# ir2110 problems

#### shortbus

Joined Sep 30, 2009
9,755
As far as the noise problem, you have the Vss(pin13) and Com(pin2) tied together.

According to an app note on these drivers, that I can't find link to right now, they put two different commons/grounds in these chips to prevent the 'noise' problem.
Pin #2 is the mosfet ground and Pin #13 is the logic circuit ground. They are to be kept separate. If you look at the circuit on page 1 of the data sheet you'll see what I mean; http://www.irf.com/product-info/datasheets/data/ir2110.pdf

The large capacitor value for the bootstrap circuit did you calculate it that large? Here is the app note for figuring the values of the bootstrap circuit; http://www.irf.com/technical-info/appnotes/an-1123.pdf By using a PWM input on the Lin only of the 2110 you can use a smaller value of bootstrap capacitor. with the Hin a steady signal and the Lin pulsing the bootstrap capacitor will keep getting recharged.

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#### praondevou

Joined Jul 9, 2011
2,942
Pin #2 is the mosfet ground and Pin #13 is the logic circuit ground. They are to be kept separate.
That would be the better, but then you'll need separate,isolated power supplies for PIC and driver...

#### ian123

Joined Aug 24, 2011
73
As far as the noise problem, you have the Vss(pin13) and Com(pin2) tied together.

According to an app note on these drivers, that I can't find link to right now, they put two different commons/grounds in these chips to prevent the 'noise' problem.
Pin #2 is the mosfet ground and Pin #13 is the logic circuit ground. They are to be kept separate. If you look at the circuit on page 1 of the data sheet you'll see what I mean; http://www.irf.com/product-info/datasheets/data/ir2110.pdf

The large capacitor value for the bootstrap circuit did you calculate it that large? Here is the app note for figuring the values of the bootstrap circuit; http://www.irf.com/technical-info/appnotes/an-1123.pdf By using a PWM input on the Lin only of the 2110 you can use a smaller value of bootstrap capacitor. with the Hin a steady signal and the Lin pulsing the bootstrap capacitor will keep getting recharged.

in an958 it shows it tied together so i assumed that is what is done
earlier in the thread i explined how i calculated the cap size

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#### ian123

Joined Aug 24, 2011
73
Mount C7 and C8 near (maybe on top of it) their respective 2110s.

Mount a bypass capacitor of 100nF ceramic directly on the PIC from "+" to gnd.

Then try again and post the result.

Ok I have changed the position of C7 and C8 also put 100nf on pic still find that if the voltage goes passed 30v with even a 1.9 amp load u3 LOin
doesnot turn on . I have scoped the pics output pin and something is pullin it down. Since they are ttl inputs to the ir2110 i am flumuxed as to what the cause is. on further pondering since i am switching the Lo side mosfets on for 10msecs before switching Hi 1 hi side mosfet on for 2 secs
is it possible that its to slow for the driver and therefore when current is drawn it pulls down the pic through some intenal resistance??

another observation is that if it were noise wouldnt it be random and not always the same pin that is being pulled down

#### praondevou

Joined Jul 9, 2011
2,942
I don't think that something (the 2110) is pulling the PICs output down. Logic input current is in the uA range.

To be sure, put a resistor in series with the PICs output, a 100R for example.

I still think the PIC stops giving out pulses...

If you want to isolate gavlanically the PIC from the 2110 you need another power supply and optocouplers.

But first I'd try to put resistors at the PICs outputs and ferrite beads on the PIC's power supply (+ and gnd).

Just to make sure, could you post a picture of the PCB?

#### ian123

Joined Aug 24, 2011
73
i will try the resistors first .
I have posted apdf of the board in a earlier thread

#### praondevou

Joined Jul 9, 2011
2,942
i will try the resistors first .
I have posted apdf of the board in a earlier thread
Not a PCB layout print. I mean a foto. Taken with a camera.

#### ian123

Joined Aug 24, 2011
73
put esistors in but still the pic goes off after scoping the output i see that the 10msec pulse is there but not the 2 sec pulse

#### ian123

Joined Aug 24, 2011
73
sorry dont have a camera here now ill have to do that tommorrow but a word of warning the bord is in a mess right now becuae of all the changes ie caps on solder side wires changed etc

#### praondevou

Joined Jul 9, 2011
2,942
Just saw something I didn't like. see picture.

edit: thinking twice, you may try it first without cutting the trace , only connecting Vss directly to the regulator because the ground trace is also the reference for the PWM output of the PIC.

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#### praondevou

Joined Jul 9, 2011
2,942
better like this:

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#### ian123

Joined Aug 24, 2011
73
Ok guys i have fixed it by isolating the supplies tommorrow i will test at a higher voltage i am sure it will work now

thanks a mill

ps: If you want i will post the schematic and board layout as it is now, but i will do extensive tests and some refinements first

#### praondevou

Joined Jul 9, 2011
2,942
Just for curiosity . Did the modification in my last post improve anything?. It's not good to have loops like this. It's also not good to pass switched power current through logic power supply traces.

#### ian123

Joined Aug 24, 2011
73
Did the mods as you suggested but still was having the same problems so i decided to go with separate grounds then all came right

thanks guys realy appreciate the help hope i can return the favour some day

#### shortbus

Joined Sep 30, 2009
9,755
Did the mods as you suggested but still was having the same problems so i decided to go with separate grounds then all came right

thanks guys realy appreciate the help hope i can return the favour some day
See, I'm not a complete idiot, some parts are still missing.

#### ian123

Joined Aug 24, 2011
73
one last request as the voltage was increased to 100volts bang the one hiside mosfet and same lo side blew taking the ir2110 with it.

my test circuit which is just two leds with 33k resistors was connected. I did not have my load connected to it

question can the hbridge run without a load at such high voltages or is it something else i am missing?

attached is the updated schematic

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#### SgtWookie

Joined Jul 17, 2007
22,227
One really good reason for the MOSFETs going "pop!" is that you did not leave enough dead-time between turning off the high/low side and turning on the other.

As the voltage across the MOSFET drain and source increases, your effective total gate charge can increase.

#### ian123

Joined Aug 24, 2011
73
good day sgtwookie thanks for your help so far

0.5 secs should be enough??

#### ian123

Joined Aug 24, 2011
73
seems my attachment didnt go through

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#### praondevou

Joined Jul 9, 2011
2,942
0.5 secs should be enough??
500ms deadtime is actually a 1000x more than enough. You just have to make sure one MOSFET stops conducting before turning on the other one of the same leg. a few microseconds usually does it.

Is R1 and R2 10k? Or just the wrong values in the schematic?