JP3937642B2 - Analog to digital converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an analog-digital conversion device suitable for use in, for example, measurement of the remaining amount of a rechargeable battery. Specifically, in analog-digital conversion that does not require much conversion accuracy, the resolution of analog-digital conversion is improved with a simple configuration.
[0002]
[Prior art]
For example, in the measurement of the remaining amount of the rechargeable battery, a conversion value obtained by analog-digital conversion of the terminal voltage of the rechargeable battery is determined using a microcomputer. In this case, the analog-digital conversion is performed using, for example, conversion means built in the microcomputer. The resolution of analog-digital conversion by such built-in conversion means is usually about 4 to 5 bits. However, it is considered that such a resolution as much as possible is preferable.
[0003]
Therefore, conventionally, a so-called dither or triangular wave signal is added to an input signal, and resolution is improved by using a statistical method from a plurality of analog-digital conversions. However, such a method increases the burden of software on the microcomputer, such as performing statistical calculations, and is difficult to implement with a so-called one-chip microcomputer that is used, for example, for measuring the remaining battery charge. Is.
[0004]
On the other hand, for example, a means is proposed in which the level of the input analog signal or reference signal is shifted in accordance with the level of the input analog signal to obtain a resolution several times the capability of the analog-to-digital conversion means used (Japanese Patent Laid-Open No. 6-1994). No. 204876, JP-A-10-163873, etc.). However, in these methods, the circuit configuration for shifting the level becomes complicated, and it is difficult to realize it for an originally small circuit such as the measurement of the remaining amount of the rechargeable battery.
[0005]
In addition, for example, a large microcomputer or a circuit itself can be made large in order to cope with such an increase in software load and a complicated circuit configuration. In the midst of demands for making the system and the like, it is practically impossible to increase the size of the microcomputer and the scale of the circuit.
[0006]
[Problems to be solved by the invention]
This application has been made in view of the above points, and the problem to be solved is a statistical technique or signal level conventionally used to improve the resolution of analog-digital conversion. In the method of shifting, the burden of software and the scale of the circuit increase, and in particular, it is practically impossible to realize it in an inexpensive and small-sized device.
[0007]
[Means for Solving the Problems]
For this reason, in the present invention, a voltage dividing circuit is detachably provided in the input path of the analog / digital converting means, and the first and second conversion values when the voltage dividing circuit is attached / detached are determined by the control means. According to this, it is extremely easy to obtain a simple configuration in which a voltage dividing circuit is detachably provided and only a simple determination of the first and second conversion values. In addition, the resolution of analog-digital conversion can be improved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
That is, in the present invention, a conversion means for converting an analog signal into a digital value, a voltage dividing circuit detachably provided on an analog signal input path of the conversion means, a determination of a conversion value from the conversion means, and a voltage dividing circuit A first conversion value from the conversion means when the voltage dividing circuit is removed and a second conversion value from the conversion means when the voltage dividing circuit is added. A desired conversion value is obtained by judgment by the control means. As a result, the resolution of analog-digital conversion can be improved very easily.
[0009]
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of an analog-digital conversion apparatus to which the present invention is applied.
[0010]
In FIG. 1, for example, an analog signal input terminal 1 for analog-to-digital conversion to an analog-to-digital conversion input (A / D) of a microcomputer 10 forming an analog-to-digital conversion device of the present invention constitutes a voltage divider circuit. 2 is connected. Further, the midpoint of connection between the resistor 2 and the analog / digital conversion input (A / D) of the microcomputer 10 is grounded through the resistor 3 and the switching element 4 constituting the voltage dividing circuit.
[0011]
The on / off state of the switching element 4 is controlled by a control signal from the control output (CNT) of the microcomputer 10 and supplied to the analog / digital conversion input (A / D) with the switching element 4 turned off, for example. The first analog-digital conversion of the analog signal is performed. Next, the second analog-digital conversion of the analog signal supplied to the analog-digital conversion input (A / D) with the switching element 4 turned on is performed.
[0012]
That is, in this circuit, when the switching element 4 is turned off, the analog signal supplied to the input terminal 1 is supplied as it is to the analog / digital conversion input (A / D) of the microcomputer 10. On the other hand, in the state where the switching element 4 is turned on, the analog signal supplied to the input terminal 1 sets the resistance values of the resistors ₂ and 3 as R ₁ and R _2, and R ₂ / (R ₁ + R ₂ ) And supplied to the analog / digital conversion input (A / D) of the microcomputer 10.
[0013]
Therefore, for example, when the conversion range of analog-digital conversion is set to 0 to 1.6 V, first, in the first state in which the switching element 4 is turned off, for example, as shown on the left side of FIG. ~ 0.4V, 0.4 ~ 0.6V, 0.6 ~ 0.8V, 0.8 ~ 1.0V, 1.0 ~ 1.2V, 1.2 ~ 1.4V, 1.4 ~ 1 It is converted into a digital value at 8 conversion levels of 6V. In this description, for simplicity, description will be made in eight ways (3 bits), but the same applies to the case of more bits.
[0014]
On the other hand, if the voltage dividing ratio of the resistors 2 and 3 is R ₂ / (R ₁ + R ₂ ) = 0.9, for example, the conversion level in the second state when the switching element 4 is turned on is Equivalently, as shown on the right side of FIG. 2, 0 to 0.22V, 0.22 to 0.44V, 0.44 to 0.67V, 0.67 to 0.89V, 0.89 to 1.10V, 1.10 to 1.33V, 1.33 to 1.56V, and 1.56 to 1.6V, which are converted into digital values at these conversion levels.
[0015]
Therefore, by integrating these, for example, in the above-described example, 0 to 0.2 V, 0.2 to 0.22 V, 0.22 to 0.4 V, 0.4 to 0.44 V, 0.44 to 0. 6V, 0.6 to 0.67V, 0.67 to 0.8V, 0.8 to 0.89V, 0.89 to 1.0V, 1.0 to 1.10V, 1.10 to 1.2V, Fifteen conversions of 1.2 to 1.33 V, 1.33 to 1.4 V, 1.4 to 1.56 V, and 1.56 to 1.6 V can be performed.
[0016]
That is, for example, a control signal for turning off the switching element 4 is first output from the control output (CNT) of the microcomputer 10 to perform the first conversion, and the conversion value at this time is stored. Next, a control signal for turning on the switching element 4 is output from the control output (CNT) of the microcomputer 10 to perform the second conversion, and the conversion value at this time is compared with the stored first conversion value. When they match, the value is set as an output conversion value, and when they are different, the intermediate value is set as an output conversion value.
[0017]
In the above example, for example, the first and second converted values are set as 0, 2, 4, 6, 8, 10, 12, and 14, and the first and second converted values are the same. When the value (0, 2, 4, 6, 8, 10, 12, 14) is converted, the intermediate value (1, 3, 5, 7, 9, 11, 13) is used. By using the converted value, 15 values of 0 to 14 can be extracted. The resolution of the analog-digital conversion provided in this way can be improved.
[0018]
Therefore, in this apparatus, a voltage dividing circuit is detachably provided in an analog signal input path of the analog-digital converting means, and the control means determines the first and second conversion values when the voltage dividing circuit is attached / detached. By obtaining a desired conversion value, the resolution of analog-to-digital conversion can be improved very easily with only a simple configuration in which a voltage dividing circuit is detachably provided and simple determination of the first and second conversion values. be able to.
[0019]
As a result, statistical methods and signal level shifting methods that have been used in the past to improve the resolution of analog-to-digital conversion increase the burden of software and the scale of the circuit. According to the present invention, it is possible to easily solve these problems, which have been practically impossible in terms of adoption.
[0020]
In the above-described apparatus, the accuracy (linearity) of analog-digital conversion is not good as is apparent from FIG. Therefore, this device cannot be used for devices that require strict accuracy (linearity), such as analog-digital conversion of audio and video signals. However, it requires extra conversion accuracy, for example, to measure the remaining amount of a rechargeable battery. In analog-to-digital conversion, the resolution of analog-to-digital conversion can be improved with a simple configuration.
[0021]
FIG. 3 is a block diagram showing the configuration of another embodiment of the analog-digital conversion apparatus to which the present invention is applied. In the embodiment of FIG. 3, the analog signal input terminal 1 for analog-digital conversion is directly connected to the analog-digital conversion input (A / D) of the microcomputer 10 forming the analog-digital conversion apparatus of the present invention. Is done.
[0022]
On the other hand, a reference voltage input terminal 5 is connected to a reference input (Vref) for analog-digital conversion of the microcomputer 10 through a resistor 6 constituting a voltage dividing circuit. The midpoint of connection between the resistor 6 and the reference input (Vref) of the microcomputer 10 is grounded through the resistor 7 and the switching element 8 constituting the voltage dividing circuit.
[0023]
The on / off state of the switching element 8 is controlled by a control signal from the control output (CNT) of the microcomputer 10. For example, the reference voltage supplied to the reference input (Vref) with the switching element 8 turned off first is used. Thus, the first analog-digital conversion of the analog signal supplied to the analog-digital conversion input (A / D) is performed. Next, the second analog-digital conversion is performed with the switching element 8 turned on.
[0024]
That is, in this circuit, when the switching element 8 is turned off, the reference voltage supplied to the input terminal 5 is supplied as it is to the reference input (Vref) of the microcomputer 10. In a state in which to turn on the switching element 8 the contrary, the reference voltage supplied to the input terminal 5 is the resistance value of the resistor 6 and 7 at the _{R 3, R 4, R 4} / (R 3 + R 4 ) And supplied to the reference input (Vref) of the microcomputer 10.
[0025]
Therefore, for example, when the conversion range of analog-digital conversion is set to 0 to 1.6 V, in the first state where the switching element 8 is turned off, as shown on the left side of FIG. .4V, 0.4-0.6V, 0.6-0.8V, 0.8-1.0V, 1.0-1.2V, 1.2-1.4V, 1.4-1.6V These are converted into digital values at the eight conversion levels.
[0026]
On the other hand, if the voltage dividing ratio of the resistors 6 and 7 is R ₄ / (R ₃ + R ₄ ) = 0.9, for example, the conversion level in the second state when the switching element 8 is turned on is Equivalently, as shown on the right side of FIG. 4, 0 to 0.18V, 0.18 to 0.36V, 0.36 to 0.54V, 0.54 to 0.72V, 0.72 to 0.90V, 0.90 to 1.08V, 1.08 to 1.26V, and 1.26 to 1.6V, and these values are converted into digital values.
[0027]
Therefore, by integrating these, for example, in the above-described example, 0 to 0.18 V, 0.18 to 0.2 V, 0.2 to 0.36 V, 0.36 to 0.4 V, 0.4 to 0. 54V, 0.54 to 0.6V, 0.6 to 0.72V, 0.72 to 0.8V, 0.8 to 0.90V, 0.90 to 1.0V, 1.0 to 1.08V, Fifteen conversions of 1.08 to 1.2V, 1.2 to 1.26V, 1.26 to 1.4V, and 1.4 to 1.6V can be performed.
[0028]
That is, for example, a control signal for turning off the switching element 8 is first output from the control output (CNT) of the microcomputer 10 to perform the first conversion, and the conversion value at this time is stored. Next, a control signal for turning on the switching element 8 is output from the control output (CNT) of the microcomputer 10 to perform the second conversion, and the conversion value at this time is compared with the stored first conversion value. When they match, the value is set as an output conversion value, and when they are different, the intermediate value is set as an output conversion value.
[0029]
In the above example, for example, the first and second converted values are set as 0, 2, 4, 6, 8, 10, 12, and 14, and the first and second converted values are the same. When the value (0, 2, 4, 6, 8, 10, 12, 14) is converted, the intermediate value (1, 3, 5, 7, 9, 11, 13) is used. By using the converted value, 15 values of 0 to 14 can be extracted. The resolution of the analog-digital conversion provided in this way can be improved.
[0030]
Therefore, in this apparatus, a voltage dividing circuit is detachably provided in the reference voltage input path of the analog-digital converting means, and the control means determines the first and second conversion values when the voltage dividing circuit is attached and detached. By obtaining a desired conversion value, the resolution of analog-to-digital conversion can be improved very easily with only a simple configuration in which a voltage dividing circuit is detachably provided and simple determination of the first and second conversion values. be able to.
[0031]
As a result, statistical methods and signal level shifting methods that have been used in the past to improve the resolution of analog-to-digital conversion increase the burden of software and the scale of the circuit. According to the present invention, it is possible to easily solve these problems, which have been practically impossible in terms of adoption.
[0032]
In the above-described apparatus, the accuracy (linearity) of analog-digital conversion is not good as is apparent from FIG. Therefore, this device cannot be used for devices that require strict accuracy (linearity), such as analog-digital conversion of audio and video signals. However, it requires extra conversion accuracy, for example, to measure the remaining amount of a rechargeable battery. In analog-to-digital conversion, the resolution of analog-to-digital conversion can be improved with a simple configuration.
[0033]
Further, in the above-described apparatus, the resolution of the analog-digital conversion can be further improved by providing the detachable voltage dividing circuit configuration in both the analog signal input path and the reference voltage input path. That is, for example, in the above-described eight analog-digital conversion means, 22 removable resolutions can be obtained by providing a removable voltage dividing circuit configuration in both and performing three conversions.
[0034]
In the above-described apparatus, the analog signal input terminal 1 is directly connected to the first analog-digital conversion input (A / D1), for example, as shown in FIG. Are connected to the second analog-digital conversion input (A / D2), and the first and second analog-digital conversion inputs are selected by the switch 9 in the microcomputer 10 and connected to the analog-digital conversion block 11. Even if it does so, the effect similar to the above-mentioned can be acquired.
[0035]
In this case, in the microcomputer 10, the number of analog-digital conversion input (A / D) terminals increases, but the number of control output (CNT) terminals can be reduced. The number of input / output terminals is unchanged. In this case, switching elements as external circuit elements can be further reduced.
[0036]
Further, in the above-described apparatus, the voltage dividing ratio of the resistors 2 and 3 or the resistors 6 and 7 is not limited to the above-mentioned 0.9, and is determined according to the basic resolution of the analog-digital conversion means used, for example. In general, it is determined so that the value after the partial pressure does not deviate from the original resolution in the region of the maximum value of the basic resolution.
[0037]
Thus, according to the analog-digital conversion device described above, the conversion means for converting the analog signal into a digital value, the voltage dividing circuit detachably provided in the analog signal input path of the conversion means, and the conversion value from the conversion means Control means for controlling determination and attachment / detachment of the voltage dividing circuit, and a first converted value from the converting means when the voltage dividing circuit is removed and a second converted value from the converting means when the voltage dividing circuit is added. The conversion value is determined by the control means to obtain a desired conversion value, so that the resolution of analog-digital conversion can be improved very easily.
[0038]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
[0039]
【The invention's effect】
Therefore, according to the first aspect of the present invention, the voltage dividing circuit is detachably provided in the reference voltage input path of the analog-digital converting means, and the first and second conversion values when the voltage dividing circuit is attached and detached are controlled. By simply obtaining the desired conversion value by means of means, it is very easy to perform analog-to-digital conversion with only a simple configuration in which a voltage dividing circuit is detachably provided and simple determination of the first and second conversion values. Resolution can be improved.
[0040]
As a result, statistical methods and signal level shifting methods that have been used in the past to improve the resolution of analog-to-digital conversion increase the burden of software and the scale of the circuit. According to the present invention, it is possible to easily solve these problems, which have been practically impossible in terms of adoption.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of an analog-digital conversion apparatus according to the present invention.
FIG. 2 is a diagram for explaining that;
FIG. 3 is a configuration diagram of another embodiment of the analog-digital conversion apparatus according to the present invention.
FIG. 4 is a diagram for explaining that;
FIG. 5 is a configuration diagram of another embodiment of the analog-digital conversion apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Microcomputer, 1 ... Input terminal, 2, 3 ... Resistor which comprises voltage dividing circuit, 4 ... Switching element, A / D ... Analog-digital conversion input of microcomputer 10, CNT ... Control output of microcomputer 10

Claims (1)

Conversion means for converting an analog signal into a digital value;
A voltage dividing circuit detachably provided in an input path of the analog signal of the conversion means;
Control means for performing determination of a conversion value from the conversion means and control of attachment / detachment of the voltage dividing circuit;
The control means determines the first converted value from the converting means when the voltage dividing circuit is removed and the second converted value from the converting means when the voltage dividing circuit is added. An analog-digital converter characterized by obtaining a desired conversion value.

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