems as far as gate controlling Drain-source?  Or something to that effect.  Ever get or offer an unequivocal answer?  I'd be curious; my guess would be no.

Humbugger
   

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It's not as complicated as it may seem...
Intelligent and well-informed points, as you well know.  This is part of why I doubt Poynt's theory about the Ainslie body diode being ruptured open.  There just isn't any opposing active device nipping at the heels a nanosecond away from total destruction in a single-MOSFET flyback/boost type circuit.  None of the scary mechanisms that synchronous and resonant switchers have to wreak havoc on body diodes that get stuck.

By the way, Dumped, you asked they key question on this matter a few posts back:  Can the body diode be thrashed yet the part still function without problems as far as gate controlling Drain-source?  Or something to that effect.  Ever get or offer an unequivocal answer?  I'd be curious; my guess would be no.

Humbugger

A question then;

Don't most if not all SMPS circuits utilize some form of flyback around the inductive element, thus protecting the MOSFET (and it's internal diode) from harm?

If the answer is YES, then the body diode never gets tested in the reverse direction, therefore it would not likely fail in this manner.

Rose's circuit does not utilize a flyback diode, and so the MOSFET body diode is being hammered continuously with HV spikes.

.99
   

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It's not as complicated as it may seem...
So here is a better switch circuit. I've spent some considerable time tweaking the SWITCH-based circuit to exhibit wave forms very close when compared side-by-side to the IRFPG50-based circuit. Both schematics are below and show the same "external" component values. The ringing in the "SWITCH" circuit was not tweaked to the exact same frequency, but it is close enough for demonstration purposes. Other than that, the traces follow quite closely.

The attached pictures are pretty much self explanatory, but feel free to ask about anything.

With reference to Vbat_diodeOUT.png, it would seem that with the body diode intact, the "Vbat" trace should not go anywhere near the 0V line (as shown by the green trace, which is the IRFPG50 circuit). The red trace (SWITCH CIRCUIT) however dips even further, to below 0V when the body diode is removed.

.99
   

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It's not as complicated as it may seem...
Here is a first attempt at getting the circuit to oscillate from Drain to Gate coupling.

I have tried a K up to "1" with L3 at both polarities, and the circuit will not go into a Nyquist oscillation.

.99
   

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It's not as complicated as it may seem...
I've noticed that with a 4 Ohm 20uH load, the VGS max voltage is exceeded for most MOSFETs.

This can't be good for the MOSFET either.

There are too many unknowns here. I guess we will have to wait if/until Rose provides more details. It's really hard to say what is causing that constant amplitude oscillation, but I'll bet it isn't providing any excess energy.

.99
   
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http://newlightondarkenergy.blogspot.com/2011/02/64-general-appeal.html

Desperate cries for attention from Rosemary.  What I can't figure out is exactly what she wants anyone to pay attention to.  Is there going to be a live broadcast?  A U-tube video?  A published report with comments from her experts?  A cut-and-paste from a local SA newspaper article?  How does the "internet audience" she is so eager to alert actually tune in to the big event?

I suspect it will be nothing more than some more blogs with a lot of claims and Ring-Around-the-Rosie explanations of the "proof" of her theory but no details of any actual testing or reproducible results.

Blogs 62 and 63 have convinced me once again that there is no hope she will ever understand the reality of her circuit or any circuit for that matter.  Or what simulations are about.  She seems to think that we are purposely trying to avoid showing evidence of OU from our best guess simulations of the circuit specifics (which she refuses to disclose). 

It's probably time to just sit back and wait to see what the big event actually consists of and how it is presented.  It's a "What will she think of next" kind of curiosity for me.  Nothing more.

Humbugger
   
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Poynt,

I got a real kick out of this one, showing the addition of Cds and Cgs to the model using the ideal switch.  I'm not going to comment except to say that you must have been really really tired.   ;D

Hum
   

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It's not as complicated as it may seem...
63 - the circuit to test for the simulation

Dear Reader,

I suspect I'm boring you all with all this repetition. But I need to make this point as poyntedly clear as possible. To anyone who wishes to simulate that waveform - I propose that it may be achieved if you assume the following circuit.

Two rechargeable batteries are in parallel. A resistor with a small associated inductance is in series with the drain of battery one - with a switch and with a positively biased diode where the cathode is against the positive terminal of battery 2.

A second rail leads from the positive of battery 2. A resistor with a small associated inductance is also placed in series with the drain of battery 2 - with a switch and with a positively biased diode where the cathode is against the positive terminal of battery 1.

The switches work in antiphase that only one battery can deliver energy at any one time. You can use a solid state MOSFET type with a body diode driven by a 555 or by a functions generator. I think you'd need one switch for each rail - but have no idea how you determine the 'on' 'off' time of them both. Hopefully you guys will know.

A common rail links the negative of both batteries. A shunt resistor is in series with both negative rails in order to determine rate of current flow.

I am not sure what is required to ensure that both batteries sustain a different pd to each other. I'm afraid you guys will need to sort that out.

The switches work in antiphase. If the battery 1 is closed, then battery 2 is open. And when battery 2 is closed battery 1 is open.

I'm reasonably satisfied that the waveform across either battery and the shunt resistor will correspond to the this one where the two waveforms are in antiphase to each other

If so, then I'd modestly propose that our own circuit seems to indicate that there's an alternate energy supply source.

Kindest regards,
Rosemary


Let's see if we can pull a schematic out of this description. I have suspected that there might be other components in the circuit, and from a particular test I did yesterday of placing a diode in series with the shunt, I was able to produce the steady oscillation. However, I disqualified that because I have no way of knowing if indeed there is a diode in series with the circuit somewhere, not necessarily in series with the shunt.

This is promising, thanks for the hints Rose. It would sure be nice if you could provide an actual schematic though. Surely there is nothing proprietary about this circuit? For the most part, it's right out of the datasheet.

Oh, to address your comments about all the spurious components in the gate of my simulation, well that 50 Ohm is what would be the output impedance of your function generator. This is a built in resistance that you can not see, but is indicated beside the BNC connector, if you would trouble yourself to have a look. what size is your Gate resistor? That must be added in series with the 50 Ohm to be accurate.

What is doing the swapping of those batteries? Is that a manual process that you employ using the switches you described? Why the two batteries, one source and one charging? Are you really only using 2x 12V batteries? Why do your scope shots show a battery voltage of about 48V?

I'll try to draw something up, and feel free to correct the errors.

.99
   

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It's not as complicated as it may seem...
Poynt,

I got a real kick out of this one, showing the addition of Cds and Cgs to the model using the ideal switch.  I'm not going to comment except to say that you must have been really really tired.   ;D

Hum

I'm glad you liked it Hum.

If you'd like to see a comparison of any of the wave forms with the actual IRFPG50, including the "gate" or VGS, just ask. You may be surprised at how close this comes.

Those capacitors should be there for the switch model to represent what is there in the real circuit. As a switch, this "model" seems to work quite well actually. Of course this model is not going to work if you try using this switch model as an amplifier or anything that uses the device in any other mode other than full cutoff or saturation.

Request a wave form....any wave form of the two. ;)

.99
   

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It's not as complicated as it may seem...
OK, I think I am understanding it now.

When you say 'switch" you actually mean the MOSFET.

So you are in effect running two of these circuits together? No wonder I can't properly reproduce the wave forms.  C.C

That's a bit of a departure Rose. Certainly not the device in that photo.

Ok, let's try again. I'll try to put together a schematic.

.99
« Last Edit: 2011-02-20, 20:10:56 by poynt99 »
   

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It's not as complicated as it may seem...
OK Rose.

Does this diagram properly depict your present circuit?

.99
   
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.

With couched admiration, I have quietly followed Rosemary Ainslie's public journey for many years
both here and elsewhere, and have never chosen to comment until today
as my interest has always been cursory at best.

It should not surprise anyone here to learn that this particular forum is avidly followed
and read by many in South Africa. I have recently taken the time to privately contact
the owners of the very same newspaper that Rosemary has been corresponding with,
and as well, and by sheer good fortune, a distinguished acamedic individual
(and former colleague) whom I have persuaded to attend her presentation.

I have been assured that unless this demonstration includes a schematic
with a detailed component description, Rosemary, along with her device,
will be immediately and summarily dismissed as fraudulent.
It appears that nonsense will not be brooked.

Eternal high praise or a lifetime of ridicule,
this journey comes to its just end on March 12th.

I have done my part for Rosemary.

Mookie

.
« Last Edit: 2011-02-20, 20:49:38 by Mookie »
   

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It's not as complicated as it may seem...
Thank you for this notice Mookie.

Much appreciated. ;)

If the demo goes ahead, I look forward to reading about your colleague's views.

Sounds like your colleague is starting off on the right foot by asking for some device details, good show. Not so sure he will get them though, unless Rose gives the above diagram the two thumbs up perhaps.  O0 O0

.99
   
Group: Guest
.

With couched admiration, I have quietly followed Rosemary Ainslie's public journey for many years
both here and elsewhere, and have never chosen to comment until today
as my interest has always been cursory at best.

It should not surprise anyone here to learn that this particular forum is avidly followed
and read by many in South Africa. I have recently taken the time to privately contact
the owners of the very same newspaper that Rosemary has been corresponding with,
and as well, and by sheer good fortune, a distinguished acamedic individual
(and former colleague) whom I have persuaded to attend her presentation.

I have been assured that unless this demonstration includes a schematic
with a detailed component description, Rosemary, along with her device,
will be immediately and summarily dismissed as fraudulent.
It appears that nonsense will not be brooked.

Eternal high praise or a lifetime of ridicule,
this journey comes to its just end on March 17th.

I have done my part for Rosemary.

Mookie

.


Mookie, I think her Blog says MARCH 12, 2011 and not March 17th as you posted. Is there some type of mix up on the dates for a reason?

This will certainly and hopefully put everything in its proper place.

 O0 ;D
Catlady
   
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OK Rose.

Does this diagram properly depict your present circuit?

.99

Poynt,

You should be aware of the post script Rose has added to her Blog #63;

"POST SCRIPT
It seems I've confused everyone. Abject apologies. The circuit described here is only theorised. I've never built it. Our circuit is substantially the same as it's ever been. Here I've proposed that this be tested only to see if a second supply will then generate the waveforms that we're getting. I thought it would be an articulate means of proving that our resistor/element is also an energy supply source. That speaks to the 'thinking' which is my best euphemism for 'thesis'. Apologies for the mix up. Clearly my writing is worse than ever I realised.

What I'm hoping Poynty - is that the waveforms will now move in antiphase. It'll be an interesting study. "

Hum
   
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Mookie, I think her Blog says MARCH 12, 2011 and not March 17th as you posted

My apologies for the typing error ...I have corrected my post.

Mookie
   
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Mookie.....I thought maybe you were sending the reporter on the wrong date or you were told by Rosemary to have the reporter come on the 17th. You know she is good at postponing things and also editing her own posts hours later. I guess we will see if the demonstration really happens.....Thank you for getting someone to go look at it.

 ;)
Catlady
   

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It's not as complicated as it may seem...
OK, thanks for the heads-up Hum.

 C.C

.99

btw, You've not yet requested to see any wave forms.  :-X?
   

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It's not as complicated as it may seem...
I wonder if Rose would be so kind as to show us a scope shot of VD, the Drain voltage?

Thanks in advance ;).

.99
   

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It's not as complicated as it may seem...
Quote
65 - some answers to some questions
Dear Reader,

This is just to asnwer some of those questions that have been put to me on forums.

Poynty - we did do a waveform directly across the load resistor - courtesy a very special little DSO. Here's the link. (Blog 54. I see I've incorrectly numbered two of them the same. In any event. You'll see which is which)

I appreciate the response, however, I am asking for a scope shot of VD (the MOSFET Drain voltage). This is not the same as the voltage across the load resistor. So far there are no scope shots of VD. What has been made available thus far, are scope shots across the shunt, scope shots of the battery line, and scope shots of the MOSFET Gate.

Please place the scope probe on the MOSFET Drain pin, and the gnd lead on your gnd bus. Done.

Thanks,
.99
   
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