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Sriram_07
Level 2
Level 2
25 sign-ins 10 likes given 10 replies posted

Hello,

In the infineon 22kw inverter reference design, there are resistors in series with Vcc and Vee (R129 and R33) of the low side gatedrivers . Can someone explain the reason why we need the resistors on the low side alone.

Thank you
R129 and R33R129 and R33

0 Likes
1 Solution

Hi,

I have checked the schematic and here is my answer for the resistor usage.

1) No, the resistor will not come in gate path because, the capacitor (C40,C39) will supply the peak current needed by the gate capacitor. So, VCC2 pin done come in path when it comes to charging to of gate capacitor and hence, 10ohm resistor will also not come in gate picture.

PFA find the attachment for more clarity.

AZIZ_HASSAN_0-1672742907832.png

Similarly, during discharge, the path will be from OUT- to VEE2 pin to bottom or lower side switch emitter and hence no additional resistor comes in picture except actual gate resistor put and internal resistor.

AZIZ_HASSAN_1-1672743071265.png

 

2) The resistor is used only in lower side switches to limit the average charge current of the capacitor (C39, C40) which provides the peak current) because they are getting supplied from same supply unlike in top switch where every switch has separate supply.

Please refer supply section in schematic to understand more.

AZIZ_HASSAN_2-1672743323898.png

 

I hope you understood.

BR,

AZIZ

 

View solution in original post

6 Replies
AZIZ_HASSAN
Moderator
Moderator
Moderator
25 likes received 100 sign-ins 50 solutions authored

Hi,

Thank you for posting at Infineon community.

I will get back to you in some time.

BR,

AZIZ

Hi,

The resistor R129 and R33 are current limiting resistors. In order to not drain the supply beyond its rating, these low value resistors are used.

BR,

AZIZ

But why are these resistors used only in low side gate drivers and ignored in the high side. And does these resistors add up to the gate resistance ?

Thank you

0 Likes

Hi,

Ya sure I will reply for that, but can you please share the name of the reference design or link to check once, whether it has any specific requirements.

BR,

AZIZ

Hi,

I have checked the schematic and here is my answer for the resistor usage.

1) No, the resistor will not come in gate path because, the capacitor (C40,C39) will supply the peak current needed by the gate capacitor. So, VCC2 pin done come in path when it comes to charging to of gate capacitor and hence, 10ohm resistor will also not come in gate picture.

PFA find the attachment for more clarity.

AZIZ_HASSAN_0-1672742907832.png

Similarly, during discharge, the path will be from OUT- to VEE2 pin to bottom or lower side switch emitter and hence no additional resistor comes in picture except actual gate resistor put and internal resistor.

AZIZ_HASSAN_1-1672743071265.png

 

2) The resistor is used only in lower side switches to limit the average charge current of the capacitor (C39, C40) which provides the peak current) because they are getting supplied from same supply unlike in top switch where every switch has separate supply.

Please refer supply section in schematic to understand more.

AZIZ_HASSAN_2-1672743323898.png

 

I hope you understood.

BR,

AZIZ