Specifications

39
Dec. 2012
Mitsubishi IPM-series Application Note
(1) tw1<<1ms
In case of short on interval or low duty as in Fig.10.5, Junction temperatures rise to the highest value at the turn-off moment
of tw2 while the case temperature is stationary. (See Fig.10.7)
Fig.10.7
Fig.10.8
Temperature difference between junction and case can be calculated by using the following formula.
ٌT(j-c)㧩R
th(j-c)
P
AV
㧙Z
th(j-c)(tw2)
P
AV
㧗Z
th(j-c)(tw2)
Pav㧩R
th(j-c)
P
AV
㧗(Pav㧙P
AV
)Z
th(j-c)(tw2)
R
th(j-c)
̖̖thermal resistance between junction and case
Z
th(j-c)(tw2)
̖̖thermal impedance between junction and case at tw2 moment
ѕTj㧩Tc㧗ٌT(j-c) (Tc is measured by thermo-couple.)
Tj(max)=150°C, therefore the allowable case temperature Tc(max) is, Tc(max)=150-ٌT(j-c).
(2) 1ms<tw1<tw2<1s
In this case, ripple should be considered in calculation of average power loss P1.
Using approximation similar to (1) Fig.10.9 is obtained for calculation.
Fig.10.9
ٌT(j-c)㧩R
th(j-c)
P
AV
㧙Z
th(tw2)
PAV㧗Z
th(j-c)(tw2)
Pav㧙Z
th(j-c)(tw1)
Pav㧗Z
th(j-c)(tw1)
P1
㧩R
th(j-c)
P
AV
㧗(Pav㧙P
AV
)Z
th(j-c)(tW2)
㧗(Pl㧙Pav)Z
th(j-c)(tw1)
R
th(j-c)
̖̖thermal resistance between junction and case
Z
th(j-c)(tw2)
̖̖thermal impedance between junction and case at tw2 moment
Z
th(j-c)(tw1)
̖̖thermal impedance between junction and case at tw1 moment
ѕTj㧩Tc㧗ٌT(j-c) (Tc is measured by thermo-couple.)
Tc(max)㧩150㧙ٌT(j-c)
Power Loss and Junction Temperature