Protection circuit for a load resistor (load), which is connected to a motor vehicle battery, and its switching output stage

摘要

The invention relates to a circuit for protection especially of an electric motor which is fed from the battery of a motor vehicle, and of a switching output stage, which is connected in series with the electric motor, in the form of an MOS field-effect transistor which is just compatible with the high starting current of the electric motor but becomes irreversibly conductive if a heavy current is applied for a longer period. This protection circuit contains a comparator at whose sampling terminal a voltage appears which is proportional to the current flow through the switching output stage. If excessive current consumption is perceived, the comparator feeds to the gate electrode of the MOS field-effect transistor an inhibiting signal to interrupt the current flow. This inhibiting signal is suppressed with the aid of a switching transistor, which is a component of a delay element, during the time period of the heavy starting current caused by the electric motor. <IMAGE>