The 2022 International Power Electronics Conference (IPEC-Himeji 2022 -ECCE Asia-)

Estimation of Both Junction Temperature and Load
Current of IGBTs from Output Voltage of Gate Driver
Hiromu Yamasaki, Katsuhiro Hata and Makoto Takamiya
The University of Tokyo, Tokyo, Japan
Abstract—For the online condition monitoring of IGBTs,a new estimation method of both the junction temperature(TJ) and the load current (IL) of IGBTs using a momentary
high-Z gate driving (MHZGD) from the output voltage(VOUT) of the gate driver is proposed, which can be integrated
into the gate driver ICs. TJ is estimated from VOUT difference
during and after the MHZGD period, and IL is estimatedfrom VOUT during MHZGD. In the 110 switchingmeasurements at 11 different TJ’s from 25 °C to 125 °C and
10 different IL’s from 12.5 A to 80 A for each of the three
IGBTs, TJ and IL estimation errors in a low test cost
parameter determination method are + 4.9 °C / − 8.4 °C and+ 1.1 A / − 4.3 A, respectively. In contrast, TJ and IL
estimation errors in a parameter determination method withsmall error are + 4.9 °C / − 8.1 °C and + 1.0 A / − 1.8 A,
respectively.

I.

IGBT
module

15V

V

AND

RG,INT

VCE

TJ

VGE,INT

TJ is estimated from V.
IL is estimated from VOUT,MHZ.

In

In
IG

15 V

15 V

IC
VCE

t1

0V

IL
0A

0V

(a) Conventional

t2 t3

0A

IG

0A

VGE,INT
VOUT

VGE,INTVOUTMHZGD V
0V

IL

IC

VOUT,MHZ
VOUT,CONV

0A

VCE

0V

(b) Momentary high-Z gate
driving (MHZGD)

Fig. 2. Waveforms at turn-off. (a) Conventional gate driving. (b)MHZGD[7].

Miller plateau is not equal to the internal gate-emitter
voltage (VGE,INT) due to IG (RG,INT + RG,EXT) drop, where IG
is the gate driving current, RG,INT is the internal gate
resistance of IGBT, and RG,EXT is the external gate
resistance. In MHZGD [7] shown in Fig. 2 (b), the period
from the start of turn-off to the end of the Miller plateau is
divided into three parts and defined as t1, t2, and t3. t2 andt3 must be during the Miller plateau period. In MHZGD, IG
is zero during t2. In this work, the zero IG is achieved using
the digital gate driver (DGD) [17]. During t2, VOUT is equal
to VGE,INT because of zero IG, and this VOUT is defined as
VOUT,MHZ. VOUT during t3 is defined as VOUT,CONV, and thedifference between VOUT,MHZ and VOUT,CONV is defined as
V, where V = |IG| (RG,INT + RG,EXT). Assuming that IG isconstant in this paper because of the constant currentsource based DGD [17], V is linearly dependent on TJ,

VOUT,MHZ USING

A. Momentary High-Z Gate Driving (MHZGD) to
Estimate TJ and IL
Fig. 1 shows a circuit schematic of a gate driver and an
IGBT. The target of this work is to estimate both TJ and IL
from VOUT. Fig. 2 shows waveforms of a conventional gate
driving and MHZGD [7] at turn-off of IGBT. In theconventional gate driving shown in Fig. 2 (a), VOUT at the©2022IEEJ

RG,EXT

Fig. 1. Circuit schematic of gate driver and IGBT.

INTRODUCTION

OF

IG

In

VOUT

In order to achieve reliable power electronics systems,
online condition monitoring for power devices is required
to predict power device failures. The development goals of
the online condition monitoring in this paper include: (1)estimation of both the junction temperature (TJ) and theload current (IL) without using temperature sensors andcurrent sensors, because TJ and IL are important parametersthat determine the reliability of power devices; and (2)measurement from the gate terminal of a power device thatcan be integrated into gate driver ICs. Many papers havebeen published on the estimation of TJ and/or IL [1-16],
however, there have been no papers achieving the twodevelopment goals. In [7], only IL is estimated using amomentary high-Z gate driving (MHZGD) and it isnecessary to give TJ as a known value for IL estimation. To
solve the problems, in this paper, a new estimation methodof both TJ and IL of IGBTs using MHZGD from the output
voltage (VOUT) of the gate driver is proposed.
II. MEASUREMENT
MHZGD

Gate
driverIC, IL453

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The 2022 International Power Electronics Conference (IPEC-Himeji 2022 -ECCE Asia-)

because RG,INT is linearly dependent on TJ [1]. Therefore,
in this paper, TJ is estimated from V, while IL is estimatedfrom VOUT,MHZ. The principle of estimating IL from
VOUT,MHZ is the same as [7], while TJ is not estimated andmust be known in advance in [7].

on the switching loss and VCE overshoot. Fig. 5 shows themeasured VOUT waveforms of TJ = 25 °C and 125 °C at IL= 12.5 A. With increasing TJ, VOUT,MHZ is reduced, because
the threshold voltage of IGBT is reduced. Fig. 6 shows themeasured VOUT waveforms of IL = 12.5 A to 80 A at TJ =25 °C. VOUT,MHZ increases with increasing IL. Fig. 7 shows
the overall view of measured VOUT,CONV and VOUT,MHZ
under 60 different conditions with 6 different TJ’s ranging
from 25 °C to 125 °C and 10 different IL’s ranging from
12.5 A to 80 A. V is the difference between VOUT,MHZ and
VOUT,CONV. In the next chapter, the methods for estimating
TJ and IL from V and VOUT,MHZ, respectively, will be
explained.

B. Measurement Setup
Fig. 3 shows the photo of the measurement setup of the
double pulse test of IGBT module (2MBI100VA-060-50,
600 V, 100 A) at 300V for the estimation of TJ and IL. The
DGD IC [17] drives the low side of the IGBT module. TJ
is assumed to be equal to the hot plate temperature. RG,EXT
is zero. In this paper, after the switching measurements are
performed under 110 different conditions with 11 different
TJ’s from 25 °C to 125 °C in 10 °C steps and 10 different
IL’s from 12.5 A to 80 A in 7.5 A steps for each of the three
IGBTs and VOUT waveform data are saved, the estimations
of TJ and IL from V and VOUT,MHZ are done. VOUT
waveforms are measured using the differential probe andV and VOUT,MHZ are extracted from the VOUT waveforms.
In the future, the measurement of V and VOUT,MHZ can bedone with an A/D converter, which can be integrated on
DGD IC15

VOUT [V]C. Measurement of V and VOUT,MHZ
Fig. 4 shows the measured waveforms at TJ = 25 °C and
IL = 80 A during the turn-off of IGBT. In this paper, t2 isfixed to 2 s. V and VOUT,MHZ generated by MHZGD are
clearly observed. Please note that MHZGD has no effect5
IL = 12.5 A

05Time [s]15VOUT [V]

MHZGD

80 A
72.5 A
65 A
57.5 A
50 A
42.5A
35 A
27.5 A
20 A
12.5 A5

0

VCE:50 V/divt1

VOUT,MHZ
VOUT,CONV

t2 t3

VOUT,CONV and VOUT,MHZ [V]10

IC:10 A/div

2 s/div

TJ = 25 ºC

05Time [s]10Fig. 6. Measured VOUT waveforms of IL = 12.5 A to 80 A at TJ = 25 °C.

Fig. 3. Measurement setup of double pulse test.

V

Current IL

10

0

MHZGD

10

Fig. 5. Measured VOUT waveforms of TJ = 25 °C and 125 °C at IL = 12.5 A.

IGBT module

VOUT:3 V/div

25 ˚C
125 ˚C

100

Digital gate
driver IC

Hot plate

Temperature TJ

MHZGD

9
8

∆V
7

6

Fig. 4. Measured waveforms at TJ = 25 °C and IL = 80 A during turn-off.

VOUT,MHZ
VOUT,CONV

0

10

20

Temperature TJ
25 ˚C
45 ˚C
65 ˚C
85 ˚C
105 ˚C125 ˚C

30 40 50 60 70
Load current (IL) [A]8090

Fig. 7. Measured VOUT,CONV and VOUT,MHZ under 60 different conditions with
6 different TJ’s and 10 different IL’s.

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The 2022 International Power Electronics Conference (IPEC-Himeji 2022 -ECCE Asia-)

III.

B. Parameter Determination Methods for TJ and IL
Estimation
Fig. 9 shows two parameter determination methods for
multiple IGBTs compared in this paper. Fig. 9 (a) shows a
low test cost method, where a five-point calibration is
performed for the first IGBT (IGBT1), and a one-pointcalibration is performed for the second and subsequent
IGBTs (IGBT2 and IGBT3). The details of the five-point
and the one-point calibrations will be explained later. Fig.
9 (b) shows a method with small error, where a five-pointcalibration is performed for all IGBTs. The two methods
have a trade-off in terms of the estimation error and thetest cost for the calibrations. The low test cost method has
the disadvantage of large estimation error, while themethod with small error has the disadvantage of high test
cost.
Fig. 10 (a) shows the steps for the five-point calibration
to find the values of seven parameters shown in Fig. 8. In
Step 1, VOUT waveforms under five conditions at (TJ, IL) =(25 °C, 12.5 A), (25 °C, 42.5 A), (25 °C, 80 A), (125 °C,
12.5 A), and (125 °C, 80 A) are measured. In Step 2, twoV’s are extracted from VOUT waveforms at (TJ, IL) =(25 °C, 12.5 A) and (125 °C, 12.5 A). In Step 3, a and b in
Eq. (1) are determined by the curve fitting as shown in Fig.
11 (a). In Step 4, three VOUT,MHZ’s are extracted from VOUT
waveforms at (TJ, IL) = (25 °C, 12.5 A), (25 °C, 42.5 A),
and (25 °C, 80 A). In Step 5, k(TR), VTH(TR), and α in Eqs.
(2) to (4) are determined by the curve fitting as shown in
Fig. 11 (b). In Step 6, two VOUT,MHZ’s are extracted from
VOUT waveforms at (TJ, IL) = (125 °C, 12.5 A) and (125 °C,
80 A). In Step 7, k(TJ = 125 °C) and VTH(TJ = 125 °C) in
Eqs. (3) to (4) are determined by the curve fitting as shownin Fig. 11 (c). In Step 8, β and γ are determined by Eqs. (3)and (4) as shown in Figs. 11 (d) and (e), respectively,
which completes the five-point calibration.
Fig. 10 (b) shows the steps for the one-point calibration
to find the values of two parameters (b and VTH(TR)). In the
one-point calibration, five parameters (a, α, β, γ, and k(TR))
of IGBT1 are reused to other IGBTs to reduce the test cost.
The intention of the one-point calibration is to express the

TJ AND IL ESTIMATIONS FROM V AND VOUT,MHZ

A. Overview of Proposed TJ and IL Estimation
Fig. 8 shows an overview of the proposed TJ and IL
estimation from V and VOUT,MHZ. When the measured V
and VOUT,MHZ are given, TJ is estimated using Eq. (1) andIL is estimated using Eqs. (2) to (4), where k(TJ) is the TJdependent constant, VTH(TJ) is the TJ-dependent thresholdvoltage of IGBT, TR is the room temperature (25 °C)
whose unit is absolute temperature, k(TR) is k(TJ) at TJ =TR, VTH(TR) is VTH(TJ) at TJ = TR, and a, b, α, β, and γ areconstants. Comparing [7] with this paper, Eqs. (2) to (4)are identical to [7], and only Eq. (1) is newly added in thispaper. The values of seven parameters (a, b, α, β, γ, k(TR),and VTH(TR)) are determined by the calibration
measurements.

Input: Measured ∆V and VOUT,MHZ∆V  aTJ  b

I L k (TJ ) VOUT,MHZ − VTH (TJ )
=− TJ 
k (TJ ) = k (TR )   TR 
VTH (TJ=) VTH (TR ) −  (TJ − TR )



(1)
(2)
(3)
(4)

7 parameters ( a , b ,  ,  ,  , k(TR ) , VTH (TR ) )Output: Estimated TJ and IL
Fig. 8. Overview of proposed TJ and I L estimation from V and
VOUT,MHZ.

IGBT1

Determine 7 parameterswith five-point calibration(Fig. 12)IGBT2Determine 2 parameterswith one-point calibration(5 parameters are reused
from IGBT1.)(Fig. 13)

Step 1 Measure VOUT waveforms under 5 conditions: (TJ, IL) = (25˚C, 12.5 A),(25˚C, 42.5 A), (25˚C, 80 A), (125˚C, 12.5 A), (125˚C, 80 A)

IGBT2Determine 7 parameterswith five-point calibration(Fig. 15)

Step 2 Extract ∆V ’s from VOUT waveforms at (25˚C, 12.5 A), (125˚C, 12.5 A)

Step 3 Derive a and b by curve fitting (Fig. 11(a))
Step 4 Extract VOUT,MHZ’s VOUT waveforms at (25˚C, 12.5 A), (25˚C, 42.5 A),(25˚C, 80 A)

Step 5 Derive k(TR), VTH(TR), and α (Fig. 11(b))

IGBT3Determine 2 parameterswith one-point calibration(5 parameters are reused
from IGBT1.)(Fig. 14)

Step 6 Extract VOUT,MHZ’s from VOUT waveforms at (125˚C, 12.5 A), (125˚C, 80 A)

IGBT3

Step 7 Derive k(TJ=125˚C) and VTH(TJ=125˚C) (Fig. 11(c))

Determine 7 parameterswith five-point calibration(Fig. 16)

Step 8 Derive  and  (Fig. 11(d)(e))(a)

Step 1 Measure VOUT waveform at (TJ, IL) = (25˚C, 12.5 A)
Step 2 Extract VOUT,MHZ and ∆V from VOUT waveform(a) Low test cost method
Low test cost
Large estimation error(b) Method with small error

Step 3 Derive b and VTH(TR) by curve fitting

Small estimation error
High test cost(b)
Fig. 10. Steps for calibrations. (a) Five-point calibration. (b) One-pointcalibration.

Fig. 9. Two parameter determination methods compared in this paper.
(a) Low test cost method. (b) Method with small error.

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The 2022 International Power Electronics Conference (IPEC-Himeji 2022 -ECCE Asia-)

1.12

1.12

1.04

1.06

b = 949[mV]1.00∆V  aTJ  b∆V [V]∆V [V]

1.08∆V  aTJ  b

(a)

0.96
0.92

Measured
Estimated

Slope= a = 1.12[mV/˚C]

25

103

100
125
50
75
Junction temperature (TJ) [˚C]

150

IGBT1
5-point calib.

0.94

0

25

TJ=TR=25˚CSlope= 101(b)Measured

100
0.1

1
VOUT,MHZ – VTH(TR) [V]103
Load current (IL) [A]

TJ=125˚C

10Current IL

5



0

10.0

VOUT, MHZ [V]Measured102

Measured

−

9.0
8.5
8.0

Slope= - = -1.18

6.5

125˚C

300

400

TJ [K]

20500

IL estimation error [A](Estimated IL – Actual IL)

25˚C

600

Measured

VTH (TJ=) VTH (TR ) −  (TJ − TR )VTH(TJ) [V ]Slope= -  = -6.63[mV/K]

10

0
200

125˚C

25˚C
300

TJ [K]

400



0

500

Fig. 11. Example of parameter determination in IGBT1. (a) Step 3 inFig. 10 (a). (b) Step 5 in Fig. 10 (a). (c) Step 7 in Fig. 10 (a). (d) and (e)Step 8 in Fig. 10 (a).

1020

30 40 50 60 70
Load current (IL) [A]

80

90

(c)

Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C+0.6 A

0

-1
0

(e)

25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚CI L k (TJ ) VOUT,MHZ − VTH (TJ )
=

1

(d)
200

IGBT1
5-point calib.

7.5

101

100

Temperature TJ

7.0

k(TJ) [A/V ]T k (TJ ) = k (TR )  J 
 TR 

10

100
125
150
25
50
75
Actual junction temperature (TJ) [˚C](b)Measured
Estimated

9.5

1
VOUT,MHZ – VTH(TJ) [V]+4.9˚C−6.2˚C

10

(c)

150

0

-10

I L k (TJ ) VOUT,MHZ − VTH (TJ )
=
2

100
0.1

IGBT1
5-point calib.

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A-5Derive k(TJ=125˚C)
and VTH(TJ=125˚C)

101

100
125
50
75
Junction temperature (TJ) [˚C]

(a)

10



TJ estimation error [˚C]
(Estimated TJ – Actual TJ)

Load current (IL) [A]

I L  k(TR ) VOUT,MHZ VTH (TR )102

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

1.00

Measured0

Current IL

10−0.7 A
IGBT1
5-point calib.
20 30 40 50 60 70 80 90
Actual load current (IL) [A](d)Fig. 12. Results of IGBT1 using five-point calibration, which issame for both methods. (a) Measured and estimated TJ dependenceof V at 10 different IL’s. (b) TJ estimation error. (c) Measured andestimated IL dependence of VOUT,MHZ at 11 different TJ’s. (d) I L
estimation error.

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1.12

1.12
Measured
Estimated

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

1.00

0.94

IGBT2
1-point calib.
0

25

100
125
50
75
Junction temperature (TJ) [˚C]

TJ estimation error [˚C]
(Estimated TJ – Actual TJ)

5

L

0.94

150

IGBT2
1-point calib.

+3.9˚C−7.9˚C
0

10.0

5

25

100
125
50
75
Junction temperature (TJ) [˚C]

150

(a)

L

IGBT3
1-point calib.
+3.1˚C

0

8.5

IGBT2
1-point calib.

7.5
7.0

VOUT, MHZ [V]Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C



0

3
2
1

10

Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C20

30 40 50 60 70
Load current (IL) [A](c)80

Temperature TJ

8.5
8.0

IGBT3
1-point calib.

7.5

6.5

90

+1.1 A

25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚CI L k (TJ ) VOUT,MHZ − VTH (TJ )
=



0

5

IGBT2
1-point calib.

0

4
3
2
1

10

20

30 40 50 60 70
Load current (IL) [A]
(c)

80

90

Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C

IGBT3
1-point calib.
+0.8 A

0

-1

-1

-2

-2

-3
0

9.0

7.0

I L k (TJ ) VOUT,MHZ − VTH (TJ )
=−8.4˚C
100
125
150
25
50
75
Actual junction temperature (TJ) [˚C](b)Measured
Estimated

9.5

9.0

8.0

0

10.0

IL estimation error [A](Estimated IL – Actual IL)

VOUT, MHZ [V]012.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

-10

100
125
150
25
50
75
Actual junction temperature (TJ) [˚C](b)Measured
Estimated

9.5

IL estimation error [A](Estimated IL – Actual IL)

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

-5

-5

6.5

Current IL

IGBT3
1-point calib.

10 Current I

0-10∆V  aTJ  b

1.00

(a)

10 Current I
12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

1.06

Current IL∆V [V]∆V [V]∆V  aTJ  b

TJ estimation error [˚C]
(Estimated TJ – Actual TJ)

1.06

Measured
Estimated-3−2.0 A10

20 30 40 50 60 70
Actual load current (IL) [A]

80

-4
-5
0

90

−4.3 A10

20 30 40 50 60 70
Actual load current (IL) [A]

80

90

(d)

(d)

Fig. 13. Results of IGBT2 using one-point calibration in low test
cost method. (a) Measured and estimated TJ dependence of V at
10 different IL’s. (b) TJ estimation error. (c) Measured andestimated IL dependence of VOUT,MHZ at 11 different TJ’s. (d) I L
estimation error.

Fig. 14. Results of IGBT3 using one-point calibration in low test
cost method. (a) Measured and estimated TJ dependence of V at
10 different IL’s. (b) TJ estimation error. (c) Measured andestimated IL dependence of VOUT,MHZ at 11 different TJ’s. (d) I L
estimation error.

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1.12

1.12

Measured
Estimated

Measured
Estimated∆V [V]∆V  aTJ  b

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

1.00

0.94

IGBT2
5-point calib.
0

100
125
50
75
Junction temperature (TJ) [˚C]

0.94

150

IGBT2
5-point calib.
+2.8˚C0−8.1˚C
0

10.0

100
125
50
75
Junction temperature (TJ) [˚C]

150

(a)
Current IL

5

IGBT3
5-point calib.
+3.3˚C

0

8.0

IGBT2
5-point calib.

VOUT, MHZ [V]

8.5

7.0

25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C



2
1

10

20

30 40 50 60 70
Load current (IL) [A]80

Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C

IGBT2
5-point calib.

Temperature TJ

8.5
8.0

IGBT3
5-point calib.

7.5

(c)

+1.0 A

25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚CI L k (TJ ) VOUT,MHZ − VTH (TJ )
=



0

2

0

1

10

20

30 40 50 60 70
Load current (IL) [A]

80

90

(c)
Temperature TJ
25 ˚C
35 ˚C
45 ˚C
55 ˚C
65 ˚C
75 ˚C
85 ˚C
95 ˚C
105 ˚C115 ˚C125 ˚C

IGBT3
5-point calib.

+0.6 A

0

-1

-1
-2
0

9.0

6.5

90

100
125
150
25
50
75
Actual junction temperature (TJ) [˚C](b)Measured
Estimated

7.0

I L k (TJ ) VOUT,MHZ − VTH (TJ )
=
0

0

9.5
Temperature TJ

7.5−7.0˚C

10.0

IL estimation error [A](Estimated IL – Actual IL)

VOUT, MHZ [V]

100
125
150
25
50
75
Actual junction temperature (TJ) [˚C]
(b)

9.0

IL estimation error [A](Estimated IL – Actual IL)

25

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A-10Measured
Estimated

9.5

6.5

12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A

-5

-5

-10

0

10

TJ estimation error [˚C]
(Estimated TJ – Actual TJ)

5

Current IL

IGBT3
5-point calib.

Current IL
12.5 A
20 A
27.5 A
35 A
42.5 A
50 A
57.5 A
65 A
72.5 A
80 A∆V  aTJ  b

1.00

(a)

10
TJ estimation error [˚C]
(Estimated TJ – Actual TJ)

25

1.06

Current IL∆V [V]

1.06−1.4 A10

20 30 40 50 60 70
Actual load current (IL) [A]

80

-2
0

90

−1.8 A10

20 30 40 50 60 70
Actual load current (IL) [A]

80

90

(d)

(d)

Fig. 15. Results of IGBT2 using five-point calibration in methodwith small error. (a) Measured and estimated TJ dependence of V
at 10 different IL’s. (b) TJ estimation error. (c) Measured andestimated IL dependence of VOUT,MHZ at 11 different TJ’s. (d) I L
estimation error.

Fig. 16. Results of IGBT3 using five-point calibration in methodwith small error. (a) Measured and estimated TJ dependence of V
at 10 different IL’s. (b) TJ estimation error. (c) Measured andestimated IL dependence of VOUT,MHZ at 11 different TJ’s. (d) I L
estimation error.

458
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Table I Measured conditions and calibrated parameters for three IGBTs. (a) Low test cost method. (b) Method with small error.
Measuredconditions(TJ, IL)

SampleCalibrated parameters(25˚C, 12.5A),(25˚C, 42.5A),(25˚C, 80A),(125˚C, 12.5A),(125˚C, 80A)

IGBT1

, , VTH(TR), k(TR), , ,(25˚C, 12.5A)

Parameters[mV/˚C][mV]

VTH(TR) [V]

949

7.01

1.12
IGBT2

, VTH(TR)

938

7.16

IGBT3

, VTH(TR)

947

7.16

k(TR) [A/V]



17.2

1.57

[mV/K]

1.18

6.63

(a)
Measuredconditions(TJ, IL)(25˚C, 12.5A),(25˚C, 42.5A),(25˚C, 80A),(125˚C, 12.5A),(125˚C, 80A)

Parameters

SampleCalibrated parameters

IGBT1
IGBT2
IGBT3

[mV/˚C][mV]

VTH(TR) [V]k(TR) [A/V][mV/K], , VTH(TR), k(TR), , ,

1.12

949

7.01

17.2

1.57

1.18

6.63

, , VTH(TR), k(TR), , ,

1.13

938

7.12

15.9

1.62

1.30

7.57

, , VTH(TR), k(TR), , ,

1.06

948

7.08

14.9

1.67

1.27

7.78

(b)
Table II Summaries of TJ and IL estimation errors. (a) Low test cost method. (b) Method with small error.
TJ estimation error [℃
℃]
Max
Min
Max-MinIL estimation error [A]Max
Min
Max-Min5-point

+4.9

-6.2

11.1

+0.6

-0.7

1.3

1-point

+3.9

-7.9

11.8

+1.1

-2.0

3.1

1-point

+3.1

-8.4

11.5

+0.8

-4.3

5.1

+4.9

-8.4

13.3

+1.1

-4.3

5.4

SampleCalibration
method

IGBT1
IGBT2
IGBT3
IGBT1-IGBT3(a)
TJ estimation error [℃
℃]
Max
Min
Max-MinIL estimation error [A]Max
Min
Max-Min5-point

+4.9

-6.2

11.1

+0.6

-0.7

1.3

IGBT2

5-point

+2.8

-8.1

10.9

+1.0

-1.4

2.4

IGBT3

5-point

+3.3

-7.0

10.3

+0.6

-1.8

2.4

+4.9

-8.1

13.0

+1.0

-1.8

2.8

SampleCalibration
methodIGBT1

IGBT1-IGBT3(b)variation of each IGBT in terms of b and VTH(TR). In Step
1, a VOUT waveform at (TJ, IL) = (25 °C, 12.5 A) is
measured. In Step 2, b and VTH(TR) in Eqs. (1) and (4) aredetermined by the curve fitting.
Tables I (a) and (b) show the measured conditions andthe calibrated parameters obtained by the low test cost
method (Fig. 9 (a)) and the method with small error (Fig. 9(b)), respectively, for three IGBTs (IGBT1 to IGBT3). In
the low test cost method (Table I (a)), the five parameters(a, α, β, γ, and k(TR)) of IGBT1 are reused to IGBT2 and
IGBT3 to reduce the test cost.

IGBT2 using the one-point calibration in the low test cost
method. Fig. 14 shows the results of IGBT3 using the onepoint calibration in the low test cost method. Fig. 15 shows
the results of IGBT2 using the five-point calibration in themethod with small error. Fig. 16 shows the results of
IGBT3 using the five-point calibration in the method withsmall error.
The details of Figs. 12 to 16 are explained using Fig. 12
as a representative example. Fig. 12 (a) shows themeasured and estimated TJ dependence of V at 10
different IL’s. The estimated curve is calculated using Eq.
(1) and Table I (a). V increases with increasing TJ
because of increasing RG,INT. V’s are in the range of 0.96
V to 1.10 V, which is reasonably explained by |IG| RG,INT =108 mA × 9 Ω = 0.972 V. Fig. 12 (b) shows the TJ
estimation error in Fig. 12 (a). Please note that TJ
estimation errors at (TJ, IL) = (25 °C, 12.5 A) and (125 °C,
12.5 A) are 0 °C, because the calibration of a and b is doneat (TJ, IL) = (25 °C, 12.5 A) and (125 °C, 12.5 A). TJ
estimation error in the range of 25 °C to 125 °C and IL =C. TJ and IL Estimation Results
As shown in Fig. 9, Figs. 12 to 16 show TJ and IL
estimation results in IGBT1 to IGBT3. Figs. 12 to 14 show
TJ and IL estimation results using the low test cost method,while Figs. 12, 15, and 16 show TJ and IL estimation results
using the method with small error. Fig. 12 shows theresults of IGBT1 using the five-point calibration, which isthe same for both methods. Fig. 13 shows the results of459
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The 2022 International Power Electronics Conference (IPEC-Himeji 2022 -ECCE Asia-)

REFERENCES

12.5 A to 80 A is within + 4.9 °C / − 6.2 °C. Fig. 12 (c)shows the measured and estimated IL dependence of
VOUT,MHZ at 11 different TJ’s. The estimated curves arecalculated using Eqs. (2) to (4) and Table I (a). Fig. 12 (d)shows the IL estimation error in Fig. 12 (c). IL estimation
error in the range of 12.5 A to 80 A and TJ = 25 °C to
125 °C is within + 0.6 A / − 0.7 A.
Tables II (a) and (b) show summaries of TJ and IL
estimation errors in the low test cost method (Fig. 9 (a)) andthe method with small error (Fig. 9 (b)), respectively, for
IGBT1 to IGBT3. Comparing the estimation errors using
the two methods, the TJ and IL estimation errors (+ 4.9 °C /− 8.4 °C and + 1.1 A / − 4.3 A) of the low test cost method
is larger those (+ 4.9 °C / − 8.1 °C and + 1.0 A / − 1.8 A)of the method with small error, as expected. The methodwith small error, however, requires five measurements at TJ= 25 °C and 125 °C for each IGBT as shown in Step 1 inFig. 10 (a), which is not practical, because the test cost is
too high. Therefore, in conclusion, the low test cost method
is recommended in this paper.

[1]

D. Comparison with Previous Works
Table III shows a comparison table of TJ and/or IL
estimation for the condition monitoring. This paper is thefirst work to successfully estimate both TJ and IL from themeasured values obtained from the gate terminal.
Table III Comparison table of TJ and/or IL estimation.
Reference

[1]

[2]

[5]

[6]

[7]

This work

Estimated value

TJ

TJ

IL

TJ, ILIL

TJ, IL

IG

VEE’

VOUT

VOUT

Measured value Peak of IG VGE,EXT

Measured value
from gate
Yes
Yes
Yes
No
Yes
terminal
TJ range [˚C] 20 − 140* 10 − 100* 25 − 75 25 − 105* 25 − 125
IL range [A]50 − 1200* 15 − 325* 1 − 50 100 − 550*

Max estimation
error

N.A.

7.5 ˚C

Additional
circuits

Peak hold

None

Yes
25 − 125

5 − 8012.5 − 80

7.7 %8.4 ˚C, 4.3 A(1)8.1 ˚C, 1.8 A(2)Plateau Peak hold,Switchdetector integrator

Constant
current DGD

0.5 A

N.A.

*Obtained from graph, (1) Low test cost method, (2) Method with small error

IV.

CONCLUSIONSFor the online condition monitoring of IGBTs, thispaper is the first work to successfully estimate both TJ and
IL using MHZGD from VOUT. TJ is estimated from V,
while IL is estimated from VOUT,MHZ. In the 110 switchingmeasurements at 11 different TJ’s from 25 °C to 125 °C
and 10 different IL’s from 12.5 A to 80 A for each of thethree IGBTs, TJ and IL estimation errors in the low test cost
method are + 4.9 °C / − 8.4 °C and + 1.1 A / − 4.3 A,
respectively. In contrast, TJ and IL estimation errors in themethod with small error are + 4.9 °C / − 8.1 °C and + 1.0
A / − 1.8 A, respectively. In this paper, the low test cost
method is recommended, because the test cost of themethod with small error is too high.
ACKNOWLEDGMENT
This work was partly supported by JST-Mirai Program,Grant Number JPMJMI20E1, Japan.

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