JP2020096299A - Digital input device having photocoupler life determination function, and arithmetic unit - Google Patents

Abstract

To provide a digital input device capable of life diagnosis of photocoupler even during digital input.SOLUTION: The digital input device includes: a photocoupler that includes a light-emitting device that receives an input signal from the outside and emits light and a light-receiving element that receives the light emitted from the light-emitting device and converts it into an electrical signal; a capacitor connected to the light-receiving element; and a life determination part that determines the life of photocoupler. The capacitor is configured so as to, when the light-receiving element receives the light from the light-emitting device, discharge by supplying an electric current to the light-receiving element. The life determination part determines the life of the photocoupler by measuring the time required to discharge the capacitor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a digital input device having a function of diagnosing the life of a photocoupler.

2. Description of the Related Art Some digital input devices called digital input boards used for inputting digital signals in computer systems use a photo coupler in a circuit that receives an input signal from an externally connected device. The photocoupler includes a light emitting diode and a phototransistor, and has a configuration in which an electric signal is converted into light by the light emitting diode, and the light is received by the phototransistor and converted into an electric signal. Can be transmitted.

It is known that the photocoupler has a small current transfer rate due to deterioration over time. As a result, the current flowing through the phototransistor is reduced, and it becomes difficult to input a signal normally.

In Patent Document 1, in order to diagnose the life of a photocoupler, a pulse signal is generated and input to the photocoupler, converted into light by a light emitting diode, and this light is received by a phototransistor and reconverted into an electric signal. However, a technique of comparing the time width of the obtained pulse waveform of the electric signal with the pulse time width of the pulse signal input to the photocoupler is disclosed. It is proposed that the remaining life can be estimated based on the pulse width after light reception by the photocoupler because the responsiveness of the photocoupler decreases when the current transfer rate decreases due to deterioration over time.

International Publication No. 2016/147361

In the photo coupler life diagnosing device of patent document 1, when diagnosing the life of the photo coupler, it is necessary to generate a pulse signal and input it to the photo coupler. Therefore, in order to periodically perform life diagnosis, it is necessary to temporarily suspend the operation of the photo coupler in operation that is performing digital input and input a pulse signal for life diagnosis to the photo coupler. It is necessary to limit the operating time of.

The present invention has been made in view of the above, and an object of the present invention is to enable life diagnosis of a photocoupler even during digital input.

The present invention, in order to achieve the above object, a light emitting element that receives an input signal from the outside and emits light, and a photocoupler that includes a light receiving element that receives the light emitted by the light emitting element and converts the light into an electrical signal, It has a capacitor connected to the light receiving element and a life determining unit for determining the life of the photocoupler. When the light receiving element receives light from the light emitting element, the capacitor discharges by supplying a current to the light receiving element. The life determining unit determines the life of the photocoupler by measuring the time required for discharging the capacitor.

The photocoupler life diagnosis device according to the present invention can diagnose the life of the photocoupler by measuring the discharge time of the capacitor during the normal digital input operation. As a result, the life of the photocoupler can be diagnosed without interrupting the digital input operation.

Block diagram showing the overall configuration of a digital input device 102 and a computing device 103 having a photocoupler life determination unit Block diagram showing the circuit configuration of the digital input/output unit 104 Block diagram showing the internal configuration of the life determination unit 105 for measuring the discharge time of the photocoupler Timing chart showing changes in V _start and V _stop Timing chart showing operation of counter 301 Block diagram showing the internal configuration of the arithmetic unit 303 Flowchart showing the process of the life determination unit 105

Hereinafter, a digital input device having a photo coupler lifetime diagnosis function according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an arithmetic device 103 including a digital input device 102 of the present embodiment, and FIG. 2 is a diagram showing a circuit configuration of a digital input unit 104 of the digital input device 102.

As shown in FIG. 1, the digital input device 102 of the present embodiment includes a digital input unit 104 including a photocoupler 203 and a capacitor 208, and a life determining unit 105 that determines the life of the photocoupler.

As shown in the circuit example in FIG. 2, the photocoupler 203 receives a light emitting element (light emitting diode as an example) 204 that receives an input signal from an external device 101 and emits light, and receives light emitted by the light emitting element 204. A light receiving element (phototransistor as an example) 205 which converts the electric signal into an electric signal is included. A capacitor 208 is connected to the light receiving element 205, and when the light receiving element 205 receives light from the light emitting element 204, current is supplied to the light receiving element 205 by supplying current from the capacitor 208, and light is converted into an electrical signal. To be done.

The capacitor 208 is discharged by supplying a current to the light receiving element 205. At this time, the discharge time of the capacitor 208, a resistance component R _i inherent in the light receiving element 205 increases with the larger increases with aging. The life determining unit 105 determines the life of the photocoupler 203 by measuring the time required for discharging the capacitor (discharge time). That is, since the discharge time becomes longer as the light receiving element deteriorates with age, it can be determined that the life of the photocoupler 203 is near when the discharge time becomes equal to or longer than the threshold.

It is desirable that a resistor 206 having one end connected to the light receiving element 205 and the other end connected to the capacitor 208 is disposed between the light receiving element 205 and the capacitor 208, as shown in FIG. As a result, the capacitor 208 supplies a current to the light receiving element 205 via the resistor 206.

The digital input device of this embodiment can be arranged in the arithmetic device 103. In the arithmetic unit 103, the signal processing unit 106 that processes the input signal received by the digital input unit 104, the digital output device 151 that outputs the output signal of the signal processing unit 106 to the outside, and the life determining unit 105 output. A life determination processing unit 110 that receives the determination result, processes it, and displays it is provided. Further, an oscillator 107 for generating a signal necessary for the operation of the life determining unit 105 and inputting it to the life determining unit 105, a first power-on signal output unit 108, and a nonvolatile storage area 109 are provided in the arithmetic unit 103. It is arranged. These configurations and operations will be clarified in the detailed description of the embodiment below.

<<Detailed Description of Arithmetic Device 103 with Digital Input Device 102>>
<Configuration of arithmetic unit 103>
As shown in FIG. 1, the arithmetic device 103 includes a digital input device 102, and an external device 101 is connected to the digital input device 102 to input an input signal to the digital input device 102. The digital input device 102 includes a digital input unit 104 and a life determining unit 105. In addition to the digital input device 102, the arithmetic device 103 also includes a signal processing unit 106, an oscillator 107, a first power-on signal output unit 108, a non-volatile storage area 109, and a life determination processing unit 110. ing.

A digital input signal from the external connection device 101 is input to the digital input unit 104, and the digital input signal is transmitted to the signal processing unit 106 via the digital input unit 104 and processed. The processing result of the signal processing unit 106 is output from the digital output device 151 to the outside (the external connection device 101 or the like).

The life determining unit 105 includes a discharge time measuring circuit 332 and a determining circuit 303. The discharge time measurement circuit 332 receives V _start , V _stop output from the digital input unit 104, the clock signal output from the oscillator 107, and P _first output output from the first power-on signal output unit 108, and receives the discharge voltage of the capacitor 208. Measure the discharge time. The determination circuit 303 determines the life of the photocoupler 203 by comparing the measured discharge time with a threshold value. The determination circuit 303 also transmits the life determination result to the life determination processing unit 110.

<Circuit Configuration and Operation of Digital Input Unit 104>
FIG. 2 is a diagram showing a circuit configuration example of the externally connected device 101 and the digital input unit 104. Here, for simplification of description, the externally connected device 101 includes a DC power supply 201 that outputs a DC voltage and a switch 202 for setting a state in which the DC voltage output by the DC power supply 201 is supplied or not supplied. The description will be made by taking as an example the case. However, the external connection device 101 is not limited to the configuration of FIG. 2, and may be any device as long as it is a device that inputs a digital input signal to the digital input unit 104.

The digital input unit 104 includes a photocoupler 203, a first resistor 206, a second resistor 207, and a capacitor 208. The photocoupler 203 includes a light emitting diode 204 and a phototransistor 205. The DC power source 201 and the switch 202 of the external connection device 101 are connected to the light emitting diode 204 side of the photocoupler 203. One end of the first resistor 206 is connected to the collector of the phototransistor 205, and the ground 210 is connected to the emitter. The other end of the first resistor 206 is connected to one end of the second resistor 207 and one end of the capacitor 208. The pull-up power source 209 is connected to the other end of the second resistor 207. A ground 210 is connected to the other end of the capacitor 208.

Next, the operation of the digital input unit 104 will be described.

There are two operations of the digital input unit 104 shown in FIG. 2 when the switch 202 of the external connection device 101 is OFF and when it is ON.

First, the operation when the switch 202 of the externally connected device 101 is OFF will be described. When the switch 202 is OFF, the current I _F which is an input signal from the external device 101 to the light emitting diode 204 is 0 A, so the phototransistor 205 is in an OFF state and the current I _C flowing through the phototransistor 205 is 0 A. is there.

While the switch 202 is OFF, the capacitor 208 is charged with electric charge from the pull-up power source 209 via the second resistor 207, and the voltage V _stop between one end of the capacitor and the ground 210 rises to the pull-up voltage Vcc. .. Therefore, the Hi(Vcc) level voltage _Vstop is output from the digital input unit 104 to the discharge time measuring circuit 332.

Next, the operation when the switch 202 of the external device 101 is ON will be described. When the switch 202 is ON, the current I _F which is the input signal from the external device 101 is supplied to the light emitting diode 204, so that the light emitting diode 204 emits light. The phototransistor 205 receives this light and turns on, and a current I _C flows through the phototransistor 205. This current I _C is generated by the charge stored in the capacitor 208 flowing in the order of the first resistor 206, the phototransistor 205, and the ground 210. Therefore, the capacitor 208 is discharged, and the voltage _Vstop between one end of the capacitor 208 and the ground 210 becomes 0V. Therefore, the low (0 V) voltage V _stop is output from the digital input unit 104 to the discharge time measuring circuit 332.

At this time, the time required for the capacitor 208 to discharge increases in proportion to the resistance component of the discharge route. When the power is turned on for the first time, the resistance component R _i existing in the phototransistor 205 is minute, but increases and increases due to deterioration over time, and the discharge time also increases. Along with this, the current transmissibility (I _C /I _F ) becomes smaller.

The discharge time measuring circuit 332 of the life determining unit 105 measures the discharge time, and the determining circuit 303 compares the measured discharge time with a threshold value calculated from the initial value of the discharge time to diagnose the life of the photocoupler. .. As a result, the life of the photocoupler can be diagnosed by utilizing the characteristic that the discharge time increases with the aging of the photocoupler.

<Structure and operation of life determining section 105>
(Structure of discharge time measuring circuit 332)
FIG. 3 is a diagram showing a detailed configuration of the discharge time measuring circuit 332 of the life determining unit 105.

The discharge time measuring circuit 332 has a counter 301 and a D latch 302. When a 16-bit counter 301 is used as an example, since 16 bits are output from Q _{1 to} Q ₁₆ , 16 D latches 302 are required.

The discharge time measuring circuit 332 receives three inputs, V _start and V _stop output from the digital input unit 104, and a clock signal output from the oscillator 107.

FIG. 4 shows a timing chart showing the operations of the power supply of the arithmetic unit 103, the DC power supply 201, the switch 202, V _start , and V _stop . Clock is a clock signal. V _start is a voltage across the light emitting diode of the digital input unit 104 shown in FIG. V _start becomes Hi level when the switch 202 is turned on, and becomes Low level when the switch 202 is turned off. V _stop is the voltage across capacitor 208. When the switch 202 of the external connection device 101 is in the OFF state, that is, when the input signal from the external connection device 101 is not input to the digital input unit 104, the capacitor 208 is charged, so V _stop is pulled up. The voltage rises to the voltage Vcc of the up power supply 209, and V _stop =Vcc.

When the switch 202 of the external connection device 101 is turned on, that is, when the input signal from the external connection device 101 is input to the digital input unit 104, the capacitor 208 is discharged and V _stop becomes 0V.

As shown in FIG. 5, the clock signal and the V _start signal are input to the counter 301. When the Hi-level V _start signal is input, the counter 301 starts counting clock signals and outputs count values Q _{1 to} Q ₁₆ . The count values Q _{1 to} Q ₁₆ are input to the input terminal 1 of the D latch 302.

The V _stop signal is input to the input terminal 2 of the D latch 302. When the V _stop signal becomes the Low level, the D latch 302 holds the count values Q _{1 to} Q ₁₆ input from the counter and outputs it to the determination circuit 303. The count values Q _{1 to} Q ₁₆ held by the D latch 302 indicate the time taken for the capacitor 208 to discharge.

The determination circuit 303 determines the life based on the input count values Q _{1 to} Q ₁₆ and outputs a life determination signal.

The operation of the counter 301 will be described more specifically with reference to the timing chart of FIG. The clock signal and V _start are input to the counter 301. As an example, when the clock frequency of the clock signal is 10 MHz, the time per clock is 0.1 μs. Counting is not started during the period when V _start is Low, but counting is started when V _start becomes Hi. Since one count is made per clock, the time for one count is 0.1 μs. Further, in the case of the 16-bit counter, the discharge time can be measured up to about 6.5 ms because it can count up to 65536.

(Structure of determination circuit 303)
FIG. 6 is a block diagram showing the internal configuration of the determination circuit 303 of the life determination unit 105. The configuration and operation of the determination circuit 303 will be described with reference to FIG. The determination circuit 303 includes a threshold value calculation unit 601, a non-volatile storage area 602, and a comparison unit 603. The output of the D-latch 302 (count values Q _1A , Q _2A ,... Q _16A representing the discharge time) is input to the comparison unit 603 and the threshold value calculation unit 601. In addition to the outputs (Q _1A , Q _2A ,... Q _16A ) of the D latch 302, the threshold value calculation unit 601 also receives P _first output from the first power-on signal output unit 108.

A non-volatile storage area 109 in the arithmetic unit 103 stores the number of times the power is turned on. The first power-on signal output unit 108 reads out the data in the non-volatile storage area 109, and outputs a Hi-level signal only when the read-out data indicates that the power is turned on for the first time. When the power is not turned on for the first time, Low is output.

When P _first is Hi, that is, when the power is turned on for the first time, the threshold calculation unit 601 calculates the threshold based on the input (Q _1A , Q _2A ,... Q _16A ) of the D latch 302. The threshold value is, for example, a value obtained by increasing the discharge time by 20% from the initial value.

The threshold calculation result (Q _1th , Q _2th ,... Q _16th ) is stored in the non-volatile storage area 602. The output (Q _1A , Q _2A ,... Q _16A ) of the D latch 302 and the threshold value (Q _1th , Q _2th ,... Q _16th ) are input to the comparison unit 603, and the respective values are compared. Then, it is determined whether or not Q _1A , Q _2A ,... Q _16A ≧Q _1th , Q _2th ,... Q _16th . When Q _1A , Q _2A ,... Q _16A ≧Q _1th , Q _2th ,... Q _16th are Yes, it is determined that the life of the photocoupler is approaching, and an abnormal signal is output. When Q _1A , Q _2A ,... Q _16A ≧Q _1th , Q _2th ,... Q _16th are No, the photocoupler determines that it is normal and outputs a normal signal.

When _Pfirst is Low, that is, when the power is not turned on for the first time, the threshold calculation unit 601 does not calculate the threshold. In the non-volatile storage area 602, the threshold value calculated when the power is first turned on is continuously stored. Further, even when the power of the device is turned off, the non-volatile storage area 602 continues to store the threshold value when the power is turned on for the first time.

(Operation of life determining section 105)
FIG. 7 is a flowchart showing the operation of the life determining unit 105 shown in FIG. Hereinafter, an operation example of the life determining unit 105 will be described with reference to FIG. 7. It should be noted that, here, although it is described that the life determining unit 105 is realized by software according to the flowchart of FIG. 7, the discharge time measuring circuit 331 is configured by hardware as shown in FIG. The functions of the threshold value calculation unit 601 and the comparison unit 603 of the determination circuit 303 can of course be realized by software, or part or all of the functions can be realized by hardware. When implemented by software, the threshold value calculation unit 601 and the comparison unit 603 are configured by a CPU and a memory, and the CPU reads and executes a program in the memory, so that the threshold value calculation unit in the flow of FIG. 7 described below is executed. A program may be created so as to realize the operations of 601 and the comparison unit 603. When implemented by hardware, for example, a part or all of the arithmetic unit 12 is configured by a custom IC such as ASIC (Application Specific Integrated Circuit) or a programmable IC such as FPGA (Field-Programmable Gate Array), The circuit may be designed so as to realize the operations of the calculation unit 601 and the comparison unit 603. Of course, the function of the discharge time measuring circuit 331 can be realized by software.

(Step 701)
The clock signal is input to the counter 301 of the discharge time measuring circuit 332. When the voltage V _start across the light emitting diode 204 output from the digital input unit 104 is Low, that is, when the input signal from the external device 101 is in the OFF state, the capacitor 208 is being charged and is not discharged. The counter 301 does not start counting.

(Step 702)
When the switch 202 of the externally connected device is turned on, the input signal is input to the digital input unit 104, and the voltage V _start across the light emitting diode 204 becomes Hi, the light emitting diode 204 emits light and the phototransistor 205 receives light. Since the current Ic flows, the capacitor 208 starts discharging, and the voltage V _stop across the capacitor 208 decreases by drawing an attenuation curve as shown in FIG. The counter 301 starts counting at the timing when V _start becomes Hi. The count values (Q ₁ , Q ₂ ... Q ₁₆ ) are input to the D latch 302.

(Step 703)
Immediately after the start of discharge, when the voltage V _stop across the capacitor 208 is Hi, the count values (Q ₁ , Q ₂ ... Q ₁₆ ) input to the terminal 1 of the D-latch 302 are directly output from the D-latch 302 (Q _1A , _Q2A ... _Q16A ).

(Step 704)
When the discharge of the capacitor 208 is completed and the voltage V _{stop at} both ends becomes Low, Low is input to the input terminal 2 of the D latch 302. As a result, the output values (Q _1A , Q _2A ... Q _16A ) of the D latch 302 are held. As a result, the output value (Q _1A , Q _2A ... Q _16A ) indicating the discharge time of the capacitor 208 is held in the D latch 302.

(Step 705)
The threshold calculation unit 601 determines whether or not the power is turned on for the first time. The determination is made based on _Pfirst output from the first power-on signal output unit 108. When P _first is Hi, it is determined that the power is turned on for the first time, and when P _first is Low, it is determined that the power is not turned on for the first time.

(Step 706)
When the threshold value calculation unit 601 determines that the power is turned on for the first time, the threshold value calculation unit 601 uses the outputs (Q _1A , Q _2A ... Q _16A ) of the D latch 302 to determine the threshold _values (Q _1th , Q _2th ... Q _16th). ) Is calculated. For example, a value that is a predetermined value times (for example, 120%) the output (Q _1A , Q _2A ... Q _16A ) of the D-latch 302, which indicates the discharge time of the capacitor 208 when the power is turned on for the first time, is calculated as the threshold value.

(Step 707)
The threshold _values (Q _1th , Q _2th ... Q _16th ) calculated by the threshold value calculation unit 601 are stored in the non-volatile storage area 602.

(Step 708)
The comparison unit 603 determines that the value (Q _1A , Q _2A ,... Q _16A ) indicating the discharge time of the capacitor 208 output from the D latch 302 is equal to or more than the threshold value (Q _1th , Q _2th ,... Q _16th ) calculated in step 706. It is determined whether there is any.

(Step 709)
When it is determined that the output value (Q _1A , Q _2A ,... Q _16A ) of the D latch 302 indicating the discharge time is equal to or greater than the threshold value (Q _1th , Q _2th ,... Q _16th ), the comparison unit 603 determines that the photocoupler It judges that the life of the is approaching, and outputs an abnormal signal.

(Step 710)
When it is determined that the output value (Q _1A , Q _2A ,... Q _16A ) of the D latch 302 indicating the discharge time is less than the threshold value (Q _1th , Q _2th ,... Q _16th ), the comparison unit 603 determines that It judges that there is no problem with the life, outputs a normal signal, and continues operation.

The life determination signal output by the comparison unit 603 is transmitted to the life determination processing unit 110 shown in FIG.

When the life determination processing unit 110 receives an abnormal signal, the life determination processing unit 110 notifies the user by, for example, displaying a message prompting the replacement of the digital input device having the photocoupler mounted on the display device 160.

When it is determined in step 705 that the power is not turned on for the first time, the process proceeds to step 708 and the operation is continued. The non-volatile storage area 602 continues to store the threshold _values (Q _1th , Q _2th ,... Q _16th ) calculated at the first power-on even after the first power-on. Furthermore, the non-volatile storage area 602 continues to store the threshold _values (Q _1th , Q _2th ,... Q _16th ) calculated when the power is turned on for the first time, even when the power of the device is cut off. As a result, the photocoupler life diagnosing circuit of the present invention can compare with the threshold value based on the discharge time when the power is turned on for the first time even when the power is turned off and then turned on again.

Since the digital input device 102 of the present embodiment includes the photocoupler life determining unit 105, the discharge time and the threshold value are compared and determined by utilizing the characteristic that the discharge time of the capacitor increases as the photocoupler ages. As a result, the life of the photocoupler can be diagnosed. This makes it possible to prevent a device failure.

In the present embodiment, the life of the photocoupler 203 of the digital input device 102 is diagnosed, but there are some digital output devices such as a digital output board that use the photocoupler 151. In that case, the life of the photocoupler of the digital output device 151 can be diagnosed by the life determining unit 105 of the present embodiment.

Further, the life determining unit 105 of the present embodiment is mounted on a digital input/output device including both a digital input device and a digital output device, and the photo coupler of the digital input device and/or the photo coupler of the digital output device is It is also possible to diagnose the life span.

Reference numeral 101 externally connected device 102 digital input device 103 arithmetic device 104 digital input unit 105 life determination unit 106 signal processing unit 107 oscillator 108 first power-on signal output unit 109 non-volatile storage area 110 life determination processing unit 201 DC power supply 202 switch 203 photocoupler 204 Light emitting element (light emitting diode)
205 Light receiving element (phototransistor)
206 First resistance 207 Second resistance 208 Capacitor 209 Pull-up power supply 210 Ground 301 Counter 302 D-latch 303 Judgment circuit 332 Discharge time measurement circuit 601 Threshold calculation unit 602 Nonvolatile storage area 603 Comparison unit

Claims (7)

A light-emitting element that receives an input signal from the outside and emits light, and a photocoupler that includes a light-receiving element that receives the light emitted by the light-emitting element and converts the light into an electrical signal,
A capacitor connected to the light receiving element,
A life determining unit that determines the life of the photocoupler,
When the light receiving element receives light from the light emitting element, the capacitor discharges by supplying a current to the light receiving element,
The digital input device, wherein the life determining unit determines the life of the photocoupler by measuring a time required for discharging the capacitor. The digital input device according to claim 1, wherein
A resistor having one end connected to the light receiving element and the other end connected to the capacitor is disposed between the light receiving element and the capacitor, and the capacitor supplies a current to the light receiving element through the resistor. And digital input device. The digital input device according to claim 1, wherein
And a discharge time measuring circuit for measuring a time taken for the light emitting element to discharge until the voltage of the capacitor reaches a predetermined value after the light emitting element receives the input signal. A digital input device comprising: a determination circuit that determines the life of the photocoupler by comparing the time required for the discharge measured by the circuit with a threshold value. The digital input device according to claim 3, wherein
The discharge time measuring circuit includes a counter and a D latch,
The counter starts counting when the two terminals of the light emitting element reach a predetermined Hi voltage, and the D latch outputs the counter when the voltage across the capacitor reaches a predetermined Low voltage. A digital input device for measuring the time required for the discharge by holding the count value output by the. The digital input device according to claim 3, wherein
The determination circuit, a threshold value calculation unit for calculating the threshold value, a storage area for storing the calculated threshold value, a threshold value in the storage area, and the time required for the discharge measured by the discharge time measurement circuit, A digital input device, comprising: The digital input device according to claim 5, wherein
The digital input device, wherein the threshold value calculation unit calculates the threshold value based on a time required for the discharge measured by the discharge measurement circuit for the first time. An arithmetic device having a digital input device for receiving an input signal from the outside and a signal processing unit for arithmetically processing an electric signal output by the digital input device,
The arithmetic device, wherein the digital input device is the digital input device according to any one of claims 1 to 6.

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