JPH084212B2 - Optically-fed analog photocoupler - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optically fed analog photocoupler (optical coupling element) that transmits an electrical analog signal in the form of an optical signal.

(Prior Art) Generally, a metal cable is used for signal transmission between devices having a physical distance. However, when a metal cable is used as a transmission line, noise may be mixed due to induced noise or mutual interference between devices. Such noise is roughly classified into in-phase noise and out-of-phase noise.

The in-phase noise is a signal line and a ground line in the transmission line that change at the same level and in the same phase. Therefore, current does not flow in the transmission line circuit, but changes in the ground level between devices. On the other hand, the out-of-phase noise is noise that the signal itself has or when an electromagnetic field is introduced between the signal line and the ground line, and therefore a potential difference is generated between the two lines and flows into the transmission circuit.

Since the transmission signal is an out-of-phase signal and it is difficult to classify it when in-phase noise is added, the in-phase noise is avoided as much as possible.

As one of the methods for preventing the mixing of the out-of-phase noise and the in-phase noise, a technique of isolating by an optical method using a photo coupler has been proposed.

Conventionally, the technology of such a photo coupler is (goods)
"Optical Parts and Products Encyclopedia" supervised by the Association for Promotion of Optoelectronic Industry Technology
(Sho 60-9-15) Some were described in Optronics P.293-299.

This type of photocoupler has a light emitting portion that is electrically insulated and optically coupled, such as an LED (light emitting diode), and a light receiving portion that includes a phototransistor.
They are provided in the package.

In the above configuration, when the input electric signal is applied to the light emitting unit, the input electric signal is converted into the optical signal by the light emitting unit, and then converted into the electric signal again by the light receiving unit and output.
Here, when the light emitting portion is configured by an LED, the LED emits light only with respect to the current (different phase signal) flowing in the line, and there is no change in the voltage level between the input terminals with respect to the change in voltage in the same phase. No current flows to the LED and no light is emitted. Therefore, it becomes possible to completely eliminate the in-phase level noise in the optical coupling.

(Problems to be Solved by the Invention) However, in the photocoupler having the above configuration, although a digital signal can be transmitted, since the linearity and temperature stability of the light emitting unit and the light receiving unit are poor, high-speed analog signal transmission, There is a problem that the optical device for signal transmission cannot be used when the speed is limited. In addition, when power supply power is to be supplied from the output side to the input side, the power supply means must be provided outside, which complicates the overall configuration and increases the installation space. .

The present invention has the following problems.
Optical power supply that solves the problem that it cannot be used when high-speed analog signal transmission and the optical device for signal transmission has a speed limit, and that the configuration becomes complicated and large when a power supply means is added. A type analog photocoupler is provided.

(Means for Solving the Problems) In order to solve the above problems, the present invention relates to an optical power feeding type analog photocoupler, in which an input analog signal is converted by an analog / digital converter (hereinafter referred to as an A / D converter). n
An input unit for converting a bit (where n is an arbitrary integer of 2 or more) digital signal and converting the n-bit digital signal into n optical signals by n electric / optical converters; The optical signal of a book is converted into n electrical signals by n optical / electrical converters, and the n electrical signals are analogized by an n-bit digital / analog converter (hereinafter referred to as D / A converter). An output section for converting into a signal and a power supply means for supplying power supply power from one of the input section and the output section to the other in the form of optical energy are housed in one module.

(Operation) According to the present invention, since the optical feeding type analog photocoupler is configured as described above, the input analog signal is converted into an n-bit digital signal by the A / D converter, and the digital signal is converted into n electrical signals. / It is converted into n optical signals by the optical converter and transmitted. The transmitted n optical signals are n optical /
The electric converter again converts the electric signals into n electric signals, and the n electric signals are converted into analog signals by the n-bit D / A converter and output. Further, the power supply means supplies the power source power from the output section to the input section or in the opposite direction in an electrically insulated state.

(Embodiment) FIG. 1 is a configuration diagram of an optically-powered analog photocoupler showing a first embodiment of the present invention.

This photo coupler includes a signal input terminal 1 for inputting an input analog signal Si, a signal output terminal 2 for outputting an output analog signal So, a power supply input terminal 3 for inputting a power supply power PS, and a power supply output terminal 4 for outputting a power supply power IPS. Has its terminal
1,4 and 2,3 are connected to the input section 10 and the output section 20, respectively.

The input section 10 has a cascaded input amplifier (IA) 11, a pulsing circuit (MOD) 12, and an electro-optical converter (E / O) 13, and is connected to a light receiving element (SC) 14 and it. It has a power supply circuit (PSCi) 15. The input amplifier 11 is a circuit that amplifies the input analog signal Si supplied from the signal input terminal 1, and the pulsing circuit 12 is a circuit that converts the output of the input amplifier 11 into a pulse signal, such as a pulse frequency modulation circuit (PFM). It is configured. The electro-optical converter 13 converts the output of the pulse conversion circuit 12 into optical signals OPTs for signal transmission, and is composed of a light emitting element such as an LED. The light receiving element 14 receives the optical signal OPTp for power transmission and generates electric energy, and is composed of, for example, a solar cell or the like. Further, the power supply circuit 15 converts the output of the light receiving element 14 into DC power DC and supplies the DC power DC to each circuit in the input unit 10 as a power supply, and also supplies it to the power supply output terminal 4 side in the form of power supply IPS. Circuit.

On the other hand, the output unit 20 has an optical / electrical converter (O / E) 21, an analog circuit (DEM) 22 and an output amplifier (OA) 23 that are connected in cascade, and also has a power supply circuit (PSCo) 24 and its connection. The light source (OS) 25 is provided. Optical / electrical converter
Reference numeral 21 is for converting the optical signal OPTs into an electrical pulse signal, and is composed of a light receiving element such as a phototransistor or a photoFET. The analogization circuit 22 is a circuit that demodulates the output of the optical / electrical converter 21 into an analog signal using a pulse frequency modulation method or the like, and the output amplifier 23 amplifies the output of the analogization circuit 22 to output the output analog signal So. This is a circuit for outputting to the signal output terminal 2 side. The power supply circuit 24 is a circuit that converts the power supply power PS supplied from the power supply input terminal 3 into DC power DC and supplies it to each circuit in the output section 20 as a power supply. Also, the light source 25 is the output of the power supply circuit 24. Is converted into an optical signal OPTp and is composed of, for example, a light bulb, a semiconductor light emitting element, or the like.

The input unit 10 and the output unit 20 are housed in one module.

 FIG. 2 is an exploded perspective view showing the mounting example of FIG.

In this photocoupler, the input amplifier 11, the pulse conversion circuit 12, and the electric / optical converter 13 of the input unit 10 in FIG. 1, the optical / electric converter 21, the analogization circuit 22, and the output amplifier 23 of the output unit 20 are included. , An optoelectronic integrated circuit (hereinafter referred to as OEIC), which are formed on an insulating substrate 30.

As an optical transmission method of the optical signals OPTs and OPTp between the input section 10 and the output section 20, various methods such as an air propagation method, a method using an optical fiber, a method using a lens, a method using an optical waveguide, and the like can be used. Therefore, it may be appropriately selected in consideration of withstand voltage of the input section 10 and the output section 20, optical coupling efficiency, and the like. Second
In the implementation example shown, the optical waveguide 31 is provided between the input section 10 and the output section 20.
Are joined by.

On the other hand, in the power supply system, the light source 25 is composed of a light bulb, and the light is received by the light receiving element 25 composed of a solar cell.

In the above configuration, when the input analog signal Si is supplied to the signal input terminal 1, the input analog signal Si is amplified by the input amplifier 11 and then converted into a pulse signal by the pulsing circuit 12. Furthermore, the pulse signal is an electrical / optical converter.
It is converted into optical signals OPTs at 13 and transmitted to the output section 2 side through the optical waveguide 31. Optical signal OPTs input to output unit 20
Is converted into an electrical pulse signal by the optical / electrical converter 21, is further reproduced by the analogization circuit 22 into an analog signal, is amplified by the output amplifier 23, and is output through the signal output terminal 2 in the form of the output analog signal So. Is output to outside.

On the other hand, when the power PS is supplied to the power input terminal 3,
The power PS is converted into DC power DC by the power circuit 24,
It is supplied to each circuit in the output section 20 as a power source and is also supplied to the light source 25. The output of the power supply circuit 24 is an optical signal from the light source 25.
Converted to OPTp and sent to the input unit 10 side. That optical signal
OPTp is converted into an electrical signal by the light receiving element 14 and then the power supply circuit
The DC power is converted into DC power at 15 and supplied to each circuit in the input unit 10 and is output to the outside through the power output terminal 4 in the form of power power IPS. This power supply power IPS is output 20
It is used as a power source for external equipment that is electrically isolated from the.

 This embodiment has the following advantages.

DC level transmission is possible. The linearity can be improved. Further, temperature stability can be improved. Therefore, the defects of the conventional light emitting unit and light receiving unit can be eliminated.

It is possible to remove the common-mode noise component without providing an external circuit.

Since the power supply system is built-in, the structure can be simplified and downsized as compared to the conventional case where the power supply system is externally provided. Further, since the input section 10 has the power supply output terminal 4 insulated from the output section 20, it is possible to supply a stable DC power that is not affected by noise.

The input section 10 and the output section 20 are provided with OE as shown in FIG.
If it is made into an IC, it can be miniaturized, highly reliable, and mass-produced.

FIG. 3 is a block diagram of an optically-powered analog photocoupler showing a second embodiment of the present invention.

This photocoupler differs from that of FIG. 1 in that the pulse conversion circuit 12 of FIG. 1 is composed of an A / D converter 12A and a parallel / serial converter (hereinafter referred to as P / S converter) 12B. At the same time, the analog circuit 22 is composed of a serial / parallel converter (hereinafter referred to as S / P converter) 22A and a D / A converter 22B.

In the above configuration, the output of the input amplifier 11 is converted into n-bit digital signals D1 to Dn by the A / D converter 12A, and P
After being converted into a serial signal by the / S converter 12B, it is converted into optical signals OPTs by the electrical / optical converter 13 and transmitted to the output unit 20. The transmitted optical signals OPTs are converted into electrical serial signals by the optical / electrical converter 21, converted into n-bit parallel signals D1 to Dn by the S / P converter 22A, and then D / A converter 22B. Is converted into an analog signal and output to the outside through the output amplifier 23.

Also in the photocoupler structure of FIG. 3, the same advantages as those of the first embodiment can be obtained.

In FIG. 3, the P / S converter 12B and the S / P converter 22A are shown.
Omitting and omitting the electric / optical converter 13 and the optical / electrical converter
It is also possible to provide a plurality of (n) 21 corresponding to the bit number (n) of the A / D converter 12A. The photocoupler having such a structure handles high-speed analog signals and can be applied even when an optical device for signal transmission has a speed limit.

Various modifications can be made in addition to the above embodiments. The following are examples of such modifications.

In FIG. 1 and FIG. 3, the power supply power PS is input to the output unit 20 side, but the power supply power PS is input to the input unit 10 side and transmitted to the output unit 20 side in the form of an optical signal. You may do it.

(Effects of the Invention) As described in detail above, according to the present invention, an input analog signal is converted into an n-bit digital signal and then converted into n optical signals for transmission, and the n optical signals are transmitted. N
Since the signal is converted into the electric signal of the book and then converted into the analog signal, a high-speed analog signal can be transmitted with a high S / N ratio (signal to noise conversion) and linearity. Moreover,
It can also be applied when the speed of the optical device for signal transmission is limited. Moreover, since the power supply means is built in, it is possible to supply power without noise, and it is not necessary to provide them externally as in the conventional case, and the entire configuration including them is simplified, The effect of miniaturization can be expected.

[Brief description of drawings]

FIG. 1 is a block diagram of an optically coupled analog photocoupler showing a first embodiment of the present invention, FIG. 2 is an exploded perspective view showing a mounting example of FIG. 1, and FIG. 3 is a second embodiment of the present invention. It is a block diagram of the optical coupling type | mold analog photocoupler which shows an example. 4 ... Power output terminal, 10 ... Input section, 12 ... Pulsing circuit, 12A ... A / D converter, 12B ... P / S converter, 13 ... Electric / optical converter, 14 ... Light receiving element, 15, 24 ... Power supply circuit, 20
...... Output section, 21 …… Optical / electrical converter, 22 …… Analogization circuit, 22A …… S / P converter, 22B …… D / A converter, 25 …… Light source, 30 …… Insulation board, 31 ... Waveguide, Si ... Input analog signal, So ... Output analog signal, OPTs, OPTp ... Optical signal, PS, IPS ... Power supply power.

Claims (4)

[Claims] 1. An analog / digital converter converts an input analog signal into an n-bit (where n is an arbitrary integer of 2 or more) digital signal, and the n-bit digital signal is converted into n electrical / optical converters. An input unit for converting the optical signals into n optical signals by a converter, and the n optical signals are converted into n electrical signals by n optical / electrical converters, and the n electrical signals are converted into n-bit digital signals. / An output section for converting into an analog signal by an analog converter and a power supply means for supplying power from one of the input section and the output section to the other in the form of light energy are housed in one module. Optically-fed analog photocoupler. 2. The power supply means is provided in the output section, a power supply circuit for inputting electric power from the outside, means for converting the output thereof into light energy, and the power supply means provided in the input section for converting the light energy into power. The optical power feeding type analog photocoupler according to claim 1, further comprising: a power supply circuit for supplying the power to the input unit and the outside. 3. The input unit, the output unit and the power supply means,
The optically-powered analog photocoupler according to claim 1, which is composed of an optoelectronic integrated circuit. 4. The optical power supply type analog photocoupler according to claim 2, wherein the power supply circuit of the input section has a power supply output terminal electrically insulated from the output section.