The opto-coupler supplies +5V to Q1 gate, but there is no path visible on your diagram to keep the source at 0V. If there is no such path Q1 will not turn on.

As to your question you can use a zener to limit the gate voltage.

 

The opto-coupler supplies +5V to Q1 gate, but there is no path visible on your diagram to keep the source at 0V. If there is no such path Q1 will not turn on.

As to your question you can use a zener to limit the gate voltage.

Can you recommend a default protect scheme? what kind of zener diode to use?

 

The maximum gate voltage is 16V. Your circuit will only supply 5V, so a 10V zener, cathode to the gate and anode to the source would do the job.

Note this bit of the datasheet below. The maximum your circuit can supply to the gate is 5V but you will lose some of that in the coupler so this will restrict the maximum current through the MOSFET.

 

The MOSFET has a lot of gate charge to be handled, and a 220 ohm
R in its path, as well as Rsat_eff in the coupler output R.

What frequency/duty cycle are you driving the Gate with ?


Regards, Dana.

 

The MOSFET has a lot of gate charge to be handled, and a 220 ohm
R in its path, as well as Rsat_eff in the coupler output R.

What frequency/duty cycle are you driving the Gate with ?


Regards, Dana.

1 kHZ, but I can use up frequency

 

The maximum gate voltage is 16V. Your circuit will only supply 5V, so a 10V zener, cathode to the gate and anode to the source would do the job.

Note this bit of the datasheet below. The maximum your circuit can supply to the gate is 5V but you will lose some of that in the coupler so this will restrict the maximum current through the MOSFET.
View attachment 185781

Thank you very much!

 

If the source of Q1 is connected to ground (at present the schematic doesn't show that) then the maximum Vgs Q1 sees should be 5V. Why do you feel the need to protect Q1 with a zener or TVs between gate and source?

 

If the source of Q1 is connected to ground (at present the schematic doesn't show that) then the maximum Vgs Q1 sees should be 5V. Why do you feel the need to protect Q1 with a zener or TVs between gate and source?

Because I can connect more than 5V to the drain, for example 24V, and when the optocoupler is closed, the gate is suspended, we can burn the transistor gate

 

1 kHZ, but I can use up frequency

Your gate drive circuit not optimal so MOSFET will spend some time in
linear region dissipating a lot of power, depending on required load current
of course.

So pay attention to heat generated in MOSFET, maybe monitor its case T to
see if you are exceeding its data sheet limits.

http://www.ti.com/lit/ml/slua618a/slua618a.pdf

https://www.infineon.com/dgdl/an-937.pdf?fileId=5546d462533600a40153559ea1481181

https://toshiba.semicon-storage.com/info/docget.jsp?did=59460


Regards, Dana.

 

when the optocoupler is closed, the gate is suspended

Not sure what you mean. When the optotransistor is non-conducting the 10k resistor R1 pulls the gate voltage down to the source voltage (0V).

 

Not sure what you mean. When the optotransistor is non-conducting the 10k resistor R1 pulls the gate voltage down to the source voltage (0V).

If different ground, it is possible to destroy the transistor

 

Your gate drive circuit not optimal so MOSFET will spend some time in
linear region dissipating a lot of power, depending on required load current
of course.

So pay attention to heat generated in MOSFET, maybe monitor its case T to
see if you are exceeding its data sheet limits.

http://www.ti.com/lit/ml/slua618a/slua618a.pdf

https://www.infineon.com/dgdl/an-937.pdf?fileId=5546d462533600a40153559ea1481181

https://toshiba.semicon-storage.com/info/docget.jsp?did=59460


Regards, Dana.

Okay, I'll read it

 

If different ground, it is possible to destroy the transistor

I daresay; but what different ground and why? Surely the 5V supply needs to be referenced to the same ground as the FET source or the gate drive will be unpredictable?