| 摘要 |
PROBLEM TO BE SOLVED: To provide a temperature detecting circuit in which high accuracy temperature detection is realized when a low constant voltage power supply is employed and the dynamic range is narrow. SOLUTION: The voltage of a constant voltage power supply is divided by resistors R3, R4A to determine a reference voltage which is then transmitted, through buffer circuits 6, 7, to a thermistor connecting terminal 3 and a reference resistor connecting terminal 4. Consequently, current I1 (a current corresponding to the ambient temperature) and current I2 (a temperature invariant reference current) flow, respectively, through a thermistor resistor R1 and a temperature invariant external reference resistor R2. The I2 is equalized to the I1 by means of current mirror circuits 9, 10, 11 and converted into a voltage before being inputted to the plus side of a comparator circuit 81 having the minus side being fed with a reference voltage for setting a temperature through division resistors R5, R6. Comparison results from the comparator circuit 81 are fed to the output terminal 51. Dynamic range of the circuit is ensured easily even under conditions of low constant voltage power supply for variation of the thermistor resistor R1 resulting in high accuracy temperature detection.
|
