An Electrical Method for Junction Temperature Measurement of Power Semiconductor
Switches
Baker, Nick
Aalborg Universy-DENMARK
Dissertation submitted: April 6th 2016
PhD supervisor: Prof. Stig Munk-Nielsen
Aalborg University, Denmark
PhD
committee: Professor Josep Guerrero (chairman)
Aalborg University
Dr. Gernot J. Riedel
ABB Cooperate Research
Professor Philip Andrew Mawby
University of Warwick
PhD Series: Faculty of Engineering and Science, Aalborg University
Abstract
Power semiconductor switches are critical components in power electronic converters and
operate in thermally stressful environments. The junction temperature of a power semiconductor
directly influences its power loss and is intrinsically linked to numerous failure mechanisms.
Knowledge of this temperature is therefore important for optimal operation and for reliability
reasons. If the junction temperature is known during the operation of a converter, real-time
condition monitoring and active thermal control systems could be developed to improve system
reliability.
Performing direct measurements of junction temperature is difficult since the power
semiconductor is generally encapsulated inside an array of packaging materials. Alternatively,
the electrical behaviour of a semiconductor largely depends on temperature. If this relationship
is known, the electrical parameters of the device can be monitored and used to estimate the
junction temperature. These are known as Temperature Sensitive Electrical Parameters (TSEPs)
and are one way to carry out non-invasive, real-time junction temperature measurements on
fully packaged devices.
Nevertheless, successful implementation of these techniques during the normal operation of a
power semiconductor is thus far limited. Often holding back their use is the need to compensate
for inherent fluctuations caused by a constantly changing electrical environment (or alternatively
requiring interruption to normal operation to force fixed electrical conditions), and significant
uncertainty over accuracy. As a result, this PhD aims to develop new methods, or improvements
to existing methods, for junction temperature measurement via TSEPs during the operation of
power semiconductor switches.
In Chapter 1, the state-of-the-art in the topic of junction temperature measurement is introduced.
A literature review of TSEPs investigated for use in operating power semiconductor switches is
then provided. From this, several implementation issues are identified and used to formulate
technical objectives for the PhD thesis.
Chapter 2 introduces the first original contribution of the thesis. Two TSEP-based methods for
junction temperature measurement, unpublished in scientific literature before the
commencement of the PhD, are presented. The measurement principles are explained, and
experimental validation is provided on Insulated-Gate-Bipolar-Transistors (IGBTs). The
foremost advantages in the presented TSEPs are that they are measured without interruption to
normal IGBT operation, and do not require compensation for varying load current conditions.
The primary method presented is referred to as the Peak Gate Current (IGPeak) method, which is
selected for further examination in Chapter 3.
In Chapter 3, the second scientific contribution of the thesis is provided. Here, the accuracy of
the IGPeak method on IGBTs is extensively examined using direct measurements of junction
temperature from an Infra-Red camera. The validation is performed on IGBT dies with differing
geometry, as well as IGBTs in both healthy and degraded conditions. Finally, IGBTs in a
paralleled configuration are investigated. These results in terms of accuracy are compared with a
traditional TSEP method commonly found in prior art.
LINK ORIGINAL
http://vbn.aau.dk/files/240989038/PHD_Nick_Baker_E_pdf.pdf
