Self-Limiting Heater
AssigneeLittelfuse, Inc.
InventorsEfrem Fesshaie, Paulius Kabisius, Jianhua Chen, Rimantas Misevicius
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Abstract
A self-limiting heater and method for building the self-limiting heater are disclosed. The self-limiting heater consists of a resistor and a PTC resistor coupled together in series with a power supply. Both resistive devices have good thermal coupling. The resistor has a minimal resistance change over changes in temperature while the resistance of the PTC resistor increases with an increase in temperature. The ohmic resistance ratio between the resistor and the PTC may be used to adjust the heater characteristics and limit the characteristic sharpness.
Claims20
A self-limiting heater comprising:
- a voltage source;
- a resistor comprising a minimal resistance change over changes in temperature;
- and
- a positive temperature coefficient (PTC) resistor, wherein the resistor and the PTC resistor:
- are coupled electrically to one another in series;
- are thermally coupled to one another;
- wherein the self-limiting heater automatically reduces its power output in response to a temperature increase up to a temperature limiting condition.
A method of manufacturing a self-limiting heater, the method comprising:
- coupling a resistive element to a copper layer of a metal-based printed circuit board (PCB);
- and
- coupling a positive temperature coefficient (PTC) element to the copper layer of the metal-based PCB, wherein the resistive element and the PTC element are in series with one another;
- wherein the metal-based PCB increases in temperature in response to a power dissipation in the resistive element and PTC element with voltage being issued from a power source;
- wherein the temperature of the self-limiting heater does not reach a temperature limiting condition.
Dependencies are inferred from the claim text.