Circuit arrangement for independent power supply of digital input circuits

摘要

The invention describes a circuit arrangement for independent power supply of digital input circuits. The input load current, which every input circuit has when it is triggered by an external sensor, is used to supply all components of the input circuit with power. The invention makes an external power supply for comparators, serial interface control, optical couplers etc. unnecessary. A minimum voltage detector captures the input potential of one or more input connections and switches the voltage potential to the supply connections of all components of the input circuit. In the inactive state of the inputs, i.e. when none of the inputs of an input circuit is triggered, no current is required, so that none is supplied to any component. The essential advantages of the invention are a considerable reduction of the sensitivity to faults and reduction of the dissipated power, and therefore of the operating temperature of the input circuit.