I need to turn it on for around 8.5µs maybe 7 - 10. At first I looked at optocouplers but the ones available where too slow.
Darlington types are more sensitive, but are generally slower than non-Darlington couplers.Cause you have used a simple type of it, will be rather to used the Darlington type of opto-couple whose functions much faster.
That's likely why he wants a transformer, since that can generate the gate voltage needed for a high-side N-MOSFET driver.The IR 2110 is good for 600V. But you will still need the 10 - 12 volts for the gate.
Wrong opinion. Faster or slower are depending of resistance load between base and emitter. The more meaning of resistance, the faster function.Darlington types are more sensitive, but are generally slower than non-Darlington couplers.
That's likely why he wants a transformer, since that can generate the gate voltage needed for a high-side N-MOSFET driver.
Maybe I'm thinking wrong here but, won't using a transformer still need a driver for high side? The transformer can raise the Microcontroler output to 10V but the gate still needs to stay 10V above the source voltage. And by adding the source voltage to the gate voltage and then into the transformer, won't that make the transformer primary voltage go higher and possibly blow out the microcontroller?
Well, I beg to differ with your opinion of my opinion.Wrong opinion. Faster or slower are depending of resistance load between base and emitter. The more meaning of resistance, the faster function.
Well, I beg to differ with your opinion of my opinion.
If I understand your fractured English you are now discussing about resistance between base and emitter (whatever "meaning of Resistance" means). How does that pertain to whether it's a darlington or not?
You are not understanding how the transformer is connected. It is the driver for the high side. The transformer secondary is connected between the high-side transistor source and gate. Thus the gate-source voltage will be equal to the transformer secondary voltage, independent of what the transistor source to ground voltage is.
I don't understand your concern about blowing out the microcontroller. There is no voltage fed back from the secondary to the primary in this configuration. The common-mode voltage of the secondary winding will move up and down in response to the source voltage, but that has no significant effect on the primary voltage.
The advantage here of a transformer over an opto-coupler is that a transformer can transfer energy from the primary to the secondary to generate the gate voltage, and a standard opto-coupler cannot.
And on the second page of the reference it says:Please take a more information about Darlington type here:
Again I'm probably wrong but the way I understand it is you need 10 volt on the gate to get current/voltage to flow from drain to source on the mosfet. As the source voltage starts to flow why would you need a transformer to raise the voltage on the gate? The source voltage is already raising the amount needed.
I thought you were using the transformer to raise the voltage from the Micro to the needed 10V to turn on the gate. Then if you added the source and gate voltage together it would feed back into the Micro through the transformer.
It's also my understanding that a High Side mosfet source is not connected to ground but a load. Say if switching 20V from drain to source the gate voltage would have to end up at 30V when mosfet is turned on, right? Unless a logic level mosfet is being used then you need 25V at the gate.
Are you reading/saying high side but thinking low side?
Also with out a gate driver the low amperage coming from the Micro output is going to take a longer time to switch the mosfet on causing more heat in the mosfet.
You seem to have missed the point that the transformer secondary is connected across the mosfet gate and source. Therefore, if there's 10V on the transformer secondary winding, there's 10V on the mosfet G-S; this is irrespective of the absolute voltage on any of the mosfet pins (source could be -100V or +100V, doesn't matter).All the other replies on this and other forums(even some by you) have stated that in a H/S N-fet,(non logic gate) the gate voltage must be kept 10V above the source voltage when on. If not the N-fet will be in the resistive/ohmic region of operation. Now your saying this isn't so?
Why would the secondary be collapsing.So your saying that as the EMF of the secondary collapses it won't create a current in the primary?
The micro output will be high for as long as you want the fet on (or vice versa if you reverse the transformer winding connection).Also because all of these are DC voltages the output from the Micro will have to be a PWM signal lasting the of time the O/P wanted it to be on.
No, it won't. The thing is, driving a transformer with a square wave on its primary will get a squarewave on its secondary (limited be the inductor saturation current, the power supply or the voltage/resistance of the coil) - the reason is that the current through the pri will increase linearly (i.e. ramp) with a voltage applied (until the supply hits max current or the core saturates) which will give the derivative signal on the output (dV/dt of a ramp is a constant voltage).Because the transformer won't work on straight DC.
Yes, you need a buffer, a transformer and probably a resistor and capacitor.Plus for the transfomer to be viable it takes a lot more components than a high side gate driver IC.
Wrong opinion. Faster or slower are depending of resistance load between base and emitter. The more meaning of resistance, the faster function.
Most people will not get a transformer to work either since practical circuits can not afford to reset the core. there are ways around this but most people do not know them and end up wondering why their switchers crash and burn ( every pulse that is not balanced pushes the core closer to saturation )
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