Heater control switch for lambda probe used for combustion engine exhaust emissions control, has current limitation and fast response, by providing voltage compensation via micro controlled field effect transistor

摘要

A switching arrangement for the resistance heater of a lambda probe, using a field effect transistor current limiting device, has a micro controller that calculates the optimum switching time to allow rapid response and prevents uncontrolled current, by incrementing the electromotive force effectively applied up to full battery voltage over this interval. A switching arrangement for the resistance heater (100) of a lambda probe, using a field effect transistor (FET) current limiting device (102), has a micro controller (104) to detect the voltage drop across the heater and control the FET to compensate for this falling voltage. The controller calculates the optimum switching time to allow rapid response and prevents uncontrolled current, which can destroy the heater, by incrementing the electromotive force effectively applied up to full battery voltage over this interval. An independent claim is included for engine management units using the above switching arrangement.