COMBINED HEATING AND CAPACITIVE SEAT OCCUPANT SENSING SYSTEM
First Claim
Patent Images
1. Combined heating and capacitive seat occupant sensing system, comprisinga heating element for producing heat when an electrical current is caused to flow across it, said heating element comprising terminals for DC-coupling said heating element to a heating current supply;
- a capacitive sensing circuit connected to said heating element so as to be able to use said heating element as an antenna electrode, said capacitive sensing circuit configured for driving a first alternating current at a first frequency into said heating element, said capacitive sensing circuit including a decision unit for deciding whether a seat occupant is present or not and for producing an output signal indicative of the decision; and
a common mode choke connected to the terminals of said heating element for DC-coupling said heating element to said heating current supply and for suppressing alternating current flow between said heating element and said heating current supply;
wherein said capacitive sensing circuit is configured for driving a second alternating current at a second frequency into said heating element,wherein said first and second frequencies, hereinafter referred to as f1 and f2, respectively, are comprised in the range from 50 kHz to 10 MHz, with f1 and f2 spaced from each other by at least 10 kHz,wherein said common mode choke is configured so as to satisfy at least one of the following conditions;
a) −
5%≦
[KREAL(f1, f2, T)−
KREAL(f1, f2, TREF)]/KREAL(f1, f2, TREF)≦
5%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KREAL(fx, fy, T) is defined as the ratio G(fy, T)/G(fx, T), where G(fx, T) and G(fy, T) is the conductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;
b) −
3%≦
[KIMAG(f1, f2, T)−
KIMAG(f1, f2, TREF)]/KIMAG(f1, f2, TREF)≦
3%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KIMAG(fx, fy, T) is defined as the ratio L(fy, T)/L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;
c) −
20%≦
[Δ
L(f1, f2, T)−
Δ
L(f1, f2, TREF)]/Δ
L(f1, f2, TREF)≦
20%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function Δ
L(fx, fy, T) is defined as the difference L(fy, T)−
L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at a temperature T, of the common mode choke at a frequency fx and fy, respectively.and wherein said decision unit is configured to decide whether a seat occupant is present or not based upon said first and second alternating currents while taking into account the at least one condition satisfied by said common mode choke in such a way as to compensate an influence of said common mode choke on said decision.
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Abstract
A combined heating and capacitive seat occupant sensing system comprises a common mode choke configured so as to satisfy at least one of a plurality of conditions, which is taken into account by a decision unit of the system in such a way that an influence of the common mode choke on the decision is compensated.
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Citations
18 Claims
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1. Combined heating and capacitive seat occupant sensing system, comprising
a heating element for producing heat when an electrical current is caused to flow across it, said heating element comprising terminals for DC-coupling said heating element to a heating current supply; -
a capacitive sensing circuit connected to said heating element so as to be able to use said heating element as an antenna electrode, said capacitive sensing circuit configured for driving a first alternating current at a first frequency into said heating element, said capacitive sensing circuit including a decision unit for deciding whether a seat occupant is present or not and for producing an output signal indicative of the decision; and a common mode choke connected to the terminals of said heating element for DC-coupling said heating element to said heating current supply and for suppressing alternating current flow between said heating element and said heating current supply; wherein said capacitive sensing circuit is configured for driving a second alternating current at a second frequency into said heating element, wherein said first and second frequencies, hereinafter referred to as f1 and f2, respectively, are comprised in the range from 50 kHz to 10 MHz, with f1 and f2 spaced from each other by at least 10 kHz, wherein said common mode choke is configured so as to satisfy at least one of the following conditions; a) −
5%≦
[KREAL(f1, f2, T)−
KREAL(f1, f2, TREF)]/KREAL(f1, f2, TREF)≦
5%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KREAL(fx, fy, T) is defined as the ratio G(fy, T)/G(fx, T), where G(fx, T) and G(fy, T) is the conductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;b) −
3%≦
[KIMAG(f1, f2, T)−
KIMAG(f1, f2, TREF)]/KIMAG(f1, f2, TREF)≦
3%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KIMAG(fx, fy, T) is defined as the ratio L(fy, T)/L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;c) −
20%≦
[Δ
L(f1, f2, T)−
Δ
L(f1, f2, TREF)]/Δ
L(f1, f2, TREF)≦
20%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function Δ
L(fx, fy, T) is defined as the difference L(fy, T)−
L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at a temperature T, of the common mode choke at a frequency fx and fy, respectively.and wherein said decision unit is configured to decide whether a seat occupant is present or not based upon said first and second alternating currents while taking into account the at least one condition satisfied by said common mode choke in such a way as to compensate an influence of said common mode choke on said decision. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Combined heating and capacitive seat occupant sensing system, comprising a heating element delivering heat upon flow of an electrical current across it, said heating element comprising terminals for DC-coupling said heating element to a heating current supply;
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a capacitive sensing circuit connected to said heating element for using said heating element as an antenna electrode, said capacitive sensing circuit configured for driving a first alternating current at a first frequency into said heating element, said capacitive sensing circuit including a decision unit for deciding whether a seat occupant is present or not and for producing an output signal indicative of the decision; and a common mode choke connected to the terminals of said heating element for DC-coupling said heating element to said heating current supply and for mitigating alternating current flow between said heating element and said heating current supply; wherein said capacitive sensing circuit is configured for driving a second alternating current at a second frequency into said heating element, wherein said first and second frequencies, hereinafter referred to as f1 and f2, respectively, are comprised in the range from 50 kHz to 10 MHz, with f1 and f2 spaced from each other by at least 10 kHz, wherein said common mode choke is configured so as to satisfy at least one of the following conditions; a) −
5%≦
[KREAL(f1, f2, T)−
KREAL(f1, f2, TREF)]/KREAL(f1, f2, TREF)≦
5%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KREAL(fx, fy, T) is defined as the ratio G(fy, T)/G(fx, T), where G(fx, T) and G(fy, T) is the conductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;b) −
3%≦
[KIMAG(f1, f2, T)−
KIMAG(f1, f2, TREF)]/KIMAG(f1, f2, TREF)≦
3%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function KIMAG(fx, fy, T) is defined as the ratio L(fy, T)/L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at temperature T, of the common mode choke at a frequency fx and fy, respectively;c) −
20%≦
[Δ
L(f1, f2, T)−
Δ
L(f1, f2, TREF)]/Δ
L(f1, f2, TREF)≦
20%, for any temperature T in the range from −
40°
C. to +150°
C.,where TREF=25°
C. and where the function Δ
L(fx, fy, T) is defined as the difference L(fy, T)−
L(fx, T), where L(fx, T) and L(fy, T) is the inductance, at a temperature T, of the common mode choke at a frequency fx and fy, respectively.wherein at least one of said first and second frequencies is selected in the range from 50 kHz to 400 kHz; and wherein said decision unit is configured to decide whether a seat occupant is present or not based upon said first and second alternating currents while taking into account the at least one condition satisfied by said common mode choke in such a way as to compensate an influence of said common mode choke on said decision. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Current AssigneeIEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
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Original AssigneeIEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
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InventorsVIRNICH, Michael, HOYER, David, THINNES, Martin, MEYERS, Thomas, PUETZ, Micheal, LAMESCH, Laurent
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Granted Patent
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Time in Patent OfficeDays
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Field of Search
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US Class Current324/686
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CPC Class CodesB60N 2/002 Seats provided with an occu...B60N 2/0021 characterised by the type o...B60N 2/5685 ResistanceB60N 2210/12 Capacitive; Electric fieldB60R 21/01532 using electric or capacitiv...B60R 21/0154 in combination with seat he...
