Ad converter correction means

Abstract

To provide an electric circuit having means for correcting a detection error that occurs when connecting a plurality of mutually different AD converters to a single analog sensor as a solution to the problem with a configuration having the plurality of mutually different AD converters connected to the single analog sensor, where there is risk of causing an error in detection accuracy due, for example, to the fact that characteristics themselves are different between the plurality of AD converters, and that the power supply sources of the AD converters are different.SOLUTION: By configuring a reference power supply that can correct the difference in characteristics between multiple AD converters and the difference in power supplies of the AD converters and a switch for selecting power supply sources of the AD converters, and controlling these by appropriate means, it is made possible to obtain correction information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to correction of measurement errors that occur when measuring a measurement object using an AD converter.

Background Art

[0002] As a means for detecting an analog electrical signal by an analog sensor, an AD converter is generally used. As an example, there is a circuit in which a thermistor element pulled up by a power supply is connected to an AD converter and used for temperature measurement by utilizing a change in the resistance value of the thermistor. In addition, in recent years, due to the strengthening of environmental regulations on power consumption of electrical equipment, when the equipment is in a power-saving state, the power supply of a multifunctional IC with high power consumption is cut off, and some functions are replaced by another IC with low power consumption to achieve power saving. When this is applied to an AD converter, a configuration in which a single analog sensor is connected to a plurality of AD converters is formed. At this time, there is a concern that an error may occur in the detection accuracy due to differences in the characteristics of the AD converters themselves among a plurality of them or differences in the power supply sources of the AD converters.

[0003] The following are examples of prior art for correcting the detection error of an analog sensor by an AD converter.

[0004] The feature of Patent Document 1 is to provide a correction means when a plurality of analog sensors are connected to a single AD converter.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the above-mentioned literature, there is no mention of correction means when a plurality of AD converters are connected to a single analog sensor. Therefore, there is a problem that the error existing between the plurality of AD converters as described in the background art cannot be corrected.

[0007] An object of the present invention is to provide analog value detection means capable of correcting detection errors existing between a plurality of AD converters.

Means for Solving the Problems

[0008] To achieve the above object, the present invention includes an analog sensor having an analog signal output function, a main IC incorporating an AD converter, a sub IC incorporating an AD converter, a main power supply for supplying power to the main IC, a sub power supply for supplying power to the sub IC, a reference power supply for supplying power to the main IC and the sub IC, a switch for switching the power supply connected to the main IC, a switch for switching the power supply connected to the sub IC, and a switch for switching the output of the analog sensor to the main IC or the sub IC, and has means for identifying and correcting error factors when detecting an analog value using the respective AD converters incorporated in the main IC and the sub IC.

Effects of the Invention

[0009] As described above, according to the present invention, analog value detection means for solving the above problems can be obtained.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0011] The following description of the embodiments is merely a specific example of the implementation of the present invention described in as much detail as possible in order to meet the requirements for description (description requirements and implementability requirements) of the specification required by laws and regulations. Therefore, it is natural that the present invention is not limited to the specific configurations of the embodiments described below as will be described later.

Embodiment

[0012] FIG. 1 is a circuit configuration diagram having correction means for a circuit in which two AD converters are connected to a single analog sensor. The analog sensor 100 has an analog output function, and for example, an optical sensor that outputs a voltage proportional to the received light intensity when receiving light can be considered. The main IC 101 is a multifunctional IC equipped with a CPU represented by an ASIC, a non-volatile memory area, a volatile memory area, etc., and has an AD converter 103. When expanding the memory area, it is also possible to connect a non-volatile memory such as a ROM and a volatile memory such as a RAM outside the main IC 101. The sub-IC 102 is an IC having an AD converter 104. The sub-IC 102 has a communication interface between the main IC 101 and can transfer the information acquired by the AD converter 104 to the main IC. The main power supply 105 supplies the power supply V1 to the main IC 101. The sub-power supply 106 supplies the power supply V2 to the sub-IC.

[0013] The reference power supply 107 supplies the power supply Vref to both the main IC 101 and the sub-IC 102. Since Vref is a power supply used for error correction of the AD converters 103 and 104 due to fluctuations in the voltages V1 and V2, the higher the voltage accuracy of Vref, the more desirable it is for the required specifications of the main IC 101 and the sub-IC 102. The SW108 switches the power supply source for the main IC 101 to either V1 or Vref. The SW109 switches the power supply source for the sub-IC 102 to either V2 or Vref. The SW110 switches the output of the analog sensor 100 to either the main IC 101 or the sub-IC 102.

[0014] The operations and flows for correcting the detection errors of the analog sensor 100 occurring in the AD converter 103 and the AD converter 104 in this embodiment will be described below with reference to FIGS. 2 to 6. In Operation 1 of FIG. 2, both the switch 108 and the switch 109 are connected to the Vref side (FIG. 6_S1). In this state, the switch 110 is connected to the main IC 101 side (FIG. 6_S2), and the detection value of the analog sensor 100 by the AD converter 103 is acquired (FIG. 6_S3). This acquired value is designated as AD_main_ref and stored in the memory area of the main IC 101. Next, in Operation 2 of FIG. 3, only the switch 110 is connected to the sub-IC 102 side from the state of Operation 1 of FIG. 2 (FIG. 6_S4). In this state, the detection value of the analog sensor 100 by the AD converter 104 is acquired (FIG. 6_S5). This acquired value is designated as AD_sub_ref and stored in the memory area of the main IC 101 through the communication interface between the main IC 101 and the sub-IC 102. Here, AD_main_ref and AD_sub_ref are compared (FIG. 6_S6), and this difference is designated as dif_1 and stored in the memory area of the main IC 101 (FIG. 6_S7). dif_1 = AD_main_ref - AD_sub_ref ···(Equation 1)

[0015] Next, in the third operation of FIG. 4, only switch 109 is connected to the sub-power supply 106 side from the state of the second operation of FIG. 2 (FIG. 6_S8). In this state, the detection value of the analog sensor 100 is acquired by the AD converter 104 (FIG. 6_S9). This acquired value is designated as AD_sub, and is stored in the storage area of the main IC 101 through the communication interface between the main IC 101 and the sub-IC 102. Here, AD_main_ref and AD_sub are compared (FIG. 6_S10), and this difference is designated as dif_2 and stored in the storage area of the main IC 101 (FIG. 6_S11). dif_2 = AD_main_ref - AD_sub ···· (Equation 2)

[0016] Next, in the fourth operation of FIG. 5, switch 108 is connected to the main power supply 105 side from the state of the fourth operation of FIG. 3 (FIG. 6_S12), and switch 110 is connected to the main IC 101 side (FIG. 6_S12). In this state, the detection value of the analog sensor 100 is acquired by the AD converter 103 (FIG. 6_S13). This acquired value is designated as AD_main, and is stored in the storage area of the main IC 101 (FIG. 6_S14). Here, AD_main and AD_sub are compared (FIG. 6_S15), and this difference is designated as dif_3 and stored in the storage area of the main IC 101 (FIG. 6_S16). dif_3 = AD_main - AD_sub ···· (Equation 3)

[0017] Here, the properties of the comparison results dif_1, dif_2, and dif_3 obtained by Equations 1, 2, and 3 and the calculation of the correction information will be described. Since dif_1 is the difference between the AD detection values by the AD converter 103 and the AD converter 104 acquired when the power supplies of the main IC 101 and the sub-IC 102 are connected to the reference power supply 107, the error between the AD converter 103 and the AD converter 104 caused by the power supply accuracy is eliminated. That is, it is equivalent to the error derived from the AD conversion performance itself of the AD converter 103 and the AD converter 104. This is defined as the correction information crr_adc and can be expressed by the following equation. crr_adc = dif_1 ···· (Equation 4)

[0018] dif_2 is the difference in the AD detection values obtained by the AD converters 103 and 104 in a state where the power supply of the main IC 101 is connected to the reference power supply 107 and the power supply of the sub-IC 102 is connected to the sub-power supply 106. Therefore, dif_2 is information in which the error derived from the AD conversion performance itself of the AD converters 103 and 104 and the error caused by the voltage accuracy of the sub-power supply 106 to the AD converter 104 are combined. However, since it has been found that the error derived from the AD conversion performance itself of the AD converters 103 and 104 is crr_adc according to Equation 4, by comparing dif_2 and crr_adc, it is possible to extract only the error caused by the voltage accuracy of the sub-power supply 106 to the AD converter 104. This is defined as correction information crr_sub_pw and can be expressed by the following formula. crr_sub_pw = dif1 ― crr_adc····(Equation 5)

[0019] dif_3 is the difference in the AD detection values obtained by the AD converters 103 and 104 in a state where the power supply of the main IC 101 is connected to the main power supply 105 and the power supply of the sub-IC 102 is connected to the sub-power supply 106. Therefore, dif_3 is information in which the error derived from the AD conversion performance itself of the AD converters 103 and 104, the error caused by the voltage accuracy of the main power supply 105 to the AD converter 103, and the error caused by the voltage accuracy of the sub-power supply 106 to the AD converter 104 are combined. However, since it has been found that the error derived from the AD conversion performance itself of the AD converters 103 and 104 is crr_adc according to Equation 4, and the error caused by the voltage accuracy of the sub-power supply 106 to the AD converter 104 is crr_sub_pw according to Equation 5, by comparing dif_3, crr_adc, and crr_sub_pw, it is possible to extract only the error caused by the voltage accuracy of the main power supply 105 to the AD converter 103. This is defined as correction information crr_main_pw and can be expressed by the following formula. crr_main_pw = dif3 ― crr_adc ― crr_sub_pw ···· (Equation 6)

[0020] By the above operations, it is possible to identify the error factors, crr_adc, crr_sub_pw, and crr_main_pw, that occur in the AD converters 103 and 104 in the configuration of FIG. 1 (FIG. 6_S17). Also, through a series of operations of the switches 108, 109, and 110 in FIGS. 2 to 5, these error factors can be identified with the minimum number of switching times, so it is characteristic that the time for circuit operations required to calculate the error factors is minimized.

Example

[0021] This chapter describes the configuration changes when the type of the analog sensor 100 changes for Example 1. Regarding the configuration and operation, since there are many parts that are the same as those in Example 1, only the differences from the configuration of Example 1 will be described using FIG. 6.

[0022] Depending on the type of the analog sensor 100, it may be necessary to connect pull-up resistors 200 and 201 to the analog sensor as shown in FIG. 6. A typical example is a circuit that detects temperature changes using a thermistor. The errors that occur when detecting an analog sensor by an AD converter when using the pull-up resistors 200 and 201 are the errors caused by the resistance accuracy of the pull-up resistors 200 and 201 and the voltage accuracy of the pull-up power supply.

[0023] However, even in this case, it is possible to identify the error factors by the same operations as the method shown in Example 1. Specifically, the error factor of the pull-up resistor 201 is included in AD_sub obtained in (FIG. 7_S9), the error factor of the above-mentioned pull-up resistor 201 is included in AD_sub obtained in (FIG. 7_S9), and the error factor of the above-mentioned pull-up resistor 200 is included in AD_main obtained in (FIG. 7_S13). However, by obtaining the correction information crr_adc, crr_sub_pw, and crr_main_pw in the same way as in Example 1, it is possible to identify including the error factors caused by the pull-up resistors.

Explanation of Symbols

[0024] 100 Analog sensor element 101 Main IC 102 Sub IC 103 AD converter 1 104 AD converter 2 105 Main power supply 106 Sub power supply 107 Reference power supply 108 Switch 1 109 Switch 2 110 Switch 3 200 Pull-up resistor 1 201 Pull-up resistor 2

Claims

1. An analog sensor having an analog signal output function, A main IC incorporating an AD converter, A sub IC incorporating an AD converter, A main power supply for supplying power to the main IC, A sub power supply for supplying power to the sub IC, A reference power supply for supplying power to the main IC and the sub IC, A switch for switching the power supply connected to the main IC, A switch for switching the power supply connected to the sub IC, A switch for switching the output of the analog sensor to the main IC or the sub IC, and It has means for identifying and correcting error factors existing between the respective AD converters when detecting an analog value using the respective AD converters incorporated in the main IC and the sub IC. A control circuit and apparatus characterized by this.

2. Regarding the means for identifying and correcting error factors existing between the respective AD converters, A switch for switching the power supply connected to the main IC, A switch for switching the power supply connected to the sub IC, The control circuit and apparatus according to claim 1, which have an operation method for acquiring information necessary for correction with the minimum necessary number of switch operations in the operation of switching the switches for switching the output of the analog sensor to the main IC or the sub IC.

3. The control circuit and apparatus according to claim 1 or 2, which have a pull-up resistor connected between the analog sensor, the main power supply, and the sub power supply.

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