HEATING ELEMENT OPERATED AS CAPACITIVE SENSING ELECTRODE
First Claim
1. A combined seat heater and capacitive occupancy sensor, comprisinga heater network including a heating element connected between a first node and a second node to dissipate heat when a heating current is caused to flow between said first and second nodes,a capacitive sensing circuit connected to said heating element to sense a capacitive load of said heating element;
- wherein said heater network comprises a first interface for connecting said first node to a first terminal of a power source and a second interface for connecting said second node to a second terminal of said power source,wherein said first interface comprises a first electronically controlled switch and a second electronically controlled switch arranged in series so as to define a first intermediate node there between;
wherein said second interface comprises a third electronically controlled switch and a fourth electronically controlled switch arranged in series so as to define a second intermediate node there between;
wherein said capacitive sensing circuit comprisesan oscillator that is AC-coupled to said first and second intermediate nodes to apply an oscillating voltage to said first and second intermediate nodes; and
current measuring means AC-coupled between said oscillator and said heating element configured to keep the AC-potential of said heating element equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage and to derive said capacitive load from a current flowing into said heating element in response to said AC-potential of said heating element being kept equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage.
1 Assignment
0 Petitions
Accused Products
Abstract
A combined seat heater and capacitive occupancy sensor comprises a heater network including a heating element (11) and a capacitive sensing circuit connected to the heating element to sense a capacitive load. A first and a second interface are provided for connecting the heating element to a first and a second terminal of a power source, respectively. Each interface comprises electronically controlled switches (3, 5; 4, 6) arranged in series and defining an intermediate node (20; 21). An oscillator (8) is AC-coupled to the intermediate nodes to apply an oscillating voltage thereto. A current measuring means (9), AC-coupled between the oscillator and the heating element, keeps the AC-potential of the heating element at least substantially equal, in amplitude and phase, to the oscillating voltage on the intermediate nodes and to derive the capacitive load from a thus resulting current flowing into the heating element.
19 Citations
14 Claims
-
1. A combined seat heater and capacitive occupancy sensor, comprising
a heater network including a heating element connected between a first node and a second node to dissipate heat when a heating current is caused to flow between said first and second nodes, a capacitive sensing circuit connected to said heating element to sense a capacitive load of said heating element; -
wherein said heater network comprises a first interface for connecting said first node to a first terminal of a power source and a second interface for connecting said second node to a second terminal of said power source, wherein said first interface comprises a first electronically controlled switch and a second electronically controlled switch arranged in series so as to define a first intermediate node there between; wherein said second interface comprises a third electronically controlled switch and a fourth electronically controlled switch arranged in series so as to define a second intermediate node there between; wherein said capacitive sensing circuit comprises an oscillator that is AC-coupled to said first and second intermediate nodes to apply an oscillating voltage to said first and second intermediate nodes; and current measuring means AC-coupled between said oscillator and said heating element configured to keep the AC-potential of said heating element equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage and to derive said capacitive load from a current flowing into said heating element in response to said AC-potential of said heating element being kept equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 14)
-
-
11. A vehicle seat equipped with a combined seat heater and capacitive occupancy sensor—
- that comprises
a heater network including a heating element connected between a first node and a second node to dissipate heat when a heating current is caused to flow between said first and second nodes, a capacitive sensing circuit connected to said heating element to sense a capacitive load of said heating element; wherein said heater network comprises a first interface for connecting said first node to a first terminal of a power source and a second interface for connecting said second node to a second terminal of said power source, wherein said first interface comprises a first electronically controlled switch and a second electronically controlled switch arranged in series so as to define a first intermediate node there between; wherein said second interface comprises a third electronically controlled switch and a fourth electronically controlled switch arranged in series so as to define a second intermediate node there between; wherein said capacitive sensing circuit comprises an oscillator that is AC-coupled to said first and second intermediate nodes to apply an oscillating voltage to said first and second intermediate nodes; and
a transimpedance amplifier AC-coupled between said oscillator and said heating element configured to keep the AC-potential of said heating element equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage and to derive said capacitive load from a current flowing into said heating element in response to said AC-potential of said heating element being kept equal, or at least substantially equal, in amplitude and phase, to said oscillating voltage. - View Dependent Claims (12)
- that comprises
Specification