Littelfuse, Inc.
Self-Limiting Heater

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.