| 摘要 |
PROBLEM TO BE SOLVED: To simplify a circuit for calculating the power of the heater of an oxygen concn. sensor. SOLUTION: A sub-microcomputer 18 controls the heater duty Duty and takes in the voltage VB of a power supply for supplying power to a heater 15 through an A/D converter 34 and uses the power supply voltage VB as the substitute data of the applied voltage of the heater 15 to calculate the power of the heater according to either one of formulae represented by heater power= VB2/R×Duty and heater power=VB2×Duty (wherein R is a heater resistance value). Since the heater resistance value R becomes almost constant in a stable area, it can be regarded as a constant. Therefore, unknown data (variable) necessary for calculating the heater power becomes only the power supply voltage VB being the substitute data of the applied voltage V of the heater and the heater duty Duty. Since the sub-microcomputer 18 itself controls the heater duty Duty, the control value thereof may be utilized as it is. |
