Generation of a diagnostic signal when the current through a power transistor reaches a level close to a limit current.

摘要

A diagnostic signal, indicative of the reaching of a predefined level, lower than a fixed maximum limit value, by the current flowing through a power transistor, is generated while employing a single comparator of a reference voltage with the voltage present across a sensing resistance, thus preventing problems arising from different offset characteristics of distinct comparators. By the use of current mirrors, the generation of a diagnostic signal when the current reaches a level that can be fixed very close to the limiting value, may be reliably triggered, irrespectively of the offset characteristic of the single comparator employed. <IMAGE>