A control circuit for a heater with variable resistance associated with a sensor for detecting oxygen in exhaust gases

摘要

The circuit comprises a measurement resistor (Rs) in series with the heater (16, 28), a detector circuit (20) for providing a signal (VOP) indicative of the current flowing in the resistor (Rs), switching devices (PW1, PW2; PW3, PW4) for controlling the connection of the heater (16, 28) to a direct-current voltage source (Vbat) and the connection of the measurement resistor (Rs) in the supply circuit comprising the source (Vbat) and the heater (16, 28), and a control unit (18, 32) arranged to drive the switching devices (PW1, PW2; PW3, PW4) in a manner such that, each time the heater (16, 28) is activated, the measurement resistor (Rs) is kept disconnected from the supply circuit of the heater (16, 28) for a predetermined period of time and the measurement resistor (Rs) is then connected in the supply circuit of the heater (16, 28). <IMAGE>