Automatic Search Method of Robust Gate Driving
Vectors for Digital Gate Drivers Against Variations
in Operating Conditions of IGBT’s
Ting-Wei Wang1, 2, Toru Sai1, Ryuzo Morikawa1, Katsuhiro Hata1, Takayasu Sakurai1,
Po-Hung Chen2, and Makoto Takamiya1
1

2

The University of Tokyo, Tokyo, Japan
National Chiao Tung University, Hsinchu, Taiwan
twwang.ee06g@nctu.edu.tw

Robust gate
driving vector(This work)

Optimization
condition

Keywords—Gate driver, IGBT, Switching loss, Temperature

Variations inoperating conditions(Temperature,load current,..)Fig. 1. Concept of robust gate driving vectors (RGV).

I. INTRODUCTION
Active gate driving of power transistors, where the gate
driving current is controlled during the turn-on/off transients,
is effective to reduce both the switching loss (ELOSS) and thecurrent overshoot (IOVERSHOOT) or voltage overshoot(VOVERSHOOT) of power transistors, where ELOSS and IOVERSHOOT VOVERSHOOT are typically are trade-offs in the conventional
fixed gate resistance driver. Among the active gate driving,
digital gate drivers [1-10] are useful, because the gate driving
current is programmable with gate driving vectors using asoftware. A 6-bit digital gate driver [6] with four 6-bit
variables synchronized to the clock signal, where a simulated
annealing algorithm is automatically finds an optimum gate
driving vector (GV) out of 644 (~1.7 × 107) combinations,
reduces ELOSS by 55% at the same VOVERSHOOT and reduces
VOVERSHOOT by 53% at the same ELOSS at the turn-off of IGBT.
As shown in [7], the optimum GV, however, changes
depending on operating conditions such as temperature and aload current (ILOAD). When an optimum GV at a particulartemperature and ILOAD is reused to another temperature and
ILOAD, ELOSS and IOVERSHOOT/VOVERSHOOT are sometimes worse
than the conventional single-step gate drive [7]. Therefore,
temperature and ILOAD dependent GVs are required [7]. The
digital gate drivers are not useful under temperature and load
current variations, when sensors for temperature and/or ILOAD
are not available. To solve the problem, robust gate driving
vectors (RGV) for the digital gate drivers to temperature and
ILOAD variations are proposed in [9]. RGV improves the tradeoff between ELOSS and IOVERSHOOT/VOVERSHOOT across nineconditions including different temperatures and ILOAD [9].

978-1-7281-5826-6/20/$31.00 ©2020 IEEE

Conv. gate
driving vector

Object function (fOBJ)

Abstract—To solve the trade-off between the switching loss
and the current/voltage overshoot of power transistors, a digital
gate driver is effective. A temperature and load current
dependent optimization of the gate driving vectors (GV) for thedigital gate drivers, however, is required [7]. Robust gate
driving vectors (RGV) to the temperature and load current
variations are proposed in [9]. The test cost to search RGV,
however, is very high. To reduce the test cost, a robust simulated
annealing (RSA) for an automatic search method of RGV is
proposed. In the proposed RSA, instead of changing theoperating conditions, GV is varied in a single operating
condition. Compared with the conventional method to search
RGV [9], the proposed RSA reduces the measurement time bymore than 85 % (from more than 5.5 hours to less than 50
minutes), which results in the reduced test cost.

Fig. 1 shows a concept of RGV. The object function (fOBJ)
is a function of ELOSS and IOVERSHOOT/VOVERSHOOT and is usedin the simulated annealing algorithm [5]. Small fOBJ means
small ELOSS and IOVERSHOOT/VOVERSHOOT. RGV is a single
universal GV that can be applied to different operating
conditions. RGV is defined as a single GV which minimize
the maximum fOBJ when the operating condition changes [9].
From a practical viewpoint, as shown in Fig. 1, minimizing
the maximum fOBJ across variations in operating conditions isimportant, because product specifications are determined by
the maximum fOBJ, thereby RGV is important. The test cost to
search RGV, however, is very high, because 90,000
measurements for full search of GVs across nine different
ILOAD and temperatures, which take more than 5.5 hours, isrequired in [9]. To reduce the test cost to search RGV, in thispaper, a robust simulated annealing (RSA) for an automatic
search method of RGV is proposed.
II. AUTOMATIC SEARCH METHOD OF ROBUST GATE DRIVINGVECTORS
Fig. 2 (a) shows a conventional automatic search method[5] of the conventional GVs in Fig. 1 using a conventional
simulated annealing (CSA). Fig. 2 (b) shows the proposed
automatic search method of RGV using RSA. Fig. 3 shows theGV and waveforms in a 6-bit digital gate driver [5]. nNMOS
shows the number of activated NMOS transistors in 63
parallel NMOS transistors in the 6-bit digital gate driver [5].
In this paper, the GV is defined as (n1, n2, n3, n4) , where n1,n2, n3, and n4 are integers from 0 to 63. In this paper, only turn-

3798

300V

Simulated annealing algorithm

15V

m-th gate vector (GV)(n1,m , n2,m , n3,m , n4,m )ILOAD

Conventional simulated annealing (CSA)
63 PMOSsIC
VCE
VGE
63 NMOSs
IGBT module

Digital gate driver IC

ELOSSIOVERSHOOT or VOVERSHOOT

fOBJ,m

Optimization loop (Repeated 2000-to-4000 times)

(a)
300V

Simulated annealing algorithmm-th GV(n1,m , n2,m , n3,m , n4,m )15V

Varied m-th GV(n1,m , n2,m , n3,m , n4,m )(n1,m +Δ, n2,m , n3,m , n4,m )(n1,m , n2,m +Δ, n3,m , n4,m )

16

ILOAD

Proposed robust simulated annealing (RSA)
63 PMOSsIC
VCE
VGE
63 NMOSs
Digital gate driver IC

IGBT module(n1,m +Δ, n2,m +Δ, n3,m +Δ, n4,m +Δ)
fOBJ,m,1
fOBJ,m,2

MAX (fOBJ,m )ELOSSIOVERSHOOT or VOVERSHOOT

X 16

fOBJ,m,16
16 measurements (Inner loop)

Optimization loop (Repeated 2000-to-4000 times)(b)Fig. 2. (a) Conventional simulated annealing (CSA). (b) Proposed robust simulated annealing (RSA) for automatic search method of RGV.

nNMOSGate vector(n1, n2, n3, n4)
n1 n2 n3n4 63
0

VGE

t

off is shown for simplicity. As shown in Fig. 2 (a), a GV isgiven to the 6-bit digital gate driver. Then, the collector
current (IC) and the collector-to-emitter voltage (VCE)
waveforms of IGBT are measured in the double pulse test.
After that, fOBJ is calculated to evaluate ELOSS and VOVERSHOOT.
ICt
VOVERSHOOT݂OBJ ൌ ඨቆ

VCEt

TSTEP = 400ns
4 time-segments

Fig. 3. Gate vector and waveforms in 6-bit digital gate driver.

‫ܧ‬LOSS‫ܧ‬LOSS,ġMAX

ଶ

ቇ ൅ቆ

ܸOVERSHOOTܸOVERSHOOT,ġMAXଶቇ ሺͳሻ

where the subscript MAX signifies the maximum of thecorresponding quantity. Based on fOBJ, the simulated
annealing algorithm provides a new GV for the next
measurement. By repeating the optimization loop more than2000 times, an optimum GV is obtained [5]. The difference3799

Gate driver IC

Hot plate

RSA (Δ=1)
60
50

50

40

40

40

30

30

30

20

20

20

10

10

10

0

n1

n2

n3

0

n4

n1

50A, 25ºC

0.9

Conv. single-step drive

0.8

● CSA
○ Varied CSA■ RSA (Δ=2)□ Varied RSA

0.3
0.2

1

n2

n3

n4

(c)

Varied CSA

4
2

8

CSA
Varied RSA

0.1

Varied CSA

0
0

n1

0.55

0.6

0.65

0.7

0.75

0.8

0.85

fOBJ

0.4

2

0

n4

6

0
0.5

0.5

CountsELOSS [mJ]

8

0.6

3

n3

Fig. 5. Optimized gate vectors. (a) CSA. (b) RSA (' = 1). (c) RSA (' = 2).

1.0

RSA (Δ=2)n2(b)CountsELOSS, MAX

Fig. 4. Photo of measurement setup.

0.7

RSA (Δ=2)
60

50

(a)

4

nNMOS

nNMOS

nNMOS

IGBT module

CSA
60

50

100

150

VOVERSHOOT [V]Reduced max (fOBJ)

4
2
0
0.5

200

Varied RSA (Δ=2)

6

0.55

0.6

0.65

0.7

0.75

0.8

0.85

fOBJ

VOVERSHOOT, MAX

Fig. 6. Measured ELOSS vs. VOVERSHOOT of five gate drives at 25°C.

Fig. 7. Histograms of fOBJ of varied CSA and varied RSA
extracted from Fig. 6.

between CSA and the proposed RSA is shown in blue
characters in Fig. 2 (b). In the proposed RSA, instead ofchanging the operating conditions in the automatic search of
GVs in CSA, GV is varied in a single operating condition to
reduce the test cost. In other words, for example, ILOAD andtemperature variations are emulated by the gate driving
current variations. The emulation is very effective to reduce
the test cost to search RGV, because the varied GV is done bya software instead of actually changing of the operating
conditions. Specifically, as shown in Fig. 2 (b), a GV isaugmented to 16 GVs by adding ' (= 1 or 2) to the m-th GV(n1,m, n2,m, n3,m, n4,m), and 16 measurements are done using 16
GVs. Then 16 fOBJ’s are calculated by using measured ELOSS
and VOVERSHOOT, and the largest fOBJ out of the 16 fOBJ’s is given
to the simulated annealing algorithm. As a result, RSA
searches RGV which minimize the maximum fOBJ acrossvariations in operating conditions. In RSA, more than 32,000(= 16 × 2000) measurements are required to search RGV.

CSA, optimum GVs are searched using both RSA and CSA at
25 °C, and ELOSS, VOVERSHOOT, and fOBJ using the optimum GVs
at 25 °C, 75 °C, and 125 °C are compared. The optimum GVs
are searched at 25 °C instead of 125 °C, because the test costat room temperature (25 °C) is lower than that at an operating
junction temperature of IGBTs (125 °C). Figs. 5 (a) to (c)show the optimum GV obtained by CSA, RGVs obtained by
RSA with ' of 1 and 2 at 25 °C, respectively. In CSA, it takes
less than 9 minutes to search the GV by repeating less than2400 optimization loops (= 2400 measurements). In contrast,
in RSA, it takes less than 50 minutes to search the RGV byrepeating less than 2500 optimization loops (= 2500 × 16 =40,000 measurements). Compared with the conventional fullsearch across nine different ILOAD and temperatures, whichtake more than 5.5 hours [9], the proposed RSA at a single
operating condition reduces the measurement time by morethan 85 %, which results in the reduced test cost.

III. MEASURED RESULTS
Fig. 2 (b) shows a circuit schematic of the measurement
setup for the double pulse test of IGBT (2MBI100TA-060-50,
600 V, 100 A) at 300 V. ILOAD is fixed to 50 A. Fig. 4 shows
the photo of the measurement setup. The IGBT module is put
on a hot plate to control the temperature. The measurement
setup is the same as [7] except for the automatic search method.
In order to clarify the advantage of the proposed RSA over

In order to confirm that RGV obtained by RSA has asmaller maximum fOBJ than that by CSA under GV variations,Fig. 6 shows measured ELOSS vs. VOVERSHOOT of the five gate
drives in turn-off state at 25 °C. The black curve shows thetrade-off curves of the conventional single-step gate drivewith varied gate driving current [7]. The dotted concentric
curves show the contour of fOBJ defined in Eq. (1). In Fig. 6,“CSA” shows the optimum GV obtained by CSA, “Varied
CSA” shows 15 varied GVs where ' = 2 is added to “CSA”
as shown in Fig. 2 (b), “RSA (' = 2)” shows the RGV obtained

3800

0.7

4

RSA (Δ=2)
ELOSS [mJ]

RSA (Δ=1)

0.5
0.4

2

0.4

2

0

50

100

150

VOVERSHOOT [V]

0.5
0.4

2

Conv. single-step drive

0.2
0.1

0
0

200
VOVERSHOOT, MAX

RSA(Δ=1)

0.6

3

1

0

0

RSA(Δ=2)

0.8

0.1

0.1

CSA

0.9

0.3

0.2

1

5

0.7

RSA (Δ=1)

0.5

125ºC
1.0

4

0.3

0.2

1

RSA (Δ=2)
CSA

0.6

3

CSA

0.3

Conv. single-step drive

0.7

0.6

3

0.9
0.8

ELOSS, MAX

Conv. single-step drive

75ºC

1.0

ELOSS [mJ]

0.9
0.8

4

ELOSS [mJ]25ºC (Optimization condition)

ELOSS, MAX

ELOSS, MAX

1.0

50

100

VOVERSHOOT [V]

(a)

150
200
VOVERSHOOT, MAX

0

50

100

VOVERSHOOT [V]

(b)

150
VOVERSHOOT, MAX(c)Fig. 8. Measured ELOSS vs. VOVERSHOOT of four gate drives at (a) 25 °C, (b) 75 °C, and (c) 125 °C using gate vectors optimized at 25 °C in Fig. 5.
1.4

fOBJ

1.2

ILOAD = 50A

by RSA with ' = 2, and “Varied RSA” shows 15 varied GVs
where ' = 2 is added to “RSA (' = 2)”. Note that “Varied
CSA” has the largest fOBJ because of the largest VOVERSHOOT of
180 V. Fig. 7 shows histograms of fOBJ of “Varied CSA” and“Varied RSA” extracted from Fig. 6. The maximum fOBJ of“Varied RSA” is clearly smaller than that of “Varied CSA”,
which supports that the concept of RGV shown in Fig. 1 isreally achieved under GV variations.

CSA
−12%

−24%

Turn-off

RSA (Δ=1)
RSA (Δ=2)

1.0

Proposed

0.8
0.6
0.4

25Υ

75Υ

In order to verify that RGV obtained by RSA has a smaller
maximum fOBJ than that by CSA under temperature variations,Figs. 8 (a) to (c) show the measured ELOSS vs. VOVERSHOOT of
the four gate drives in turn-off state at 25 °C, 75 °C, and 125°C, respectively, using GVs optimized at 25 °C shown in Fig.
5. The black curves show the trade-off curves of the125Υ

Temperature

Optimization condition

Fig. 9. Measured temperature dependence of fOBJ for three gate
drives extracted from Fig. 8.

25ΥΥ(Optimization condition)

125Υ

VOVERSHOOT = 163V
VCE: 50V/div
IC: 10A/div

IC: 10A/div

CSA

VGE: 10V/div

nNMOS

30

VGE: 10V/div

50

49

Reused

63

−51%

nNMOS
30

400ns

50

49

400ns

Time

Time

VOVERSHOOT = 80V

VCE: 50V/div

RSA (Δ=2)(Proposed)

IC: 10A/div

IC: 10A/div

VGE: 10V/div

VGE: 10V/div

nNMOS
39

7

38

Reused nNMOS

63

39

5

0
400ns

63

0

0

0

0

VCE: 50V/div

7

38

63

5

0
Time

VCE: 50V/div

400ns

Time

Fig. 10. Gate driving vectors and measured waveforms of CSA and proposed RSA (' = 2) at 25 °C and 125 °C.

3801

conventional single-step gate drive with varied gate driving
current [7]. At 25 °C in Fig. 8 (a), fOBJ’s of CSA, RSA (' = 1),
and RSA (' = 2) are smaller than those of the conventional
single-step gate drives. In contrast, when the temperature isincreased from 25 °C to 75 °C and 125 °C, fOBJ’s of CSA, RSA(' = 1), and RSA (' = 2) are increased, because the GVs are
optimized at 25 °C. Fig. 9 shows the measured temperaturedependence of fOBJ for CSA, RSA (' = 1), and RSA (' = 2)
extracted from Fig. 8. At 25 °C, fOBJ of CSA is the smallest as
expected. In contrast, at 125 °C, fOBJ of the proposed RSA ('= 2) is the smallest. Quantitatively, compared with fOBJ of CSA
and RSA (' = 1), fOBJ of the proposed RSA (' = 2) is reduced
by by 24 % and 12 %, respectively. Thus, under temperature
variations, the maximum fOBJ of the proposed RSA (' = 2) isthe smallest among three GVs, which supports that theconcept of RGV shown in Fig. 1 is really achieved. Fig. 10shows the gate driving vectors and measured waveforms of
CSA and the proposed RSA (' = 2) at 25 °C and 125 °C. The
corresponding ELOSS and VOVERSHOOT are shown in Figs. 8 (a)and (c). In CSA, when the GV searched at 25 °C is reused at
125 °C, large VOVERSHOOT of 163 V is observed, while
VOVERSHOOT of RSA at 125 °C is 80 V. RSA reduces
VOVERSHOOT by 51 %, which indicates that RGV obtained by
RSA is really robust to temperature variations.
IV. CONCLUSIONSIn order to reduce the test cost to search RGV, which is asingle universal GV that can be applied to different operating
conditions, RSA for the automatic search method of RGV is
proposed. Compared with the conventional full searchmethod of RGV [9], the proposed RSA at a single operating
condition reduces the measurement time by 86 %, which
results in the reduced test cost. When GVs searched at 25 °C
are reused to 125 °C, compared with CSA, the proposed RSA(' = 2) reduces fOBJ and VOVERSHOOT by 24 % and 51 %,respectively.
ACKNOWLEDGMENT
This work was supported in part by the Ministry of
Science and Technology (MOST), Taiwan, under Grant
109-2636-E-009-019 and in part by the Higher Education
Sprout Project of the National Chiao Tung University and

Ministry of Education (MOE), Taiwan. (Corresponding
author: Po-Hung Chen.)
REFERENCES[1]

H. Kuhn, T. Koneke, and A. Mertens, “Considerations for a digital gateunit in high power applications,” in Proc. IEEE Power Electron. Spec.
Conference, Jun. 2008, pp. 2784–2790.
[2] L. Dang, H. Kuhn, and A.Mertens, “Digital adaptive driving strategies
for high-voltage IGBTs,” in Proc. IEEE Energy Conversion Congress
and Exposition, Sep. 2011, pp. 2993–2999.
[3] M. Takamiya, K. Miyazaki, H. Obara, T. Sai, K. Wada, and T. Sakurai,“Power electronics 2.0: IoT-connected and AI-controlled powerelectronics operating optimally for each user,” in Proc. IEEE 29th
International Symposium on Power Semiconductor Devices and ICs,
May 2017, pp. 29 -32.
[4] D. Colin, and N. Rouger “High speed digital optical signal transfer for
power transistor gate driver applications,” in Proc. IEEE 29th
International Symposium on Power Semiconductor Devices and ICs,
May 2017, pp. 37-40.
[5] K. Miyazaki, S. Abe, M. Tsukuda, I. Omura, K. Wada, M. Takamiya,
and T. Sakurai, “General-purpose clocked gate driver IC with
programmable 63-level drivability to optimize overshoot and energy
loss in switching by a simulated annealing algorithm,” IEEE Trans. on
Industry Applications, vol. 53, no. 3, pp. 2350-2357, May-Jun. 2017.
[6] H. Dymond, J. Wang, D. Liu, J. Dalton, N. McNeill, D. Pamunuwa, S.
Hollis, and B. Stark, “A 6.7-GHz active gate driver for GaN FETs tocombat overshoot, ringing, and EMI,” IEEE Trans. on PowerElectronics, vol. 33, no. 1, pp. 581-594, Jan. 2018.
[7] T. Sai, K. Miyazaki, H. Obara, T. Mannen, K. Wada, I. Omura, M.
Takamiya, and T. Sakurai, "Load current and temperature dependent
optimization of active gate driving vectors," in Proc. IEEE Energy
Conversion Congress and Exposition, Sep. 2019, pp. 3292-3297.
[8] Y. Cheng, T. Mannen, K. Wada, K. Miyazaki, M. Takamiya, and T.
Sakurai, "Optimization platform to find a switching pattern of digital
active gate drive for reducing both switching loss and surge voltage,"
IEEE Transactions on Industry Applications, vol. 55, no. 5, pp. 50235031, Sep./Oct. 2019.
[9] T. Sai, K. Miyazaki, H. Obara, T. Mannen, K. Wada, I. Omura, T.
Sakurai, and M. Takamiya, "Robust gate driving vectors to load current
and temperature variations for digital gate drivers," in Proc. IEEE
International Future Energy Electronics Conference, Nov. 2019, pp.
87-94.
[10] T. Sai, K. Miyazaki, H. Obara, T. Mannen, K. Wada, I. Omura, T.
Sakurai, and M. Takamiya, "Stop-and-go gate drive minimizing test
cost to find optimum gate driving vectors in digital gate drivers," inProc. IEEE Applied Power Electronics Conference and Exposition,
March 2020, pp. 3096-3101.

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