Overcurrent protection circuit for electrical load

摘要

Has sensor element for determining quantity proportional to current through current-limiting element and switch element controlled from it. An overcurrent protection circuit (10) for an electrical load (1), especially a safety relay building block with an auto-start function, lies across a current-limiting element like a PTC-resistance at the operating voltage. To the current-limiting element is assigned a sensor element (20) for determining a quantity proportional to a current through the current-limiting element. The overcurrent protection circuit has a switch element (24) that is controlled from the sensor element, which lies across the current limiting element at operating voltage and maintains the current flow through the latter until the operating voltage is switched off. The overcurrent protection circuit has an opto-transistor and the sensor element is an LED path of this transistor, lying parallel to the current-limiting element.