JPS61105140A - Photoelectric mutual converter - Google Patents

Abstract

PURPOSE:To attain mutual conversion of a signal with an optical coupling element by using a semiconductor element having a PN junction as a light emitting element at a time and using as a photodetector at another time and arranging a couple of such semiconductor elements oppositely. CONSTITUTION:A data signal from an external signal processor is inputted to an input interface circuit 50 at the transmission side. The data signal to be transmitted is superimposed on a modulation wave through a gate circuit 8 at the transmission side and becomes a serial data signal successively. Then the signal is converted into light by a photodetection/light emitting diode 11 at the transmission side through an internal signal gate switch 61 of a light emitting control circuit 60 at the transmission side and becomes a modulation light data signal. A modulation light serial data signal is inputted to a photodetection/light emitting diode 11 as a photodetector at the reception side as incident light and the light current according to the data signal is inputted to a photodetection circuit 2 at the reception side as a reverse current. Since the output of the photodetection circuit 2 at the reception side is a serial data signal including a carrier frequency superimposed on the modulation wave, the modulation wave is eliminated by a waveform shaping circuit 35 at the reception side through a detection circuit 30 at the reception side and decoded into the same serial data signal the same as that at the transmission side.

Description

Detailed Description of the Invention [Field of Application of the Invention J The present invention relates to a photovoltaic device that detects the presence or absence of light or the intensity of light, and also operates as an optical signal generator that converts an electrical signal into an optical signal by switching a circuit. This invention relates to mutual conversion devices.

[Background of the invention]

Semiconductor light emitting elements and semiconductor light receiving elements such as light emitting diodes, photodiodes, and phototransistors are known as photoelectric conversion elements.

A light-emitting diode is a solid-state light-emitting element that is composed of a PN junction of a semiconductor crystal and emits light when a voltage is applied to the junction and a current flows. The color of light emitted from a light emitting diode is determined by the semiconductor material that makes up the device. For example, gallium phosphorus (GaAs)
P) is red or green, gallium phosphorus (GaAsP)
) is yellow-green to red, gallium aluminum, arsenic GaAjA
It is known that red color can be obtained with s. Among these, gallium arsenide phosphorus is a mixed crystal of gallium phosphorus and gallium sec, and various luminescent colors are produced depending on the ratio of μ element As and phosphorus P, from yellow-green to yellow, lilac, and red. ing. FIG. 5 shows the relative spectral outputs of these main light emitting diodes.

Figure 6 shows a typical structure of a light emitting diode.
101 and 102 are lead frames; 110 is a light emitting semiconductor chip placed and connected on the lead frame 101; 12
0 is a wire lead connecting the lead frame 102 and the electrode of the light emitting semiconductor chip 110, and 130 is an envelope. As shown in the figure, the envelope 130 is molded into a lens shape from a transparent synthetic resin, and gives directionality to the light from the light emitting semiconductor chip 110, which has a light distribution close to that of a completely diffused surface. It goes without saying that the envelope may be made of a transparent material such as glass, in addition to the resin-sealed type, to form a chamber for accommodating the light emitting semiconductor chip.

FIG. 7 shows the basic structure of the light emitting semiconductor chip 110, with N
Power is supplied to the PN junction consisting of the hawk semiconductor layer 111 and the P-type semiconductor 112 through the respective electrodes 118 and 114. It is thought that light emission mainly occurs in the P-type region near the junction surface, and the light is extracted through the P-type semiconductor rmx12 or the N-type semiconductor #111. Therefore, it is also known to form a pressure reflective surface on the back side of the P-type semiconductor layer 112 or the N-type semiconductor layer l11 and utilize the reflected light.

The light emitting intensity of such a light emitting diode changes in proportion to the current, and the response speed is as fast as several 100 ns at most.

On the other hand, a photodiode known as a light-receiving element is constructed of a PN junction of a semiconductor crystal, similar to a light emitting diode, and utilizes photovoltaic force at this PN junction. There is a solar cell that uses this photovoltaic force as one source, and the principle is the same as that of a photodiode. The semiconductor materials that make up the photodiode elements are:
Germanium (Ge), silicon (Si), gallium phosphide (GaAsP), etc. are known, and the latter two are widely used because they operate in the range of near infrared to visible light.

The relative spectral sensitivities of photodiodes made of silicon and gallium arsenide phosphorus are shown in FIG.

FIG. 8 shows a typical structure of a photodiode, in which 151 and 152 are lead frames, 161 is an N-type semiconductor layer, 162 is a P-type semiconductor layer, and 163 and 164 are t-poles of the respective semiconductor layers. , 170 is an antireflection film made of silicon oxide or the like, and 180 is a protective envelope. P16 when the photodiode is irradiated with light? Charges are accumulated in the −161 type semiconductor layer H and the N type semiconductor layer,
Although the potential barrier of the PN junction is lowered, this change appears externally as a voltage. When these ends are short-circuited, a short-circuit current flowing in the opposite direction is obtained, and this value is proportional to the amount of incident light.

When using a photodiode for signal detection or sight detection, a yJI amplifier is mainly used, and a circuit like the one shown in Figure 9 is also used as a circuit to obtain a voltage proportional to the short-circuit current. A circuit as shown in FIG. 10 is used as a circuit for obtaining a voltage proportional to the open-circuit voltage. In the figure, PD is a photodiode, OP is an operational amplifier, Ish is a short circuit current, Rf is a feedback resistor, and Re
is the resistance, Mop is the open circuit voltage, and Vout is the output voltage. Further, the response speed of a photodiode is proportional to the light-receiving area of the element, and some have a response speed of several microseconds to several ounces.

In this way, light 1. A light emitting diode and a photodiode as a conversion element are respectively known as a light emitting element and a light receiving element, and most of them are used independently.

By the way, in Tono's photoelectric conversion elements, the role of each semiconductor element is specified, and the reality is that the light-emitting semiconductor element is used only for light emission, and the light-receiving semiconductor element is used only for light reception.

[Purpose of the invention]

The present invention relates to a photoelectric mutual conversion device that uses one PN junction in a semiconductor for two purposes: light emission and light reception. For example, a semiconductor element having one PN junction can sometimes be used as a light emitting element, and In some cases, it is used as a light-receiving element, and furthermore, a pair of semiconductor elements of this spear is arranged facing each other, and mutual conversion of signals is attempted to be performed with one optical coupling element.

[Summary of the invention]

The present invention utilizes a photoelectric interconversion element using a conversion semiconductor chip having a light-emitting region formed by a PN junction formed on a single crystal substrate using a ■-V group compound semiconductor such as gallium arsenide phosphorus, which can perform arbitrary circuit switching. Current supply means for supplying forward current through means and open circuit voltage or short circuit 1! The present invention provides a photoelectric mutual conversion device to which a photodetection means using an electric current is connected. According to such a configuration, for example, when a current supply means is connected to the photoelectric mutual conversion element, the photoelectric mutual conversion element operates as a light emitting element, and when a photodetection means is connected, it operates as a light receiving element. It can operate as an element. Furthermore, in the case of a photocoupler device configured by a pair of photoelectric mutual conversion devices of this type facing each other, for example, when one operates as a light emitting device, the other is set to operate as a light receiving device. Therefore, mutual conversion is possible with one optical coupling element.

[Embodiments of the invention]

FIG. 1 is a block diagram showing an embodiment of a photodetector according to the present invention. In the figure! is a light-receiving/emitting diode as a photoelectric mutual conversion element that serves both as a light-receiving element and a light-emitting element. Reference numeral 2 denotes a photodetection circuit configured as photodetection means, including a signal detection circuit 21 using an operational amplifier as shown in FIG. 9, and an adjustable voltage amplification circuit 22 for amplifying its output. Consisted of. Reference numeral 3 designates switch operation circuits, including a comparison circuit 31 that compares the signal output voltage of the photodetector circuit 2 with a set voltage and outputs a step voltage depending on the magnitude thereof, and an operation level setting circuit 82 that produces the set voltage. A hold circuit that latches and holds the step output voltage of the comparison circuit 81? 4--1 and a reset circuit MK for manually or automatically releasing the hold.
-4 is a changeover switch circuit provided as a circuit changeover means,
It may be constituted by a contact circuit, or it may be a non-contact type switch 1 constituted by a semiconductor element such as a transistor/transistor or a logic gate IC as a reserved changeover switch. When attempting to automatically switch circuits, a non-contact method is more convenient and requires less power, so it is appropriate. Reference numeral 5 denotes an output interface circuit, which is composed of an amplifying circuit for driving a relay or a lamp of an external control circuit. Reference numeral 6 denotes a light emitting power supply circuit configured as a current supply means for supplying current for light emission to the light receiving/emitting diode l, and is constituted by a DC power source 61 and a current control impedance 62.

A case will be described in which a photoelectric conversion device having such a configuration operates as a photodetection device. Changeover switch circuit 4
The switching contact at is connected to the light detection side contact A.

In this state, when incident light Lin enters the light receiving/emitting diode l, a photocurrent 1sh proportional to the amount of incident light flows through the signal detection circuit 2,1, and a signal based on the photocurrent 1sh is obtained. This signal is amplified by the voltage amplification circuit 22 and is amplified by the photodetection circuit 22.
The output is taken out to the outside. This output voltage Vou
Since t is obtained as a value proportional to the amount of incident light, if this output voltage Vout is taken out as it is, it can be used as a side light output signal.

On the other hand, when obtaining a control signal at a certain value of the incident light Lin, the voltage corresponding to the incident light Lin' at the operating point set in advance in the operating level setting circuit 82 and the output voltage Vout of the photodetector circuit 2 described above are used. Comparison circuit 31
For example, when the output voltage Vout becomes less than or equal to a set voltage, a step voltage is output from the comparison circuit 31. Then, this comparison output is the hold circuit 3
4, the operation output of the switch operation circuit 3 is latched and held.

The held switch operation output is used as a control signal for an external control circuit via the output interface circuit 5, and is used to control lighting of illumination lights, for example.

By the way, if this held output of the switch operation circuit 8 is used as an operation signal for the changeover switch circuit 4, the following operation becomes possible. That is, the light receiving/emitting diode 1 is connected to the light detection side terminal A in the changeover switch circuit 4 and is operated as a light receiving element. Switch to contact B on the light emitting power supply side. As a result of this operation, the DC power source 61 and the current control impedance 62 are connected to the light receiving/emitting diode 1, the operation as a light receiving element is stopped, and a forward current If flows to switch the operation button as a light emitting element. In this way, when the light emitting/receiving diode 1 is connected to the light emitting power supply circuit 6, the receiving/emitting diode 1 operates as a light emitting element and outputs the emitted light Lout. By operating this light receiving/emitting diode 1 as a light emitting element, it is possible to visually know that a control signal has been outputted through this element.

Note that when the light receiving/emitting diode l is switched from the light receiving operation to the light emitting operation, the signal output of the photodetector circuit 2 is made zero, but the step-like output of the comparison circuit 31 at this time is such that the signal output is equal to the operating level setting circuit. When the set value of 82 is exceeded, the switch operation output of the switch operation circuit 8 appears as a sudden change in rising or falling. When the light receiving/emitting diode l operates as a light receiving element, the difference between the case where the light receiving/emitting diode l is disconnected from the photodetection circuit and the case where the incident light Lin is zero is difficult to grasp, so the sudden change in the operating output described above is difficult. It is preferable to provide a hold circuit 34 with a launch hold that operates as a trigger for a direct change. That is, once the hold circuit 34
When activated, the hold state is maintained until it is reset or the cent circuit 33 is activated.

This reset circuit may be operated either automatically or automatically, and an appropriate method can be selected depending on the purpose of use of such a photodetector.

Next, how to use this photodetector will be explained.

The light receiving and emitting elements 1 are distributed at appropriate positions indoors and installed at positions suitable for monitoring the lighting load condition of the building as soon as outdoor light enters. Further, the illumination load is controlled by the control output of this photodetector.

Under such conditions, if the external light is sufficiently slow and the light receiving output of the light receiving/emitting diode 1 is sufficiently large, the control output is zero. When the outdoor light decreases and the signal output of the photodetection circuit 2 falls below the set value of the operating level setting circuit 32, the comparison circuit 31
The output changes in a stepwise manner, and at the same time as outputting a control output, a switching signal is given to the changeover switch circuit 4. As a result, the light receiving/emitting diode 1 operates as a light emitting element, the signal output of the photodetecting circuit 2 is zero, and the output of the comparing circuit 31 is maintained in the step-like state. E7 Therefore, the hold circuit 34 is not particularly required in this case, but the hold circuit 34 is provided when the light from the light receiving/emitting diode IK lighting lamp is incident or to enable the reset circuit 83 to switch the operation signal. It's better to be prepared.

This operation signal passes through the output interface circuit 5 and turns on the illumination lamp as a control output. The lighting state of this illumination lamp can be visually recognized by the operation of the light receiving/emitting diode 10 as a source wire.

The reset circuit 33 can be of any type, such as a manual circuit, an automatic reset signal generation circuit using a timer circuit, or a reset signal generation circuit based on a completely independent photodetection circuit.

When the reset circuit 33 operates and the switching contact of the changeover switch circuit 4 returns to the light detection side contact A+cb, the light receiving/emitting diode I returns to the operation as a light receiving element again, and the incident light Lin
i/Ll outputs a signal according to the scene. Therefore, the incident light Lin at the time when the reset signal is input manually
When the signal output of the light detection circuit 2 based on Tsukuru. That is, the reset circuit 8
There is no waste in resetting H by providing a conditional circuit that allows manual input only when the output of the photodetector circuit 20 exceeds the set value of the operation level setting circuit 32.

According to the operation described above, it can be used in a system that uses outdoor light and illumination lights to automatically turn on the illumination lights by detecting outdoor light.
This is useful because it can be used both to detect outdoor light and to display the operation of lighting lights.

In addition, the same operation as that described above is performed, and the incident light L
It can be used to monitor deterioration of the main skein when it is desired to ensure that the in is above a certain value. In this case, the output interface circuit 5 is not necessary, and when the incident light Lin falls below a set value, the operation of the light receiving/emitting diode 1 is switched from receiving light to emitting light, thereby making it possible to indicate deterioration or dirt in the light source. Of course, it can also be used to monitor combustion flame extinction or as a smoke detector.

In the above explanation, the method that operates when the incident light decreases is taken as an example, but the operation output of the comparison circuit 31P of the switch operation circuit 3 is made to have the opposite polarity so that the sound of the incident light becomes louder than the set level. Needless to say, if it is configured to perform a switch operation from time to time, it can be used as a photoelectric switch at the time of light seedling.

FIG. 2 shows a specific example of a photodetector according to the present invention.

In the figure, the LED is a red light-emitting diode made of gallium phosphorus, which is used as a light-receiving and light-receiving diode.

According to experiments, when this type of light emitting diode LEL+ was used as a light receiving element, it was possible to obtain sufficient signal output with commercial sensitivity for any light such as daylight, incandescent lamps, and white fluorescent lamps. .

When a light-emitting diode (LED) is used as a light-receiving element, the operation of the element is considered to be similar to that of a photodiode because its PN junction 44r structure is similar to that of a photodiode. The change in the value showed a linear proportional relationship similar to that of the photodiode, however, according to experiments.

Using a light emitting diode as a light receiving element compared to a photodiode 1. In this case, since the structure is mainly for light emission, the photocurrent output is about 10 to 10 times that of a photodiode, depending on its effective light-receiving area, and is 10" to 10'
An output of about several nA to several 100 nA can be obtained in the range of lx. Therefore, compared to the case of using a photodiode, it is 10' to 10! Although it requires an amplification gain of about twice that, it is a value that can be obtained relatively easily by using a MOS-FET type amplifier or the like. In addition, the light emitting diode L
ED has the advantage that the error is small because the current is very small at a few pA.

On the other hand, when using a light-emitting diode LED as a light-receiving element to obtain an open-circuit voltage, two
The open circuit output voltage will be ~3 times higher. The open circuit voltage is directly related to the amount of incident light. Since it is not in IIl section, light hi: fi! II
Although it is not suitable for determining the presence or absence of light, it can be used to detect the presence or absence of light, and it is advantageous because the amplification gain may be smaller than that of photoelectric detection.

It has been experimentally estimated that the absorption spectral sensitivity of a light emitting diode LED is similar to that of a photodiode made of the same material. It is known that changing the ratio of arsenic and phosphorus in a gallium dins phosphorus light emitting diode changes the peak of the emission spectral distribution, and it is thought that the spectral sensitivity of the photodiode also changes. Although a gallium phosphorus green light emitting diode has a narrow spectral output range, it was confirmed that when used as a light receiving element, it has almost no sensitivity to red light. From these points, it is inferred that the absorption sensitivity decreases rapidly, at least for light in a long wavelength region exceeding the peak value of the spectral output as a light emitting diode. In this way, ■−v
Light-emitting diodes using group compound semiconductors generally also have the ability to function as light-receiving elements, and their absorption sensitivity is characterized by their spectral output. This is essentially different from a silicon photodiode, which has absorption sensitivity over an extremely wide wavelength range.

Now, in FIG. 2, the photodetection circuit 2 is constituted by an operational amplifier OP which constitutes a signal detection circuit and an operational amplifier OP which constitutes a voltage amplification circuit. The variable resistor RV is used to adjust the sensitivity of the signal detection circuit.

The switch operation circuit 8 includes an operational amplifier OP that constitutes a comparison circuit that compares the signal of the operation level setting circuit formed by the variable resistor RV and the output of the voltage neutralization circuit.
, and inputs the signal of the comparison circuit to a hold circuit 34 composed of a slip circuit having a reset gate,
One output is output as a control output via an operational amplifier OP4 forming an output interface circuit, and the other output is input to the changeover switch circuit 4. In addition,
The reset circuit connected to the reset gate is a reset switch using a manual switch R5, and the reset terminal is connected to an automatic reset circuit AR such as a timer or a separately provided reset control signal generation circuit. The changeover switch circuit 4 uses, for example, an analog switch AS, which is alternately opened and closed based on the level of the input signal.

According to such a circuit configuration, when the incident light Lin enters the light emitting diode LED and the photocurrent Ish flows, an output voltage proportional to this value is generated by the amplifier OP.

This signal is input to a comparison circuit and compared with a set value. When the incident light Lin is sufficiently large, the output of the operational amplifier OP is "low", and the output of the operational amplifier OP is "low".
The output of the hold circuit 84 that provides the input signal of P4 is "high", and the output to the changeover switch circuit 4 is "low". In this state, the photodetection side switch of the analog switch As receives a photocurrent Ish.

Close in forward direction. Next, when the output voltage of the photodetection circuit 2 decreases and drops below the reference value, the input to the hold circuit 34 is halved and becomes "high", and the output of the hold circuit 84 is also inverted. As a result, the conduction state of the analog switch AS is also reversed, and the forward voltage ■,! ,
o is applied, forward current If flows, and normal operation is switched. Further, a "high" signal is normally input to the reset gate, and when resetting, this signal is changed to "low". Note that when "high" and "low" oscillation inputs are applied to the reset gate, the light emitting diode LED blinks and the control signal is output as a continuous pulse. - Fig. 3 shows another embodiment, in which two light receiving/emitting diodes are arranged in pairs and are opposed to each other via a transmission path, and are applied to a transmitting/receiving device for transmitting data signals in communications. In the figure, S is a first transceiver, which is paired with a second transceiver to constitute one set of transceiver apparatus. In addition, the first
, second transceiver S, , S, g are formed of transceivers having the same configuration, but the second transceiver S is partially omitted from illustration.

When one of the first and second transceivers S1 and S operates as a transmitter, the other operates as a receiver. The state shown in FIG. 8 shows a case where the first transceiver S1 is operating as a receiver and the second transceiver S is operating as a transmitter. 11 is a light receiving/emitting diode;
A second transceiver S via an optical transmission line 10 such as an optical fiber cable.

A light emitting/receiving coupler which operates in pair with a light emitting/receiving diode 11 provided on the side is constituted. 2 is a photodetection circuit similar to that explained in FIG. 1, which amplifies the photodetection signal to a desired value to obtain a signal output. 80 is a detection circuit for a signal output obtained as a serial data signal received as modulated light, for example. The detected signal output is input to a waveform shaping circuit 85 constituting the switch operation circuit 8, and is shaped and decoded. This decoded signal is input to a hold circuit 34 which uses a part of it as a strobe signal to obtain a step-like latched output, and at the same time is input to an output interface circuit 5 which sends a signal to an external signal processing device. Ru. 4 is a changeover switch circuit that switches the transmission/reception state based on the signal from the hold circuit 84. Note that this switching may be accomplished by, for example, adding a transmission end signal in an arbitrary form at the end of the transmission side signal, and the hold circuit 84 may switch the connection of the changeover switch circuit 4 based on the transmission end signal.

Reference numeral 50 denotes an input interface circuit that inputs a data signal to be transmitted from an external signal processing device, and switches the serial trap signal mode as necessary, for example, in the case of a parallel data signal. an oscillation circuit for modulating a carrier frequency wave for modulating and transporting a serial data signal to be transmitted, 8
is a gate circuit for superimposing a data signal to be transmitted on this modulated wave. Reference numeral 60 denotes a light emission control circuit, which controls the light receiving/emitting diode II based on the modulation signal output of the gate circuit 8.
The signal current flowing through the K is controlled to form a light emission signal of the light receiving/emitting diode 11.

Note that if the data signal does not need to be a modulated optical signal, the numbering circuit 7. The gate circuit 8 and the detection circuit 30 can be omitted.

Next, the transmitting/receiving device 31%S having the configuration as shown in FIG.
The operation of t will be explained.

Initially, both the transmitting side and the receiving side are placed facing each other in a light-receiving state.

A data signal from an external signal processing device is input to an input interface circuit 50 on the transmitting side, and is converted into a serial mode signal if necessary. Then, the start bit signal of the serial data signal to be transmitted is extracted and used as a reset signal, and the hold circuit 84, which is one of the components of the switch operation circuit 3 on the transmitting side, is released, and the inhibit signal that is the output is released. Then, the oscillation circuit 7 on the transmitting side is activated to generate a modulated wave. Further, another output of the hold circuit 34 on the transmitting side is used as a switching signal to switch the internal switch of the changeover switch circuit 4 on the transmitting side from the light receiving circuit side to the light emitting circuit side. The data signal to be transmitted passes through the gate circuit 8 on the transmitting side and becomes a serial data signal superimposed on a modulated wave. Then, through the internal signal gate switch 61 of the light emission control circuit 60 on the transmitting side, the light emitting/receiving diode IIK on the transmitting side sends out a modulated optical data signal that is not converted into light to a signal transmission path IO using, for example, an optical fiber cable.

On the receiving side, a modulated optical serial data signal is input as incident light to a light receiving/emitting diode 11 serving as a light receiving element, and a photocurrent according to the data signal is input as a reverse current to a photodetecting circuit 2 on the receiving side.

Since the output of the photodetector circuit 2 on the receiving side is a serial data signal containing a carrier frequency riding on a variable V# wave, it is passed through the receiving side detection circuit 30 and the modulated wave is removed by the receiving side waveform shaping circuit 35. The data is then decoded into the same serial data signal as on the transmitting side.

At this time, the 7th earth bit of the decoded serial data signal is extracted and the holding circuit 84 on the receiving side is kept in the latch hold state. Therefore, on the receiving side, the oscillation circuit 7 remains stopped, and the internal switch of the changeover switch circuit 4 on the receiving side is also held on the light receiving circuit side, and the reception operation of the data signal transmitted from the transmitting side ends. Continue until.

The serial data signal decoded by the waveform shaping circuit 85 on the receiving side passes through the output interface circuit 5 on the receiving side.
If necessary, it is converted into a parallel mode signal and output to an external signal processing device.

In this embodiment, a photodetector equipped with an optical signal generation function 1 having the same configuration is used as a transmitting/receiving device in a data signal transmission path of optical communication.When transmitting data signals from the receiving side in reverse, the above It is transmitted through the same transmission path in the opposite direction of the operating path.

Conventionally, in this type of optical communication system, the light-emitting element on the transmitting side has been a GaAjAaK light-emitting diode that emits near-infrared light with a wavelength of 800 to 1200 mn+, or a semiconductor laser, which has advantages such as low attenuation characteristics especially in long-distance transmission paths. A 34-photodiode is used as a light-receiving element on the receiving side, and a transmission line formed by two optical fiber cables is used between the transmitter and the receiver. Simultaneous transmission of data signals between transmitters and receivers is also possible, and especially in the transmission of long-distance, large-scale systems, simultaneous transmission and reception as well as signal multiplexing are required.

However, in relatively small-scale data signal transmission systems between devices over short distances, alternate communication is often used as an answer to data signal transmission from one side, rather than simultaneous communication. This is a method that allows Therefore, if two transmission lines are used separately for transmission and reception, one of the transmission and reception lines is temporarily in a dormant state.

According to the embodiment of the present invention as shown in FIG.
Optical communication is possible using a bidirectional alternate transmission system for serial data signals.

FIG. 4 is a circuit diagram showing a specific embodiment of the transmitting/receiving device shown in FIG. 3, in which a red light emitting diode LED made of phosphorus from Gallium Co., Ltd. is used as the receiving/emitting diode. The configuration of the photodetector circuit 2 is similar to that of the photodetector shown in FIG. That is, the light emitting diode LED operates as a light receiving element, and the signal based on the photocurrent obtained thereby is detected and amplified by an operational amplifier OP, and then increased to a predetermined value by the next operational amplifier OP. covered.

This output is taken out as a detection signal by a detection circuit consisting of a diode D, and is waveform-shaped and decoded. This signal waveform shaping is performed by an integrating circuit and a comparison circuit including an operational amplifier OPs. This signal output is input as a received signal to an external signal processing device fK.

On the other hand, a part of the signal is given as a Hestrope signal to a hold circuit 84 made up of a flip-flop circuit.

The oscillation circuit 7 is formed as an excavator configured using an operational amplifier OP, and modulates a transmission signal applied from the outside into a variable UI4 signal at an oscillation frequency. The gate circuit 8 is composed of an analog switch and is controlled by a transmission signal. By adding and controlling the external modulation signal to an internal signal gate switch constituted by an analog switch, the light emitting diode LED can be made to blink based on the modulation signal.

In general, many light emitting diodes have a small area as a semiconductor device, and in order to make the luminance of the light emitted appear high, the envelope is formed into a lens shape, and the light emitting diode is often provided with directivity. Note that even if the area is increased, the luminance will hardly increase due to diffused light emission, so increasing the area will not have much effect in terms of brightness in one direction. On the other hand, in the case of photodiodes, the output depends on the light-receiving area, so many of them generally have a large light-receiving area. The present inventors have discovered that the m-V group compound semiconductor represented by gallium a-phosphorus has an emission wavelength distribution and an absorption wavelength distribution centered on visible light, and that a light-emitting diode can also operate as a light-receiving element. Confirmed by experiment. Therefore, by improving the area of the semiconductor chip, the lens structure of the envelope, etc., it is possible to manufacture light emitting/receiving elements with even higher sensitivity than currently known light emitting diodes.

〔Effect of the invention〕

As explained above, the present invention provides a charging interconversion device in which a current supply means for supplying a forward current to a photoelectric interconversion element via an arbitrary circuit switching means and a photodetection means for detecting light by photovoltaic force are connected. This is what we provide. Therefore, 1
Since a single element can be used with 2AI functions of light emission and light reception, the circuit configuration can be combined and can be constructed at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a photodetector according to the present invention, FIG. 2 is a circuit diagram showing a specific embodiment thereof, FIG. 3 is a block diagram of a data signal transmitting/receiving device according to the present invention, and FIG. 4 is a block diagram of a photodetector according to the present invention. A circuit diagram showing a specific example, Fig. 5 is a characteristic diagram showing the spectral output or spectral sensitivity of each Yuzu light emitting diode and photodiode, Fig. 6 is a sectional view showing the structure of the light emitting diode, and Fig. 7 is a light emitting A structural diagram of a semiconductor element that constitutes a diode,
FIG. 8 is a structural diagram of a semiconductor element constituting a photodiode, FIG. 9 is a circuit diagram showing an optical signal detection circuit using short circuit current, and FIG. 1O is a circuit diagram showing an optical signal detection circuit using open circuit voltage. In the figure, l is a light receiving/emitting diode, 2 is a photodetection circuit, and 3 is a photodetector circuit.
4 is a switch operation circuit, 4 is a changeover switch circuit, 5 is an output interface circuit, 6 is a light emitting power supply circuit, 60 is a light emission control circuit, 7 is an excavation circuit, and 8 is a gate circuit. $9 Diagram Rf

Claims (1)

[Claims] 1. A photoelectrical mutual conversion element, a current supply means connected to the photoelectrical mutual conversion element via an arbitrary circuit switching means, which causes the photoelectrical mutual conversion element to operate as a light emitting element, and the photoelectrical mutual conversion element to operate as a light receiving element. What is claimed is: 1. A photoelectric mutual conversion device characterized by comprising a photodetection means for detecting