Circuit for driving a heater at a constant power

摘要

A current-limiting resistor is connected between a power-supply line and a heater provided near the oxygen-detecting element of limiting-current type oxygen sensor. A power MOSFET is connected between the heater and a ground line. The resistor and the heater have such resistances that a current I2 flowing through the resistor and the heater when the heater has a resistance R2 is about I1{square root}{square root over ((R1/R2))}, where I1 is a current flowing through the resistor and the heater when the heater has a resistance R1.