TK, PW:

Thanks for that discussion.  I thought that I read a month or so ago that when Vgs was +5 volts or higher that the MOSFET was fully on.  Hence my attempt to put the pieces of the puzzle together based on Rosemary's comments.  I stand corrected.

Rosemary:

What an abysmal smug attitude you displayed for this episode.  I will have to assume that you are wrong just like TK said.  And at the same time, to your shame, you saw what this forum is all about - the exchange of ideas.

Your feeble attempt to portray us as people that don't understand power analysis was just that, a feeble attempt.  Your inability to understand how your own simple circuit works and your continued belligerence and your refusal to engage like we just saw paints a very sorry picture.

Just do the dim bulb test, that's all that you've got.

MileHigh

Thanks for this picowatt.  I was hoping we'd also get your endorsement.  Delighted to see that your expertise is indeed as lacking in credential as I expected. 

Quote from: picowatt on May 09, 2012, 02:07:19 AM
TK,

So, now what's the problem?

If channel 1 is the shunt voltage, I agree with your off screen measurements and it looks like about 320ma is flowing when the FG output is positive.  320ma across the 11R load resistor means that the load resistor is dissipating around 1.13 watts.  If Vbatt is 60 volts, there is about 56.5 volts across Q1 so Q1 is getting hot as it dissipates approx 18 watts.  Total dissipation (ignoring the small dissipation in the csr) is just under 20 watts.

PW

Rosie Posie

Now - picowatt... 'LEARN' - as you put it.  And TK - 'listen up'.  And PhiChaser - and for that matter MileHigh -  'pay attention' - if you're to benefit from my rather elementary lesson in the fundamentals of power analysis.  A duty cycle typically includes two parts.  The one part is while a switch is 'on' or  and the circuit thereby closed.  The other part is while the switch is 'off' and the circuit thereby open.  The length of 'on' and the level of 'on' is infinitely variable - as is the length of 'off' and the level of 'off'.  As it applies to the use of a MOSFET - the 'gate' leg of that transistor has an APPLIED SIGNAL.  NOTA BENE.  The gate affords a path for the flow of current from the circuit supply source from the drain leg to the source leg.  This flow of current from the function generator only induces a voltage across that gate.  In our example the current flow is from the function generator.  This then induces a voltage or signal across that gate.  It is that induced VOLTAGE that allows a flow of current from the circuit's supply source OR NOT.  When the induced voltage is positive then our IRFPG50 enables the flow of current from the circuit's battery supply source.  And correspondingly - when that induced voltage is negative then it does NOT allow the flow of current from the circuit's battery supply source.

Now - also typically and in our referenced test example - when the switch is 'OFF' - which corresponds to the period where that distinctive oscillation is apparent during the period where the negative signal is applied to Q1 - then there is some reason to 'question' the source of that current flow that induces the oscillation.  For now we will 'ignore' that part of the question and just concentrate on how TK did 'THE MATH' which you and MileHigh and PhiChaser went to some considerable lengths to endorse.

In calculating watts the object is to determine what the 'average' energy is - applied or dissipated - during any single switched cycle.  Since a cycle incorporates two periods which typically comprises an 'off' period together with an 'on' period - then the time over which that energy is applied in each cycle - needs must be 'factored in'.  Therefore correctly one computes that on period OVER TIME.  If the ON period is only ON for a fraction of the time then to compute the energy delivered or dissipated one must factor in that TIME.  Therefore, correctly - and as in that example that you and TK referenced, the ON time is for a period - of roughly 1/6th of each switching cycle.  Therefore WHEN you compute the energy delivered or dissipated - you also have to factor in that TIME period.  Therefore TAKE that plus/minus 20 WATTS that you and Leon calculated - and DIVIDE it by 6.  AND then you will see that the energy delivered by the battery is actually ONLY and at the MOST 3.33 (recurring) WATTS. 

NOW.  Leon and picowatt and MileHigh and PhiChaser.  Tell me how 3.33 watts applied to our element resistor can take the temperature over that resistor element to greater than 200 degrees centigrade - over the space of about an hour - with the temperature measured directly ON that element resistor - and OPEN TO AIR.  That it is then plunged into about half a liter of cold water - when it then rapidly raises that water temperature from ambient to upwards of 80 degrees centigrade - before it stabilises.  Then tell us how that SAME amount of energy - but at a higher applied frequency - can then take that water to boil in the space of 10 more minutes - with such a continual and rapid rise in temperature that it was considered advisable to bring that test to a conclusion.  3.33 watts would simply NOT cut it.

And guys, back to that argument where its force is applied with a cudgel dipped in tar... In order to compute the amount of energy ACTUALLY dissipated from the wattage gauged during ONLY 1/6th of the duty cycle - is GROSSLY FLAWED.  But even allowing for this - as picowatt et al are trying to promote the argument that this is the ONLY period of each duty cycle that energy is applied to the element resistor - then one needs to MULTIPLY those watts.  Effectively the watt measurement is the 'average' determined over each duty cycle period per second.  The Joules dissipated or delivered is determined as product over the entire test period.  BUT.  They are BOTH based on units PER SECOND.  But the watts measured is always qualified by the time of each duty cycle.  Therefore 20 watts needs must be DIVIDED by 6 to allow for the time during which the duty cycle is ON.

Golly.     And I'm meant to be the amateur here.

Rosie Pose

Guys, I take it that you've all seen the error.  You may recall that occasional reference that Leon aka TinselKoala, Eric, and on and on... makes regarding my claim that a watt is the measure of 1 Joule per second - and likewise a Joule is the measure of 1 watt per second?  That 'thing' that he's brought to our attention with the monotony of a hammer blow and with an identical level of mind numbing repetition?  You may recall it?  LOL.  Admittedly it was not included in EVERY post.  But probably on every PAGE of this thread.  Pretty much. More or less...  Well.  As ever - it seems that our Little Leon has been overreached himself.  He presumes to apply his own rather quixotic power analysis to just about everything within reach.  And then he parades an ENTIRELY incorrect interpretation of power related to joules or watts - whichever you please - while his entourage of vigilantes - including MilesEverSo, picowat and PhiChaser go that extra mile with him to ENDORSE that utterly erroneous example of our Little Leon doing 'THE MATH'     Well.  That makes it a 'CLEAN SWEEP'.  All that TAR that is busily being smeared by all those vigilantes?  They were wielding that tar brush with so much abandon that it's now slipped.  Right off target.  And now they've managed to blackened their own faces.  To a man.  And with it they've also blackened any hope of authority to comment on any power measurements EVER again.  If it weren't quite so sad it could even have been amusing.  In any event.  Let's hope that's made it clear for them.  The comfort is that I have a functional intelligence at my disposal - which albeit rather mundane and rather prosaic and certainly rather average - it is, nonetheless, MORE than enough.  It's not as if I'm up against the combined force of a combined high IQ.  I am only up against a combined force of 4 or 5 or 6 of them with nothing more than a gross average intelligence.  And I really mean gross.  And I really mean AVERAGE.  And I'm not sure that I mean 'intelligence' unless it's a misnomer.  LOL. 

Kindest regards,
Rosemary

Quote from: Rosemary Ainslie on May 09, 2012, 10:00:20 AM
Now - picowatt... 'LEARN' - as you put it.  And TK - 'listen up'.  And PhiChaser - and for that matter MileHigh -  'pay attention' - if you're to benefit from my rather elementary lesson in the fundamentals of power analysis.  A duty cycle typically includes two parts.  The one part is while a switch is 'on' or  and the circuit thereby closed.  The other part is while the switch is 'off' and the circuit thereby open.  The length of 'on' and the level of 'on' is infinitely variable - as is the length of 'off' and the level of 'off'.  As it applies to the use of a MOSFET - the 'gate' leg of that transistor has an APPLIED SIGNAL.  NOTA BENE.  The gate affords a path for the flow of current.  This flow of current then induces a voltage across that gate.  In our example the current flow is from the function generator.  This then induces a voltage across that gate.  It is that induced VOLTAGE that allows a flow of current from the circuit's supply source OR NOT.  When the induced voltage is positive then our IRFPG50 enables the flow of current from the circuit's supply source.  And correspondingly - when that induced voltage is negative then it does NOT allow the flow of current from the circuit supply source.

Now - also typically and in our referenced test example - when the switch is 'OFF' - which corresponds to the period where that distinctive oscillation is apparent during the period where the negative signal is applied to Q1 - then there is some reason to 'question' the source of that current flow that induces the oscillation.  For now we will 'ignore' that part of the question and just concentrate on how TK did 'THE MATH' which you and MileHigh and PhiChaser went to some considerable lengths to endorse.

In calculating watts the object is to determine what the 'average' energy is applied or dissipated during any single switched cycle.  Since a cycle incorporates two periods which typically comprises an 'off' period together with an 'on' period - then the time over which that energy is applied in each cycle - needs must be 'factored in'.  Therefore correctly one computes that on period OVER TIME.  If the ON period is only ON for a fraction of the time then to compute the energy delivered or dissipated one must factor in that TIME.  Therefore, correctly - and as in that example that you and TK referenced, the ON time is for a period - of roughly 1/6th of each switching cycle.  Therefore WHEN you compute the energy delivered or dissipated - you also have to factor in that TIME period.  Therefore TAKE that plus/minus 20 WATTS and divide it by 6.  AND then you will see that the energy delivered by the battery is actually ONLY and at the MOST 3.33 (recurring) WATTS. 

NOW.  Leon and picowatt and MileHigh and PhiChaser.  Tell me how 3.33 watts applied to our element resistor can take the temperature over that resistor element to greater than 200 degrees centigrade - over the space of about an hour - with the temperature measured directly ON that element resistor - and OPEN TO AIR.  That it is then plunged into about half a liter of cold water - when it then rapidly raises that water temperature from ambient to upwards of 80 degrees centigrade - before it stabilises.  Then tell us how that SAME amount of energy - but at a higher applied frequency - can then take that water to boil in the space of 10 more minutes - with such a continual and rapid rise in temperature that it was considered advisable to bring that test to a conclusion.  3.33 watts would simply NOT cut it.

And guys, back to that argument where the force is applied with a cudgel dipped in tar... In order to compute the amount of energy ACTUALLY dissipated from the wattage gauged during ONLY 1/6th of the duty cycle - is GROSSLY FLAWED.  But even allowing for this - as picowatt et al are trying to promote the argument that this is the ONLY period of each duty cycle that energy is applied to the element resistor - then one needs to MULTIPLY those watts.  Effectively the watt measurement is the 'average' determined over each duty cycle period.  The Joules dissipated or delivered is determined as product over the entire test period.  They are BOTH based on units PER SECOND.  But the watts measured is always qualified by the time of each duty cycle.  Therefore 20 watts needs must be DIVIDED by 6 to allow for the time during which the duty cycle is ON.

Golly.     And I'm meant to be the amateur here.

Rosie Pose

Good one Rosemary.  So your only problem was with the instantaneous measurements?  Cool. 

Looks like everyone was correct, so what's the beef?

During the portion of the cycle discussed, 20 watts or so is indeed flowing.  Now, if you want the average draw, you are indeed correct as well.  Nice to see so much agreement for a change.  I thought the reading of the 'scope was in question, you know, like the FIG 3 discussion.

So, what's the beef?  What is this 'scope shot supposed to be showing anyway?  I didn't see the discussion.

Rather lengthy post for stating the obvious, don't you thiink?

PW