JP3953093B2 - A / D converter - Google Patents

Description

  The present invention relates to an A / D converter for converting an analog signal into a digital signal.

  Conventionally, in order to prevent Hi failure or LO failure of the analog signal side circuit, the A / D conversion device has (power supply voltage −α) and (ground + β) when the analog signal side circuit is operating normally. It was designed to operate at a voltage between, and safety measures were taken to confirm that the A / D conversion result was between α and β.

  FIG. 2 shows a configuration of a conventional A / D conversion apparatus. Reference numeral 1 denotes an A / D conversion unit which inputs an analog value and outputs it as a digital value to the next stage. Reference numeral 2 denotes a digital reference voltage device. The constant region from (power supply voltage) to (power supply voltage−α) and the constant region from (ground voltage) to (ground voltage + β) are defined as abnormal regions, and the operation region is defined between β and α. A value obtained by converting each value into a digital value is stored. A determination device 3 compares the output of the A / D converter 1 with the reference value of the digital reference voltage device 2.

  If the output value of the A / D conversion unit 1 is an operation region, the output of the A / D conversion unit 1 described above is output to the next stage if it is an abnormal region. As described above, in this A / D converter, an area where the circuit on the analog signal side normally operates and an abnormal area when a circuit failure occurs are obtained in advance. The area is stored in the digital reference voltage device 2 as a digital value. Based on the value, an abnormality on the analog signal side was detected by comparing with the determination device 3.

  However, in the above configuration, the digital value becomes indefinite due to a failure of the A / D conversion unit 1 or a disconnection between the determination devices 3 connected to the A / D conversion unit 1. If the value enters the operation region stored in the digital reference voltage device 2, there is a problem that the abnormality of the analog signal cannot be detected in a wide region where the analog signal is desired to be detected.

  In order to solve this problem, in addition to the conventional A / D converter, the present invention stores the digital signal value output from the A / D converter at a constant timing obtained by the timer device, It has a determination device for selecting a value based on the previous digital signal value of the arithmetic / storage device from the set values in the setting device set in advance in multiple stages, and for use in the determination.

  According to the above invention, even when the change in the analog detection signal is greatly different in the area taken by the signal value, the determination device is based on the previous digital signal value stored in the calculation / storage device. Since the setting value set in multiple stages is selected and used for determination, the setting value can be determined small. As a result, it is possible to detect the indefiniteness of the digital signal in the region where the analog signal is detected with higher accuracy.

As described above, according to the present invention, due to a failure of the A / D conversion unit that could not be detected in the past, disconnection between the A / D conversion unit and the analog detection signal, disconnection between the A / D conversion unit and the arithmetic storage device, etc. It is possible to detect indefinitely the generated digital value, and measures such as stopping the system operation when indefinite detection is possible. Therefore, it is possible to obtain an effective effect that an A / D conversion device with higher safety can be obtained.

  The first embodiment of the present invention includes an A / D conversion unit, a timer device that operates the A / D conversion unit for each set time, and provides timing for converting an analog detection signal into a digital signal, Each time a digital signal is output from the A / D converter connected to the A / D converter, the value is stored and the difference between the previously stored digital signal value and the current digital signal value is stored. Is calculated and output to the next stage and connected to this calculation / storage device, and the difference between the output and the analog detection signal that cannot be changed within the set time of the timer device in advance is converted to a digital value. Compare the value stored as the set value. If the output of the calculation / storage device is within the set value, the current digital signal value in the calculation / storage device is set to the next stage. To the next stage And it has a determination device for outputting.

  Then, the digital signal value output from the A / D converter is constantly stored at a fixed timing obtained by the timer device, and the calculation result of the calculation / storage device for obtaining the difference from the digital signal value of the previous storage is obtained. The determination device determines whether or not the set value stored in the setting device is entered in advance. As a result, it is determined whether the change in the analog detection signal is within an expected value. Therefore, it is possible to detect indefinite digital values caused by a failure of the A / D converter or a disconnection between the A / D converter and the determination device. In the region where the analog signal is detected, it can be detected with high accuracy. Further, the accuracy is improved by setting the setting value in the setting device small.

  According to this invention, if the determination device that has received the calculation result of the calculation / storage device determines that the A / D conversion unit has failed or the disconnection between the A / D conversion unit and the determination device is out of the set value, An indefinite state of the digital signal can be detected, and the indefinite operation can be prevented by stopping the operation of the apparatus.

  The second embodiment of the present invention compares the output of the arithmetic / storage device with the set value in the setting device, and if the output of the arithmetic / storage device is within the set value, If the current digital value is the next stage or larger than the set value, the previous digital signal value in the arithmetic storage unit is replaced with the current digital signal value, and the previous digital signal value is output to the next stage. It has a determination device that outputs an abnormal signal to the next stage when a large determination is repeated n times.

  If the determination device that has received the output of the arithmetic / storage device does not repeat the determination larger than the set value in the setting device n times, no abnormality determination is made. This makes it possible to ignore the superimposition of external noise on the analog detection signal and the single malfunction of each device due to the external noise, and to obtain a device that is less susceptible to disturbances.

  Further, the third embodiment of the present invention is an A / D converter and a timer device that operates the A / D converter every set time and provides timing for converting an analog detection signal into a digital signal. Each time a digital signal is output from the A / D converter, the value is stored, and the previously stored digital signal value and the current digital signal value are stored. Is connected to this arithmetic / storage device, and the difference between the output and the analog detection signal that cannot be changed within the set time of the timer device in advance is a digital value. Is compared with one value stored as a set value in multiple stages, and if the output of the calculation / storage device is within the set value, the current digital signal value in the calculation / storage device is Output to When larger than the set value, an abnormal signal is output to the next stage, and the set value in the set device that has been set in multiple stages in advance is selected based on the previous digital value of the arithmetic / storage device, and used for determination It is equipped with.

  Even when the change in the analog detection signal varies greatly in the area taken by the signal value, the determination device is set in multiple stages in the setting device based on the previous digital signal value stored in the calculation / storage device. Since the set value is selected and used for determination, the set value can be determined to be small. As a result, it is possible to detect the indefiniteness of the digital signal in the region where the analog signal is detected with higher accuracy.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 shows the configuration of the A / D conversion apparatus of the present invention. In FIG. 1, the A / D conversion unit 4 outputs from the A / D conversion unit 4 at a constant timing obtained by the timer device 5. The arithmetic / storage device 6 stores the digital signal value, which is the output signal, every time, and obtains the difference between the previously stored digital signal value and the current digital signal value. The determination device 8 determines whether or not the calculation result from the calculation / storage device 6 falls within the set value stored in the setting device 7 in advance.

  The operation of the A / D converter configured in this way will be described. The A / D converter 4 performs the same operation as that of the conventional A / D converter. The A / D converter 4 has a sufficiently short value as compared with the change in the analog detection signal obtained by the timer device 5 (for example, about 0.1 second to about 0. At a constant timing of (01 seconds), it is converted into a digital signal value corresponding to the analog detection signal value described above and output to the next stage. Every time this signal is received, the arithmetic / storage device 6 stores it every time.

  Further, the difference between the digital signal value stored last time (one time before this time) and the current digital signal value is calculated and obtained. In the setting device 7, a value obtained by converting a difference between analog detection signal values that cannot be changed between certain timings from the timer device 5 into a digital value (for example, when a change in room temperature is used as an analog detection signal, the timer device 5 If the timing is 0.1 to 0.01 seconds, there will always be a change of 1K or less, with a margin added to this 1K, and the difference between the obtained analog detection signal values of about 1 to 3K is converted into a digital value and set. Value.

  However, since accuracy is determined by the above-mentioned margin, it is necessary to consider the required accuracy of the analog signal to be detected). Is stored as a set value. The determination device 8 compares the calculation result from the calculation / storage device 6 with the set value, and if the calculation result is within the set value, outputs the current digital signal value in the calculation / storage device 6 to the next stage. To do. If it is not present, an error message is output to the next stage. By the way, since the previous digital signal value of the calculation / storage device 6 is not used as data for the initial determination of the determination device 6, consideration is given so that the determination is not performed once because a correct calculation result cannot be obtained.

  As a result, in addition to the conventional failure detection of the analog signal side circuit, the failure of the A / D conversion unit 4, the disconnection between the analog detection signals connected to the A / D conversion unit 4, the A / D conversion unit 4 and the An indefinite detection of a digital value caused by disconnection or the like between connected arithmetic / storage devices 6 can be performed.

1 is a block diagram illustrating a configuration of an A / D conversion device according to a first embodiment of the present invention. Block diagram showing the configuration of a conventional A / D converter

Explanation of symbols

4 A / D converter 5 Timer device 6 Arithmetic / storage device 7 Setting device 8 Judgment device

Claims (1)

An A / D conversion unit, a timer device that operates the A / D conversion unit for each set time, and provides a timing for converting an analog detection signal into a digital signal, and is connected to the A / D conversion unit, Every time a digital signal is output from the A / D converter, the value is stored, and the difference between the previously stored digital signal value and the current digital signal value is obtained and output to the next stage. A value obtained by connecting a difference between an output and an analog detection signal that cannot be changed within a set time of the timer device in advance as a digital value is stored as a set value in multiple stages. Compared with one value, if the output of the calculation / storage device is within the set value, the current digital signal value in the calculation / storage device is output to the next stage, and if it is greater than the set value, an abnormal signal is output. Setting values in advance in the set to multiple stages Aru setting device to output the stage operation-select on the basis of value to the previous digital value of the memory device, A / D conversion apparatus having a determination device used for the determination.

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