Application constraints

AN3432

16/24

Doc ID 019041 Rev 1

Figure 12.

As shown on Figure 12, the junction temperature is 152°C in conduction. At turn-off this

temperature would generate initial losses of 9.5 W making the equilibrium point impossible

since both temperature and leakage will increase in a thermal runaway manner due to the

poor cooling.

To solve this problem, there are two options:

compound…)

Select a diode with much less leakage current as STPS2045C, as shown in Figure 13, even

if the junction temperature at turn off is higher than STPS20L45 due to its higher forward

voltage drop and power losses. Therefore, there is no thermal runaway risk anymore.

0

1

2

3

4

5

6

7

8

9

10

-40

-20

0

20

40

60

80

100

120

140

160

180

200

P(W)

Pthermal(Tj )

Tj@t 0 =152 °C

Prev(Tj )

Pcond(Tj )

Thermal runaway

Prev(Tj@t0)>Pcond(Tj@t0)

Tj (°C)