Collapse effe5ct of field-effect transistors in power applications 6

This pulse has such a high power, but the resulting temperature change is only 3 ℃. But don't forget that the rated power consumption recorded in the specification book is derived under steady-state conditions. Under instantaneous conditions, pulses like this can cause field-effect transistors to withstand greater power losses.

In the above example, it is impossible to find the instantaneous condition curve of 1uS in Figure 6. If the pulse width we obtain is too short and outside the range of the curve in this graph, we know that the instantaneous thermal resistance of a single pulse is proportional to the root mean square of time. Therefore, Z θ jc (1uS) can be obtained as follows:

Zθjc(1uS)=Zθjc(10uS)xÖ1uS/10uS=4.72x10-3xÖ0.1=1.49x10-3

Among them, Z θ jc (10uS) can be obtained from Figure 6  transistors

The thermal resistance effect mentioned above is obtained based on square waves. Can we obtain the thermal resistance effect for different waveforms or shapes. However, it is foreseeable that this requires very complex calculations and mathematical operations to obtain the desired results, and it is best to use approximation methods to obtain the desired thermal resistance effect. Figure 7 provides two examples to illustrate the approximation method, one is a triangular wave and the other is a sine wave.transistors