Heater control apparatus for oxygen sensor

摘要

In a heater control of an oxygen sensor, a heater control circuit (80) is rendered fully conductive at 100% duty initially to supply full power to a heater (26) until the resistance value of the heater (26) reaches a predetermined initial value corresponding to a predetermined temperature. Then, the duty of the heater control circuit (80) is feedback controlled so that the heater temperature becomes a target value until the internal resistance of the oxygen sensor (S) reaches a target temperature, and further, after the internal resistance of the oxygen sensor S reaches the target temperature, the duty of the heater control circuit (80) is feedback controlled so that the element temperature of the sensor S becomes a target value. $$