Kapanadze Cousin - DALLY FREE ENERGY

[d3x0r]

Current is required to charge that capacitance. Isn't it ?

I know the gate is a capacitance, I use them all the time. I understand how a mosfet works the regular way, but I'm unaware if they can be used in alternate ways.


Cheers

P.S. I said "to" not "through". Just to be sure, I never stated that "current flowed through the gate". Although being a capacitor displacement current is at play. Is it not ?

..

Oh right, my bad...  The are TINY   you can turn up the current speed and see it.... but it's only a very slight time after the other one turns off
I'm also thinking that the diode is really a bad idea.  It will drag the drain down before the gate and falsely cause the mosfet to open.


There are basically 3 states after it starts oscillating.  1 side on, the other off, (the other side cannot go on with side one on), both sides off, and then reversed on/off.


If your choke is too small it won't work well.  If it is too large it won't work well.... if you capacitor between the coils is too large it won't work well

[TinselKoala]

Takes a few seconds to get to a stable state.


Thee is no current going through mosfet gates; they are tiny capacitors.... 


http://www.youtube.com/watch?v=a3H-lrMB0PY  (some guy explaining mosfets)


Transistors require current flow, mosfets require voltage (pressure)

Then why do commercial mosfet driver chips brag about the high currents they can deliver to the gates?

A mosfet gate has a certain capacitance that needs to be "filled" in order for the drain-source channel to be turned on. This requires _current_ to accomplish, just like charging up any other capacitance. For good highspeed switching of a mosfet, your driver needs to be able to supply a good amount of current, amps even, very fast.

It is true that in the DC case, a mosfet gate does not normally allow current to flow to the other terminals. If you are using your mosfet as a DC switch, then you can get away with your concept of "zero current", except of course the charging current needed to charge the gate in the first place (and the current path from gate to ground which will allow the mosfet to turn off). But in the AC case, the mosfet gate capacitance can indeed pass substantial current to the source.

http://www.youtube.com/watch?v=v6lLu7tvCZE

http://www.youtube.com/watch?v=WzUcx3haZbA

[Farmhand]

Posted by Tinsel

An exceedingly simple way to provide complementary drive signals to two mosfets from a single oscillator is to use a trifilar phase transformer with three windings of equal turn count. The oscillator drives one winding, and the two other windings are each connected to the mosfet gates and sources, but with opposite phase orientations. So with each half-cycle of the oscillator, one mosfet gets a positive pulse to its gate, turning it on, and the other gets a negative pulse, turning it off. On the next half-cycle, the opposite happens. This is the technique I used in my TinselKoil 2.0 to drive the main H-Bridge which switches the power to the coil's main primary.

Yes I see, so simple. I think you and someone else, SeaMonkey I think, told me that before, now I get it. I can see it. Excelent, I think I just got some motivation to pull out some 1200 volt IGBT's and try some stuff. hehehehe

[d3x0r]

Then why do commercial mosfet driver chips brag about the high currents they can deliver to the gates?

A mosfet gate has a certain capacitance that needs to be "filled" in order for the drain-source channel to be turned on. This requires _current_ to accomplish, just like charging up any other capacitance. For good highspeed switching of a mosfet, your driver needs to be able to supply a good amount of current, amps even, very fast.

High current to gates will be good for sharp turn on gates; but in a controlled dosage, so it's a high current (but tiny time).  Espcially if the mosfet is already stressed by a high voltage, partial on's are the worse.  The driver would be tuned for the mosfet so it has a current source (capacitor) available to quickly dump to the mosfet;  It's also got good switching to be able to pull the voltage back off the mosfet (good dump to ground).  In this circuit, the pull to ground is 50% of the duty cycle (by the other mosfet)... so the ground side isn't as critical...


But since they measure gate capacitance in (1 actually more like 30-50) pF, even at 1mA it fills in 1ns (or 30-50).


In this case almost any current is quick enough to turn on.

[d3x0r]

I've tried to work with electrical enginneers; they don't help; they say everything I'm doing is backwards... upside down?  Like using NPN instead of PNP....


I built an alternative nano pulser for this dally project
http://www.overunityresearch.com/index.php?topic=369.msg30056#msg30056


I built it using knowledge of the theory of having capacitance and RC delay.  Generates good short pulse without complexity of nand gates.