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# Bootstrap capacitor with IRFP250N and controller IR2110

Level 1
Level 1

Hello everyone, I am currently trying to get the bootstrap capacitor value for these IRFP250N components and IR2110 driver, using the formula of dt98-2.
https://www.irf.com/technical-info/designtp/dt98-2.pdf

https://www.infineon.com/dgdl/Infineon-IR2110-DataSheet-v01_00-

https://pdf1.alldatasheet.com/datasheet-pdf/view/68504/IRF/IRFP250N.html

Here is some data I have, taken from the components:
Qg=123nC
Iqbs=230uA
Frequency=20000 Hz
Qls=5nC
ICbs= 3uA
Vcc= 15v
Vf=0.7
Vls= ¿? this value I am assuming as 2,5 but I don't know what value to put here, I have doubts to know the exact value.
Vmin=8.5

finally the result I multiply it by a factor of 15, in total it gives me a value of 3.4 uF approximately.

so my question is the following, does this bootstrap capacitor work? the other question is if I can use this value of vls or what exact value of vls should I use and what bootstrap capacitor should I implement, thanks.

1 Solution

# Re: Bootstrap capacitor with IRFP250N and controller IR2110

Moderator
Moderator

Vls is the Voltage drop across the low side FET, it is Rdson *Id of the low side mosfet, so I think 2.5V is too high here, you may use a lower data,  for exmple, 75mohm *20A=0.15V or a closer data.

3 Replies

# Re: Bootstrap capacitor with IRFP250N and controller IR2110

Moderator
Moderator

Vls is the Voltage drop across the low side FET, it is Rdson *Id of the low side mosfet, so I think 2.5V is too high here, you may use a lower data,  for exmple, 75mohm *20A=0.15V or a closer data.

# Re: Bootstrap capacitor with IRFP250N and controller IR2110

Level 1
Level 1

Dear @Daisy_T

I appreciate your quick response and collaboration, however I have a doubt with that answer that you gave, well according to the data sheet RDS(on)=0.075 Ω and I has two values or 30 or 21, but as you say that I lowered then I will take I=21
therefore
Vls=0.075 Ω*21A=1.5 A
so it would be correct as I have it, with that result obtained?
I believe that the correct value that gives you is 1.5 V, right? that gives me in the calculator.

Moderator
Moderator

Yes, it is 1.5V.