IXYS
Thyristor/Diode Module Types M##700-12io1 and M##700-18io1
8.0 Computer Modelling Parameters
8.1 Thyristor Dissipation Calculations
DT
2
-VT 0 + VT 0 + 4× ff 2 ×r ×WAV
WAV =
T
Rth
IAV =
and:
2× ff 2 ×r
T
DT = Tj max -TK
Where VT0 = 0.85 V, rT = 0.27 mW for the thyristor and VT0 = 0.72 V, rT = 0.143 mW for the diode.
Rth = Supplementary thermal impedance, see table below and
ff = Form factor, see table below.
Supplementary Thermal Impedance
Conduction Angle
Square wave
Sine wave
30°
60°
90°
120°
180°
270°
d.c.
0.0976
0.0950
0.0955
0.0933
0.0942
0.0924
0.0933
0.0917
0.0920
0.0902
0.0907
0.090
Form Factors
90°
Conduction Angle
Square wave
Sine wave
30°
3.464
3.98
60°
120°
1.732
1.879
180°
1.414
1.57
270°
d.c.
1
2.449
2.778
2
1.149
2.22
8.2 Calculating thyristor VT using ABCD Coefficients
The on-state characteristic IT vs. VT, on page 6 is represented in two ways;
(i) the well established VT0 and rT tangent used for rating purposes and
(ii) a set of constants A, B, C, D, forming the coefficients of the representative equation for VT in terms of
IT given below:
VT = A + B ×ln
(
IT + C × IT + D × IT
)
The constants, derived by curve fitting software, are given below for both hot and cold characteristics.
The resulting values for VT agree with the true device characteristic over a current range, which is
limited to that plotted.
25°C Coefficients
125°C Coefficients
A
B
C
D
0.7860338
9.929062×10-3
1.94704×10-4
7.409213×10-3
A
B
C
D
-0.099137717
0.1987038
4.23812×10-4
-0.01453705
Data Sheet. Types M##700-12io1W and M##700-18io1W Issue 1
Page 4 of 12
June, 2019