2N5191 Datasheet, PDF (5/8 Pages) ON Semiconductor – POWER TRANSISTORS SILICON NPN

2N5191 2N5192
DESIGN NOTE: USE OF TRANSIENT THERMAL RESISTANCE DATA
tP
PP
PP
t1
1/f
Figure A
DUTY CYCLE, D = t1 f -
t1
tP
PEAK PULSE POWER = PP
A train of periodical power pulses can be represented by
the model shown in Figure A. Using the model and the
device thermal response, the normalized effective transient
thermal resistance of Figure 12 was calculated for various
duty cycles.
To find θ_JC(t), multiply the value obtained from Figure 12
by the steady state value θ_JC.
Example:
The 2N5190 is dissipating 50 watts under the following
conditions: t1 = 0.1 ms, tp = 0.5 ms. (D = 0.2).
Using Figure 12, at a pulse width of 0.1 ms and D = 0.2,
the reading of r(t1, D) is 0.27.
The peak rise in function temperature is therefore:
∆T = r(t) x PP x θ_JC = 0.27 x 50 x 3.12 = 42.2_C
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