Exploring the Inductive Resistor Heater

[picowatt]

PW, you don't seem to understand what I am talking about. Your very argument about battery capacity is against the law of energy conservation. Your lengthy argument only seem to mislead and misinform people.


lanenal

Lanenal,

If I understand you correctly, you wish to treat a lead acid battery as if it were an ideal capacitor.

There are a lot of EV companies out there that wish this were true!  But, sadly, it is not.

There are many factors associated with most battery chemistries that affect the total energy they can deliver, or their efficiency during the charging or discharging process. 

To treat them as ideal capacitors falls very short of depicting their true nature.

PW

[lanenal]

Explain how this is done, since you claim that the mosfet CANNOT pass more than the leakage current.

Can you show me where did I claim that? You probably misunderstood me somehow. I was only saying that Greg's 100nA could be referring to leakage current. I also said that gate current depends on quite a few factors.

[lanenal]

Lanenal,

If I understand you correctly, you wish to treat a lead acid battery as if it were an ideal capacitor.

There are a lot of EV companies out there that wish this were true!  But, sadly, it is not.

There are many factors associated with most battery chemistries that affect the total energy they can deliver, or their efficiency during the charging or discharging process. 

To treat them as ideal capacitors falls very short of depicting their true nature.

PW

PW,


My initial layout of math is linear, in my PS I only briefly touched on how to treat the nonlinear case. In fact, there I put forth a capacity expansion ratio. And that's still a simplification. In its most general form, the ratio should also change with voltage, and the conclusion still holds even in this most general form as long as the ratio is always greater than 1, which is the mathematical equivalent of saying: the capacity expands with pulsing load.


lanenal

[lanenal]

What happens when the "hidden cap" is getting charged? Is the "hidden cap" between the Gate and GND, or between the Gate and Source and the Gate and Drain?

Good question, and my answer was:


The current depends on the frequency, max voltage difference, the current limiting resistor, and the capacity of the hidden cap.

[TinselKoala]

Can you show me where did I claim that? You probably misunderstood me somehow. I was only saying that Greg's 100nA could be referring to leakage current. I also said that gate current depends on quite a few factors.

Did I misunderstand, or did you? This is what Gmeast is claiming and what you apparently are defending:

Another important note here regarding the Gate Driver: The power the gate driver is drawing either in-circuit or on its own support battery is NOT supplementing the HEATING of RL. Aside from its overhead from 'just being there', as it does its 'driver thing' the increase in power draw is from doing what it has to do to source and sink the current required in charging and discharging the gate capacitance in order to maintain the required gate charge voltage whether turning it 'ON' or 'OFF'. This 'sourcing and sinking' is isolated from the rest of the MOSFET except for a leakage of 100nA ... 100 billionths of an Amp ... the published data for the UCC2732x drivers.


So, this is the reason why the gate driver's power is not considered in Exploring the Inductive Resistor heater. The ultimate goal is to have the components self-oscillate instead of relying on controlling circuitry such as a PWM and Driver arrangement ... something I've almost figured out how to do ... but not quite.

Yet as PW has described and I have shown empirically, this is manifestly NOT TRUE. The Gate-Source and Gate-Drain capacitances of the mosfet act like any other capacitances: they pass AC or pulsed DC currents. A substantial part of the power at 1.5 MHz applied to the Gate by the gate driver CAN INDEED make it "through" the gate to be dissipated in the load, or in the mosfet itself as heat.

Gmeast seems to be basing his claim that the gate driver power can be neglected as input power, on the 100 nA DC leakage current in the datasheet. He does not appear actually to have measured, to see if his assumption is correct or not, and I don't believe he could have described the situation accurately to his "consultants" who told him that no more than 100 nA could possibly be conducted across the Gate-Source or Gate-Drain capacitances.

Hopefully by now you will agree, lanenal, that this is not proper. It would seem that you must either agree that a lot of current can indeed pass, as I show in the video, and therefore Gmeast is wrong, OR.... if Gmeast is right, you need to explain how I did what I did in the video.