Datasheet avalanche ratings

AN2344

16/27

Where,

T= Period of the pulses train, and

Considering the repetitive avalanche application (but it can be applied to several operative

modes) the calculation of the peak temperature must also take into account the conduction

and switching losses. Figure 10. shows the power profile of a typical switching, while Figure

11. illustrates the superimposition application.

Figure 10.

Modeling triangular pulses using rectangular pulses example

Figure 11.

Triangular-to-rectangular pulse superimposition principle application

It is well known that a triangular power pulse can be modeled as a peak power 0.7 amplitude

rectangular pulse with a 0.71 actual width. Moreover, a ramp power shape can be modeled

as a 0.56 width step pulse with a 0.89 actual amplitude (Table 2.). Figure 12. shows the

triangular power pulse simulated thermal impedance temperature response (blue line), as

compared to the rectangular approximation (red line). The average power can be calculated

from each peak power result:

Equation 12

P

AVE

t

1

T

----0.5

P

1

•

t

2

T

----0.5

P

2

•

t

3

T

----0.5

P

3

•

++

=