# US 9,435,697 B2 · Temperature detecting circuit

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- Number: US 9,435,697 B2
- Document ID: US9435697B2
- Status: Granted
- Kind: B2
- Application number: 14/076,271
- Filed: 2013-11-11
- Published: 2014-05-15
- Granted: 2016-09-06
- Earliest claimed: 2012-11-12
- Assignees: Honda Motor Co., Ltd.
- Applicants: Honda Motor Co., Ltd.
- Inventors: Hiroyasu Ozaki; Koichi Takaku; Taneaki Miura; Koichi Kato; Saneto Asano
- Web page: https://patentgrep.com/patent/US9435697B2

## CPC

- G01K 7/22: the element being a non-linear resistance, e.g. thermistor (G01K7/26 takes precedence)
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)

## Abstract

A temperature detecting circuit includes a first thermistor, a second thermistor, a first pull-up resistor, and a second pull-up resistor. The first thermistor has a first positive-side terminal. The second thermistor has a second positive-side terminal. The first thermistor and the second thermistor have different detection sensitivities to temperature. The first pull-up resistor is connected between the first thermistor and a power supply. The second pull-up resistor is connected between the second thermistor and the power supply. The first pull-up resistor and the second pull-up resistor have different resistances. The first pull-up resistor and the second pull-up resistor have such resistances that, in a state where the first positive-side terminal and the second positive-side terminal are short-circuited to each other, the first thermistor detects a temperature as a temperature lower than an actual temperature, and the second thermistor detects a temperature as a temperature higher than an actual temperature.

## Claims

### Claim 1

A temperature detecting circuit comprising:
a first thermistor having a first positive-side terminal;
a second thermistor having a second positive-side terminal, the first thermistor and the second thermistor having different detection sensitivities to temperature;
a first pull-up resistor connected between the first thermistor and a power supply; and
a second pull-up resistor connected between the second thermistor and the power supply, the first pull-up resistor and the second pull-up resistor having different resistances, the first pull-up resistor and the second pull-up resistor having such resistances that, in a state where the first positive-side terminal and the second positive-side terminal are short-circuited to each other, the first thermistor detects a temperature as a temperature lower than an actual temperature, and the second thermistor detects a temperature as a temperature higher than an actual temperature.

### Claim 2 (depends on 1)

The temperature detecting circuit according to claim 1, wherein when Ra denotes a resistance of the first thermistor, Rb denotes a resistance of the second thermistor, Rc denotes a resistance of the first pull-up resistor, and Rd denotes a resistance of the second pull-up resistor, the resistances Ra, Rb, Rc, and Rd have a relationship expressed by Ra<Rb and Ra/(Ra+Rc)<Rb/(Rb+Rd).

### Claim 3 (depends on 1)

The temperature detecting circuit according to claim 1, further comprising:
a failure sensor configured to sense, if voltage signals from the first thermistor and the second thermistor are equal to each other, that a positive terminal short-circuit failure has occurred in the first thermistor and the second thermistor.

### Claim 4 (depends on 3)

The temperature detecting circuit according to claim 3, further comprising:
a temperature sensor 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 temperature sensor 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; and
a limiting controller configured to place a limitation on an object to be limited, in one of
a case in which a temperature sensed by the temperature sensor becomes lower than a predetermined lower temperature or exceeds a predetermined higher temperature which is higher than the predetermined lower temperature, and
a case in which the positive terminal short-circuit failure is sensed by the failure sensor.

### Claim 5 (depends on 1)

The temperature detecting circuit according to claim 1, wherein the first thermistor and the second thermistor are placed inside a container whose internal temperature fluctuates when fluid is supplied into or released from the container.

### Claim 6 (depends on 1)

The temperature detecting circuit according to claim 1,
wherein the first pull-up resistor is connected to the first positive-side terminal of the first thermistor, and
wherein the second pull-up resistor is connected to the second positive-side terminal of the second thermistor.