METHOD AND SYSTEM FOR CONTROLLING A HEATING ELEMENT WITH TEMPERATURE SENSITIVE CONDUCTIVE LAYER
First Claim
1. A method for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor and separating them from one another, the method comprising:
- heating the heater conductor in a heating mode by causing DC power current from a direct current (DC) source to flow through the heater conductor and increase its temperature;
periodically terminating the heating mode and entering into a measurement mode in which an alternating current (AC) source provides an excitation signal to enable measurement of resistance of the NTC layer; and
controlling initiation of the heating mode based on the measurement of the resistance of the NTC layer in the measurement mode.
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Accused Products
Abstract
Methods and system for controlling a heater conductor in a heating element including a sensor conductor separated from the heater conductor by an NTC layer. The heating element is coupled to a control circuit and the flow of electricity from a direct current source through the circuit is controlled such that a change of the resistance of the NTC layer is indicative of the temperature of the heater conductor. This resistance is detected based on a time or amplitude analysis and based thereon, a heating mode of the heater conductor is controlled. In a variation, the circuit is operated in a two-period measurement mode wherein the energy transferred through the NTC layer in one period is equal and opposite to the energy transferred through the NTC layer in the other period.
16 Citations
51 Claims
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1. A method for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor and separating them from one another, the method comprising:
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heating the heater conductor in a heating mode by causing DC power current from a direct current (DC) source to flow through the heater conductor and increase its temperature; periodically terminating the heating mode and entering into a measurement mode in which an alternating current (AC) source provides an excitation signal to enable measurement of resistance of the NTC layer; and controlling initiation of the heating mode based on the measurement of the resistance of the NTC layer in the measurement mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor and separating them from one another, the system comprising:
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a direct current (DC) source; a first switch operatively coupled between said DC source and a first end of said heater conductor; a second switch operatively coupled between a second end of said heater conductor and ground; an alternating current (AC) generator; a third switch operatively coupled between said AC generator and said sensor conductor; and a controller that controls heating of the heater conductor in a heating mode by closing said first and second switch while said third switch is open thereby causing DC power current from said DC source to flow through the heater conductor and increase its temperature, said controller being further arranged to periodically terminate the heating mode and enter the system into a measurement mode in which said AC generator provides an excitation signal to enable measurement of resistance of said NTC layer by opening said first and second switches and closing said third switch, said controller being further arranged to control initiation of the heating mode based on the measurement of the resistance of the NTC layer in the measurement mode. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A system for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor and separating them from one another, the system comprising:
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a direct current (DC) source; a first switch operatively coupled between said DC source and a first end of said sensor conductor; a second switch operatively coupled between a second end of said sensor conductor and ground; an alternating current (AC) generator; a third switch operatively coupled between said AC generator and said heater conductor; and a controller that controls heating of the heater conductor in a heating mode by closing said first and second switch while said third switch is open thereby causing DC power current from said DC source to flow through the heater conductor and increase its temperature, said controller being further arranged to periodically terminate the heating mode and enter the system into a measurement mode in which said AC generator provides an excitation signal to enable measurement of resistance of said NTC layer by opening said first and second switches and closing said third switch, said controller being further arranged to control initiation of the heating mode based on the measurement of the resistance of the NTC layer in the measurement mode. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A method for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater device and the sensor conductor to separate them from one another, the method comprising:
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heating the heater conductor in a heating mode by causing DC power current from a direct current (DC) source to flow through the heater conductor and increase its temperature; periodically terminating the heating mode and entering into a measurement mode in which; in a first period, closing a switch to cause DC current from the DC source to flow through the NTC layer and charge a capacitor, detecting when the voltage of the capacitor reaches a threshold via a threshold detector, and determining a time delay between closure of the switch and the capacitor reaching the threshold via a time delay detector, and in a second period following the first period, causing the capacitor to discharge through the NTC layer such that an amount of energy transferred through the NTC layer during the first and second periods is equal; and controlling initiation of the heating mode via a controller based on the time delay. - View Dependent Claims (28, 29, 30, 31)
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32. A system for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor to separate them from one another, the system comprising:
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a direct current (DC) source; a first switch operatively coupled between said DC source and a first end of said heater conductor; a second switch operatively coupled between a second end of said heater conductor and ground; a third switch operatively coupled between said DC source and a first end of said sensor conductor; a fourth switch operatively coupled between a second end of said sensor conductor and ground; a capacitive element arranged relative to said NTC layer to be charged and discharged through said NTC layer; a controller that controls heating of the heater conductor in a heating mode by closing said first and second switches thereby causing DC power current from said DC source to flow through said heater conductor and increase its temperature, said controller being arranged to periodically terminate the heating mode and enter the system into a measurement mode in which in a first period, said third switch is closed and said first, second and fourth switches are open causing DC power current from said DC source to flow through said NTC layer and charge said capacitive element; a threshold detector that detects when the voltage of said capacitive element reaches a threshold; and a time delay detector that determines a time delay between closure of said third switch and said capacitive element reaching the threshold, and said controller being further arranged to enter the system into a second period of the measurement mode following the first period in which said fourth switch is closed and said first, second and third switches are open to cause said capacitive element to discharge through said NTC layer until said capacitive element is fully discharged, whereby an amount of energy transferred through said NTC layer during the first and second periods is equal, said controller being further arranged to control initiation of the heating mode based on the time delay detected by said time delay detector. - View Dependent Claims (33, 34, 35, 36)
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37. A method for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor to separate them from one another, the method comprising:
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heating the heater conductor in a heating mode by causing DC power current from a direct current (DC) source to flow through the heater conductor and increase its temperature; periodically terminating the heating mode and entering into a measurement mode in which; in a first measurement period, causing DC power current from the DC source to flow through the NTC layer in a first direction, and in a second measurement period following the first measurement period, causing DC power current from the DC source to flow through the NTC layer in a second direction opposite to the first direction, and controlling time of the flow of DC power current through the NTC layer in the second direction to provide that energy transferred through the NTC layer in the second measurement period is substantially equal to energy transferred through the NTC layer in the first measurement period; and controlling initiation of the heating mode via a controller based on the magnitude of the DC current passed through the NTC layer in at least one of the first and second measurement periods. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45)
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46. A system for controlling heating of a heater conductor of a heating element including a sensor conductor and a negative temperature coefficient (NTC) layer interposed between the heater conductor and the sensor conductor to separate them from one another, the system comprising:
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a direct current (DC) source; a first switch operatively coupled between said DC source and a first end of said heater conductor; a second switch operatively coupled between a second end of said heater conductor and ground; a third switch operatively coupled between said DC source and a first end of said sensor conductor; a fourth switch operatively coupled between a second end of said sensor conductor and ground; and a controller that controls heating of the heater conductor in a heating mode by controlling said switches to cause DC power current from said DC source to flow through said heater conductor and increase its temperature, said controller being arranged to periodically terminate the heating mode and enter the system into a measurement mode in which in a first period, said switches are controlled to cause DC power current from said DC source to flow through said NTC layer in a first direction, said controller being further arranged to, in a second measurement period following the first measurement period, control said switches to cause DC power current from said DC source to flow through said NTC layer in a second direction, said controller being further arranged to control a time of the flow of DC power current through said NTC layer in the second direction to provide that energy transferred through said NTC layer in the second measurement period is substantially equal to energy transferred through said NTC layer in the first measurement period and to control initiation of the heating mode based on the energy being transferred through said NTC layer in at least one of the first and second measurement periods. - View Dependent Claims (47, 48, 49, 50, 51)
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Specification