Have you written this?
Isn't Q(0) initial charge? I think so. Is q=0? Doubtfully.
Let's finish this!
gearheadgene!
Your nick is OK! You are learning, trying. No problem. I'm doing it too.
Pafi said:
I am at a loss how to explain things this simple. But we are talking about charging and discharging.
And in this particular instance, we are talking about discharging. So the mosfet at t=0 is fully charged and Q(t=0)=q. The end state is to have it fully discharged, Q(t=T)=0. so in the whole discussion, q is never zero. It reprsents the amount of charge that turns a mosfet fully on, and consequently it is the amount of charge the driver needs to remove from the gate to turn the mosfet (from fully on) to fully off.
Let me know what else you have an issue with.
Pafi said:
me too... 🙂
A few methods for active gate control... it is for Motors, but who knows?
http://www.ewh.ieee.org/soc/pels/Education/Tutorials/pesc01_gatedrive.pdf#search="gate drive"
That link is much better than the links you posted earlier... The second link in post 53 has very poorly drawn waveforms... very misleading in fact.
The duration of the Miller step matches the duration of the transistion in drain voltage. The author is correct is in stating that it is not in step with the current waveform... I can't agree with his windbag mathematics.
😉
The duration of the Miller step matches the duration of the transistion in drain voltage. The author is correct is in stating that it is not in step with the current waveform... I can't agree with his windbag mathematics.
😉
Right!
I will go to their site again and in the bottom left corner “Rate This Article” = 1 (Worse)
😀
I will go to their site again and in the bottom left corner “Rate This Article” = 1 (Worse)
😀
Yup, that recent link has a few neat ideas.
Don't forget though those "active" drivers (never seen a passive one) are all for motor control... much slower frequencies.
I'd imagine the ideas carry over very well, but I think the real issue is with dead time control.
Don't forget though those "active" drivers (never seen a passive one) are all for motor control... much slower frequencies.
I'd imagine the ideas carry over very well, but I think the real issue is with dead time control.
classd4sure said:
looks like you haven't tried transformer based gate driver. and a optical coupler or magnetic coupler may belong in that category as well.
yeah, the whole PWM thing came out of motor control, and it hasn't prevented its use in lowly audio as well.
fokker said:
If you'd consider those passive, I dare say you haven't looked at them close enough.
classd4sure said:
maybe you should define "passive" for us. hopefully it is different from your definition of efficiency.
TOINO said:Take a loock at page 56.
I like that one!
that in essence is gearheadgene's current-drive idea: using a current source to speed up the turn-on / turn-off of the switcher.
On further reflection, it is probably true that most drivers are indeed current-driven. Taken the discrete driver in the philipse ucd for example. The lower pnp transistor is activitated by the voltage signal (off the resistor on its b-e junction), and drains the charge off the gate. it may not be a constant current but the removal of the charge is certainly less dependant than the voltage differential between the voltage input signal (which activates the upper pnp) and Vgs.
fokker said:
Who is us? Are you performing for an audience, or do you always speak of yourself in the plural form. I'd find either very believable.
Where do you come up with "efficiency". I believe the term you were struggling to understand was application specific. Get your facts in order.
Figured out your gate driver IC yet or have you just been too busy blowing wind.
classd4sure said:
thanks for your non-answer. I believe the question for you is which part within a transformer would you consider active? the copper wires? the laminated steel core? the epoxy packaging? the shield / shoe or the screws?
alternatively if you have defined "activie" differently, as you defined "efficiency", maybe you can lay it out for us in the open so that we can follow you.
As to "efficiency", I will let you memory come to you first.
Ok, I'll pretend for a moment that it's a sincere question.
The transformer simply provides galvanic isolation. It's not a driver in itself. That's why you might say it's a transformer "based" driver.
The active aspect, is obviously what drives the transformer. Further to which, if you actually do a little reading on such a driver, you'll see there's some active circuitry in the secondary /gate side of it as well, which can be anything from a simple turn off pnp transistor, to a pass transistor+turn off.
Now, if I have to explain the same for an opto coupler you're just going to look silly, so I won't bother.
There's no such thing as a passive driver, "driver" very much implies active devices.
Good 'nuff?
The transformer simply provides galvanic isolation. It's not a driver in itself. That's why you might say it's a transformer "based" driver.
The active aspect, is obviously what drives the transformer. Further to which, if you actually do a little reading on such a driver, you'll see there's some active circuitry in the secondary /gate side of it as well, which can be anything from a simple turn off pnp transistor, to a pass transistor+turn off.
Now, if I have to explain the same for an opto coupler you're just going to look silly, so I won't bother.
There's no such thing as a passive driver, "driver" very much implies active devices.
Good 'nuff?
classd4sure said:
Wow, that's nice. so how's that active carbon film resistor or active film capacitor doing in your class D amp? they must be pretty active too, 🙂
fokker said:
Now you've just leaped well beyond the boundary of being completely absurd, and aren't worth the time.
Guys, refrain from picking on each other. It's a plain waste of time and IIRC this is not the first warning.
/Hugo
/Hugo
So initial charge is NOT zero. Previously you said that it IS zero.
There is nothing to talk about. You made a mistake. You should admit it, and step over.
No, it's not. It is not simply a current driver, but a complex controlled driver consist of two independent controlled current source, a miller plateau sensor, plus a regular gate driver, and the goal is not to speed up switching, but to reduce EMI and overshoot by reducing di/dt. This is a very useful and interesting article, but very different from gearheadgene's idea. As you can see on next page this gate charging method can be achieved without current generator, with conventional, but variable driver stage. Current generator is only an intermedial theoretical step.
Pafi said:
I thought I had said from very beginning that the case we are concerned about is to get the mosfet fully charged up or fully discharged off. so the initial state is either Q(0)=q (fully charged up), or Q(0)=0 (fully discharged off).
so depending on which case you wanted to talk about, the initial charge is one of the two.
Let me know what else you have an issue with. I am really at a loss as to how one can have an issue with that.
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