Hi all,

I am making an inverter (only resistive loads) and am using two IR2111 MOSFET drivers to control an H-Bridge. I would like to know if I am on the right path here.

My PWM switching frequency is 31.3kHz and I want to extract 60Hz after filtering(not shown in schematic). My issue is more on the design of the driver circuitry.

I am relatively new to drivers and bootstrapping but I believe my calculation is correct after looking through the datasheets.
I used 10 Ohms as the gate resistor but I am not sure if that is correct.

IR211 Driver datasheet
CSD18502KCS MOSFET datasheet

See attachment for the Schematic if the image is not clear enough

 

The only thing I think I see is that the inputs should swing from ground to 12 volts. I don't thin 5 volts is enough with 15 volt Vcc.

 

http://tahmidmc.blogspot.ca/2013/01/using-high-low-side-driver-ir2110-with.html
Max.

 

The only thing I think I see is that the inputs should swing from ground to 12 volts. I don't thin 5 volts is enough with 15 volt Vcc.

Hmm on the chart i see on the data sheet the 5V should work fine with the 15V.

http://tahmidmc.blogspot.ca/2013/01/using-high-low-side-driver-ir2110-with.html
Max.

Also on the link posted I see they are using Gate to Source Resistors. Should these always be added in?

 

I have successfully used them also the gate diodes.
Max.

 

I have successfully used them also the gate diodes.
Max.

Ah i see thank you. I'm assuming these are more for protective measures correct?

 

This was what I was looking at.

When you put the small gate resistor on the top FET it makes you use a bigger cap for the bootstrap. If the driver is always connected it is not needed.

 

Here is a bit more info on the gate source Resistors
http://tahmidmc.blogspot.ca/2012/10/magic-of-knowledge.html
When IR came out with the IR2xxx series, they were sending out populated sample boards for testing the IR2110 and a bit later sent a rev note to add the gate resistor/diode combination for added safety margin to further delay the turn-on without affecting the turn off.
It also reduces the peak current spike during reverse recovery time.
Max.

 

This was what I was looking at.

When you put the small gate resistor on the top FET it makes you use a bigger cap for the bootstrap. If the driver is always connected it is not needed.

My driver will always be connected. If that's the case then what your saying is that I probably don't even need the gate resistors?

Also for the Logic levels from the micro controller, I looked at this part of the datasheet (Vin)

 

The gate resistors are a good idea in either case. Since your IC has dead time built in you probably don't deed the diode. it's just the gate to source on the top FETs that can cause problems. If you want to use them use bigger ones than posted in the blog so they won't discharge your boost cap so quickly.
You need to use the spec I posted. The input would need to go above 9.5 volts with the 15 volt supply. You could probably add a 2n7002 to allow the input to go to 15 volts and swap the inputs.

 

You need to use the spec I posted. The input would need to go above 9.5 volts with the 15 volt supply. You could probably add a 2n7002 to allow the input to go to 15 volts and swap the inputs.

Do you think i can use the current transistors i have instead of a 2n7002? (CSD18502KCS posted in the first post). They also have an Rds(on) at 4.5V

 

It might be better to just buy a cheap transistor if you cant find a little logic level FET. Almost any NPN transistor would work, say a 2N2222. I think they are only about $0.10.
The big FET might switch a little slow from the micro.

 

I have successfully used them also the gate diodes.
Max.

CAN YOU SHARE THE MICROCONTROLLER AND CODE FOR TAHMID'S CIRCUIT

 

Any PWM code I have will be in assembly, usually for the 18F series.
Many of the 16F and the 18F series include the ECCP module which includes the half bridge/full bridge requirements.
Here is a code register values generator PGM.
http://www.micro-examples.com/public/microex-navig/doc/097-pwm-calculator.html
When using the Pic ECCP you use each of the two signals that turn on fully to switch the particular lower Mosfet of the bridge.
The top Mosfet will use the PWM input for that side, otherwise the charge pump for the 2110 will not work.
Bootstrap capacitor calc https://www.silabs.com/support/isolation-bootstrap-calculator
Max.