Output Capacitor Calculation 1ED3122MU12H

[asrikrishnagovi]

Hello, I'm using the gate driver 1ED3122MU12H for my three phase inverter application. I would like to know about the output capacitor's calculations, which I've found in the application note for the family of drivers.

My query is, how should one go about looking for the frequency responses while selecting an output capacitor based on these formulas? Thanks and Regards 

[Malleswararao]

Hi @asrikrishnagovi ,

Thanks for posting your question in the Infineon community.

I need some more information about your question as below.

Can you share which application notes you are referring to?

May I know which output capacitor calculations you are looking for?

Thanks,

Malleswararao

[asrikrishnagovi]

The formula was taken from page 8 EiceDRIVER™ 1ED31xxMU12H (1ED-X3 Compact) (infineon.com)

I'm referring to the output supply capacitors . Wanted to know how to look for appropriate frequency response of the capacitors based on the capacitance value I obtain. 

[Malleswararao]

Hi @asrikrishnagovi,

Thanks for your data.

For better understanding and time being, I will consider the same conditions which are given in the application notes to explain.

with the above data, C2 is 5.34uF without a 20% margin and

with a 20% margin C2 is 6.4uF

with this, I want to put 4.7uF capacitors 2 no's in parallel.  due to DC bias, Frequency response & temperature characteristics. please go through the below explanation.

From the above graph, it is observed that  the capacitance value is reduced by 22.7% with 15Vdc 

The capacitance change with DC BIAS (4.7uf / 2 Nos in parallel) is  2* 4.7uF* 0.773 = 7.26uF

From the above graph, it is observed that again capacitance value is reduced by 25.9% at an ambient temperature of 60degC

The capacitance change with temperature is  = 7.26uF*0.741 =  5.38uF

which is matching with our above calculation of C2.

Now we need the Peak current capability of the capacitor for that, it is necessary to calculate IGBT(FP100R12KT4) gate Peak current. As per datasheet conditions as shown below high lighted and internal gate resistance is 

with the above graph at 15kHz, resistance is 0.02ohms

Conclusion :

it is required a 4.7uF / 50V  capacitor of 2 no's in parallel to connect to the output supply for the above example case.

Accordingly, you may select a suitable capacitor for your application.

Thanks,

Malleswararao

[asrikrishnagovi]

What is the significance of this Capacitor? Is it similar to the bootstrap capacitor in case of non-isolated drivers, supplying the actual required gate charge, or is this capacitor needed as a supply filter? 

[Malleswararao · Accepted solution]

Hi @asrikrishnagovi,

yes. correct 

it is the same as a bootstrap capacitor in the case of non-isolated drivers, supplying the required gate charge.

Thanks,

Malleswararao