Current-sensing circuit for a power semiconductor device, in particular an integrated intelligent power semiconductor switch specifically for applications in motor vehicles

摘要

The invention relates to a circuit for measuring the current through a power transistor, which is built up of at least two groups of parallel-switched base transistors. A first large group of transistors carries the power current and the second group carries a current to be measured which is proportional to the power current when the base emitter voltage or the gate-source voltage (in the case of bipolar or field effect transistors) of all the transistors in the groups is the same. The voltage difference between the parallel-switched emitters or sources of the two groups is measured by means of a differential amplifier and the emitter or source voltage of the first group is impressed on the emitters or sources of the second group with a control transistor driven by the differential amplifier. Except in extreme cases (for example, a short-circuit) the current to be measured through the second group follows the power current through the first group on a proportional basis.