| 摘要 |
PROBLEM TO BE SOLVED: To provide an impression voltage control device suppressed in an excessive voltage impression to an air-fuel ratio sensor, while continuing to detect the air-fuel ratio by carrying a current to the air-fuel ratio sensor even when a battery voltage is decreased.SOLUTION: An impression voltage control device includes: an upstream operational amplifier 81 connected to an upstream terminal 200a of an air-fuel ratio sensor 200; a constant voltage part 90 connected to a downstream terminal 200b; a filter 85 into which a sensor current flows; a changeover switch 87 provided between an upstream feedback wiring 83 connecting an inverse input terminal and an output terminal of an upstream operational amplifier and the filter; and a control part 10 for controlling switching of the changeover switch on the basis of a battery voltage. The control part puts the changeover switch into a closed state from an opened state after the elapse of the predetermined time when the battery voltage is equal to or more than a first level, and the changeover switch is put into the closed state from the opened state when the battery voltage is changed into a state below a second level from the state equal to or more than the second level.SELECTED DRAWING: Figure 1 |
