US 8,772,679 B2Granted

Method and system for controlling a heating element with temperature sensitive conductive layer

AssigneeWeiss Controls, Inc.

InventorLenny Novikov

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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.

Claims5

Dependent claims

A method for controlling the temperature of flexible heating wire powered by a direct current (DC) power source, the heating wire comprising at least two conductors in electrical contact with a Negative Temperature Coefficient polymer layer (NTC layer) disposed between said at least two conductors;

the method comprising:
supplying power from said DC power source to at least one of said at least two conductors for a fixed period of time, called a heating period, to increase a temperature of said flexible heating wire, while connecting the other of the at least two conductors to prevent current flow through the NTC layer,
measuring a resistance of the NTC layer by passing a current flow through the NTC layer in both positive and negative directions and providing equal energy transfer in both the positive and negative directions to prevent polarization of the NTC layer,
comparing the resistance value of the NTC layer with a predetermined value, and
initiating a next heating period with DC power if the resistance of the NTC layer is above the predetermined value, and initiating the next heating period without DC power if the resistance of the NTC layer is not greater than the predetermined value.

2 more elements

Dependencies are inferred from the claim text.