JPH08305403A - Analog signal output circuit - Google Patents

Abstract

PURPOSE: To suppress an adverse influence on a plant with the abnormality of an analog output signal to a minimum by speedily detecting the operational abnormality of a DAC by comparing circuit signals before and after the DAC as the component of a circuit in an AO card to be used for a digital controller. CONSTITUTION: This circuit is provided with a first switcher 20 for switching digital output signals outputted from hold circuits from 11-1 to 11-n, second switcher 21 for switching the output signal of a DAC 12, ADC 22 for performing analog/digital conversion for the output signal of the second switcher 21, and comparator 23 for comparing the digital signal outputted from the first switcher 20 with the digital signal outputted from the ADC 22 and corresponding to the signal of the compared result of the comparator 23, the fault detection of the DAC 12 is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog signal output circuit suitable for being applied to a digital controller for reading and processing analog and digital signals and outputting an analog signal, such as a digital controller for a prime mover plant.

[0002]

2. Description of the Related Art Conventionally, in a digital control device of a prime mover plant for reading and processing analog and digital signals, as shown in FIG. 2, an analog signal input circuit (AI) 1 for receiving an analog signal from a plant 6, a plant 6, a digital signal input circuit (DI) 2 for receiving a digital signal, an analog signal output circuit (AO) 3 (3 ') for sending an analog signal to the plant 6, and a digital signal output circuit for sending a digital signal to the plant 6 ( DO) 4 and a computer 5 are provided.

In the digital controller having the above-mentioned structure, various signals from the plant 6 are read into the computer 5 via the analog signal input circuit 1 and the digital signal input circuit 2 and after the control calculation is performed by the computer 5. , And sends the calculation result to the plant 6 via the analog signal output circuit 3 and the digital signal output circuit 4 to control the plant 6.

As shown in FIG. 3, a conventional analog signal output circuit (hereinafter referred to as an AO card) 3'used in the above digital control device is a hold circuit 11-1 for receiving a digital signal from a computer 5. ~ 11-n, receive signals from the hold circuits 11-1 to 11-n (hereinafter DA
12-1 to 12-n, buffer amplifiers 13-1 to 13-n that receive output signals of the DACs 12-1 to 12-n, and gate control circuit 1 that controls the hold circuits 11-1 to 11-n.
It is composed of 4 etc.

The operation of the AO card 3'transmits a digital signal from the computer 5 to the hold circuits 11-1 to 11-n via the data bus 15. Hold circuit 11-1
.About.11-n temporarily hold the transmitted digital signal and transmit the output signal to the DACs 12-1 to 122.

The DACs 2-1 to 12-n convert the transmitted digital signal into an analog signal, and the buffer amplifier 13
An analog signal is sent to the plant 6 via -1 to 13-n.

The gate control circuit 14 outputs a hold circuit switching signal 17 based on the switching control signal transmitted from the computer 5 through the switching control line 16, and the hold circuits 11-1 to 11-are generated by this signal. Control n.

The hold circuits 11-1 to 11-n read the digital signal output from the computer 5 onto the data bus 15 when the hold circuit switching signal 17 is transmitted,
Hold temporarily.

The hold circuits 11-1 to 11-n temporarily hold the DACs 12-1 to 12-n in order to prevent fluctuations when converting a digital signal into an analog signal.

The above-mentioned conventional AO card 3'shown in FIG.
However, there is a problem that it is difficult to find an unstable phenomenon of the hold circuits 11-1 to 11-n and a failure of the DACs 12-1 to 12-n.

[0011]

As described above, in the AO card used in the conventional digital control device, there is a problem that it is difficult to find the instability phenomenon of the hold circuit and the failure of the circuit such as the DAC. Had.

The present invention has been made in view of the above situation,
In the AO card used in the digital controller,
To provide an analog signal output circuit for a digital control device which detects an abnormal operation of a hold circuit, a DAC and the like, which are components of the circuit, at an early stage and minimizes an adverse effect on a plant due to an abnormal analog output signal. With the goal.

[0013]

SUMMARY OF THE INVENTION The present invention is an analog signal output circuit of a computer system having a plurality of hold circuits, a digital-analog converter, and a buffer circuit for performing digital control. A first switch for selecting a signal, a second switch for selecting an output signal of the digital-analog converter, an analog-digital converter for analog-digital converting an output signal of the second switch, the first switch A comparator for comparing the signal output from the switch 1 and the signal output from the analog-digital converter is provided, and a signal corresponding to the output signal of the hold circuit and the digital-analog converter is provided to the comparator. It is characterized in that the analog circuit failure is detected by performing digital comparison by using the above-mentioned method.

As a first example, the first switch 20 for switching the digital output signals output from the hold circuits 11 (11-1 to 11-n) will be described.
A second switch 21 for switching the output signal of the DAC (digital-analog converter) 12, an ADC (analog-digital converter) 22 for converting the output signal of the second switch 21 into an analog signal, and the first switch described above. The comparator 23 for comparing the digital signal output from the switching device 20 and the digital signal output from the ADC 22 is provided, and the failure of the ADC 12 is detected by the signal of the comparison result of the comparator 23.

When the hold circuit 11 is unstable, for example, chattering or malfunctions, the switch 20 is switched by the gate delay signal 18 obtained by delaying the switch signal 17 of the gate control circuit 14, and the hold circuits 11 (11-1 to 11-11). -n)
Since the output signal of 1 is transmitted to the comparator 23 as the reference signal, the unstable phenomenon of the hold circuit 11 can be detected by the large fluctuation of the reference signal.

[0016]

The digital signal from the computer 5 is transmitted to the hold circuits 11-1 to 11-n via the data bus 15. The operation of the hold circuits 11-1 to 11-n is restricted (switching control) by the gate control circuit 14.

The outputs of the hold circuits 11-1 to 11-n are D
AC12-1 to 12-n and the switching device 20
Is transmitted to one input terminal of the comparator 23 via. DAC
The output signals of 12-1 to 12-n are buffer circuits 13-1 to 13-1.
It is transmitted to the plant 6 via 3-n, is transmitted to the other input end of the comparator 23 via the switching device 21 and further via the ADC 22.

The comparator 23 compares the output signals of the hold circuits 11-1 to 11-n transmitted from the switch 20 with the signals corresponding to the output signals of the DACs 12-1 to 12-n transmitted from the ADC 22. To do.

As a result of this comparison, when an abnormality is detected due to the mismatch of the digital signals, the number of channels of the AO card 3 which is abnormal is transmitted to the computer 5 via the data bus 24.

The computer 5 can notify the operator of the AO card abnormality by using the display monitoring device (not shown) in response to the abnormality signal from the comparator 23. Switch 2 here
Switching between 0 and 21 is controlled by the gate control circuit 14 like the hold circuits 11-1 to 11-n. That is, the signal obtained by delaying the hold circuit switching signal 17 by several 100 μs is the gate delay signal 18 for switching the switch 20,
The signal delayed by μs is the gate delay signal 19 for switching the switch 21.

[0021]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an analog signal output circuit according to an embodiment of the present invention.

In FIG. 1, a digital signal corresponding to an analog output signal from the computer 5 is transmitted to the hold circuits 11-1 to 11-n via the data bus 15 and the hold circuits 11-1 to 11-11. The signal for switching -n is transmitted to the gate control circuit 14 via the gate switching control line 16.

The gate control circuit 14 sends a hold circuit switching signal 17 based on the signal transmitted from the gate switching control line 16 to hold circuits 11-1 to 11-n.
Specify one of the channels.

In this way, the hold circuits 11-1 to 11
The output signal of the computer 5 sequentially transmitted via the database 15 is temporarily held in -n. This held digital signal, that is, the hold circuits 11-1 to 11-1
The output signals of 1-n are converted into analog signals by the DACs 12-1 to 12-n and transmitted to the plant 6 as analog output signals via the buffer circuits 13-1 to 13-n.

On the other hand, the digital output signals of the hold circuits 11-1 to 11-n and the analog output signals of the DACs 12-1 to 12-n are separately transmitted to the switch 20 and the switch 21, respectively.

The switching devices 20 and 21 are the hold circuits 11-1 to 11-1.
Similar to 11-n, it is switched by the gate switching delay signals 18 and 19 from the gate control circuit 14. Switch 20
Of the digital signal of the switch 23 to the reference value side of the comparator 23.
The analog output signal of 1 is digitally converted by the ADC 22 and then transmitted to the comparison value side of the comparator 23.

The comparator 23 digitally compares the two transmitted signals and transmits the comparison result (normal or abnormal) to the computer 5 via the data bus 24. Calculator 5
When the signal transmitted from the comparator 23 is abnormal,
An abnormal occurrence of the AO card 3 is displayed as an alarm on a monitor display device (not shown).

As a result, the operator of the plant 6 can know the abnormality of the AO card 3 of the digital control device at an early stage, and can obtain the information for operating the plant 6 stably.

As described above, according to the embodiment of the present invention,
An AO card 3 that converts a digital signal from the computer 5 into an analog signal and outputs the analog signal to the plant 6.
In this case, the hold circuit 11 (11-1 to 11-n) for temporarily holding the digital signal and the hold circuit 11 (1
The output signals of the DAC 12 (12-1 to 12-n) for converting the output signals of 1-1 to 11-n) into digital analog signals are branched,
Each of the branched circuits is provided with switching devices 20 and 21, respectively, and the output of the switching device 20 is directly transmitted to the comparator 23, and the output signal of the switching device 21 is transmitted to the comparator 23 via the ADC 22. At 23, an abnormality of the AO card is detected by digitally comparing these signals. Thereby, the abnormality of the AO card 3 can be known at an early stage.

[0030]

As described in detail above, according to the present invention, an AO card (analog signal output circuit) of a computer system having a plurality of hold circuits, a digital-analog converter and a buffer circuit for digital control is provided. Where a first switch for selecting the output signal of the hold circuit,
A second switch for selecting an output signal of the digital-analog converter, an analog-digital converter for analog-digital converting the output signal of the second switch, the first switch
And a comparator for comparing the signal output from the switching device with the signal output from the analog-digital converter,
With the configuration in which the signal corresponding to the output signal of the hold circuit and the digital-analog converter is digitally compared by the comparator, the abnormality of the AO card can be detected at an early stage, and the plant output due to the abnormality of the analog output signal can be transmitted to the plant. The adverse effects can be minimized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an AO card according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a digital control device.

FIG. 3 is a block diagram showing a configuration of a conventional AO card.

[Explanation of symbols]

3 ... AO card (analog signal output circuit), 5 ... computer, 6 ... plant, 11 ... hold circuit, 12 ... DAC
(Digital-analog converter), 13 ... buffer circuit,
14 ... Gate control circuit, 15 ... Data bus, 16 ... Gate switching signal control line, 17 ... Hold circuit switching signal, 1
8, 19 ... Gate switching delay signal, 20, 21 ... Switching device,
22 ... ADC (analog-digital converter), 23 ... comparator, 24 ... data bus.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G05B 23/02 302 7531-3H G05B 23/02 302S (72) Inventor Tomohiro Yamaguchi Arai Town, Takasago City, Hyogo Prefecture Niihama 1-1-1, Mitsubishi Heavy Industries, Ltd. Takasago Plant

Claims (1)

[Claims] 1. An analog signal output circuit of a computer system for digital control, comprising a plurality of hold circuits for receiving digital signals from the computer, and a plurality of hold circuits for converting the digital signals held by the hold circuits into analog signals. A digital-analog converter, a plurality of output buffer circuits for outputting the analog signals converted by the digital-analog converter to a control target, a first signal selecting means for selecting an output signal of the hold circuit, and the digital signal Second signal selecting means for selecting an output signal of the analog converter, converting it into a digital signal and outputting the digital signal; control means for controlling the hold circuit and the first and second signal selecting means; And a comparator for comparing and collating each digital signal selected by the second signal selecting means. Analog output signal circuits and performs fault detection of an analog circuit by a signal comparison result.