Importance

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Abstract

A circuit of a detection switch for generating an output signal for driving a load device in accordance with the detection result by a detector is composed with a reduced number of components externally attached to an IC substrate which mounts integrally main circuit units such as a power source circuit unit, a detection circuit unit and an output circuit unit. The output circuit unit comprises a comparator which compares a judgment signal from the detection circuit unit with a reference signal when the load device is driven by DC power, or compares the voltage of an external DC power source with a predetermined voltage when the device driven by AC power, and an output driver which generates a driving signal for the load device in response to the output signal from the comparator. The detection circuit unit produces the judgment signal only when either the output circuit unit or the power source circuit unit is active. Further, the output circuit unit comprises an NPN output circuit with a protection function for load short-circuit breaks its current path based on the judgment signal and a switching output circuit operating in engagement with the NPN output circuit. A limiter and a switching circuit are provided between the NPN output circuit and the load device. The limiter supplies the NPN output circuit with an excess current exceeding a predetermined value flowing through the load device and the switching circuit controls the limiter in accordance with the output from the switching output circuit. Further, the detection switch circuit is connected with a display lamp for displaying the operation of the switch, and the output circuit unit has a selector for selecting the judgment signal or the output signal for display according to the connection of an external jumper.

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First Claim