Temperature detecting circuit

摘要

A temperature detecting circuit includes a first thermistor, a second thermistor, a first pull-up resistor, a second pull-up resistor, and a controller. The controller is configured to sense a temperature based on a voltage signal from the first thermistor if a temperature corresponding to a voltage signal from one of the first thermistor and the second thermistor is below a threshold temperature. The controller is configured to sense a temperature based on a voltage signal from the second thermistor if a temperature corresponding to a voltage signal from one of the first thermistor and the second thermistor is higher than or equal to the threshold temperature. A resistance Ra of the first thermistor, a resistance Rb of the second thermistor, a resistance Rc of the first pull-up resistor, and a resistance Rd of the second pull-up resistor have a relationship expressed by RaRd.

主权项

1. A temperature detecting circuit comprising:
a first thermistor that has a resistance Ra; a second thermistor that has a resistance Rb; a first pull-up resistor that is connected between the first thermistor and a power supply, the first pull-up resistor having a resistance Rc; a second pull-up resistor that is connected between the second thermistor and the power supply, the second pull-up resistor having a resistance Rd; and a controller comprising circuitry configured to sense a temperature based on a voltage signal from the first thermistor if a temperature corresponding to a voltage signal from one of the first thermistor and the second thermistor is below a threshold temperature, the circuitry being configured to sense a temperature based on a voltage signal from the second thermistor if a temperature corresponding to a voltage signal from one of the first thermistor and the second thermistor is higher than or equal to the threshold temperature, the resistances Ra, Rb, Rc and Rd having a relationship expressed by RaRd, wherein the controller includes
a memory configured to store a reference temperature corresponding to each of predetermined temperature intervals, in association with each of the predetermined temperature intervals, anda failure sensor configured to calculate, every time a temperature sensed based on a voltage signal from one of the first thermistor and the second thermistor becomes a temperature at each of the predetermined temperature intervals, a difference between temperatures sensed from voltage signals from both the first thermistor and the second thermistor, and to compare the difference with the reference temperature,wherein the failure sensor determines that an offset failure has occurred if the difference that exceeds the reference temperature is obtained in a temperature range wider than a predetermined temperature range, andwherein the failure sensor determines that a gain failure has occurred if the difference that exceeds the reference temperature is obtained in a temperature range narrower than the predetermined temperature range.