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AkshayLaturkar
Level 1
Level 1
First question asked Welcome!

I would like to know the difference between the following two ratings (MOSFET dv/dt ruggedness and reverse body diode dv/dt ratings). Since MOSFET and body diode are parallel to each other, won't the minimum of these two ratings would be the max dv/dt?

Any reference material or help on this would be useful.

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1 Solution
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

   Thank you for posting on the Infineon community.

The rate of change of drain to source voltage over time of a MOSFET during its switching transient is indicated by its dv/dt rating.
The dv/dt affects the normal operation of a MOSFET during the following conditions,

MOSFET dv/dt ruggedness:
The below figure explains the MOSFET dv/dt transition during the switching period. A reference to the dv/dt ramp of the MOSFET drain-source voltage means the change in gate to drain voltage.

Abhilash_P_0-1676621254417.pngAbhilash_P_1-1676621308158.png


dv/dt ruggedness while considering the diode parameter:
In some of the inductive loaded circuits where MOSFETs are used in upper and lower arms    ( for example: inverters ), during reverse recovery the current flows through the intrinsic body diode in switching conditions. The diode dV/dt ruggedness is the maximum slope of the voltage waveform at which the diode could be dynamically switched. The following case discusses this diode dv/dt during reverse recovery.

Consider the following test circuit,

Abhilash_P_2-1676621397504.png

Lets assume the Mosfet on the upper leg to be Q2 and the MOSFET on the lower leg to be Q1. 
When an inductor current is flowing through the MOSFET Q2  and it turns OFF. When Q2 turns off, the inductor current flows back through the body diode of Q1 as a freewheel current IF as shown in the figure. At this time, the MOSFET Q1 has a voltage equal to the forward voltage VF across the body diode. Next, when Q2 turns on again, the current starts flowing through Q2 and the body diode of Q1 enters reverse recovery, causing its drain-source voltage to rise sharply. The rate of change of the drain-source voltage equals the dv/dt rate of the body diode during reverse recovery. Figure  shows the waveforms of the body diode current and voltage. The dv/dt of the body diode can be seen in the Vdiode waveform in the below figure. The rate of fall of diode voltage is referred to as dv/dt. 

Abhilash_P_3-1676622433721.png

Please refer the following application notes for more details:

Application note 1
Application note 2 

I hope the explanation has helped you understand the difference between the 2 dv/dt ratings. 

 

Regards,
Abhilash P

 

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Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

   Thank you for posting on the Infineon community.

The rate of change of drain to source voltage over time of a MOSFET during its switching transient is indicated by its dv/dt rating.
The dv/dt affects the normal operation of a MOSFET during the following conditions,

MOSFET dv/dt ruggedness:
The below figure explains the MOSFET dv/dt transition during the switching period. A reference to the dv/dt ramp of the MOSFET drain-source voltage means the change in gate to drain voltage.

Abhilash_P_0-1676621254417.pngAbhilash_P_1-1676621308158.png


dv/dt ruggedness while considering the diode parameter:
In some of the inductive loaded circuits where MOSFETs are used in upper and lower arms    ( for example: inverters ), during reverse recovery the current flows through the intrinsic body diode in switching conditions. The diode dV/dt ruggedness is the maximum slope of the voltage waveform at which the diode could be dynamically switched. The following case discusses this diode dv/dt during reverse recovery.

Consider the following test circuit,

Abhilash_P_2-1676621397504.png

Lets assume the Mosfet on the upper leg to be Q2 and the MOSFET on the lower leg to be Q1. 
When an inductor current is flowing through the MOSFET Q2  and it turns OFF. When Q2 turns off, the inductor current flows back through the body diode of Q1 as a freewheel current IF as shown in the figure. At this time, the MOSFET Q1 has a voltage equal to the forward voltage VF across the body diode. Next, when Q2 turns on again, the current starts flowing through Q2 and the body diode of Q1 enters reverse recovery, causing its drain-source voltage to rise sharply. The rate of change of the drain-source voltage equals the dv/dt rate of the body diode during reverse recovery. Figure  shows the waveforms of the body diode current and voltage. The dv/dt of the body diode can be seen in the Vdiode waveform in the below figure. The rate of fall of diode voltage is referred to as dv/dt. 

Abhilash_P_3-1676622433721.png

Please refer the following application notes for more details:

Application note 1
Application note 2 

I hope the explanation has helped you understand the difference between the 2 dv/dt ratings. 

 

Regards,
Abhilash P

 

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