LT Spice says it's good so it must be some capacitance issue like the others are saying:
View attachment 259919 View attachment 259920

Thanks for the test
Regards,
Julie

 

What are the rise and fall times of your Hin signal?

 

Simple test. Change the load from 27 ohms, 1A to 50 ohms 0.5A or 100 ohm 0.25A and tell me what the turn off time is.
If the problem is the Drain current is very low, we will know soon.

Test two. There is a chance the Gate Driver is broken. Short out 24V supply. (0 ohms, 0 volts) What does the signal look like D-S of the MOSFET? Looking for rise and fall time. (fall time!)

 

In no way am I an expert, but is D2 in the correct place in the schematic in post #1? Shouldn't it be between Vb and ground, not where it is, between Vcc and Vb?

 

but is D2 in the correct place

Correct diode. See data sheet.

 

is D2 in the correct place in the schematic in post #1?

Yes. It's part of the bootstrap arrangement.

 

What are the rise and fall times of your Hin signal?

The same 100ns Ton 400ns Toff

 

Simple test. Change the load from 27 ohms, 1A to 50 ohms 0.5A or 100 ohm 0.25A and tell me what the turn off time is.
If the problem is the Drain current is very low, we will know soon.

Test two. There is a chance the Gate Driver is broken. Short out 24V supply. (0 ohms, 0 volts) What does the signal look like D-S of the MOSFET? Looking for rise and fall time. (fall time!)

I will test that

 

The same 100ns Ton 400ns Toff

Then the gate Toff time can never be faster than the 2011's Hin signal 400ns turn-off time.

 

The same 100ns Ton 400ns Toff

Then the gate Toff time can never be faster than the 2011's Hin signal 400ns turn-off time.

This depends on how the Hin signal is measured. If it is measured with one probe the two signals, G and S, will have almost the same waveform and the same 400nS.

 

The little IR2011 was designed for small to medium MOSFETs not the very large MOSFET.
The data sheet is not clear but it looks like (internally) there is 15 ohms in the IC. Rds on of the MOSFETs inside the part.
It will take some time for 15 ohms to discharge the Gate charge. I am using a Gate Driver with 1/2 ohms, off/on, and it is small for my job.

Please post a picture of you project.
ronsimpson

 

Simple test. Change the load from 27 ohms, 1A to 50 ohms 0.5A or 100 ohm 0.25A and tell me what the turn off time is.
If the problem is the Drain current is very low, we will know soon.

Test two. There is a chance the Gate Driver is broken. Short out 24V supply. (0 ohms, 0 volts) What does the signal look like D-S of the MOSFET? Looking for rise and fall time. (fall time!)

I made the test changing 27ohm by 54ohm (load of the mosfet) and you are right , the Toff is now 800µs , so the load charge on the modfet side as an impact on Cbs discharge even if I don't understand why (it seems that the discharge goes finally through the mosfet )
Thanks
JulieA

 

(it seems that the discharge goes finally through the mosfet )

There is a very large capacitor D-S inside the MOSFET. It charges up fast because the MOSFET passes the current. It discharges by the load. If you take the load to 100 ohms it will take 1.6mS. The MOSFET was designed to see a 95A load which would discharge the cap much faster.

 

There is a very large capacitor D-S inside the MOSFET. It charges up fast because the MOSFET passes the current. It discharges by the load. If you take the load to 100 ohms it will take 1.6mS. The MOSFET was designed to see a 95A load which would discharge the cap much faster.

I Understand,

Regards