Temperature control apparatus

Claim 1

A temperature control apparatus for and oxygen sensor, comprising: a substrate having upper and lower major surfaces; an oxygen sensor including a gas sensor arranged on one of said major surfaces; a heater having a heating resistance on the other of said major surfaces; a Wheatstone bridge having four sides and having the heating resistance of said heater in one said side thereof and resistances in the remaining three sides to achieve a voltage balance to set a target temperature when said oxygen sensor reaches a predetermined temperature, said Wheatstone bridge serving as a temperature setting means and being adapted to produce an output voltage; a differential amplifier coupled to said Wheatstone bridge for amplifying the output voltage from said Wheatstone bridge; ramp rate setting means for setting a voltage rise rate; ramp function generating means coupled to said ramp rate setting means for generating a low voltage output when said power is turned on and for gradually increasing the voltage output therefrom in accordance with the voltage rise rate set by said ramp rate setting means linearly as a function of time after the power is turned on; selecting means coupled to said differential amplifier and to said ramp function generating means for selecting the smaller of the output voltage from said differential amplifier and the output voltage from said ramp function generating means and for producing a selected voltage; and supply power control means coupled to said selecting means for controlling power to be supplied to said Wheatstone bridge in accordance with the voltage output of said selecting means.