# MOSFET selection criteria

Joined Apr 11, 2016
10
Hello!
I'm designing a buck converter, Vin between 280V and 340V, and Vout=120V, where Iout minimum= 2A and Iout maximum=10A where the Fsw=50kHz.
I'm confused about selecting the mosfet transistor and its parameters.
any help in selecting the mosfet?

#### dl324

Joined Mar 30, 2015
11,263
You need to select a MOSFET with appropriate $$\small V_{DSS}$$ and $$\small V_{GSS}$$ parameters. Post a schematic if you want more specific answers.

Joined Apr 11, 2016
10
I'm designing this converter for my power electronics project. Here is the case problem in pdf

#### Attachments

• 120.5 KB Views: 7

#### dl324

Joined Mar 30, 2015
11,263
I'm designing this converter for my power electronics project. Here is the case problem in pdf
This should be in the Homework Help forum. In any other forum, someone might do the work for you and most instructors would consider that to be cheating.

In any case, draw a schematic. For homework, this site's policy is that you must show your work and members are expected to guide you to solutions; not give them to you.

Joined Apr 11, 2016
10
Thank you, its my first time to post here.
Here is my circuit diagram.
I've found the inductance and capacitance of the low pass filter.
I've calculated the inductance at the boundary of CCM/DCM, and then found the capacitance.
in the project given, current ripple is given to be 0.5 A.
1st question is should I calculate the inductance at ccm/dcm boundaries (using Vin max and Iount min), or using the given current ripple?
2nd question according to the given, is the attached mosfet good?

#### Attachments

• 19.1 KB Views: 6
• 46.3 KB Views: 5

#### dl324

Joined Mar 30, 2015
11,263
Question 2: What are the maximum drain-source/gate-source voltages and drain current that the MOSFET will be subjected to? Can the device you selected handle them?

Question 1: Your assignment description has a conflict. It says operation mode is CCM but has DCM in parenthesis.

Joined Apr 11, 2016
10
Its a typing error, the converter is working in CCM.
this is my problem that I don't know what parameters or calculations I need to select the mosfet

#### bertus

Joined Apr 5, 2008
20,653
Hello,

The attached PDF's might give you an idea on the mosfets.

Bertus

#### Attachments

• 200.6 KB Views: 7
• 108.1 KB Views: 6
• 352.7 KB Views: 5

#### dl324

Joined Mar 30, 2015
11,263
Try page 2 in this ap note.

#### Attachments

• 39.7 KB Views: 4

#### dl324

Joined Mar 30, 2015
11,263
this is my problem that I don't know what parameters or calculations I need to select the mosfet
This is the easy part. SD breakdown need to exceed your maximum in/out voltage differential by a safety margin. Your drive circuitry needs to operate the gate at an acceptable voltage.