TEMPERATURE CONTROLLING DEVICE OF OXYGEN CONCENTRATION SENSOR

• Main Authors: NAKAJIMA TOYOHEI, MIENO TOSHIYUKI
• Format: Patent
• Language: English
• Published: 19.06.1989
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

PURPOSE:To apply a duty control to a current supplied to a current-heated element and thereby to detect an overheated state rapidly, by providing a means to supply a minute current to a heater and by detecting a heater current value even when a switching element is OFF. CONSTITUTION:When an output level of a comparator circuit 44 turns to be H, a transistor (Tr) 32 turns ON, a voltage VB is impressed on a series circuit of a heater 20 and a resistor 31, a heater current is caused to flow thereby, and the opposite-end voltage of the resistor 31 is supplied as a heater current value IH to a differential amplifier 40. At the same time, the voltage VB is impressed also on a series circuit of resistors 33 and 34 and a partial voltage is supplied as a reference voltage Vr1 to the differential amplifier 40. A voltage corresponding to a difference voltage between the opposite-end voltage of the resistor 31 and Vr1 is outputted from the circuit 40 to an integrating circuit 43. When the circuit 44 delivers an L output, the Tr 32 turns OFF and a minute current flows to the series circuit of the heater 20 and the resistor 31 and the series circuit of the resistors 33 and 34 through a resistor 46. The opposite- end voltage of the resistor 31 and Vr1 are obtained from this minute current, and the voltage corresponding to the difference voltage thereof is outputted from the circuit 40 to the circuit 43.