Hand-in Assignment 1
T1, 2024 – ELEC4614
John Fletcher
5 February 2024
You are required to submit this hand-in assignment for ELEC4614. The mark from this assignment will contribute to
10% of your final class mark. You are expected to submit this hand-in assignment via the MOODLE ELEC4614 website
(not the OpenLearning site) before 3pm on Friday week 4 of term. Late submissions will not be accepted. You must
include a signed cover sheet declaring that the work submitted is your own work and this must be the first page of
the assignment. The link for this cover sheet is found in the Assignment 1 section of the OpenLearning site.
Areas where students often lose marks:
- Not reading the question properly
- Not answering the question asked
- Not clearly showing their workings
- Not following the instructions in the question
- Not understanding the theory, or lectures
- etc
ASSIGNMENT 1 [worth 20 Marks and 10% of the final mark]
This assignment is designed to assist you in understanding datasheets for power electronic devices and
identifying the important data and specifications.
During the lectures on power semiconductor devices we have discussed why MOSFETs are preferred
for low voltage (<200V) applications and that IGBTs are preferred for higher voltage applications
(>600V). We have also discussed that the Rds(on) of a MOSFET increases as the voltage rating
increases and that the increase is nonlinear.
Using a power semiconductor device manufacturer LittelFuse’s catalogue:
Power Semiconductor & IC Selection Guide Page 46 (littelfuse.com)
On page 46-48 of the catalogue there is a list of MOSFETs with voltage ratings from 100V to 300V. For
each of the devices with voltage ratings [100V, 150V, 200V, 250V, 300V] and current rating of 120A,
tabulate the Rds(on) and the conduction losses in the device assuming they operate at the current
rating of the device and have a duty ratio of 0.5 (equal times spent in the ON and the OFF condition).
Comment on why Rds(on) increases with increased voltage blocking capability.
[8 marks]
On the same page of the catalogue, select the 100V devices and tabulate the devices that have current
ratings of [75A, 120A, 140A, 170A] and include in the table Rds,on, Qg the gate capacitance, trr, and
Rthjc. What trends in these parameters can you note and what is the reason for their change?
[8 marks]
Finally, on page 31, selecting a 1200V XPT IGBT how does the Vce and the RthJC change as the current
rating of the IGBT increases? In 2-3 sentences explain why.
[4 marks]