Seat heater and capacitive occupancy sensor combination

• US 9,332,592 B2
• Filed: 06/29/2012
• Issued: 05/03/2016
• Est. Priority Date: 07/08/2011
• Status: Active Grant

• Current Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Original Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Inventors: Lamesch, Laurent
• Primary Examiner(s): Paschall, Mark
• Application Number:
  US14/131,348
• Publication Number:
  US 20140131344A1
• Time in Patent Office: 1,404 Days
• Field of Search: 219/492, 219/497, 219/501, 219/506, 219/507, 219/202
• US Class Current: 1/1
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60N 2/5685 Resistance
• CPC Class Codes: H05B 3/02 Details

Abstract

In a combined seat heater and capacitive occupancy sensor, the present invention proposes to perform two measurements with two different frequencies. In a first step, the carrier frequency is set to a first known carrier frequency, the complex current through inductance and unknown capacitance and complex drive voltage are measured. In a second step, the carrier frequency is set to a second known carrier frequency, the complex current through inductance and unknown capacitance and complex drive voltage are measured. The measured complex values are used in a formula which yields the unknown capacitance.

Claims

1. A combined heater and capacitive occupancy sensor, comprising:

a heater network including a heating element connected between a first node and a second node and configured to dissipate heat when a heating current is caused to flow between said first and second nodes, said first and second nodes being connected via a common mode choke to a heater power supply;

a capacitive sensing network connected to said heating element, said capacitive sensing network configured to apply an oscillating signal to said heating element and to derive a capacitive load of said heating element from a current flowing into or a voltage resulting on said heating element in response to an application of said oscillating signal;

said capacitive sensing network comprising an AC signal source and a current meter connected in series to one of said first and second nodes and a control and detection circuit configured for measuring a voltage applied to and a current flowing into said heating element in response to said voltage,

wherein said AC signal source is configured for generating AC signals with at least a first carrier frequency and at least a second carrier frequency, said second carrier frequency being different from said first carrier frequency, and wherein said control and detection circuit is configured for measuring said voltage and said current at least for said two different carrier frequencies generated by said AC signal source.

2. The combined heater and capacitive occupancy sensor according to claim 1, wherein said control and detection circuit is configured for determining an unknown capacity C_x of said heating element towards ground as

3. The combined heater and capacitive occupancy sensor according to claim 1, wherein said capacitive sensing network comprises a reference impedance and a switch to operatively connect the second reference impedance between the heating element and ground.

4. The combined heater and capacitive occupancy sensor according to claim 3, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula:

5. The combined heater and capacitive occupancy sensor according to claim 3, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula:

6. The combined heater and capacitive occupancy sensor according to claim 4, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula:

7. The combined heater and capacitive occupancy sensor according to claim 2, wherein said capacitive sensing network comprises a reference impedance and a switch to operatively connect the second reference impedance between the heating element and ground.

8. The combined heater and capacitive occupancy sensor according to claim 7, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula:

9. The combined heater and capacitive occupancy sensor according to claim 7, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula:

10. The combined heater and capacitive occupancy sensor according to claim 8, wherein said control and detection circuit is configured for determining said unknown capacitance by means of the formula: