Extended Analytic Selectivity Analysis of a Vehicular Electronic Fuse's Thermal Model-Based Wire Protection Algorithm

To realize autonomous driving functions, a fail-operational vehicular power system is mandatory. This necessitates the selective isolation of short circuit faults and thermal wire overloads by the fusing elements. In future vehicular power systems, electronic fuses are inserted to implement an algorithm-based thermal wire protection. During the design process of the vehicular power system, the selectivity of the fusing elements has to be investigated and their selective coordination has to be ensured. The analytic triggering time determination represents an efficient methodology to examine the selectivity of wire protection algorithms of vehicular electronic fuses. In this contribution, an existing methodology is extended to consider also current measurement accuracy and hardware-related switching off delay in analytic selectivity analyses. Different types of current measurement accuracies are shown and corresponding analytic formulations are introduced. Using the extended methodology, the effect of the current profile parameters and the sampling time on the triggering time is examined. The sampling time can have a decisive influence on the triggering time and thus, the sampling time has to be considered in selectivity analyses. Furthermore, the selectivity of two cascaded eFuses with different current measurement accuracies is analyzed. For a given system which is selective in case of no measurement inaccuracy, it is shown that unfavorable constellations of the current measurement accuracies can lead to selectivity violations.

I. Introduction and Motivation

Autonomous driving functions can be designated as one of the major goals in the automotive industry. For realization, higher Automotive Safety Integrity Levels (ASIL) have to be fulfilled. Thus, a fail-operational vehicular power system and correct operation of safety-critical components even in case of a fault are required [1]. An occurring short circuit or thermal overload of a wire has to be selectively isolated by the fusing elements and unaffected parts of the vehicular power system must not be switched off unintentionally. To ensure this requirement, selectivity analyses have to be carried out during the design process of the vehicular power system and its fusing elements.