Circuit arrangement, temperature detector, electronic device, and temperature detection method

0001The present invention relates to a circuit device, a temperature detection device, an electronic device, a temperature detection method, and the like.

0002Conventionally, a temperature detection device using a thermopile has been known as a non-contact temperature detection device. This temperature detection device has a thermopile (infrared sensor) that detects infrared radiation of a target object, and a thermistor that is provided in the vicinity of the thermopile and detects its own temperature (ambient temperature). The thermopile has the property of generating an electromotive force (electromotive voltage) due to the temperature difference between the object temperature and its own temperature. Therefore, it becomes possible to detect the object temperature based on the detection voltage detected by using the thermopile and the detection voltage detected by using the thermistor. As a conventional technique of a temperature detection device using such a thermopile, for example, there is a technique disclosed in Patent Document 1.

<p num="0003"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2002-228523</text></patcit></p>

<p num="0004"> However, in the conventional temperature detection device using a thermopile, the temperature detection is performed only by using an analog circuit, and the temperature is corrected only by adjusting the gain. Therefore, it is difficult to detect the temperature in a wide temperature range and adjust the temperature according to the characteristics of the thermopile.</p><p num="0005"> 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 enable highly accurate temperature detection according to the characteristics of the thermopile.</p>

<p num="0006"> One aspect of the present invention is to perform A / D conversion on the first detection voltage detected using a thermopile, output the first detection value of a digital value, and perform the second detection detected using a thermister. A detection circuit that performs A / D conversion on the voltage and outputs the second detected value of the digital value, and the self-temperature obtained from the second detected value, and the second electromotive voltage corresponding to the self-temperature from the self-temperature. A control unit that obtains a value, obtains a first electromotive voltage value corresponding to the object temperature from the first detected value and the second electromotive voltage value, and obtains the object temperature from the first electromotive voltage value. Related to including circuit equipment.</p><p num="0007"> According to one aspect of the present invention, the first detection value of the digital value corresponding to the first detection voltage by the thermopile and the second detection value of the digital value corresponding to the second detection voltage by the thermistor are required. Then, the self-temperature is obtained from the second detected value, the second electromotive voltage value is obtained from the self-temperature, the first electromotive voltage value is obtained from the first detected value and the second electromotive voltage value, and the first electromotive voltage value is obtained. The object temperature can be obtained from. In this way, the first electromotive voltage value and the second electromotive voltage value corresponding to the characteristics of the thermopile can be obtained by digital processing using the first detected value and the second detected value of the digital value, and the object temperature can be obtained. 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.</p><p num="0008"> Further, in one aspect of the present invention, the first storage unit that stores the value of the object temperature and the first electromotive voltage value in association with each other, and the value of the self-temperature and the second electromotive voltage value are associated with each other. The control unit stores the second electromotive voltage value by using the self-temperature value obtained from the second detection value and the second storage unit. The object temperature may be obtained by using the first electromotive voltage value obtained from the first detected value, the second electromotive voltage value, and the first storage unit.</p><p num="0009"> By doing so, it becomes possible to obtain the temperature of the object by a simple arithmetic process using the first storage unit and the second storage unit, and it is possible to reduce the processing load of the control unit and the like.</p><p num="0010"> Further, in one aspect of the present invention, the control unit performs a conversion process based on the characteristic coefficient parameter of the thermopile on the first detection value, and the conversion process is performed on the first detection value and the second detection value. The object temperature may be obtained by using the first electromotive voltage value obtained from the electromotive voltage value and the first storage unit.</p><p num="0011"> In this way, it is possible to set the characteristic coefficient parameters according to the thermopile used and obtain the object temperature using the first storage unit and the second storage unit, and it becomes possible to obtain the characteristics of various thermopile. Correspondingly, it becomes possible to realize highly accurate temperature detection.</p><p num="0012"> Further, in one aspect of the present invention, the control unit performs a conversion process based on the characteristic coefficient parameter of the thermopile on the first detection value, and the conversion process is performed on the first detection value and the second detection value. The first electromotive voltage value may be obtained from the electromotive voltage value.</p><p num="0013"> In this way, by setting the characteristic coefficient parameters according to the thermopile used, it becomes possible to realize highly accurate temperature detection corresponding to the characteristics of various thermopile.</p><p num="0014"> Further, in one aspect of the present invention, a parameter storage unit for storing the characteristic coefficient parameter of the thermopile may be included.</p><p num="0015"> In this way, by writing and storing the characteristic coefficient parameters corresponding to the thermopile used in the parameter storage unit, it is possible to realize temperature detection processing appropriate for the characteristics of the thermopile, and the thermopile with various characteristics can be realized. Will be able to correspond to.</p><p num="0016"> Further, in one aspect of the present invention, the characteristic coefficient parameter of the thermopile may be a parameter set according to the characteristic of the thermopile and the gain of signal amplification in the detection circuit.</p><p num="0017"> In this way, the thermopile characteristic coefficient parameters can be set, for example, for each circuit device product according to the thermopile characteristics used and the gain of the detection circuit.</p><p num="0018"> Further, in one aspect of the present invention, the control unit may perform offset correction processing on the thermopile and the detection circuit.</p><p num="0019"> In this way, even if there is a variation in the offset voltage of the thermopile or the offset voltage of the detection circuit, the adverse effect of this variation on the temperature measurement result can be reduced by performing the offset correction processing.</p><p num="0020"> Further, in one aspect of the present invention, the control unit may perform gain correction processing on the temperature characteristics.</p><p num="0021"> In this way, even if there is a variation in the inclination of the temperature characteristics or the like, the adverse effect of this variation on the temperature measurement result can be reduced by performing the gain correction processing.</p><p num="0022"> Further, another aspect of the present invention relates to a temperature detecting device including the circuit device according to any one of the above, the thermopile, and the thermistor.</p><p num="0023"> Further, another aspect of the present invention relates to an electronic device including the circuit device according to any one of the above.</p><p num="0024"> In another aspect of the present invention, the first detection voltage detected by using a thermopile is subjected to A / D conversion to obtain the first detection value of the digital value, and the second detection value is detected by using a thermister. A / D conversion of the detected voltage is performed to obtain the second detected value of the digital value, the self-temperature is obtained from the second detected value, and the second electromotive voltage value corresponding to the self-temperature is obtained from the self-temperature. It is related to a temperature detection method in which a first electromotive voltage value corresponding to an object temperature is obtained from the first detected value and the second electromotive voltage value, and the object temperature is obtained from the first electromotive voltage value.</p>

0025<figref num="1">A configuration example of the circuit device of the present embodiment and the temperature detection device including the circuit device.</figref><figref num="2">The explanatory view of the whole operation of the circuit apparatus of this embodiment.</figref><figref num="3">Explanatory drawing of the structure of the detection circuit for a thermopile.</figref><figref num="4">FIGS. 4 (A) and 4 (B) are explanatory views of the configuration of the thermistor detection circuit.</figref><figref num="5">5 (A) and 5 (B) are explanatory views of the temperature detection method of the present embodiment.</figref><figref num="6">Fig. 6 (A) and Fig. 6 (B) are examples of temperature tables stored in the first storage unit and the second storage unit.</figref><figref num="7">The explanatory view of the detailed processing example of the temperature detection method of this embodiment.</figref><figref num="8">Configuration example of the electronic device of this embodiment.</figref>

0026Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unreasonably limit the content of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as a means for solving the present invention. Not necessarily.

00271. Circuit device, temperature detector FIG. 1 shows a configuration example of the circuit device of this embodiment and the 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, a storage unit 70, a parameter storage unit 80, an output unit 90, and an I / F unit 100 can be included. Further, the temperature detection device of the present embodiment includes a circuit device, a thermopile 2, and a thermistor 4. The thermopile 2 is, for example, an element (electric component) that converts thermal energy into electrical energy. The thermopile 2 can be realized, for example, by connecting a plurality of thermocouples in series (or in parallel). Thermistor 4 is, for example, a resistor having a large change in electrical resistance with respect to a temperature change. The circuit device and the temperature detection device of the present embodiment are not limited to the configuration shown in FIG. 1, and various modifications such as omitting some of the components or adding other components can be performed.

0028The 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 terminals (pads, etc.) of the circuit device. Further, 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 the node of the power supply VSS (GND).

0029The detection circuit 10 performs A / D conversion on the first detection voltage VD1 detected by using the thermopile 2 and outputs the first detection value DT1 of the digital value. Further, the detection circuit 10 performs A / D conversion on the second detection voltage VD2 detected by the thermistor 4 and outputs the second detection value DT2 of the digital value.

0030Specifically, 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, the signal of the voltage across the thermopile 2 is amplified, and the first detection voltage VD1 is output. Then, the A / D conversion circuit 40 performs A / D conversion on the first detection voltage VD1 and outputs the first detection value DT1 of the digital value.

0031The thermistor detection circuit 30 includes a reference current source 32 (reference current generation circuit). Then, the thermistor detection circuit 30 outputs the second detection voltage VD2 generated by the reference current from the reference current source 32 flowing through 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 the second detection value DT2 of the digital value.

0032The control unit 50 performs various control processes of the circuit device and various arithmetic processes. This control unit 50 can be realized by a logic circuit such as a gate array circuit, a processor, or the like.

0033The storage unit 70 includes a first storage unit 72, a second storage unit 74, and a third storage unit 76. The storage unit 70 can be realized by, for example, a memory such as a ROM. The parameter storage unit 80 stores various parameters. The parameter storage unit 80 can be realized by, for example, a non-volatile memory (memory capable of electrically programming information) such as OTP (One Time Programmable ROM).

0034The output unit 90 outputs the temperature detection result measured by the control unit 50 to the outside. The I / F (interface) unit 100 performs interface processing with an external device. Through this I / F unit 100, the external device (microcomputer, controller, etc.) can set various parameters and the like to the circuit device.

0035FIG. 2 is a diagram illustrating the overall operation of the circuit device of the present embodiment. In this embodiment, first, the functions of the circuit device are set and adjusted, and then the actual temperature is measured using the thermopile 2 and the thermistor 4.

0036The function setting / adjustment shown in FIG. 2 is performed, for example, when the circuit device (temperature detection device) is manufactured. Specifically, first, various function settings of the circuit device and parameters of the sensor coefficient are written in the parameter storage unit 80 (OTP) (step S1). The function setting is, for example, a setting such as a temperature measurement range, a measurement time, or an output format of a temperature measurement result. The sensor coefficient is the sensitivity coefficient of thermopile 2 or the like.

0037Next, the measurement is performed at the control temperature (step S2). The measurement at this 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 control temperature is a temperature setting in which the self temperature = 25 degrees and the object temperature = 70 degrees (or the self temperature = 25 degrees, the object temperature = 25 degrees, etc.). Then, based on the measurement result at the control temperature, the correction parameter for temperature measurement is calculated and written in the parameter 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 time of actual temperature measurement.

0038Then, the actual temperature is measured using the circuit device whose functions have been set and adjusted in this way (step S4). Then, the control unit 50 performs a correction calculation based on the detection results (DT1, DT2) of the detection circuit 10 and the correction parameters obtained in step S3, and outputs the temperature measurement results such as the object temperature and the self-temperature. (Step S5).

0039Figure 3 shows a configuration example of the thermopile detection circuit 20. The thermopile detection circuit 20 includes an amplifier circuit 22, a gain adjustment circuit 24, and a reference voltage generation circuit 26. The thermopile detection circuit 20 is not limited to the configuration shown in FIG. 1, and various modifications such as omitting some of the components or adding other components can be performed.

0040The amplifier circuit 22 is composed of, for example, an operational amplifier OPA1 using a switched capacitor circuit. In the amplifier circuit 22 (operational amplifier OPA1), one end (positive side 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.

0041The 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 equation (1).

0042VAQ = -GC VTP + VREF (1) The gain adjustment circuit 24 (programmable gain amplifier) is composed of 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 adjustment circuit 24 is set.

0043The gain adjustment circuit 24 amplifies the output voltage VAQ of the amplifier circuit 22 with a set gain with reference to the reference voltage VREF, and outputs the first detection voltage VD1. For example, if 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, which is the output voltage of the gain adjustment circuit 24, can be expressed by the following equation (2).

0044VD1 =-(R2 / R1) (VAQ-VREF) + VREF =-GA (VAQ-VREF) + VREF (2) From the above equations (1) and (2), the first detection voltage VD1 can be expressed as the following equation (3).

0045VD1 = GC / GA / VTP + VREF (3) The A / D conversion circuit 40 performs A / D conversion for the first detection voltage VD1. Then, the first detected value DT1 (first voltage data) of the digital value obtained by the A / D conversion of the first detected voltage VD1 is output to the control unit 50. The A / D conversion circuit 40 also performs A / D conversion for the reference voltage VREF, and also outputs the digital value corresponding to the reference voltage VREF to the control unit 50.

0046Although the offset voltages of the amplifier circuit 22 (operational amplifier OPA1) and the gain adjustment circuit 24 have not been described in detail above, the control unit 50 also performs correction processing (offset cancellation processing) of these offset voltages. .. The gain GA and reference voltage VREF values of the gain adjustment circuit 24 can be variably set via the I / F section 100 of FIG. This makes it possible to set the gain GA and the reference voltage VREF in consideration of the sensitivity, temperature range, accuracy, etc. of the thermopile 2.

0047FIGS. 4 (A) and 4 (B) are diagrams illustrating the configuration of the thermistor detection circuit 30. As shown in FIG. 4 (A), the thermistor detection circuit 30 includes a reference current source 32. Then, the voltage generated by the reference current IREF from the reference current source 32 flowing through 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 for 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 (ROM3) based on the second detected value DT2. For example, FIG. 4B is a diagram showing an example of the temperature characteristics of the detection voltage of the thermistor 4. As shown in FIG. 4 (B), 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 detected value DT2 (VD2) in association with each other. For example, a temperature table in which the self-temperature value and the second detected value DT2 are associated with each other 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 for the self-temperature value corresponding to the second detected value DT2 using, for example, the temperature table stored in the third storage unit 76.

0048As described above, the circuit device of the present embodiment includes the detection circuit 10 and the control unit 50. The detection circuit 10 performs A / D conversion on the first detection voltage VD1 detected by using the thermopile 2 and outputs the first detection value DT1 of the digital value. Further, the detection circuit 10 performs A / D conversion on the second detection voltage VD2 detected by the thermistor 4 and outputs the second detection value DT2 of the digital value.

0049Then, the control unit 50 obtains the self-temperature (TTH described later) from the second detected value DT2, and obtains the second electromotive voltage value (VTH described later) corresponding to the self-temperature from the self-temperature (TTH). Then, the first electromotive voltage value (VTP0 described later) corresponding to the object temperature (TP described later) is obtained from the first detected value DT1 and the second electromotive voltage value (VTH), and the first electromotive voltage value (VTP0) is used. Obtain the object temperature (TP).

0050Specifically, the circuit device of the present embodiment includes the first storage unit 72 and the second storage unit 74 as shown in FIG. The first storage unit 72 stores the value of the object temperature (TP) and the first electromotive voltage value (VTP0) in association with each other. For example, a temperature table for the first electromotive voltage value in which the value of the object temperature and the first electromotive voltage value are associated with each other is stored. The second storage unit 74 stores the self-temperature (TTH) value and the second electromotive voltage value (VTH) in association with each other. For example, a temperature table for the second electromotive voltage value in which the self-temperature value and the second electromotive voltage value are associated with each other is stored.

0051Then, the control unit 50 obtains the second electromotive voltage value (VTH) by using the self-temperature (TTH) value obtained from the second detection value DT2 and the second storage unit 74. For example, the second electromotive voltage value is obtained by reading the second electromotive voltage value associated with the obtained self-temperature value from the second storage unit 74. Then, the control unit 50 uses the first electromotive voltage value (VTP0) obtained from the first detected value DT1 (VTP) and the second electromotive voltage value (VTH) and the first storage unit 72 to use the object. Find the temperature (TP). For example, the object temperature is obtained by searching the object temperature value corresponding to the first electromotive voltage value using the temperature table stored in the first storage unit 72.

0052As described with reference to FIGS. 4 (A) and 4 (B), the self-temperature (TTH) can be obtained by using the second detected value DT2 and the third storage unit 76.

0053Further, the control unit 50 performs a conversion process based on the thermopile characteristic coefficient parameter (GS described later) on the first detected value DT1 (VTP). Then, the first electromotive voltage value (VTP0) is obtained from the first detected value DT1 subjected to the conversion process and the second electromotive voltage value (VTH). Specifically, the control unit 50 obtains the object temperature (TP) by using the first detected value DT1 that has been subjected to the conversion process based on the characteristic coefficient parameter (GS) and the first storage unit 72.

0054Further, the parameter storage unit 80 stores the characteristic coefficient parameter (GS) of the thermopile 2. The characteristic coefficient parameter (GS) of the thermopile 2 is a parameter set according to the characteristic (S) of the thermopile 2 and the gain (GC, GA) of the signal amplification in the detection circuit 10. For example, as described with reference to FIG. 3, the detection circuit 10 (thermopile detection circuit 20) includes an amplifier circuit 22 and a gain adjustment circuit 24. For example, the characteristic coefficient parameter (GS) of the thermopile 2 is a parameter set according to the characteristic (S) of the thermopile 2 and the gain GC of the amplifier circuit 22 and the gain GA of the gain adjustment circuit 24. If such a characteristic coefficient parameter (GS) is prepared, it becomes possible to obtain the object temperature for the thermopile 2 having various characteristics (sensitivity) by using the first storage unit 72.

0055Further, the control unit 50 performs offset correction processing for the thermopile 2 and the detection circuit 10. The offset correction process of the thermopile 2 is, for example, a process for canceling the offset voltage (VTPOF described later) of the thermopile 2. The offset correction process of the detection circuit 10 is, for example, a process for canceling the offset voltage of the amplifier circuit 22 (operational amplifier OPA1) and the gain adjustment circuit 24 (operational amplifier OPA2) of FIG. This offset correction process is realized, for example, by the process of step S14 in FIG. 7, which will be described later.

0056Further, the control unit 50 performs gain correction processing (magnification correction processing) on the temperature characteristics. This gain correction process is, for example, a correction process (correction of the gain of the inclination) for the inclination of the temperature characteristic. For example, in the gain correction process, the characteristic coefficient (sensitivity, etc.) of the thermopile 2 and the circuit constant (gain of the operational amplifier, etc.) of the detection circuit 10 vary, so that the gradient (gain) of the temperature characteristic such as the temperature of the object varies. This is a process for correcting this variation when This gain correction process is realized, for example, by the process of step S15 in FIG. 7, which will be described later. For example, in the first storage unit 72 and the second storage unit 74, a temperature table having temperature characteristics as shown in FIGS. 6 (A) and 6 (B), which will be described later, is calculated based on the formula of FIG. 5 (B). Has been and is remembered. However, there are variations in the slope of the temperature characteristics in the actual device with respect to the slopes of the temperature characteristics in FIGS. 6 (A) and 6 (B). In the gain correction process for the temperature characteristics, this variation is corrected.

00572. Temperature detection method of this embodiment Next, the temperature detection method (temperature detection method) of the present embodiment will be described in detail. In this embodiment, the object temperature and the self-temperature are detected by the method described below.

0058FIG. 5 (A) is an example of a formula (theoretical formula) for calculating the electromotive voltage VTP (electromotive force) generated by the thermopile 2. TP is the object temperature, TTH is the self-temperature (thermistor temperature), and S is the characteristic coefficient of the thermopile 2. This characteristic coefficient S (unit: V) corresponds to the electromotive voltage generated by the thermopile 2 when, for example, the self-temperature TTH = 25 degrees and the object temperature TP = 70 degrees. G is the characteristic variation coefficient (0.8 to 1.2), and VTPOF is the offset voltage of the thermopile 2. G corresponds to gain variation. VTPOF corresponds to the electromotive voltage generated by 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 a factor of element variation of the thermopile 2.

0059As shown in Fig. 5 (B), the electromotive voltage VTP is the first electromotive voltage VTP0, which is the electromotive voltage of the thermopile alone, the second electromotive voltage VTH, which is the electromotive voltage generated by the self-temperature TTH, and the offset voltage V0 ( = VTPOF). The first electromotive voltage VTP0 is an electromotive voltage generated by the 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 occurs even when the temperature difference between the object temperature TP and the self-temperature TTH is 0.

0060The S in FIG. 5 (B) has a different meaning from the characteristic coefficient S in the thermopile 2 in FIG. 5 (A), and the S in FIG. 5 (B) is the ROM coefficient when the temperature data is stored in the storage unit 70. S.

0061In the present embodiment, for example, the calculation result of the first electromotive voltage VTP0 when the ROM coefficients S = 472 and G = 1.0 are 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 associated and stored in the first storage unit 72.

0062Further, 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 the temperature determination data. Specifically, the value of the self-temperature TTH and the value of the second electromotive voltage VTH are associated and stored in the second storage unit 74.

00636 (A) and 6 (B) show examples of temperature tables (temperature determination data) stored in the first storage unit 72 and the second storage unit 74. As shown in FIG. 6 (A), for example, when -31 degrees TP &lt;204 degrees, ROM coefficient S = 472 and ROM1 (TP) which is the value (ROM value) of the first electromotive voltage VTP0 at each object temperature TP. ) Is calculated. On the other hand, for example, when 204 degrees TP 401 degrees, ROM1 (TP) is calculated with the ROM coefficient S = 118. Further, as shown in FIG. 6B, ROM2 (TTH), which is the value (ROM value) of the second electromotive voltage VTH at each self-temperature TTH, is calculated, for example, at -21 ° C TTH 106 ° C.

0064The 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) fits within 12 bits = 4096. There is. In this case, when the object temperature TP reaches 204 degrees, ROM1 (TP) = 4103, which exceeds the number of significant digits of 12 bits = 4096. Therefore, when TP 204 degrees, the ROM coefficient S = 472/4 = 118. Is set to. Then, by multiplying the measurement result to be determined at the time of temperature determination by 1/4, the case where TP 204 degrees is dealt with.

0065In this embodiment, the temperature detection method described below is adopted, focusing on the fact that the electromotive voltage VTP of the thermopile 2 can be represented as shown in FIG. 5 (B).

0066First, in the present embodiment, as described with reference to FIG. 1, A / D conversion is performed for the first detection voltage VD1 and the second detection voltage VD2 detected by using the thermopile 2 and the thermistor 4, and the first is performed. Obtain the detected value DT1 and the second detected value DT2. The first detection value DT1 corresponds to the electromotive voltage VTP.

0067Then, the self-temperature TTH is obtained from the second detected value DT2. For example, as described in FIGS. 4 (A) and 4 (B), the self-temperature TTH corresponding to the second detection value DT2 obtained by A / D conversion of the second detection voltage VD2 of the thermistor 4 The self-temperature TTH is obtained by searching the value using the temperature table of the third storage unit 76.

0068Next, the 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. 5B, 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 is 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 detected value DT2, the corresponding second electromotive voltage VTH value is read from the second storage unit 74.

0069Then, based on the first detected value DT1 (VTP) and the obtained second electromotive voltage VTH value, the value of the first electromotive voltage VTP0 corresponding to the object temperature TP is obtained. For example, as is clear from the equation shown in FIG. 5 (B), 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 calculated. By subtracting, the value of the first electromotive voltage VTP0 can be obtained.

0070Next, 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 object temperature TP value corresponding to the value of the first electromotive voltage VTP0 using the temperature table of the first storage unit 72. That is, the value of the first electromotive voltage VTP0 is calculated in advance with the ROM coefficient S = 472 (118), and is 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 detected value DT1 (VTP) and the second electromotive voltage VTH (and the offset voltage V0) is set in the first storage unit 72. The object temperature TP is obtained by searching using the temperature table.

0071As 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. This makes it possible to obtain the object temperature TP with a small processing load even when the thermopile 2 having various characteristic coefficients is used.

0072That 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 the temperature is corrected only by adjusting the gain, it is difficult to perform the adjustment process according to the wide temperature range and the characteristic coefficient of the thermopile 2.

0073On 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 the digital value, and the target is digitally processed. The object temperature TP is required. Specifically, as shown in Fig. 5 (B), the object is made by effectively utilizing the fact that the equation of the electromotive voltage VTP is divided into the terms of the first electromotive voltage VTP0, the second electromotive voltage VTH, and the offset voltage V0. We are looking for temperature TP. Therefore, compared to the method of the comparative example in which the object temperature TP is obtained by analog processing by an analog circuit, it is possible to obtain the object temperature TP with high accuracy even when 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 according to the thermopile 2 having a specific characteristic coefficient, it is difficult to correspond to 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. Therefore, it is possible to obtain the object temperature TP with high accuracy by performing correction processing corresponding to the thermopile 2 having various characteristic coefficients.

0074For example, in the present embodiment, as described in FIGS. 6 (A), 6 (B), etc., the ROM coefficient S is set to a specific value (for example, S = 472, S = 118), and FIG. 5 (B). ), The values 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 correspond to the thermopile 2 having various characteristic coefficients, the characteristic coefficient parameter GS of the thermopile 2 described later is prepared. This characteristic coefficient parameter GS is written in the parameter storage unit 80 (OTP), for example, at the time of manufacturing a circuit device. Then, at the time of actual temperature measurement, conversion processing based on the characteristic coefficient parameter GS is performed on the first detected value DT1, and based on the converted first detected value DT1 and the value of the second electromotive voltage VTH, Find the value of the first electromotive voltage VTP0. 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.

0075In this way, even when thermopile 2 with various characteristic coefficients is used, the characteristic coefficient parameter GS is set to the value corresponding to the thermopile 2 and the correction process is executed to execute the correction process to obtain the object temperature TP. Can be obtained with high accuracy. Further, the first storage unit 72 and the second storage unit 74 need only store the calculation result when the ROM coefficient S is a specific value. Therefore, the storage capacity used by the first storage unit 72 and the second storage unit 74 can be saved, and the object temperature TP by digital processing can be obtained by using the first storage unit 72 and the second storage unit 74 having a small storage capacity. It becomes possible to realize arithmetic processing.

0076Further, according to the present embodiment, the storage unit is divided into two first storage units 72 and a second storage unit 74, and the first storage unit 72 stores the calculation result for the first electromotive voltage VTP0 and is second. The storage unit 74 stores the calculation result for the second electromotive voltage VTH. Then, as shown in FIG. 5 (B), the object temperature TP is obtained by utilizing the fact that the equation of the electromotive voltage VTP is divided into the 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 it is possible to obtain the object temperature TP with high accuracy while reducing the processing load of the control unit 50.

00773. Detailed processing example Next, a detailed processing example of the temperature detection method of the present embodiment will be described with reference to FIG.

0078First, the electromotive voltage VTP generated by the thermopile 2 is detected and amplified by the amplifier circuit 22 and the gain adjustment circuit 24 (PGA) of the detection circuit 10 (step S11). The first detection voltage VD1 after amplification can be expressed as the following equation (4).

0079VD1 = VREF + VTP x GC x GA (4) Here, GC is the gain of the amplifier circuit 22, and GA is the gain of the gain adjustment circuit 24.

0080Next, the first detected voltage VD1 after amplification is input to the A / D conversion circuit 40, and A / D conversion is performed to the first detected value DT1 of the digital value (step S12). The first detection value DT1 which is the A / D conversion result can be expressed by the following equation (5).

0081DT1 = (VD1 / VD28) x 4096 = (VREF + VTP x GC x GA) / VD28 x 4096 (5) VD28 is the input full-scale voltage (input voltage range) of the A / D conversion circuit 40, for example, VD28 = 2.8V. The bias voltage in FIG. 3 is set to, for example, VBS = VD28 / 2. The A / D conversion circuit 40 is a circuit that performs 12-bit (= 4096) A / D conversion, and the resolution is VD28 / 4096.

0082Next, as shown in the following equation (6), the part 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). ).

0083DT1-ADVREF = (VREF + VTP x GC x GA) / VD28 x 4096-ADVREF = (VTP x GC x GA) / VD28 x 4096 (6) Here, as explained in FIG. 5 (B), VTP can be expressed as the following equation (7).

0084VTP = VTP0-VTH + V0 (7) Therefore, the above equation (6) can be expressed as the following equation (8) by substituting the above equation (7).

0085{(VTP0-VTH + V0) x GC x GA} / VD28 x 4096 (8) Next, the process of subtracting the part related to the offset voltage V0 of the thermopile 2 (AD conversion value ADVTPOF corresponding to VTPOF) is performed (step S14). This is the process of subtracting ADVTPOF from the above equation (8), as shown in the following equation (9).

0086{(VTP0-VTH + V0) x GC x GA} / VD28 x 4096-ADVTPOF = {(VTP0-VTH) x GC x GA} / VD28 x 4096 (9) The ADVTPOF to be subtracted here can include the offset voltage (residual offset voltage) of the operational amplifiers OPA1 and OPA2 of the thermopile detection circuit 20 shown in FIG. 3 in addition to the offset voltage of the thermopile 2.

0087Next, gain correction is performed using the gain correction parameter GAJ (step S15). Gain correction parameter GAJ is a parameter for correcting the variation in gain (slope of temperature characteristics). That is, the gain of the actual device varies with respect to the design gain. Therefore, as shown in step S2 of FIG. 2, the actual device is measured at the control temperature, and the gain correction parameter GAJ of the actual device is calculated based on the measurement result. Then, at the time of the actual temperature measurement in step S4 of FIG. 2, as shown in step S5, the correction calculation of the temperature measurement result is performed using this gain correction parameter GAJ or the like.

0088Next, in order to determine the temperature value from 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 the process of multiplying the above equation (9) by the characteristic coefficient parameter GS, as shown in the following equation (10). The value after multiplying the characteristic coefficient parameter GS is described as ROM (VTP0-VTH). By multiplying by GS, it is converted to a value that matches the ROM value.

0089{(VTP0-VTH) x GC x GA} / VD28 x 4096 x GS = ROM (VTP0-VTH) (10) Here, the characteristic coefficient parameter GS can be expressed as the following equation (11).

0090GS = {(472/4096) × VD28)} / (S × GC × GA) (11) This 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 (11), the characteristic coefficient parameter GS is set according to S representing the characteristics of the thermopile 2 and the gains GC and GA of the signal amplification in the detection circuit 10. Specifically, in step S1 of FIG. 2, the characteristic coefficient parameter GS is written to the parameter storage unit 80 (OTP) as a sensor coefficient 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. ..

0091Next, 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 self-temperature TTH value obtained by 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. 6 (B), if the ROM value corresponding to the self-temperature TTH is ROM2 (TTH), then ROM (VTH) = ROM2 (TTH).

0092Next, as shown in the following equation (12), ROM (VTH) is added to ROM (VTP0-VTH), which is the value after multiplying the characteristic coefficient parameter GS, and the first thermopile 2 is used alone. Find the value of the electromotive voltage VTP0 (step S18). The value obtained by this addition is described as ROM (VTP0).

0093ROM (VTP0-VTH) + ROM (VTH) = ROM (VTP0) (12) Finally, the object temperature TP is obtained using the ROM (VTP0) obtained as in the above equation (12) and the temperature table (temperature determination data) of the first storage unit 72 (step S19). For example, using the temperature table of the first storage unit 72 shown in FIG. 6 (A), ROM 1 (TP), which is a ROM value corresponding to each object temperature TP, is sequentially read out. Then, the ROM (VTP0) is compared with the read ROM1 (TP), and the temperature at which ROM (VTP0) = ROM1 (TP) is obtained as the object temperature TP. The temperature corresponding to ROM1 (TP), which minimizes the difference between the values of ROM (VTP0) and ROM1 (TP), may be obtained as the object temperature TP. Further, the interpolation calculation may be performed from the data of a plurality of ROM1 (TP), and the temperature corresponding to the ROM (VTP0) may be obtained as the object temperature TP.

0094In the above method of the present embodiment, for example, the ROM coefficients S and G in FIG. 5 (B) are set to predetermined values (for example, S = 472, G = 1.0), and VTP0 and VTH in the equation in FIG. 5 (B) are set. The obtained values of VTP0 and VTH are stored in the first storage unit 72 and the second storage unit 74 as shown in FIGS. 6 (A) and 6 (B).

0095Further, based on the gain GC and GA which are the circuit constants of the circuit device and the characteristic coefficient S of the thermopile 2 used, the characteristic coefficient parameter GS = {(472/4096) × VD28 described in the above equation (11). } / (S × GC × GA) is calculated. Then, as shown in step S1 of FIG. 2, the obtained characteristic coefficient parameter GS is written in the parameter storage unit 80 (OTP) as a sensor coefficient parameter at the time of manufacturing the circuit device or the like. As a result, the appropriate characteristic coefficient parameter GS according to the product specifications of each circuit device (each temperature detection device) is stored in the parameter storage unit 80. Therefore, while saving the used storage capacity of the first storage unit 72 and the second storage unit 74, it is possible to support the thermopile 2 having various characteristics and to support various product specifications.

0096Further, the measurement is performed at the control temperature as shown in step S2 of FIG. 2, and the correction parameters for correcting the element variation are calculated as shown in step S3. Specifically, the gain correction parameter GAJ in step S15 and the offset voltage (ADVTPOF) in step S14 in FIG. 7 are obtained as correction parameters. That is, there are variations in the characteristic coefficient S such as the sensitivity of the thermopile 2, the circuit constants such as the gain GC and GA of the detection circuit 10, and the offset voltage due to the element variation. Therefore, as shown in step S2 of FIG. 2, the measurement is performed at the control temperature, the correction parameter is obtained based on the measurement result, and the correction parameter is written in the parameter storage unit 80 (OTP). Then, as shown in step S5, at the time of actual temperature measurement, the correction calculation of the temperature measurement result is performed based on the correction parameters stored in the parameter storage unit 80. By doing so, even if the characteristic coefficient S of the thermopile 2 or 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 will be possible.

00974. Electronic equipment FIG. 8 shows a configuration example of an electronic device including the circuit device 210 and the temperature detection device 200 of the present 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 a temperature detection device 200. Further, the temperature detection device 200 includes the circuit device 210, the thermopile 2, and the thermistor 4 of the present embodiment. The electronic device of the present embodiment is not limited to the configuration shown in FIG. 8, and various modifications such as omitting some of the components or adding other components can be performed. The electronic devices to which this embodiment is applied include air conditioning equipment such as an air conditioner, IH equipment such as an IH cooker and an IH rice cooker, a fax device, a printing device, a thermometer, a human detector, and a flame detector. Various devices such as a gas detector or a light meter can be assumed.

0098The processing unit 300 performs various control processing and arithmetic processing of electronic devices, and is realized by, for example, 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.

0099The storage unit 310 serves as a storage area for the processing unit 300 and the like, and is realized by, for example, DRAM, SRAM, HDD, or the like. The operation unit 320 is for 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.

0100Although the present embodiment has been described in detail as described above, those skilled in the art will easily understand that many modifications that do not substantially deviate from the novel matters and effects of the present invention are possible. Therefore, all such modifications are included in the scope of the present invention. For example, a term described at least once in a specification or drawing with a different term in a broader or synonymous manner may be replaced by that different term anywhere in the specification or drawing. Further, the configuration and operation of the circuit device, the temperature detection device, the electronic device, and the like are not limited to those described in the present embodiment, and various modifications can be performed.

01012 thermopile, 4 thermistor, 10 detection circuit, 20 Thermopile detection circuit, 22 Amplifier 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 storage unit, 72 1st storage unit, 74 2nd storage, 76 3rd storage, 80 parameter storage, 90 output, 100 I / F section, 200 temperature detector, 210 circuit device, 300 processing section, 310 storage unit, 320 operation unit, 330 input / output unit, 340 bus