Capacitive sensor configured for using heating element as antenna electrode
First Claim
1. A capacitive sensor, configured for being connected between a heating element and a heating current supply and for using said heating element as antenna electrode, comprising:
- a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply, said common mode choke further comprising a third winding inductively coupled with said first and second windings; and
a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode based on said measured voltage and/or current;
wherein said measurement node is operatively coupled to said third winding and galvanically isolated from said heating element, and wherein said AC signal is inductively injected into said heating element through said measurement node and said third winding.
2 Assignments
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Accused Products
Abstract
A capacitive sensor configured for connection between a heating element and a heating current supply comprises a common mode choke (CMC) for AC-decoupling the heating element from the heating current supply. The CMC comprises first and second inductively coupled windings, the first winding for connection between a first terminal of the heating current supply and a first terminal of the heating element and the second winding for connection between a second terminal of the heating element and a second terminal of the heating current supply. The capacitive sensor further comprises a control and evaluation circuit for injecting an AC signal into the heating element via a measurement node, measuring a voltage on and/or a current across the measurement node, and to derive an impedance between the heating element and a counter electrode from the measurement. The CMC comprises a third winding inductively coupled with the first and second windings, the third winding being operatively coupled with the measurement node.
7 Citations
12 Claims
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1. A capacitive sensor, configured for being connected between a heating element and a heating current supply and for using said heating element as antenna electrode, comprising:
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a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply, said common mode choke further comprising a third winding inductively coupled with said first and second windings; and a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode based on said measured voltage and/or current; wherein said measurement node is operatively coupled to said third winding and galvanically isolated from said heating element, and wherein said AC signal is inductively injected into said heating element through said measurement node and said third winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An occupancy sensor for a vehicle seat having a capacitive sensor configured for being connected between a heating element for said vehicle seat and a heating current supply and for using said heating element as antenna electrode, said capacitive sensor comprising:
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a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply, said common mode choke further comprising a third winding inductively coupled with said first and second windings; and a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode based on said measured voltage and/or current; wherein said measurement node is operatively coupled to said third winding and galvanically isolated from said heating element, and wherein said AC signal is inductively injected into said heating element through said measurement node and said third winding.
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12. A hands-on or hands-off detector for a steering wheel having a capacitive sensor configured for being connected between a heating element for said steering wheel and a heating current supply and for using said heating element as antenna electrode, said capacitive sensor comprising:
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a common mode choke having first and second inductively coupled windings, said first winding for being connected between a first terminal of said heating current supply and a first terminal of said heating element and said second winding for being connected between a second terminal of said heating element and a second terminal of said heating current supply, said common mode choke further comprising a third winding inductively coupled with said first and second windings; and a control and evaluation circuit configured to inject an AC signal into said heating element via a measurement node, to measure a voltage on and/or a current across said measurement node, and to derive an impedance between said heating element and a counter electrode based on said measured voltage and/or current; wherein said measurement node is operatively coupled to said third winding and galvanically isolated from said heating element, and wherein said AC signal is inductively injected into said heating element through said measurement node and said third winding.
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Specification