JP2015215177A - Circuit device, temperature detector, electronic apparatus and temperature detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit device capable of setting an output temperature range in a variable manner, and further to provide a temperature detector, an electronic apparatus, a temperature detection method and the like.SOLUTION: A circuit device includes: a detection circuit 10 performing A/D conversion for a first detection voltage VD1 detected by using an infrared sensor, outputting a first detection value DT1 of a digital value, performing A/D conversion for a second detection voltage VD2 detected by using a temperature sensor and outputting a second detection value DT1 of a digital value; a control section 50 obtaining a digital value of an object temperature on the basis of the first detection value DT1 and the second detection value DT2; and an output section 90 performing D/A conversion of the digital value of the object temperature and outputting an output voltage corresponding to the object temperature. The output section 90 outputs the output voltage where a temperature range of the object temperature represented by the output voltage is set in a variable manner.

Description

  The present invention relates to a circuit device, a temperature detection device, an electronic apparatus, a temperature detection method, and the like.

  Conventionally, a temperature detection device using a thermopile is known as a device that performs temperature detection without contact. This temperature detection device has a thermopile (infrared sensor) that detects infrared radiation of a target object, and a thermistor (temperature sensor) that is provided in the vicinity of the thermopile and detects self temperature (ambient temperature). The thermopile has a property of generating an electromotive force (electromotive voltage) due to a temperature difference between the object temperature and the self temperature. Therefore, the object temperature can be detected based on the detection voltage detected using the thermopile and the detection voltage detected using the thermistor.

JP 2006-189369 A

  However, since conventional temperature detection devices using a thermopile or the like perform temperature detection using only an analog circuit, measurement conditions (for example, gain for amplifying an electromotive voltage) corresponding to a desired temperature range are fixed. It was. Therefore, the temperature range that can be output is fixed, and the application is limited.

  Patent Document 1 discloses a technique of a radiation thermometer in which a CPU outputs an analog signal corresponding to a measured temperature value via an analog output circuit. However, Patent Literature 1 does not disclose a specific method for realizing an analog output by the CPU, such as an output temperature range.

  According to some aspects of the present invention, it is possible to provide a circuit device, a temperature detection device, an electronic device, a temperature detection method, and the like that can variably set the output temperature range.

  One embodiment of the present invention performs A / D conversion on the first detection voltage detected using the infrared sensor, outputs the first detection value of the digital value, and detects the second detected using the temperature sensor. A detection circuit that performs A / D conversion on the detection voltage and outputs a second detection value of a digital value, and a control for obtaining a digital value of the object temperature based on the first detection value and the second detection value And an output unit that performs D / A conversion of a digital value of the object temperature and outputs an output voltage corresponding to the object temperature, and the output unit is represented by the output voltage The present invention relates to a circuit device that outputs the output voltage in which the temperature range of the object temperature is variably set.

  According to one aspect of the present invention, the first detection value and the second detection value of the digital value are obtained by A / D conversion, and the digital value of the object temperature is obtained from the first detection value and the second detection value of the digital value. Is required. And the digital value of target object temperature is converted into the output voltage corresponding to target object temperature by the D / A conversion. For example, using a thermopile as an infrared sensor or a thermistor as a temperature sensor, digital processing is possible by A / D converting the detection voltage obtained from the infrared sensor and temperature sensor, and the temperature range of the output voltage can be set variably It becomes possible to do.

  In one aspect of the present invention, the control unit converts the digital value of the object temperature in the temperature range into a digital value in the input range of the D / A conversion based on the setting information of the temperature range. Processing may be performed, and the output unit may D / A convert the digital value of the object temperature after the conversion process and output the output voltage.

  By performing the conversion process on the digital value in this way, the digital value of the object temperature within the temperature range set by the setting information can be converted into the digital value within the input range of D / A conversion. When the digital value after this conversion is D / A converted, the temperature range of the output voltage becomes the temperature range set by the setting information. By the conversion process based on such setting information, the temperature range of the output voltage can be variably set.

  In the aspect of the invention, the control unit may perform the conversion process in which the output voltage changes linearly with respect to the object temperature.

  According to one embodiment of the present invention, since the object temperature can be digitally processed, the temperature characteristic of the object temperature can be linearly converted in the digital processing. As a result, the amount of change in output voltage with respect to the same amount of temperature change does not depend on the temperature, and the accuracy of temperature detection can be made constant in the subsequent circuit.

  In one embodiment of the present invention, the setting information may be a lower limit value of the temperature range and a temperature change amount represented by 1 LSB of the D / A conversion.

  Since the upper limit of the temperature range is determined by the lower limit value of the temperature range and the temperature change amount represented by 1 LSB, it is possible to variably set the temperature range of the object temperature by setting these setting information. .

  Moreover, in 1 aspect of this invention, the memory | storage part which memorize | stores the said setting information is included, The said control part may perform the said conversion process based on the said setting information memorize | stored in the said memory | storage part.

  In this way, a storage unit that stores setting information is provided, setting information is variably set in the storage unit, and conversion processing is performed based on the set setting information, thereby realizing variable setting of the temperature range. it can.

  In the aspect of the invention, the control unit performs a correction process on the first detection value, and the object temperature is calculated from the first detection value and the second detection value on which the correction process has been performed. The digital value may be obtained.

  According to one aspect of the present invention, since the first detection voltage detected using the infrared sensor can be A / D converted into a digital value, correction can be performed in digital processing. Since this correction process provides a highly accurate digital value of the object temperature, an output voltage representing the object temperature can be output with high accuracy by D / A converting the digital value.

  In the aspect of the invention, the correction process may be at least one of a gain correction process for temperature characteristics, a correction process for offsets, and a conversion process based on a thermopile characteristic coefficient parameter.

  In one embodiment of the present invention, these correction processes can be performed digitally. By this correction processing, it is possible to obtain a high-accuracy analog output in which variations in characteristics of the thermopile and the detection circuit are corrected.

  In one aspect of the present invention, the control unit obtains a self temperature from the second detection value, obtains a second electromotive voltage value corresponding to the self temperature from the self temperature, and determines the first detection value and the first detection value. The first electromotive voltage value corresponding to the object temperature may be obtained from the two electromotive voltage values, and the object temperature may be obtained from the first electromotive voltage value.

  If it does in this way, the 1st electromotive voltage value corresponding to the characteristic of a thermopile and the 2nd electromotive voltage value will be calculated by digital processing using the 1st detection value of the digital value, and the 2nd detection value, and object temperature Can be obtained. Therefore, it is possible to realize a circuit device that enables highly accurate temperature detection according to the characteristics of the thermopile. Further, by dividing the electropile voltage of the thermopile into the first electromotive voltage value and the second electromotive voltage value, the object temperature can be obtained by a simple calculation process, and the processing load of the control unit can be reduced. .

  In the aspect of the invention, the control unit obtains a digital value of the self temperature from the second detection value, and the output unit performs D / A conversion of the digital value of the self temperature, An output voltage corresponding to may be output.

  Thus, by outputting the output voltage corresponding to the self temperature as well as the object temperature, system control according to the self temperature becomes possible. For example, since the self temperature depends on the environmental temperature, control using the object temperature and the environmental temperature is possible.

  Moreover, in one aspect of the present invention, an interface unit that outputs a digital value of the object temperature may be included.

  In this way, not only an analog output voltage but also a digital value of the object temperature can be output. In one embodiment of the present invention, since a digital value is obtained by A / D conversion, analog processing in the external device can be made unnecessary by outputting the digital value to the external device.

  Another aspect of the present invention relates to a temperature detection device including any one of the circuit devices described above, the infrared sensor, and the temperature sensor.

  Still another embodiment of the present invention relates to an electronic apparatus including any one of the circuit devices described above.

  Still another embodiment of the present invention performs A / D conversion on the first detection voltage detected using the infrared sensor, outputs the first detection value of the digital value, and is detected using the temperature sensor. A / D conversion is performed on the second detection voltage, a second detection value of a digital value is output, a digital value of the object temperature is obtained based on the first detection value and the second detection value, The present invention relates to a temperature detection method in which a digital value of the object temperature is D / A converted to output an output voltage, and the temperature range of the object temperature represented by the output voltage is variably set.

The structural example of the circuit device of this embodiment and a temperature detection apparatus containing the same. Explanatory drawing of the whole operation | movement of the circuit apparatus of this embodiment. The detailed structural example of an output part. Example of output voltage characteristics with respect to object temperature. Example of output voltage characteristics with respect to self-temperature. Example of temperature range setting information. The flowchart of a conversion process. Explanatory drawing of the structure of the detection circuit for thermopile. FIGS. 9A and 9B are explanatory diagrams of a configuration of a thermistor detection circuit. 10A and 10B are explanatory diagrams of the temperature detection method of the present embodiment. 11A and 11B show examples of temperature tables stored in the first storage unit and the second storage unit. Explanatory drawing of the detailed process example of the temperature detection method of this embodiment. 1 is a configuration example of an electronic apparatus according to an embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Circuit Device and Temperature Detection Device FIG. 1 shows a configuration example of a circuit device of this embodiment and a temperature detection device including this circuit device. The circuit device (IC) of this embodiment includes a detection circuit 10 and a control unit 50. Further, the characteristic storage unit 70, the storage unit 80 (parameter storage unit), the output unit 90, and the I / F unit 100 can be included. In addition, the temperature detection device of the present embodiment includes a circuit device, an infrared sensor, and a temperature sensor. As the infrared sensor, a current collecting element type, a thermocouple type, or a bolometer type sensor element may be used. The temperature sensor may use a thermocouple or a thermistor as a sensor element. 1 includes a thermopile 2 as an infrared sensor and a thermistor 4 as a temperature sensor. The thermopile 2 is an element (electric part) that converts heat energy into electric energy. The thermopile 2 can be realized, for example, by connecting a plurality of thermocouples in series (or in parallel). The thermistor 4 is a resistor having a large change in electrical resistance with respect to a change in temperature, for example.

  The detection circuit 10 performs detection processing of the thermopile 2 and the thermistor 4. For example, one end (positive electrode side) and the other end (negative electrode side) of the thermopile 2 are electrically connected to the detection circuit 10 via a terminal (pad or the like) of the circuit device. One end of the thermistor 4 is electrically connected to the detection circuit 10 via a terminal (pad or the like) of the circuit device. The other end of the thermistor 4 is connected to a node of the power supply VSS (GND).

  The detection circuit 10 performs A / D conversion on the first detection voltage VD1 detected using the thermopile 2 and outputs a first detection value DT1 as a digital value. The detection circuit 10 performs A / D conversion on the second detection voltage VD2 detected using the thermistor 4, and outputs a second detection value DT2 as a digital value.

  Specifically, the detection circuit 10 includes a thermopile detection circuit 20, a thermistor detection circuit 30, and an A / D conversion circuit 40. The thermopile detection circuit 20 is connected to one end and the other end of the thermopile 2 and outputs the first detection voltage VD1 to the A / D conversion circuit 40. For example, signal amplification of the voltage at both ends of the thermopile 2 is performed, and the first detection voltage VD1 is output. The A / D conversion circuit 40 performs A / D conversion on the first detection voltage VD1, and outputs a first detection value DT1 as a digital value.

  The thermistor detection circuit 30 includes a reference current source 32 (reference current generation circuit). The thermistor detection circuit 30 outputs the second detection voltage VD2 generated when the reference current from the reference current source 32 flows to the thermistor 4 to the A / D conversion circuit 40. The A / D conversion circuit 40 performs A / D conversion on the second detection voltage VD2, and outputs a second detection value DT2 as a digital value.

  The control unit 50 performs various control processes and various arithmetic processes of the circuit device. The control unit 50 can be realized by a logic circuit such as a gate array circuit, a processor, or the like.

  The characteristic storage unit 70 includes a first storage unit 72, a second storage unit 74, and a third storage unit 76. The characteristic storage unit 70 can be realized by a memory such as a ROM. The storage unit 80 stores various parameters. The storage unit 80 can be realized by a non-volatile memory (a memory capable of electrically programming information) such as an OTP (One Time Programmable ROM).

  The output unit 90 D / A converts the temperature detection result measured by the control unit 50 into an analog signal and outputs it to the outside. The I / F (interface) unit 100 performs interface processing with an external device. Through this I / F unit 100, the control unit 50 outputs the temperature detection result as a digital signal to an external device (microcomputer, controller, etc.). In addition, the external device can set various parameters and the like to the circuit device via the I / F unit 100.

  FIG. 2 is a diagram for explaining the overall operation of the circuit device of this embodiment. In the present embodiment, first, after setting and adjusting the function of the circuit device, actual temperature measurement using the thermopile 2 and the thermistor 4 is performed.

  The function setting / adjustment shown in FIG. 2 is performed, for example, when a circuit device (temperature detection device) is manufactured. Specifically, first, various function settings and sensor coefficient parameters of the circuit device are written in the storage unit 80 (OTP) (step S1). The function setting is, for example, a setting of a temperature measurement range, a measurement time, an output format of a temperature measurement result, or the like. The sensor coefficient is a sensitivity coefficient of the thermopile 2 or the like.

  Next, measurement at the control temperature is performed (step S2). The measurement at the control temperature is a measurement (temperature detection process) performed by setting the self temperature (ambient temperature) or the object temperature to a predetermined temperature. For example, the management temperature is a temperature setting such that self temperature = 25 degrees and object temperature = 70 degrees (or self temperature = 25 degrees, object temperature = 25 degrees, etc.). Then, based on the measurement result at the control temperature, a correction parameter for temperature measurement is calculated and written in the storage unit 80 (step S3). The correction parameter is a parameter used when calculating the object temperature or the self temperature based on the detection result of the temperature measurement at the actual temperature measurement.

  Then, the actual temperature measurement is performed using the circuit device that has been set and adjusted in this way (step S4). Then, the control unit 50 performs a correction operation based on the detection results (DT1, DT2) of the detection circuit 10 and the correction parameter obtained in step S3, and outputs a temperature measurement result such as the object temperature or the self temperature. (Step S5).

2. Output Unit FIG. 3 shows a detailed configuration example of the output unit 90. The output unit 90 includes a first D / A conversion circuit 91, a second D / A conversion circuit 92, and a power supply circuit 93. The output unit 90 may be configured to output the output voltage by switching the input data of the D / A conversion circuit using one D / A conversion circuit instead of the two D / A conversion circuits.

  As described above, based on the first detection value DT1 from the thermopile 2 and the second detection value DT2 from the thermistor 4, the control unit 50 obtains the digital value DTP of the object temperature and the digital value DTH of the self temperature.

  The first D / A conversion circuit 91 D / A converts the digital value DTP of the object temperature and outputs an output voltage ATP of an analog signal corresponding to the object temperature. The second D / A conversion circuit 92 D / A converts the digital value DTH of the self temperature, and outputs an output voltage ATH of an analog signal corresponding to the self temperature. The first D / A conversion circuit 91 and the second D / A conversion circuit 92 can be realized by various D / A conversion circuits such as a ladder resistance method and a capacitor array method.

  The power supply circuit 93 generates a power supply voltage VD28 from a system power supply supplied from the outside of the circuit device, and supplies the power supply voltage VD28. For example, VD28 = 2.8V. In this case, the output full scales of the first D / A conversion circuit 91 and the second D / A conversion circuit 92 are 2.8V. For example, when 10-bit D / A conversion is performed, the D / A conversion value is 2.8 V with respect to the full scale 1023 of the input digital value. The power supply voltage VD28 may be supplied to an analog unit (for example, the detection circuit 10) other than the output unit 90.

  FIG. 4 shows an example of the output voltage ATP output from the first D / A conversion circuit 91. In this example, the temperature range of the object temperature is set to -30 degrees to 400 degrees. As will be described later, the temperature range can be arbitrarily set.

  When the first D / A conversion circuit 91 is a 10-bit D / A conversion circuit, for example, the input digital value DTP ranges from 0 to 1023. Actually, 160 to 859 excluding the upper and lower digital values are used as the input digital value DTP. That is, the control unit 50 outputs a digital value DTP = 160 to 859 corresponding to the object temperature -30 to 400 degrees, and the first D / A conversion circuit 91 sets the digital value DTP to 160 to 859. Correspondingly, output voltage ATP = 0.44V to 2.35V is output. This is because it is desired to use a range in which the characteristics of the output voltage ATP (for example, linear characteristics with respect to the input digital value) are good.

  The output voltage ATP is a characteristic that is linear (inclination constant) with respect to the object temperature. Specifically, as will be described later with reference to FIG. 10B, the control unit 50 searches the characteristic storage unit 70 from the first detection value DT1 by the thermopile 2 and the second detection value DT2 by the thermistor 4 to search for the target object. Find the temperature and self-temperature. The object temperature is obtained as a digital value, and the digital value may be, for example, the value of the object temperature itself or may be some code value corresponding to the object temperature. Then, the control unit 50 converts the digital value of the object temperature into the input digital value DTP of the first D / A conversion circuit 91. In this conversion processing, the input digital value DTP is converted linearly with respect to the object temperature (temperature step per 1 LSB is uniform). The first D / A conversion circuit 91 performs D / A conversion with a linear characteristic (uniform voltage step per 1LSB) on the input digital value DTP, so that the output voltage ATP linear with respect to the object temperature. Is obtained.

  FIG. 5 shows an example of the output voltage ATH output from the second D / A conversion circuit 92. In this example, the temperature range of the self temperature is set to −30 degrees to 110 degrees. As will be described later, the temperature range can be arbitrarily set.

  The self-temperature output voltage ATH is obtained in the same manner as the above-described object temperature output voltage ATP. That is, the range of the input digital value DTH of the second D / A conversion circuit 92 is, for example, 0 to 1023, of which 160 to 860 is used as the input digital value DTH. That is, the control unit 50 converts the detected self temperature from −30 degrees to 110 degrees into a digital value DTH = 160 to 860, and the second D / A conversion circuit 92 converts the digital value DTH to 160 to 860. Correspondingly, output voltage ATH = 0.44V to 2.35V is output. The output voltage ATH has a linear characteristic with respect to the self temperature.

  The conversion process between the object temperature and the self temperature will be described with reference to FIG. FIG. 6 is a table showing conversion process setting information (setting parameters). This setting information is written in the storage unit 80 (OTP) in step S1 of function setting / adjustment in FIG. In step S5 of temperature measurement, the setting information is read from the storage unit 80, and a conversion process is performed on the corrected temperature measurement result.

The setting information about the object temperature includes a parameter thpg for setting the resolution of D / A conversion and a parameter thpl for setting the lower limit of the temperature range. The parameter thpg is set by the following equation (1), and Δt is a temperature step per 1 LSB of the input digital value. The parameter thpl is set by the following equation (2), and t_low is the lower limit value of the temperature range.
thpg = 256 × 0.125 / Δt (1)
thpl = (t_low + 30) × 8 (2)

  By setting these lower limit values and the temperature step per 1LSB, the temperature range of D / A conversion can be set. For example, in the example of FIG. 4, thpg = 52 and thpl = 0 are set, and Δt = 0.615 and t_low = −30 degrees. Since the upper limit of the temperature range is −30+ (860−160) × Δt = 400 degrees, the temperature range of D / A conversion is −30 degrees to 400 degrees.

When the detected object temperature is TP, the control unit 50 converts the input digital value DTP of D / A conversion according to the following equation (3). For example, in the example of FIG. 4, when TP = −30 degrees, the input digital value for D / A conversion is DTP = 160, and when TP = 400 degrees, the input digital value for D / A conversion is DTP = 859.
DTP = 160 + ((TP−t_low) / Δt) (3)

The self-temperature conversion process is the same as described above. That is, the parameter thtg for setting the resolution of D / A conversion is set by the following equation (4), and the parameter thtl for setting the lower limit of the temperature range is set by the following equation (5).
thtg = 256 × 0.125 / Δt (4)
thtl = (t_low + 30) × 8 (5)

When the detected self temperature is TTH, the control unit 50 converts the input digital value DTH of D / A conversion by the following equation (6). For example, in the example of FIG. 5, thtg = 160 and thtl = 0 are set, and Δt = 0.2 and t_low = −30 degrees. When TTH = −30 degrees, the input digital value for D / A conversion is DTH = 160, and when TP = 110 degrees, the input digital value for D / A conversion is DTH = 860. That is, the temperature range of D / A conversion is set to -30 degrees to 110 degrees.
DTH = 160 + ((TTH−t_low) / Δt) (6)

  FIG. 7 shows a detailed flowchart of the conversion process. Although the conversion process of the object temperature TP will be described with reference to FIG. 7, only the setting information is different for the self temperature TTH, and can be realized by the same flow.

  When the processing of FIG. 7 is started, the control unit 50 acquires the object temperature TP as a measurement value from a memory (not shown) (for example, RAM), and acquires the lower limit value t_low from the storage unit 80 (OPT) (step S31). ). Next, it is determined whether or not the object temperature TP is larger than the lower limit value t_low (step S32).

  When the object temperature TP is larger than the lower limit value t_low, calc_buf = TP−t_low is calculated, and the sign part (for example, MSB) of calc_buf is set to “0” (step S33). On the other hand, when the object temperature TP is equal to or lower than the lower limit value t_low, calc_buf = t_low−TP is calculated, and the sign part of calc_buf is set to “1” (step S34).

  Next, the D / A conversion gain 1 / Δt is acquired from the storage unit 80 (OTP), and calc_multi = calc_buf * 1 / Δt is calculated (step S35). At this time, an integer part and a decimal part (for example, data excluding MSB) of calc_buf are used. Next, it is determined whether or not the sign part of calc_buf is “1” (step S36).

  When the sign part of calc_buf is “0”, calc_shift = 160d + calc_multi is calculated (step S37). At this time, the integer part of calc_multi is used. “D” of “160d” indicates that “160” is a decimal number. On the other hand, if the sign part of calc_buf is “1”, it is determined whether or not the integer part of calc_multi is greater than 160d (step S38).

  When the integer part of calc_multi is larger than 160d, calc_shift = 0 is set (step S39). On the other hand, when the integer part of calc_multi is 160d or less, calc_shift = 160d-calc_multi is calculated (step S40). At this time, the integer part of calc_multi is used. Next, it is determined whether or not the overflow digit (for example, the 11th bit from the LSB) of calc_shift is “1” (step S41).

  When the overflow digit of calc_shift is “0”, DTP = calc_shift is set (step S42). At this time, a significant digit of calc_shift (for example, data of 10 bits from the LSB) is used. On the other hand, when the overflow digit of calc_shift is “1”, DTP = 10′h3FF is set (step S43). “10′h” indicates that a 10-bit value is expressed in hexadecimal.

  In the above flow, the conversion process of the above equation (3) is realized in steps S33, S35, S37, and S42. In steps S32 and S38 to S40, processing is performed when the object temperature TP falls below the lower limit value t_low. That is, if DTP (calc_shift) becomes negative, DTP = 0 is set in step S39, and if positive, conversion processing of the above equation (3) is performed in step S40. In steps S41 and S43, overflow processing is performed. That is, if it is determined in step S41 that DTP (calc_shift) exceeds “10′h3FF”, DTP is limited to 10′h3FF in step S43.

  According to the above embodiment, the detection circuit 10 performs A / D conversion on the first detection voltage VD1 detected using the thermopile 2 (infrared sensor), and outputs the first detection value DT1 as a digital value. Then, A / D conversion is performed on the second detection voltage VD2 detected using the thermistor 4 (temperature sensor), and a second detection value DT2 of a digital value is output. The control unit 50 obtains a digital value DTP of the object temperature based on the first detection value DT1 and the second detection value DT2. And the output part 90 performs D / A conversion of the digital value DTP of target object temperature, and outputs the output voltage ATP corresponding to target object temperature. At this time, the output unit 90 outputs the output voltage ATP in which the temperature range of the object temperature represented by the output voltage ATP is variably set by the parameters thpg and thpl.

  In the conventional method of detecting temperature only by analog processing, there is a problem that the temperature range to be output is fixed and the application is limited. In this regard, according to the present embodiment, the analog signal detected from the thermopile 2 and the thermistor 4 is once converted into a digital value, so that the temperature range to be D / A converted can be variably adjusted by processing the digital signal. It becomes possible to do. Since the temperature range can be set freely, analog output that matches the temperature range and resolution to be measured can be performed according to the application of the final product incorporating the temperature detection device. Further, since the desired temperature range is made to correspond to the lower limit (for example, 0.44 V to 2.35 V) of the output voltage ATP, high-resolution analog output can be obtained in the desired temperature range. Further, as will be described later, it is possible to perform correction processing in the processing of digital signals, thereby enabling high-accuracy analog output of the object temperature.

  Specifically, the control unit 50 converts the digital value of the object temperature within the temperature range into the digital value within the input range of the D / A conversion based on the temperature range setting information (parameters thpg, thpl in FIG. 6). A conversion process for converting to DTP is performed. And the output part 90 D / A converts the digital value DTP of the target object temperature after conversion processing, and outputs the output voltage ATP.

  As described with reference to FIG. 4 and the like, the temperature range (for example, −30 degrees to 400 degrees) to be converted into the range (160 to 859) of the input digital value DTP for D / A conversion is set by the setting information. As a result of performing the conversion process according to this setting, the set temperature range is D / A converted corresponding to the lower limit (for example, 0.44 V to 2.35 V) of the output voltage ATP. In this way, the temperature range represented by the range from the upper limit to the lower limit of the output voltage ATP can be set variably.

  In addition, the conventional method of detecting temperature only by analog processing has a problem that only an output with non-linear temperature characteristics can be obtained. That is, as shown in FIG. 10A, the electromotive voltage VTP of the thermopile 2 has a non-linear characteristic with respect to the object temperature TP. When the non-linear electromotive voltage VTP is amplified and output in an analog manner, the output voltage becomes non-linear with respect to the object temperature. Since the amount of change in the output voltage with respect to the same amount of temperature change varies depending on the temperature, there is a possibility that the accuracy of temperature detection varies in the subsequent circuit.

  In this regard, in the present embodiment, as described with reference to FIG. 4 and the like, the control unit 50 performs a conversion process in which the output voltage ATP changes linearly with respect to the object temperature.

  That is, once the electromotive voltage VTP of the thermopile 2 is A / D converted into a digital value, the temperature characteristic of the output voltage ATP can be linearly converted in digital processing. As a result, the amount of change in output voltage with respect to the same amount of temperature change does not depend on the temperature, and the accuracy of temperature detection can be made constant in the subsequent circuit.

  As described with reference to FIG. 6 and the like, the temperature range setting information includes a temperature range lower limit value t_low (parameter thpl) and a temperature change amount Δt (parameter thpg) represented by 1 LSB of D / A conversion. The circuit device of this embodiment includes a storage unit 80 (OTP) that stores the setting information, and the control unit 50 performs a conversion process based on the setting information stored in the storage unit 80.

  As described above, by providing the storage unit 80 that stores the setting information, variable setting of the temperature range can be realized. Also, by using these setting information, the object temperature can be converted into an input digital value for D / A conversion by the above equation (3). Since the object temperature TP corresponding to the upper limit of the input digital value can be determined from the above equation (3), the temperature range of the object temperature can be set by the above setting information. Further, since the temperature change amount Δt expressed by 1LSB corresponds to the gradient of the output voltage ATP with respect to the temperature, a linear characteristic is realized by this setting information.

  In addition, there is a problem that it is difficult to correct the temperature detection result in the conventional method of detecting the temperature only by analog processing.

  In this regard, in the present embodiment, as will be described later with reference to FIG. 12 and the like, the control unit 50 performs the correction process on the first detection value DT1 by the thermopile 2, and the first detection value DT1 subjected to the correction process. And a second detection value DT2 from the thermistor 4 to obtain a digital value DTP of the object temperature.

  That is, it is possible to perform correction in digital processing by once A / D converting the electromotive voltage VTP of the thermopile 2 into a digital value. By this correction process, a highly accurate digital value of the object temperature is obtained, and an output voltage representing the object temperature with high precision is obtained by D / A conversion of the digital value.

  As shown in FIG. 12, the control unit 50 performs, as correction processing, gain correction processing for temperature characteristics (step S15), correction processing for offsets (step S14), and conversion processing (steps based on the characteristic coefficient parameter GS of the thermopile 2). At least one of S16) is performed.

  These correction processes correct the characteristic variation (individual difference) of the thermopile 2 and the detection circuit 10. In this embodiment, since this characteristic variation can be digitally corrected, an analog output in which the variation in temperature characteristic is suppressed can be obtained.

  Although the analog output of the object temperature has been described above, in this embodiment, the analog output of the self temperature is also performed. That is, the control unit 50 obtains the digital value DTH of the self temperature from the second detection value DT2 by the thermistor 4, and the output unit 90 performs D / A conversion of the digital value DTH of the self temperature to obtain the self temperature. The corresponding output voltage ATH is output.

  Thus, by outputting the self temperature in analog, it is possible to cope with an application using the self temperature. Since the self temperature depends on the environmental temperature, control such as changing the control according to the self temperature (for example, changing the output of the IH heater) is possible even if the object temperature is the same.

  In addition, the circuit device of the present embodiment includes an I / F unit 100 (interface unit) that outputs a digital value DTP of the object temperature. The I / F unit 100 may output a digital value DTH of the self temperature.

  Conventionally, analog output is performed to an external device. However, in this embodiment, digital values of the object temperature and the self temperature can be obtained, and the digital values can be output to the external device. By outputting a digital value, processing is simplified in an external device such as a processor, and the processing load can be reduced.

3. Thermopile detection circuit Hereinafter, the temperature detection method of the present embodiment will be described in detail. First, the detection circuit 10 will be described in detail.

  FIG. 8 shows a configuration example of the thermopile detection circuit 20. The thermopile detection circuit 20 includes an amplification circuit 22, a gain adjustment circuit 24, and a reference voltage generation circuit 26.

  The amplifier circuit 22 is configured by an operational amplifier OPA1 using a switched capacitor circuit, for example. In the amplifier circuit 22 (operational amplifier OPA1), one end (positive terminal) of the thermopile 2 is connected to the first input terminal (inverting input terminal), and the other end of the thermopile 2 is connected to the second input terminal (non-inverting input terminal). (Negative terminal) is connected. The node of the first input terminal of the amplifier circuit 22 is set to the bias voltage VBS. Further, the reference voltage VREF generated by the reference voltage generation circuit 26 is supplied to the amplifier circuit 22 as a reference voltage for the output voltage VAQ.

The amplifier circuit 22 amplifies the electromotive voltage VTP = THPP-THPM generated in the thermopile 2. For example, when the gain of the amplifier circuit 22 is GC (for example, GC = 20), the output voltage VAQ of the amplifier circuit 22 can be expressed as, for example, the following expression (7).
VAQ = -GC · VTP + VREF (7)

  The gain adjustment circuit 24 (programmable gain amplifier) includes an operational amplifier OPA2 and resistors RA1 and RA2. One end of the resistor RA1 is connected to the output terminal of the amplifier circuit 22 (operational amplifier OPA1), and the other end of the resistor RA1 is connected to the first input terminal (inverting input terminal) of the operational amplifier OPA2. One end of the resistor RA2 is connected to the first input terminal of the operational amplifier OPA2, and the other end of the resistor RA2 is connected to the output terminal of the operational amplifier OPA2. The reference voltage VREF generated by the reference voltage generation circuit 26 is supplied to the second input terminal (non-inverting input terminal) of the operational amplifier OPA2. The resistor RA2 is a variable resistor whose resistance value is variable. By setting the resistance value of the resistor RA2, the gain of the gain adjusting circuit 24 is set.

The gain adjustment circuit 24 amplifies the output voltage VAQ of the amplification circuit 22 with a set gain with reference to the reference voltage VREF, and outputs a first detection voltage VD1. For example, when the resistance values of the resistors RA1 and RA2 are R1 and R2, the gain of the gain adjustment circuit 24 is GA = R2 / R1. Therefore, the first detection voltage VD1 that is the output voltage of the gain adjustment circuit 24 can be expressed as the following equation (8).
VD1 =-(R2 / R1). (VAQ-VREF) + VREF
= -GA. (VAQ-VREF) + VREF (8)

From the above equations (7) and (8), the first detection voltage VD1 can be expressed as the following equation (9).
VD1 = GC / GA / VTP + VREF (9)

  The A / D conversion circuit 40 performs A / D conversion for the first detection voltage VD1. Then, the first detection value DT1 (first voltage data), which is a digital value obtained by A / D conversion of the first detection voltage VD1, is output to the control unit 50. The A / D conversion circuit 40 also performs A / D conversion on the reference voltage VREF and outputs a digital value corresponding to the reference voltage VREF to the control unit 50.

  Although the offset voltage of the amplifier circuit 22 (the operational amplifier OPA1) and the gain adjustment circuit 24 has not been described in detail above, the control unit 50 also performs correction processing (offset cancellation processing) of these offset voltages. . Further, the values of the gain GA and the reference voltage VREF of the gain adjustment circuit 24 can be variably set via the I / F unit 100 of FIG. Thereby, the gain GA and the reference voltage VREF can be set in consideration of the sensitivity, temperature range, accuracy, and the like of the thermopile 2.

4). Thermistor Detection Circuit FIGS. 9A and 9B are diagrams illustrating the configuration of the thermistor detection circuit 30. As shown in FIG. 9A, the thermistor detection circuit 30 includes a reference current source 32. A voltage generated when the reference current IREF from the reference current source 32 flows to the thermistor 4 is output to the A / D conversion circuit 40 as the second detection voltage VD2. Then, the A / D conversion circuit 40 performs A / D conversion on the second detection voltage VD2, and sends the second detection value DT2 of the digital value obtained by the A / D conversion of the second detection voltage VD2 to the control unit 50. Output. The control unit 50 obtains the self temperature by referring to the third storage unit 76 (ROM 3) based on the second detection value DT2. For example, FIG. 9B is a diagram illustrating an example of temperature characteristics of the detection voltage of the thermistor 4. As shown in FIG. 9B, the self temperature can be obtained from the detection voltage of the thermistor 4. For example, the third storage unit 76 stores the self-temperature value and the second detection value DT2 (VD2) in association with each other. For example, a temperature table in which the self-temperature value is associated with the second detection value DT2 is stored. Therefore, the control unit 50 can obtain the self temperature by using the second detection value DT2 from the A / D conversion circuit 40 and the third storage unit 76. For example, the self temperature can be obtained by searching the self temperature value corresponding to the second detection value DT2 using, for example, a temperature table stored in the third storage unit 76.

5. Next, the temperature detection method (temperature detection method) of this embodiment will be described in detail. In the present embodiment, the object temperature and the self temperature are detected by the method described below.

  FIG. 10A is an example of a calculation formula (theoretical formula) for the electromotive voltage VTP (electromotive force) generated by the thermopile 2. TP is an object temperature, TTH is a self-temperature (thermistor temperature), and S is a characteristic coefficient of the thermopile 2. The characteristic coefficient S (unit: V) corresponds to the electromotive voltage generated by the thermopile 2 when the self temperature TTH = 25 degrees and the object temperature TP = 70 degrees, for example. G is a characteristic variation coefficient (0.8 to 1.2), and VTPOF is an offset voltage of the thermopile 2. G corresponds to gain variation. VTPOF corresponds to an electromotive voltage generated by the thermopile 2 when, for example, the self temperature TTH and the object temperature TP are equal (for example, TTH = TP = 25 degrees). These G and VTPOF affect the electromotive voltage VTP as an element variation factor of the thermopile 2.

  As shown in FIG. 10B, the electromotive voltage VTP includes a first electromotive voltage VTP0 that is an electromotive voltage of the thermopile alone, a second electromotive voltage VTH that is an electromotive voltage generated by the self temperature TTH, and an offset voltage V0 ( = VTPOF). The first electromotive voltage VTP0 is an electromotive voltage generated by a temperature difference between the object temperature TP and the self temperature TTH. The second electromotive voltage VTH is an electromotive voltage caused only by the self temperature TTH. The offset voltage V0 is an electromotive voltage that is generated even when the temperature difference between the object temperature TP and the self temperature TTH is zero.

  S in FIG. 10B has a different meaning from the characteristic coefficient S of the thermopile 2 in FIG. 10A, and S in FIG. 10B is a ROM when temperature data is stored in the characteristic storage unit 70. The coefficient S.

  In the present embodiment, for example, the calculation result of the first electromotive voltage VTP0 when the ROM coefficient S = 472 and G = 1.0 is stored in the first storage unit 72 as temperature determination data. Specifically, the value of the object temperature TP and the value of the first electromotive voltage VTP0 are stored in the first storage unit 72 in association with each other.

  Further, the calculation result of the second electromotive voltage VTH when S = 472 and G = 1.0 is stored in the second storage unit 74 as temperature determination data. Specifically, the value of the self-temperature TTH and the value of the second electromotive voltage VTH are stored in the second storage unit 74 in association with each other.

  11A and 11B show examples of temperature tables (temperature determination data) stored in the first storage unit 72 and the second storage unit 74. FIG. As shown in FIG. 11A, for example, in the case of −31 degrees ≦ TP <204 degrees, ROM coefficient S = 472 and ROM1 (TP value) which is the value (ROM value) of the first electromotive voltage VTP0 at each object temperature TP. ). On the other hand, for example, when 204 degrees ≦ TP ≦ 401 degrees, ROM1 (TP) is calculated with ROM coefficient S = 118. Further, as shown in FIG. 11B, ROM2 (TTH), which is the value (ROM value) of the second electromotive voltage VTH at each self-temperature TTH, for example, is calculated at −21 degrees ≦ TTH ≦ 106 degrees.

  The number of significant digits of the first storage unit 72 (second storage unit 74) is 12 bits = 4096, and the ROM coefficient S = 472 is set so that ROM1 (TP) is within 12 bits = 4096. Yes. In this case, when the object temperature TP becomes 204 degrees, ROM1 (TP) = 4103, which exceeds the effective number of bits of 12 bits = 4096. Therefore, when TP ≧ 204 degrees, the ROM coefficient S = 472/4 = 118. Is set. Then, the case where TP ≧ 204 degrees is dealt with by doubling the measurement result to be determined at the time of temperature determination.

  In this embodiment, paying attention to the fact that the electromotive voltage VTP of the thermopile 2 can be expressed as shown in FIG. 10B, a temperature detection method described below is adopted.

  First, in the present embodiment, as described with reference to FIG. 1, the first detection voltage VD1 and the second detection voltage VD2 detected using the thermopile 2 and the thermistor 4 are subjected to A / D conversion to obtain the first A detection value DT1 and a second detection value DT2 are obtained. The first detection value DT1 corresponds to the electromotive voltage VTP.

  Then, the self temperature TTH is obtained from the second detection value DT2. For example, as described with reference to FIGS. 9A and 9B, the self-temperature TTH corresponding to the second detection value DT2 obtained by A / D converting the second detection voltage VD2 of the thermistor 4 is obtained. By searching for the value using the temperature table of the third storage unit 76, the self temperature TTH is obtained.

  Next, a value of the second electromotive voltage VTH corresponding to the self temperature TTH is obtained based on the obtained self temperature TTH. Specifically, as described in FIG. 10B, the value of the second electromotive voltage VTH corresponding to the self temperature TTH is read from the second storage unit 74 based on the value of the self temperature TTH. That is, the value of the second electromotive voltage VTH is calculated in advance with the ROM coefficient S = 472, and stored in the second storage unit 74 in association with the value of the self temperature TTH. Then, based on the self-temperature TTH obtained based on the second detection value DT2, the value of the corresponding second electromotive voltage VTH is read from the second storage unit 74.

  Then, based on the first detection value DT1 (VTP) and the obtained value of the second electromotive voltage VTH, the value of the first electromotive voltage VTP0 corresponding to the object temperature TP is obtained. For example, as is apparent from the equation shown in FIG. 10B, the value of the second electromotive voltage VTH is added to the value of the electromotive voltage VTP corresponding to the first detection value DT1, and the value of the offset voltage V0 (VTPOF) is obtained. By subtracting, the value of the first electromotive voltage VTP0 can be obtained.

  Next, the object temperature TP is obtained based on the obtained value of the first electromotive voltage VTP0. Specifically, the object temperature TP is obtained by searching the value of the object temperature TP corresponding to the value of the first electromotive voltage VTP0 using the temperature table of the first storage unit 72. That is, as the ROM coefficient S = 472 (118), the value of the first electromotive voltage VTP0 is calculated in advance and stored in the first storage unit 72 in association with the value of the object temperature TP. Then, the value of the object temperature TP corresponding to the value of the first electromotive voltage VTP0 obtained from the first detection value DT1 (VTP) and the second electromotive voltage VTH (and the offset voltage V0) is stored in the first storage unit 72. The object temperature TP is obtained by searching using the temperature table.

  As described above, in the present embodiment, the object temperature TP and the self-temperature TTH are obtained from the first detection voltage VD1 of the thermopile 2 and the second detection voltage VD2 of the thermistor 4. Thereby, even when the thermopile 2 having various characteristic coefficients is used, the object temperature TP can be obtained with a small processing load.

  That is, as a method of the comparative example of the present embodiment, a method of obtaining the object temperature TP only by analog processing by an analog circuit can be considered. However, in the method of this comparative example, since temperature correction or the like is performed only by gain adjustment, it is difficult to perform adjustment processing in accordance with a wide temperature range and the characteristic coefficient of the thermopile 2.

  On the other hand, in the present embodiment, the first detection voltage VD1 of the thermopile 2 and the second detection voltage VD2 of the thermistor 4 are converted into the first detection value DT1 and the second detection value DT2 of digital values, and are processed by digital processing. The object temperature TP is obtained. Specifically, as shown in FIG. 10B, the object of the object is effectively utilized by dividing the expression of the electromotive voltage VTP into the terms of the first electromotive voltage VTP0, the second electromotive voltage VTH, and the offset voltage V0. The temperature TP is obtained. Therefore, compared to the method of the comparative example in which the object temperature TP is obtained by analog processing using an analog circuit, the object temperature TP can be obtained with high accuracy even when the thermopile 2 having various characteristic coefficients is used. Become. That is, in the method of the comparative example, when the circuit constant of the analog circuit is set in accordance with the thermopile 2 having a specific characteristic coefficient, it is difficult to deal with the thermopile 2 having a characteristic coefficient different from this setting. On the other hand, in the present embodiment, the object temperature TP is obtained by digital processing using the first detection value DT1 and the second detection value DT2. Accordingly, the object temperature TP can be obtained with high accuracy by performing correction processing corresponding to the thermopile 2 having various characteristic coefficients.

  For example, in this embodiment, as described with reference to FIGS. 11A and 11B, the ROM coefficient S is set to a specific value (for example, S = 472, S = 118), and FIG. ) Of the first electromotive voltage VTP0 and the second electromotive voltage VTH (temperature table) are calculated and stored in the first storage unit 72 and the second storage unit 74. Further, in order to cope with the thermopile 2 having various characteristic coefficients, a characteristic coefficient parameter GS of the thermopile 2 described later is prepared. The characteristic coefficient parameter GS is written in the storage unit 80 (OTP) when the circuit device is manufactured, for example. Then, during actual temperature measurement, a conversion process based on the characteristic coefficient parameter GS is performed on the first detection value DT1, and based on the first detection value DT1 subjected to the conversion process and the value of the second electromotive voltage VTH, The value of the first electromotive voltage VTP0 is obtained. Then, the object temperature TP is obtained by searching the value of the object temperature TP corresponding to the obtained value of the first electromotive voltage VTP0 using the temperature table of the first storage unit 72.

  In this way, even when the thermopile 2 having various characteristic coefficients is used, the characteristic temperature parameter GS is set to a value corresponding to the thermopile 2 and the correction process is executed, whereby the object temperature TP Can be obtained with high accuracy. In addition, the first storage unit 72 and the second storage unit 74 need only store the calculation results when the ROM coefficient S is a specific value. Therefore, the used storage capacity of the first storage unit 72 and the second storage unit 74 can be saved, and the first storage unit 72 and the second storage unit 74 having a small storage capacity can be used to control the object temperature TP by digital processing. Arithmetic processing can be realized.

  Further, according to the present embodiment, the storage unit is divided into two first storage units 72 and second storage units 74, and the first storage unit 72 stores the calculation result for the first electromotive voltage VTP0, and the second storage unit 72 The storage unit 74 stores a calculation result for the second electromotive voltage VTH. Then, as shown in FIG. 10B, the object temperature TP is obtained by utilizing the fact that the expression of the electromotive voltage VTP is divided into terms such as the first electromotive voltage VTP0 and the second electromotive voltage VTH. Therefore, it is possible to simplify the arithmetic processing for obtaining the object temperature TP, and to obtain the object temperature TP with high accuracy while reducing the processing load of the control unit 50.

6). Detailed Processing Example Next, a detailed processing example of the temperature detection method of the present embodiment will be described with reference to FIG.

First, the electromotive voltage VTP generated by the thermopile 2 is detected and amplified by the amplification circuit 22 and the gain adjustment circuit 24 (PGA) of the thermopile detection circuit 20 (step S11). The first detection voltage VD1 after amplification can be expressed as the following formula (10).
VD1 = VREF + VTP × GC × GA (10)

  Here, GC is the gain of the amplifier circuit 22, and GA is the gain of the gain adjustment circuit 24.

Next, the amplified first detection voltage VD1 is input to the A / D conversion circuit 40, and A / D converted to the first detection value DT1 as a digital value (step S12). The first detection value DT1, which is the A / D conversion result, can be expressed as in the following equation (11).
DT1 = (VD1 / VD28) × 4096
= (VREF + VTP × GC × GA) / VD28 × 4096 (11)

  VD28 is an input full-scale voltage (input voltage range) of the A / D conversion circuit 40. For example, VD28 = 2.8V. The bias voltage in FIG. 8 is set to VBS = VD28 / 2, for example. The A / D conversion circuit 40 is a circuit that performs 12-bit (= 4096) A / D conversion, and has a resolution of VD28 / 4096.

Next, as shown in the following expression (12), a portion related to the reference voltage VREF (A / D conversion value ADVREF corresponding to VREF) is subtracted from the first detection value DT1 which is the A / D conversion result (step S13). ).
DT1-ADVREF
= (VREF + VTP × GC × GA) / VD28 × 4096−ADVREF
= (VTP × GC × GA) / VD28 × 4096 (12)

Here, as described with reference to FIG. 10B, VTP can be expressed as the following equation (13).
VTP = VTP0−VTH + V0 (13)

Therefore, the above equation (12) can be expressed as the following equation (14) by substituting the above equation (13).
{(VTP0−VTH + V0) × GC × GA} / VD28 × 4096 (14)

Next, a process of subtracting the portion related to the offset voltage V0 of the thermopile 2 (AD converted value ADVTPOF corresponding to VTPOF) is performed (step S14). This is a process of subtracting ADVTPOF from the above equation (14) as shown in the following equation (15).
{(VTP0−VTH + V0) × GC × GA} / VD28 × 4096-ADVTPOF
= {(VTP0−VTH) × GC × GA} / VD28 × 4096 (15)

  The ADVTPOF subtracted here can include offset voltages (residual offset voltages) of the operational amplifiers OPA1 and OPA2 of the thermopile detection circuit 20 in FIG. 8 in addition to the thermopile 2 offset voltage.

  Next, gain correction is performed using the gain correction parameter GAJ (step S15). The gain correction parameter GAJ is a parameter for correcting the gain variation (temperature characteristic gradient) of the amplifier circuit 22 and the gain adjustment circuit 24. That is, the actual device gain varies with respect to the designed gain. Therefore, as shown in step S2 of FIG. 2, the actual device is measured at the management temperature, and the gain correction parameter GAJ of the actual device is calculated based on the measurement result. Then, at the actual temperature measurement in step S4 in FIG. 2, as shown in step S5, the temperature measurement result is corrected using the gain correction parameter GAJ and the like.

Next, in order to determine the temperature value with the temperature determination data (temperature table) of the first storage unit 72 and the second storage unit 72, a process of multiplying the characteristic coefficient parameter GS is performed (step S16). This is a process of multiplying the above equation (15) by the characteristic coefficient parameter GS as shown in the following equation (16). The value after multiplying by the characteristic coefficient parameter GS is described as ROM (VTP0−VTH). By multiplying by GS, it is converted into a value suitable for the ROM value.
{(VTP0−VTH) × GC × GA} / VD28 × 4096 × GS
= ROM (VTP0-VTH) (16)

Here, the characteristic coefficient parameter GS can be expressed as the following formula (17).
GS = {(472/4096) × VD28)} / (S × GC × GA) (17)

  The characteristic coefficient parameter GS is a conversion coefficient for matching the A / D conversion result value with the temperature table stored in the first storage unit 72 or the like. As shown in the above equation (17), the characteristic coefficient parameter GS is set according to S representing the characteristics of the thermopile 2 and gains GC and GA of signal amplification in the detection circuit 10. Specifically, in step S1 of FIG. 2, the characteristic coefficient parameter GS is written as a sensor coefficient in the storage unit 80 (OTP) at the time of manufacture. In this case, the value of the characteristic coefficient parameter GS to be written is set for each product according to the circuit constants (GC, GA) of the circuit device and the characteristics (sensitivity) of the thermopile 2 used by the circuit device. .

  Next, the ROM (VTH), which is the value of the second electromotive voltage VTH, is obtained by referring to the second storage unit 74 based on the value of the self-temperature TTH obtained from the second detection value DT2 of the thermistor detection circuit 30. (Step S17). For example, in the temperature table of the second storage unit 74 shown in FIG. 11B, if the ROM value corresponding to the self temperature TTH is ROM2 (TTH), ROM (VTH) = ROM2 (TTH).

Next, as shown in the following equation (18), ROM (VTH) is added to ROM (VTP0−VTH) which is a value after multiplying by the characteristic coefficient parameter GS, and the first of the thermopile 2 itself is added. The value of the electromotive voltage VTP0 is obtained (step S18). A value obtained by this addition is described as ROM (VTP0).
ROM (VTP0−VTH) + ROM (VTH) = ROM (VTP0) (18)

  Next, the object temperature TP is obtained using the ROM (VTP0) obtained as in the above equation (18) and the temperature table (temperature determination data) of the first storage unit 72 (step S19). For example, ROM1 (TP), which is a ROM value corresponding to each object temperature TP, is sequentially read using the temperature table of the first storage unit 72 shown in FIG. Then, the ROM (VTP0) and the read ROM1 (TP) are compared, and the temperature at which ROM (VTP0) = ROM1 (TP) is obtained as the object temperature TP. In addition, you may obtain | require the temperature corresponding to ROM1 (TP) from which the difference of the value of ROM (VTP0) and ROM1 (TP) becomes the minimum as object temperature TP. Further, interpolation calculation may be performed from a plurality of ROM1 (TP) data, and the temperature corresponding to the ROM (VTP0) may be obtained as the object temperature TP.

  Next, the object temperature TP is converted into the input digital value DTP of the first D / A conversion circuit 91, and the self temperature TTH is converted into the input digital value DTH of the second D / A conversion circuit 92 ( Step S20). Next, the first D / A conversion circuit 91 D / A converts the input digital value DTP to output an output voltage ATP corresponding to the object temperature TP, and the second D / A conversion circuit 92 inputs The digital value DTH is D / A converted to output an output voltage ATH corresponding to the self temperature TTH (step S21).

  In the method of the present embodiment described above, for example, ROM coefficients S and G in FIG. 10B are set to predetermined values (for example, S = 472, G = 1.0), and VTP0 in the equation in FIG. , VTH values are obtained, and the obtained VTP0 and VTH values are stored in the first storage unit 72 and the second storage unit 74 as shown in FIGS. 11 (A) and 11 (B).

  Further, based on the gains GC and GA, which are circuit constants of the circuit device, and the characteristic coefficient S of the thermopile 2 used, the characteristic coefficient parameter GS described in the above equation (17) = {(472/4096) × VD28) } / (S × GC × GA). Then, the obtained characteristic coefficient parameter GS is written in the storage unit 80 (OTP) as a sensor coefficient parameter when the circuit device is manufactured, as shown in step S1 of FIG. As a result, an appropriate characteristic coefficient parameter GS corresponding to the product specifications of each circuit device (each temperature detection device) is stored in the storage unit 80. Accordingly, it is possible to deal with the thermopile 2 having various characteristics while saving the used storage capacity of the first storage unit 72 and the second storage unit 74, and it is possible to cope with various product specifications.

  Further, measurement is performed at a control temperature as shown in step S2 of FIG. 2, and correction parameters for correcting element variations are calculated as shown in step S3. Specifically, the gain correction parameter GAJ in step S15 in FIG. 12, the offset voltage (ADVTPOF) in step S14, and the like are obtained as correction parameters. That is, there are variations due to element variations in the characteristic coefficient S such as the sensitivity of the thermopile 2, circuit constants such as the gains GC and GA of the detection circuit 10, and the offset voltage. Therefore, as shown in step S2 of FIG. 2, measurement is performed at the management temperature, and a correction parameter is obtained based on the measurement result and written in the storage unit 80 (OTP). Then, as shown in step S <b> 5, at the actual temperature measurement, the temperature measurement result is corrected based on the correction parameter stored in the storage unit 80. By doing so, even when the characteristic coefficient S of the thermopile 2, the circuit constant of the detection circuit 10, or the offset voltage varies, the temperature measurement result such as the object temperature TP can be obtained with higher accuracy. It becomes possible.

7). Electronic Device FIG. 13 shows a configuration example of an electronic device including the circuit device 210 and the temperature detection device 200 of this embodiment. The electronic device includes a processing unit 300, a storage unit 310, an operation unit 320, an input / output unit 330, a bus 340, and the temperature detection device 200. The temperature detection device 200 includes the circuit device 210, the thermopile 2, and the thermistor 4 of the present embodiment.

  Electronic devices to which this embodiment is applied include air conditioner equipment such as air conditioners, IH equipment such as IH cookers and IH rice cookers, FAX devices, printing devices, thermometers, human detection devices, flame detection devices, and gas. Various devices such as a detection device or a light meter can be assumed.

  The processing unit 300 performs various control processes and arithmetic processes of the electronic device, and is realized by a processor such as an MPU or an ASIC such as a display controller. The processing unit 300 performs various processes based on the temperature measurement results such as the object temperature and the self temperature detected by the temperature detection device 200.

  The storage unit 310 is a storage area of the processing unit 300 and the like, and is realized by, for example, a DRAM, an SRAM, an HDD, or the like. The operation unit 320 is used by the user to input various operation information. The input / output unit 330 exchanges data and the like with the outside, and is realized by a wired interface (USB or the like), a wireless communication unit, or the like.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. In addition, the configurations and operations of the circuit device, the temperature detection device, and the electronic device are not limited to those described in the present embodiment, and various modifications can be made.

10 detection circuit, 20 thermopile detection circuit, 22 amplification circuit,
24 gain adjustment circuit, 26 reference voltage generation circuit, 30 thermistor detection circuit,
32 reference current source, 40 A / D conversion circuit, 50 control unit, 70 characteristic storage unit,
72 first storage unit, 74 second storage unit, 76 third storage unit, 80 storage unit,
90 output unit, 91 first D / A conversion circuit, 92 second D / A conversion circuit,
93 power supply circuit, 100 I / F section, 200 temperature detection device, 210 circuit device,
300 processing unit, 310 storage unit, 320 operation unit, 330 input / output unit, 340 bus,
ATH output voltage corresponding to self temperature, output voltage corresponding to ATP object temperature,
DTH self-temperature digital value, DTP object temperature digital value,
t_low Lower limit of temperature range,
thpg, thpl, thtg, thtl parameters (setting information),
TP object temperature, TTH self-temperature, Δt 1LSB temperature change

Claims (13)

A / D conversion is performed on the first detection voltage detected using the infrared sensor, and the first detection value of the digital value is output, and the A / D regarding the second detection voltage detected using the temperature sensor. A detection circuit that performs conversion and outputs a second detection value of the digital value;
A control unit for obtaining a digital value of an object temperature based on the first detection value and the second detection value;
An output unit that performs D / A conversion of the digital value of the object temperature and outputs an output voltage corresponding to the object temperature;
Including
The output unit is
A circuit device that outputs the output voltage in which a temperature range of the object temperature represented by the output voltage is variably set. In claim 1,
The controller is
Based on the setting information of the temperature range, performing a conversion process of converting a digital value of the object temperature of the temperature range into a digital value of the input range of the D / A conversion,
The output unit is
A circuit device, wherein the digital value of the object temperature after the conversion process is D / A converted and the output voltage is output. In claim 2,
The controller is
The circuit device characterized by performing the conversion process in which the output voltage changes linearly with respect to the object temperature. In claim 2 or 3,
The circuit device is characterized in that the setting information includes a lower limit value of the temperature range and a temperature change amount represented by 1 LSB of the D / A conversion. In any of claims 2 to 4,
A storage unit for storing the setting information;
The controller is
A circuit device that performs the conversion process based on the setting information stored in the storage unit. In any one of Claims 1 thru | or 5,
The controller is
A circuit device, wherein a correction process is performed on the first detection value, and a digital value of the object temperature is obtained from the first detection value and the second detection value subjected to the correction process. In claim 6,
The circuit device is characterized in that the correction process is at least one of a gain correction process for temperature characteristics, a correction process for offsets, and a conversion process based on a characteristic coefficient parameter of a thermopile. In any one of Claims 1 thru | or 7,
The controller is
A self temperature is obtained from the second detection value, a second electromotive voltage value corresponding to the self temperature is obtained from the self temperature, and a second object voltage corresponding to the object temperature is obtained from the first detection value and the second electromotive voltage value. A circuit device characterized by obtaining one electromotive voltage value and obtaining the object temperature from the first electromotive voltage value. In any one of Claims 1 thru | or 8.
The controller is
Obtaining a digital value of the self-temperature from the second detection value;
The output unit is
A circuit device that performs D / A conversion of the digital value of the self temperature and outputs an output voltage corresponding to the self temperature. In any one of Claims 1 thru | or 9,
A circuit device comprising an interface unit for outputting a digital value of the object temperature. A circuit device according to any one of claims 1 to 10,
The infrared sensor;
The temperature sensor;
A temperature detecting device comprising:   An electronic apparatus comprising the circuit device according to claim 1. A / D conversion is performed on the first detection voltage detected using the infrared sensor, and the first detection value of the digital value is output, and the A / D regarding the second detection voltage detected using the temperature sensor. Perform the conversion and output the second detected value of the digital value;
Based on the first detection value and the second detection value, a digital value of the object temperature is obtained,
A temperature detection method, wherein a digital value of the object temperature is D / A converted to output an output voltage, and a temperature range of the object temperature represented by the output voltage is variably set.

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