JP2002084169A - Digital signal input device and its soundness monitoring method - Google Patents

Abstract

(57) [Problem] A digital signal input device has a problem that an increase in heat generation and an increase in size of the device cannot be avoided as the number of input points of digital signals increases. SOLUTION: A plurality of time-division photocouplers PC1 to PC4 are connected in parallel to one insulating photocoupler 4 via a CR filter unit 2 and a Zener diode 3. The time-division photocouplers PC1 to PC4 are sequentially and selectively closed in accordance with the time-division control signals input to the time-division photocouplers PC1 to PC4, so as to take in the time-division digital signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal input device having a function of inputting digital signals of a plurality of input systems and a method of confirming the soundness of the device.

[0002]

2. Description of the Related Art In the prior art shown in FIG. 3, a digital signal input device for inputting digital signals of four input systems includes four current limiting resistors 1, four CR filter units 2, and four Zener units. The digital signal input unit 10 was provided with the diode 3 and the four insulating photocouplers 4 and configured to receive digital signals of four systems. Different digital signals are input to these digital signal input units 10 for each system.

When the digital signal is "1", FIG.
As shown schematically, the switches SW1 to SW4 are closed, the circuit is closed, and the power is supplied from the power supply 5. Hereinafter, in the present specification, the case where the digital signal is "1" is referred to as an ON signal, and the case where the digital signal is "0" is referred to as an OFF signal. When the circuit is closed, a current for causing the light emitting portion built in the insulating photocoupler 4 to emit light flows and consumes power. Therefore, current also flows to each portion and the current limiting resistor 1 and the zener diode 3 generate heat. I was

[0004]

In the digital signal input device having the above configuration, the current limiting resistor 1, the CR filter unit 2, the Zener diode of the digital signal input unit 10 and the Zener diode according to the increase in the number of input digital signal systems. 3,
It is necessary to increase the number of insulating photocouplers 4 by the same number, and the amount of heat generation increases as described above. However, from the viewpoint of heat countermeasures, an increase in the amount of heat generated must be avoided, and the increase in the number of digital signal systems is restricted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a digital signal input device which is thermally stable even when the number of digital signal input systems is increased. Another object of the present invention is to provide a method for monitoring the soundness of the digital signal input device.

[0006]

In order to solve the above-mentioned problems, a digital signal input device according to the first aspect of the present invention comprises:
A time-division control unit having a plurality of time-division switching elements for controlling the output of an input digital signal, combining a plurality of input-system digital signals in a time-division manner, and outputting as a single-system digital signal; And a digital signal input unit for outputting a time-division digital signal output from the division control unit after being electrically insulated by an isolating photocoupler.

According to a second aspect of the present invention, there is provided a digital signal input device according to the first aspect, wherein a time division photocoupler is used as a time division switching element in the time division control unit. I do.

According to a third aspect of the present invention, in the digital signal input device according to the first or second aspect, the digital signal input section flows into a light emitting section of the insulating photocoupler. A current limiting resistor for limiting a current to be applied, and a filter unit for removing noise of a digital signal input to the insulating photocoupler,
A zener diode for determining a threshold voltage of an input voltage to a light emitting unit of the insulating photocoupler.

According to a fourth aspect of the present invention, there is provided a method for monitoring the soundness of a digital signal input device, wherein the digital signal input device according to any one of the first to third aspects is used for all time division switching. Monitor the output of the isolating photocoupler when the element or all the time-division photocouplers are open, and determine that the digital signal input device has failed if the isolating photocoupler outputs an ON signal. It is characterized by doing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a digital signal input device showing an embodiment of the present invention. As shown in FIG. 1, this digital signal input device has a digital signal input unit 1 having a current limiting resistor 1, a CR filter unit 2, a Zener diode 3, an insulating photocoupler 4, and a pull-up resistor 6.
0 and a time division control unit 20 having time division photocouplers PC1 to PC4. Note that the switches SW1 to SW4 and the power supply 5 in FIG. 1 are illustrated to schematically explain the state of a circuit based on a digital signal, which will be described later. Absent.

Next, the operation of each section will be briefly described together with the flow of a digital signal. This digital signal input device is adapted to receive four digital signals DI1 to DI4. The time-division photocouplers PC1 to PC4 of the time-division control unit 20 are connected to input terminals for digital signals at their output sides (light-receiving unit side and transistor side).
Has one end connected, and plays a role as a time-division switching element for controlling whether to output a digital signal to a subsequent stage.

For example, when the digital signal DI1 is taken in, the input section (light emitting section,
A time-division control signal is output to the diode section) to select the time-division photocoupler PC1, and the digital signal DI1 is output so as to make the output section (light-receiving section / transistor section) of the time-division photocoupler PC1 conductive. To do. Hereinafter, when a digital signal is output to the subsequent stage, the output unit is closed by imagining a switch, and when the digital signal is not output to the subsequent stage, the output unit is opened.

Similarly, when taking in the digital signal DI2, a time-division control signal for opening the output section of the time-division photocoupler PC1 is output, and then a time-division control signal for closing the output section of the time-division photocoupler PC2 is output. The split photocoupler PC2 is selected so that the digital signal DI2 is output. Similarly, for the digital signals DI3 and DI4, the time-division photocouplers PC3 and PC4 are selected to output the digital signals DI3 and DI4. The timing of selecting these PC1 to PC4 is shown in FIG.
The timing shown in FIG.

In the timing chart shown in FIG. 2, only the switches SW1 and SW3 schematically shown in FIG. 1 are closed, the signals DI1 and DI3 are turned on, and the signals DI2 and DI4 are always turned off. The time-division control signal is output at the timing indicated by PC1 to PC4 in FIG.
~ PC4. The time-division photocouplers PC1 to PC4 perform time-division control, and generate and output time-division digital signals shown in the DI state shown in FIG.

The DI state means that, for example, the time division control signals from PC1 and PC3 are input and the time division photocoupler P
If C1 and PC3 are selected, the digital signal DI
1, DI3 (ON signal) is transmitted from the insulating photocoupler 4 to DI
Output as status. Subsequently, time division control signals from PC2 and PC4 are input, and the time division photocouplers PC2 and PC4 are input.
If PC4 is selected, digital signals DI2, D
I4 (off signal) is output from the insulating photocoupler 4 as a DI state. As shown in FIG. 2, the DI state output in this manner is such that the output of the DI state of the isolating photocoupler 4 is turned on at the timing when the signal DI1 and the signal DI3 are captured, and the period between the signal DI2 and the signal DI4. Turns off the output in the DI state. Here, in order to make the output level in the DI state as shown in FIG. 2, it is necessary to invert the output of the insulating photocoupler 4 in FIG. 1, but the circuit configuration for that purpose is not shown.

A check period is provided after the input of the time-division control signals DI1 to DI4. The period of this check is defined as all the time-division photocouplers PC1 to PC1.
The PC 4 is opened, and no digital signal is output. At this time, if the output is an ON signal, it can be determined that there is an abnormality in the apparatus.

For example, a state is shown in which the time division photocoupler PC1 is short-circuited and the signal DI1 is constantly output. In the check period, all the time-division photocouplers PC1 to PC4 should be controlled to be off, but the output signal DI1 of the time-division photocoupler PC1 is turned on.
Since the state also appears as “ON” in the DI state, it can be determined that the state is abnormal. When it is determined that the state is abnormal, the digital signals DI1 to DI4 input to the insulating photocoupler 4 at that time are canceled because there is a possibility that the digital signals DI1 to DI4 are wrong values. Note that these soundness checking functions are invalid when all the digital signals are “off”.

As described above, the time-division photocouplers PC1 to PC1 are used.
At the same timing, only one PC 4 is selected and closed in order, so that the four digital signals are converted into time-division digital signals. The time-divided digital signal is output to the CR filter unit 2.

The CR filter unit 2 removes a high-frequency noise signal mixed in the time-divided digital signal and outputs the signal to a subsequent stage. The zener diode 3 determines a threshold voltage of an input voltage for turning on the input side (light emitting unit side / diode side) of the insulating photocoupler 4, and also determines the threshold voltage of the insulating photocoupler 4 due to noise that cannot be completely removed by the CR filter unit 2. It has a function to prevent malfunction.

In the photocoupler 4 for insulation, a current flows on the input side (light emitting unit side / diode side) in response to the digital signal which is an on / off signal, and emits light. The output side is opened and closed according to the presence or absence of light emission. In this case, the electric signal is converted into an optical signal and then converted into an electric signal again, thereby ensuring the insulation on the input / output side, and removing the noise component.

The pull-up resistor 6 is an insulating photocoupler 4
Are connected on the output side (light receiving unit side / transistor side), a current flows according to opening and closing of the output side, and a time-divided digital signal is output at a predetermined voltage. The DI state, which is the output, is input to a circuit (not shown) (generally, a logic circuit or the like) connected to the subsequent stage of the isolating photocoupler 4. As described above, from the isolating photocoupler 4, DI signal is output at the timing shown in FIG.
A time-divided digital signal indicating the state is output.

Next, the heat value will be described. For explanation, a power supply 5 and switches SW1 to SW4 as shown in FIG.
In the following description, it is assumed that a digital signal of four systems is a signal generated by turning on and off the switches SW1 to SW4. When the digital signal is turned on (SW1 is closed) and the time-division photocoupler PC1 is closed by the time-division control signal,
The circuit is closed by the path of the power supply 5, the switch SW1, the time-division photocoupler PC1, the zener diode 3, the input side of the insulating photocoupler 4, and the current limiting resistor 1, and a current flows. Further, the switch SW2, the time division photocouplers PC2, SW3 and the time division photocouplers PC3, SW
4 and the time-division photocoupler PC4, a similar circuit is formed.

In this case, in this embodiment, one heat-generating component such as the Zener diode 3, the insulating photocoupler 4, and the current limiting resistor 1 is provided. Therefore, the number of components that generate heat and the amount of heat generation can be reduced as compared with the related art. In addition, the reduction in the number of parts is effective in miniaturization.

The effect of reducing the number of components and the amount of generated heat will be specifically described. First, a comparison of the number of parts with the conventional product is shown in the following table.

[0025]

[Table 1]

Among them, the major contributors to miniaturization are the reduction in the number of current limiting resistors and zener diodes. It uses a physically large current limiting resistor or Zener diode (a component with a large allowable power consumption), depending on the input specifications (eg, DC 110 V, current 10 mA to 50 mA) in the digital signal input in the power field. Therefore, the reduction effect is large.

That is, when the number of digital signal input systems is n
With the system, in the present invention, the number of parts can be reduced to 1 / n as compared with the related art. Conversely, a photocoupler for time division control is required, but the physical effect is greater if the current limiting resistor and the Zener diode can be reduced. This is because not only the parts themselves are large, as described above, but these parts generate heat, so it is necessary to arrange the parts while securing a space area that does not have the effect of heat generation. This requires a larger area.

The present invention also relates to the effect of reducing the calorific value,
For example, digital signal input specifications in the power field are an input voltage of DC 110 V and an input current of 10 mA to 50 mA.
Assuming that the input current is 10 mA and the digital signal input is an “ON” signal in all systems, the conventional is 110 V × 10
mA × 4 systems = 4.4 W. In the present invention, 110V
× 10mA × 1 system × 4/5 = 0.88W. That is, the calorific value of the present invention is 1/5 that of the related art. The reason why 4/5 is multiplied in the calculation formula of the present invention is that, in addition to the four points of the number of digital signal systems, four points are energized out of five points corresponding to the check period. It is.

[0029]

As described above, according to the present invention, the heat generation time per signal system is shortened by time-dividing the signals of many systems and transmitting them to the subsequent stage as one time-divided digital signal. As a result, the total heat generation can be reduced. In addition, the number of heat-generating portions is reduced only by being installed in one digital signal input portion, and the size of the device can be reduced accordingly. Furthermore, by monitoring the output of the isolating photocoupler when the drive of the time-division switching element makes one cycle and all the elements are open, a failure is determined,
Abnormal detection becomes easier. In general, it is possible to provide a digital signal input device that is thermally stable even when the number of digital signal input systems increases, and a method of monitoring the soundness of the digital signal input device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of FIG.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current limiting resistor 2 CR filter part 3 Zener diode 4 Isolation photocoupler 5 Power supply 6 Pull-up resistor DI1 to DI4 Digital signal PC1 to PC4 Time division photocoupler 10 Digital signal input section 20 Time division control section

Claims (4)

[Claims] 1. A time-division control device comprising a plurality of time-division switching elements for controlling the output of an input digital signal, wherein the digital signals of a plurality of input systems are combined in a time-division manner and output as one digital signal. And a digital signal input unit for outputting a time-division digital signal output from the time-division control unit after being electrically insulated by an isolating photocoupler. 2. The digital signal input device according to claim 1, wherein a time division photocoupler is used as a time division switching element in said time division control unit. 3. The digital signal input device according to claim 1, wherein the digital signal input unit includes: a current limiting resistor for limiting a current flowing into a light emitting unit of the insulating photocoupler; A digital signal input device, comprising: a filter unit for removing noise of a digital signal input to a photocoupler; and a zener diode for determining a threshold voltage of an input voltage to a light emitting unit of the insulating photocoupler. 4. The insulating device according to claim 1, wherein all of the time-division switching elements or all of the time-division photocouplers are open using the digital signal input device according to any one of claims 1 to 3. A method for monitoring the soundness of a digital signal input device, comprising: monitoring an output of a photocoupler; and determining that the digital signal input device has failed if the insulating photocoupler outputs an ON signal.