Collapse effect of field-effect transistors in power applications 2

1. Evaluation method: Safe operating range of single pulse UIS (Unconstrained Inductive Switching)

The general evaluation of the breakdown effect of field-effect transistors is based on a single pulse UIS. As shown in Figure 1. This method simply defines several basic parameters for the tested component. For example, the maximum peak current (IAS) flowing through the field-effect transistors during the collapse time, the initial junction surface temperature (Tj) before the start of UIS, and the time tAV elapsed during the collapse. The chart curve corresponding to IAS and tAV can provide users with an understanding of the performance ability of this component towards UIS, and provide an objective and fair measurement basis.

2. Conditions for overvoltage generation

In application, the conditions for overvoltage can be divided into the following two types. One is to exceed the maximum rated voltage of the field-effect transistors, but without causing any collapse phenomenon. This phenomenon can be used to determine the operational capability of the component by calculating the temperature of the junction surface of the field-effect transistor. Another type refers to when the criteria for a crash have been reached and the crash has already occurred, at which point the evaluation method of UIS can provide the best tool for analyzing this phenomenon.