How to get through the problem related to MOSFET Switching?

[SACHIN C]

FvM,
Yes i mean #1 floating supply at the top,in which 2nd 7815 Input is connected with diode & 4.4uF/63VDC capacitor for floating, as the capacitor ground is not connected to bridge diode ground.i am getting 15VDC at the output .
Shall i need to connect diode & capacitor at output of 7815 & Bootstrap resistor is required?



Thanks & waiting for support to enhance the knowledge,:smile:

 

[FvM]

The circuit is effectively working as a bootstrap supply.

 

[SACHIN C]

FvM,
yeap,but pls guide me if there is any correction
Also pls guide me whether i need to connect diode & capacitor at output of 7815 & Bootstrap resistor is required?

Thanks & waiting for support to enhance the knowledge,:smile:

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FvM,
Also i came across the TI PDF they are recommending to use bypass capacitor across Totem-Pole of Transistor,do we need to connect & what value?
100nF will do?
Base resistor =2.2K & Base-Collector resistor=2.2k is correct?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[SACHIN C]

Dear All,
Also i came across the TI PDF they are recommending to use bypass capacitor across Push -Pull of Transistor using for driving high current MOSFET ,do we need to connect & what value?
100nF will do?
Base resistor =2.2K & Base-Collector resistor=2.2k is correct?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[SACHIN C]

Dear All,
If i am providing Drain to Source Voltage through Dimmer via Bridge Rectifier,filter Capacitor 4700uF/450VDC(2 series for half bridge)which also serves Bus Link Capacitor will it create any problem while testing?
Currently dead band is fine but,due to ringing it takes 5A also inbetween when both Gate Waveform ringing shows in phase?

Pls guide me its urgent am not able to understand,also i used snubber 22ohm/0.25W & 10nF/630VDC ,
After using Snubber the Waveform ringing & shoots reduced so shall i need to fine the Snubber?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[SACHIN C]

Dear All,
To test the half bridge at high voltage around 800VDC across Buslink capacitor,i need to connect 2 Mosfet(600VDC Capacity each) in series as a Single Mosfet for half bridge set up,
So if we connect same gate resistor for 2 Mosfet it will slow down the Mosfet,because track after gate resistor will appear like parallel?
If using two different resistor,shall i need to use same value resistor for each?

Two Mosfet in series will create another floating point for each pair?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[SACHIN C]

4-Mosfet(each 600VDC) connected in series for 800VDC maximum,the topology used is half bridge so two Mosfet form a single device for half bridge.I have checked the setup for 400VDc voltage with two Mosfet now for testing at higher voltage i am going with above mention setup.
But,the 4 Mosfet needs seperate driver or same driver used earlier to drive two Mosfet can serve the function.
Because,i observed the gate waveform for upper Mosfet was 30Vp-p(Waveform appears divided both side up & down of ground),2nd Mosfet 15Vp-p,3rd Mosfet 32Vp-p(Waveform appears divided both side up & down of ground),4th Mosfet 15vp-p gate voltage respective.

My worry is that, waveform appearing across gate -source of 1st & 3rd Mosfet which is divided up & down of ground will harm the Mosfet or not because negative voltage of n-channel?

Or that is fine waveform appearing just because of series connection?
Connecting Mosfet in a series,need extra driver ?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[Venkadesh_M]

Post any waveforms or schematics, by words will make hard to read for everyone.....

 

[SACHIN C]

hi Venkadesh_M,
pls find the attached file for circuit,in which in place of driver ic on/off gate is used for simulation point of view


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[Venkadesh_M]

It will surely work on parallel MOSFETS and I am not sure about the series mosfets, I also have some doubts on such connections...... left to answered by experts.......

Here how to turn ON the floating mosfet with the 15V....

 

[FvM]

find the attached file for circuit,in which in place of driver ic on/off gate is used for simulation point of view

Driving series connected FETs from the same gate voltage looks like a bad joke. I thought I was in a serious discussion before.

You know that highest Vgs maximum rating is +/-20 V?

 

[Venkadesh_M]

Driving series connected FETs from the same gate voltage looks like a bad joke. I thought I was in a serious discussion before.

You know that highest Vgs maximum rating is +/-20 V?

Please answere my question also..

regards
Venkadesh M.

 

[FvM]

If you refer to the question brought up by the picture in post #30, you need a floating gate driver that generates a Vgs relative to the FET source terminal. Bootstrap drivers like IR2110 are serving this purpose, but they don't work well for a single ended switch, except special cases.

 

[Venkadesh_M]

If you refer to the question brought up by the picture in post #30, you need a floating gate driver that generates a Vgs relative to the FET source terminal. Bootstrap drivers like IR2110 are serving this purpose, but they don't work well for a single ended switch, except special cases.

Is there is any way to do it without a driver IC?

 

[SACHIN C]

You know that highest Vgs maximum rating is +/-20 V?[/QUOTE]

 

[Venkadesh_M]

I mean how driver ICs floating it up without knowing the Vdd voltage?

 

[SACHIN C]

Driving series connected FETs from the same gate voltage looks like a bad joke. I thought I was in a serious discussion before.

You know that highest Vgs maximum rating is +/-20 V?

The Mosfet which we are using is of +-30V Vgs maximum rated.

Thanks & waiting for support to enhance the knowledge,:smile:

 

[FvM]

I mean how driver ICs floating it up without knowing the Vdd voltage?

Almost everything that's done in a driver IC can be done with discrete transistors and supplementing electronic parts. I just mentioned the driver ICs as an example for a driver concept. Another possible concept is using pulse transformers, but it may need pulse shaping circuits on the secondary to speed up switching. It would be my preferred method for voltage levels beyond optocoupler maximum ratings.

The Mosfet which we are using is of +-30V Vgs maximum rated.

Still a bit below 800V switched voltage you are targetting to.

Even if the parallel gates schematic is only used for low voltage simulation purposes, it doesn't help for the application because the switching behaviour is completely different from floating driver operation.

 

[Venkadesh_M]

Almost everything that's done in a driver IC can be done with discrete transistors and supplementing electronic parts. I just mentioned the driver ICs as an example for a driver concept. Another possible concept is using pulse transformers, but it may need pulse shaping circuits on the secondary to speed up switching. It would be my preferred method for voltage levels beyond optocoupler maximum ratings.


Still a bit below 800V switched voltage you are targetting to.

Yeah i also have the think of pulse transformers but I believe it is impossible to integrate it inside a IC.. so here is my problem how it is possible to level up to such a high voltage, is there any way without pulse transformer??

 

[SACHIN C]

Driving series connected FETs from the same gate voltage looks like a bad joke. I thought I was in a serious discussion before.

Discussion always remains serious from Unknowledgeable person point of view,but it is taken as joke or granted by knowledgeable person......
i don't know why it is so,because this forum is made to help Unknowledgeable person this is why we post some query which might be joke from some person point of view but that might be serious from another person point of view....

Thanks & waiting for support to enhance the knowledge,:smile:

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