Patent ID: 7061738
Filing Date: 2006-06-13
Classification: H02H

Abstract:
1. Protective circuit for limiting a voltage for a device to be protected, comprising: an input terminal and an output terminal, a common line and a voltage detector connected between the input terminal and the common line, said device to be protected being located in an output circuit of the protective circuit and being separable by means of a controllable switching device provided in serial arrangement between the input terminal and the output terminal, said voltage detector being in operative connection with the controllable switching device; said switching device being a micromechanical component having a control circuit with a high input resistance and an output circuit galvanically separated from the control circuit and switchable via said control circuit, said output circuit in the opened switching state having a galvanic separation of its output terminals; the voltage detector being provided in the form of a core cell which includes a transistor as an electronic switch, a diode as a voltage sensor, an operating resistor and at least one further resistor; the first terminal of the operating resistor being connected to a terminal of the transistor selected from the group of terminals consisting of collector and drain, whereby a first junction is formed; a first terminal of the diode and a first terminal of the at least one further resistor being connected to a terminal of the transistor selected from the group of terminals consisting of gate and base, whereby a second junction is formed; a second terminal of the diode being connected such that the diode and the at least one further resistor form a voltage divider for at least a part of an input voltage present between the input terminal and the common line, the second terminal of the diode forming a third junction; a second terminal of the at least one further resistor being connected to a terminal of the transistor selected from the group of terminals consisting of source and emitter, whereby a fourth junction is formed; and the control circuit of the controllable switching device being connected between the first junction and a junction selected from the group consisting of the second, third and fourth junctions.