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MOSFET (Si/SiC) Forum Discussions

User21813
Level 1
First question asked
Level 1
Hi,
We are planning to use 2 FETs with partnumber IRF7749L1TRPbF in parallel for each side in each leg in a inverter circuit. The rated current flowing through each leg is 125A (i.e. 67.5A in each FET). As our switching freq is 10KHz and duty cycle is 50% the turn on time (pulse width will be) 50us. Can this FET operate safely in this conditions?
I have checked and found from SOA graph that it can operate around 70A at 100us pulse width. Can this margin of 2.5A be safe? Can we use this FET for our application?
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1 Solution
Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator
Hi,

Safe Operating area is the area in which the MOSFET can operate without being damaged or degraded.
Now let us understand the boundary limitations of SOA curve. Following image shows a SOA curve with the different boundary limitations,

5228.attach

From the above figure, it is clear that the pulsed duration has different limits. The limit which has to be considered for this application circuit is the secondary breakdown limit. From your application, the switching frequency is 10Khz and the duty cycle is 50%.
From the time period and the duty we can arrive at the pulse width or the turn on duration of the MOSFET to be 50us. This 50us is less than the specified limit in the SOA curve for the specified MOSFET.
The SOA curve of the MOSFET is as shown below,

5229.attach

From the graph, the 50us is above the limit of SOA curve. So please try increasing the switching frequency or reducing the duty cycle for your application.

Regards,
Abhilash P

View solution in original post

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1 Reply
Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator
Hi,

Safe Operating area is the area in which the MOSFET can operate without being damaged or degraded.
Now let us understand the boundary limitations of SOA curve. Following image shows a SOA curve with the different boundary limitations,

5228.attach

From the above figure, it is clear that the pulsed duration has different limits. The limit which has to be considered for this application circuit is the secondary breakdown limit. From your application, the switching frequency is 10Khz and the duty cycle is 50%.
From the time period and the duty we can arrive at the pulse width or the turn on duration of the MOSFET to be 50us. This 50us is less than the specified limit in the SOA curve for the specified MOSFET.
The SOA curve of the MOSFET is as shown below,

5229.attach

From the graph, the 50us is above the limit of SOA curve. So please try increasing the switching frequency or reducing the duty cycle for your application.

Regards,
Abhilash P
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