Aalborg Universitet
A novel electro-thermal model for wide bandgap semiconductor based devices
Sintamarean, Nicolae Christian; Blaabjerg, Frede; Wang, Huai
Published in:
Proceedings of the 15th European Conference on Power Electronics and Applications, EPE 2013
DOI (link to publication from Publisher):
10.1109/EPE.2013.6631982
Publication date:
2013
Document Version
Early version, also known as pre-print
Link to publication from Aalborg University
Citation for published version (APA):
Sintamarean, N. C., Blaabjerg, F., & Wang, H. (2013). A novel electro-thermal model for wide bandgap
semiconductor based devices. In Proceedings of the 15th European Conference on Power Electronics and
Applications, EPE 2013 (pp. 1-10). IEEE Press. https://doi.org/10.1109/EPE.2013.6631982
General rights
Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners
and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.
- Users may download and print one copy of any publication from the public portal for the purpose of private study or research.
- You may not further distribute the material or use it for any profit-making activity or commercial gain
- You may freely distribute the URL identifying the publication in the public portal -
Take down policy
If you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access to
the work immediately and investigate your claim.
Downloaded from vbn.aau.dk on: August 09, 2022
© 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for
all other uses, in any current or future media, including reprinting/republishing this material for
advertising or promotional purposes, creating new collective works, for resale or redistribution to
servers or lists, or reuse of any copyrighted component of this work in other works.
ISBN: 978-90-75815-17-7 and 978-1-4799-0114-2
Proceedings of the European Conference on Power Electronics and Applications (EPE, ECCE Europe),
Lille, France, 3-5 September, 2013.
A Novel Electro-Thermal Model for Wide Bandgap Semiconductor Based Devices
Nicolae-Christian Sintamarean
Frede Blaabjerg
Huai Wang
Suggested Citation
N. C. Sintamarean, F. Blaabjerg, and H. Wang, "A novel electro-thermal model for wide bandgap
semiconductor based devices," in Proc. European Conference on Power Electronics and Applications
(EPE), 2013, pp. P.1-P.10.
A Novel Electro-Thermal Model for Wide Bandgap Semiconductor
Based Devices
C. Sintamarean, F. Blaabjerg, H. Wang
Department of Energy Technology, Center of Reliable Power Electronics
Aalborg University, Pontoppidanstraede 101, 9220 Denmark
E-Mail: ncs@et.aau.dk, fbl@et.aau.dk, hwa@et.aau.dk
Keywords
«Electro-Thermal Model», «Thermal coupling», «Junction-Case temperature estimation», «Thermal
Cycling», «Safe Operation Area».
Abstract
This paper propose a novel Electro-Thermal Model for the new generation of power electronics WBG-
devices (by considering the SiC MOSFET-CMF20120D from CREE), which is able to estimate the
device junction and case temperature. The Device-Model estimates the voltage drop and the switching
energies by considering the device current, the off-state blocking voltage and junction temperature
variation. Moreover, the proposed Thermal-Model is able to consider the thermal coupling within the
MOSFET and its freewheeling diode, integrated into the same package, and the influence of the
ambient temperature variation. The importance of temperature loop feedback in the estimation
accuracy of device junction and case temperature is studied. Furthermore, the Safe Operating Area
(SOA) of the SiC MOSFET is determined for 2L-VSI applications which are using sinusoidal PWM.
Thus, by considering the heatsink thermal impedance, the switching frequency and the ambient
temperature, the maximum allowed drain current is determined according to the thermal limitations of
the device. Finally, dynamic study of MOSFET junction and case temperature is also performed by
considering the variation of the ambient temperature and of the load current.
Introduction
The converter availability in the application is the most important aspect which depends on the
component reliability, efficiency and its maintenance. Therefore, highly reliable components are
required in order to minimize the downtime during the lifetime of the converter and implicitly the
maintenance costs [1],[2]. Temperature is the most important stressor which involves failure among
the converter components, especially in semiconductor devices, capacitors and PCBs [3],[4].
Therefore, the maximum electrical ratings and the thermal limitations of the semiconductor devices
plays a key role in the robustness design and reliability of power electronics converters [1].
The producers should guarantee that under all mentioned operating conditions, the case and junction
temperature of all devices do not exceed their designed physical limits otherwise, it may involve
failures of the product [5]. This problem has a higher impact for the new generation of power
converters based on WBG-devices, due to their superior Electro-Thermal properties which involves a
higher temperature operating point, compared to the Si-based devices [6]. Therefore, it is important to
carry out a thermal loading analysis of the devices, in order to determine if they are performing within
the maximum allowed physical limits, especially for the worst case scenario. This paper deals with a
novel Electro-Thermal Model which estimates the device parameters by considering also the
temperature impact, the ambient temperature variation, the thermal-coupling between MOSFET-Diode
and the heatsink thermal impedance for PWM controlled 2L-VSI.
Proposed Electro-Thermal Model
The Electro-Thermal Model deals with the analysis of both electrical and thermal performances, which
interacts with each other by the power dissipation of the electronics devices [7].
The main goal of the proposed model is to estimate the junction and case temperature for the new
generation of power electronics devices. The Electro-Thermal Model has been implemented for the
SiC diode (C4D20120A) and MOSFET (CMF20120D) from CREE in Matlab/Simulink by using M-
functions. According with Fig. 1, three types of models are involved in the electro-thermal analysis:
the device model, the power loss model and the thermal model.
Tvj_2
Tvj_3
Tvj_1
I[A]
E[mJ]
Tvj_on1
Tvj_on2
Tvj_off1
Tvj_off2
EON/Off estimation
E=f(ID,Vdc,Tj)
EON
ID_meas
VDC
EOff
VDS
TJ_est
ID[A]
VDS[V]
VDS estimation
VDS=f(ID,Tj)
Device Model
Thermal Model
Pcond_loss
Psw_loss
TJ_est
+
Ptotal_loss
fsw
Conduction
Loss
Switching
Loss
Ploss Model
ID_meas
Electro-Thermal Model
Zth=f(t)
Zth_jcMOSFET
Zth_ca
Zth[k/W]
t[s]
Zth[k/W]
t[s]
+
+
Tc_est
+
+
Ta
Blocking
Loss
IL[mA]
Vdc[V]
IL estimation
I=f(Vdc,Tj)
I[A]
E[mJ]
EON/Off estimation
E=f(ID,Vdc,Tj)
IL
VDC
PB_loss
EON
ID_meas
VDC
EOff
VDS
Pcond_loss
Psw_loss
TJ_est
fsw
Electro-Thermal Model
Device
Model
Ploss
Model
Thermal
Model
Ta
Tc_est
IL
PB_loss
ID_meas
VDC
Fig. 1: Proposed Electro-Thermal model structure for device junction and case temperature estimation
Device model
The main purpose of the Device-Model is to estimate the voltage drop across the device, the leakage
current and the switching energies as a function of the current, the off-state blocking voltage and
junction temperature. Furthermore, the estimated parameters and the switching frequency will be used
into the P
Loss
Model where, the instantaneous conduction (P
C
), blocking/leakage (P
B
) and switching
losses (P
SW
) of the device are calculated. Moreover, the total losses (P
tot_loss
) and the ambient
temperature are feed into the thermal model which estimates the device case and the junction
temperature. Finally, by providing the junction temperature as a feedback to the device model, the
temperature impact is considered. The total losses (P
tot_loss
) of the device are given by:
BSWClosstot
PPPP
_
(1)
Conduction losses
The MOSFET (diode) conduction losses are produced by the on-state drain-source (forward) voltage
drop V
DS
(V
F
) across the power device and the instantaneous value of the current I
D
(I
F
), which is
flowing through it. As shown in Fig. 3, they occur only during the on-state of the device and they are
calculated as:
TonToff
Toff
DDS
on
C
dttitv
T
tP )()(
1
)(
(2)
The current I
D
(I
F
) is known thus, the V
DS
(V
F
) has to be estimated in order to have an accurate
calculation of the conduction losses. The on-state voltage is related to the device current and the
junction temperature variations.
Shockley Model
RAC
A
C
G
Ideal Switch
RDS
D S
(a)Diode Model
(b)MOSFET model
Fig. 2: Proposed Shockley-based diode model (a) and MOSFET model (b) by considering also the
internal resistance variation
In order to achieve an accurate estimation of the diode forward voltage drop V
F
in the whole working
area, the Shockley model [8] in combination with the resistance model is proposed (Fig. 2(a)).
Therefore, the used equation for diode on-state voltage drop estimation has the following form:
FAC
S
F
ThF
IR
I
I
VnV
1ln
(3)
Where n=4 is a constant which has been determined in order to improve the estimation accuracy of the
on-state voltage V
F
. Furthermore, the thermal voltage V
Th
, the saturation current I
S
and the on state
resistance R
AC
are modeled as a function of the junction temperature T
j
. The V
Th
estimation according
with T
j
variation, is achieved by implementing (4) where k=1.38∙10
-23
J/K is the Boltzmann constant
and q=1.60∙10
-19
J/V is the elementary electron charge.
q
Tk
V
j
Th
(4)
Moreover, the saturation current I
S
is determined by considering:
refJ
TT
S
eI
(5)
Where α and β are found by applying the least square method considering the values available from
the datasheet graph for different temp curves.
Finally the on-state resistivity variation according with the temperature is obtained in (6).
0
1 RTTaR
refj
(6)
Where R
0
is the initial resistance at temperature T
ref
, a is the temperature coefficient and T
ref
is the
reference temperature for which a is mentioned.
The MOSFET is modeled as an ideal switch in series with a resistance (Fig. 2 (b)). Thus, in order to
include the on state drain source resistance variation as a function of T
j
, the equation (6) is used.
Therefore, the MOSFET on-state voltage drop estimation is performed as:
0
1 RTTaIV
refjDDS
(7)
Finally, the obtained parameters values for the mentioned devices are emphasized in Table I.
Table I: Diode and MOSFET models parameters
SiC Devices
from CREE
Parameters
On-state resistance
Saturation current
Thermal voltage
Diode
C4D20120A
019.0115.27301177.0
jAC
TR
2.25
15.273
00042.0
J
T
S
eI
19
23
106.1
1038.1
j
Th
T
V
MOSFET
CMF20120D
07356.0115.27300407.0
jDS
TR
-
-
Blocking losses
The MOSFET blocking losses are produced by the leakage current I
LM
and the off-state blocking
voltage V
DD
of the power device. They occur only during the off-state time of the device and they are
calculated using:
ToffTon
Ton
LDD
off
B
dttitv
T
tP )()(
1
)(
(8)
The leakage current depends on the blocking voltage capability and the temperature of the
semiconductor chip. The value of this current is very low, therefore, these losses can be neglected, but
for improving the model accuracy, they are considered in this paper. The same procedure is applied
when calculating the conduction and P
B
of the diode. The main difference is that for conduction losses
are considered the on-state forward voltage V
F
of the diode and its freewheeling current I
F
, and for
blocking losses are considered the leakage current of the diode I
LD
and its reverse blocking voltage V
R
.
Switching losses
When a transition from OFF to ON (or opposite) is performed, the voltage and the current do not
change instantaneously. There is a transient period, emphasized in Fig. 3, which produces the P
sw
.
These losses are related to the off-state blocking voltage V
DD
, the instantaneous drain current I
D
, the
switching frequency f
SW
and the T
j
. They are calculated using the equation (9).
SWoffonSW
fEEP )(
(9)
In equation (9) E
on
and E
off
represent the turn-on and turn-off energies. These energies are not easy to
calculate, since they depend on the dynamics of the commutation process. The estimation of the E
on
and E
off
is done by using the equations (10) and (11).
DDrr
fvri
DDDonDrronM
tt
DDSon
VQ
tt
IVEEdttitvE
fvri
2
)()(
0
(10)
