Capacitive proximity switch

Circuit arrangement for locking or unlocking at least one door lock of a motor vehicle with an electronic activation circuit and with a capacitive proximity switch for detecting a change in a capacitance ΔC relative to a setpoint capacitance Cset by the approach or retreat of an object in a sensitive area of the proximity switch having an electrode system with at least one response electrode, an evaluation unit and a switching output, a measured value which corresponds to the change in capacitance being compared to a operating threshold and a switching signal being produced at the switching output depending on the measured value,

• wherein the evaluation unit is adapted to produce an evaluation of the measured value which corresponds to the change in capacitance ΔC over time, and based on the time behavior of the measured value, the evaluation unit is adapted to deactivate a first operating threshold S1 and to activate a second operating threshold S2, the second operating threshold S2 which is reached only at a change in capacitance ΔC2 which is caused by a target object coming into or out of the sensitive area of the proximity switch with is greater than the first operating threshold S1, which is reached at a smaller change in the capacitance ΔC1 which can be caused by a false object coming into or out of the sensitive area of the proximity switch,
• wherein the operating threshold S1 is a default operating threshold for producing the switching signal when the measured value has been reached, while the second operating threshold S2 is activated for producing the switching signal only when the measured value has reached the second operating threshold S2,
• wherein a response electrode of the capacitive proximity switching arrangement is integrated in a door handle,
• wherein unlocking or locking of the door lock only takes place when a change in capacitance ΔC is caused by the hand of an individual, which hand is entering or leaving a sensitive area of the proximity switch, which change in capacitance produces a measured value which is greater than the activated operating threshold S1, S2 so that, at the operating output of the capacitive proximity switch there is a switching signal, and when triggered by the switching signal of the capacitive proximity switch, the individual has been recognized as the authorized individual by the electronic activation circuit.