Rosemary Ainslie circuit demonstration on Saturday March 12th 2011

[Rosemary Ainslie]

3rd example
Settings same as previous

This one to show that on a range of samples limited to the 'oscillation' only - then there is INVARIABLY the mean average voltage across the shunt in the negative.  But I'll redo some of these at the weekend and post them here as Harti requires.  The cycle mean result here is meaningless as the sample range does not include a full cycle.  But the principle holds.  It's always negative.  Hopefully I'll find another example.

[Rosemary Ainslie]

4th example
Settings same as previous

I'll make this my last example.  Just to highlight the typical waveforms that we were showing at the demo.  No apparent advantage - and YET.  The instantaneous wattage analysis shows an infinite COP.

I hope I've made  the demo objectives clearer now.

Kind regards,
Rosemary

[Rosemary Ainslie]

So guys.  I hope that now clarifies things.  We are well able to fine tune the circuit to get a negative mean average over the shunt.  Even at runaway wattage levels evident from the resistor element.  That wasn't what we were pointing to.  We were showing that the hidden benefit is always in the 180 degree antiphase relationship between the battery and the shunt.  Or that was the intention.  It seems to have eluded you all - and no doubt - I should have made this clearer. 

The point is this.  When that burst oscillation mode is evident - then also, there is invariably a gain - based on instantaneous wattage analysis.  So.  I hope that's clearer.

Kindest regards,
Rosemary

[Rosemary Ainslie]

Actually I've found 1. But I'll definitely post more of these at the weekend.

Regards,
Rosemary

[cHeeseburger]

And Guys, in this repeated effort to cast aspersions - as freely as confetti at a wedding - is the new claim that the VV math trace is, confused by us all, as a reflection of wattage.  I challenge ANY ONE OF THOSE MISINFORMANTS ON POYNTY'S FORUM to show any SINGLE reference by any one of us - either in the demonstration or on any posts here - or on my blog that  we have referred to that math trace representing a WATTAGE VALUE.

I assume your challenge here is open to anyone.  So...please observe the presentation video starting at 8:25 in (very near the end).  The mystery presenter clearly points to the VxV math trace and says clearly that it shows 5 Watts.  So your challenge is rather easy, Rosemary.

On a different subject, but related, is another observation that I think is worth considering.  Seems we have all in the past (self included) assumed that the current in the shunt represents the current in the battery.  To and from, as it were.  This would certainly be the case under a DC analysis, where the MOSFET gate is correctly considered an open circuit without current flow.

At a frequency of 1.5MHz and each MOSFET having (from the data sheet) 2800pF of capacitance from Gate to Source, with five in parallel that is 14nF or 0.014 microfarads  which is substantial.  We see the 1.5MHz oscillations appear on the gate voltage traces in Rosemary's scope shots. 

That means substantial RF current is circulating in the resonant LCR tank consisting of the MOSFET input capacitance, the Shunt resistance and inductance, the wiring inductances and the complex impedance of the gate drive cable, which, by the close-up photos, is not a 50 ohm coaxial cable matched to the generator and is of unknown characteristic impedance and length.  This RF current loop includes the shunt but does not include the battery.  Thus the shunt current is not the same as the battery current.

The energy circulating in this resonant circuit is what is responsible for wiggling the gate and causing the 1.5MHz oscillations and the currents involved are fairly significant.  The energy to sustain the current circulation in the gate loop is injected from the drain node of the MOSFET via the drain-gate capacitance as the drain voltage swings up and down by hundreds of volts.

Lastly, for anyone trying to figure out what the difference is between the high power and low power modes, it's quite simple:

In the low power mode, the gate drive high voltage is always kept below the 3-4V gate turn-on threshold.  When the gate drive gets close to or briefly hits the turn-on threshold, it stops the oscillations but does not result in actual turn-on of the MOSFETs.  This is why no current flows during the non-oscillating portions of the drive duty cycle.  And why the load heat drops to a few watts as supplied by just the oscillating portion of the burst envelope.

In the high power mode, the drive offset is adjusted so that during the non-oscillating half of the period the MOSFETs are actually turned on and DC current flows out of the battery through the load.  This normal DC current adds a great deal more heat to the load, so we get 44W now.  50W flows out of the battery.

These numbers are not made up.  They are there for all to see.  The scope traces show that when the MOSFET gates are driven above 3-4V there is always positive current flow.  Please don't take my word for this...check out the facts yourself.  There are no real mysteries involved.

cHeeseburger