JPH0823244A - Signal transmitter - Google Patents

Abstract

PURPOSE:To perform high-accuracy signal transmission by mutually electrically insulating input and output terminals with an isolator, outputting an input signal after converting its signal level, and negatively feeding it back to the inverted input of a differential amplifier with a feedback circuit. CONSTITUTION:When the conversion efficiency of a photocoupler PC 9 is dispersed and deviation DELTAV exists in a signal Vout, the dispersion of conversion efficiency in the case of photoelectric conversion at a photodiode 21 of a PC 20 is absorbed by a differential amplifier 15 to be negatively fed back and connected. On the other hand, the output signal Vout containing the deviation DELTAV is converted to a signal V4 by the PC 20 and inputted to a differential amplifier 3. At the amplifier 3, a transmission signal Vin is superimposed on the signal V4, which contains the deviation 4V, inputted to an inverted input part 5 and a signal V1 is outputted. Thus, the signal Vout from the PC 9 is converged into a signal converted by the PC 9 without dispersing the transfer signal Vin. As a result, the dispersion of conversion efficiency at the PC 9 can be absorbed inside a device 1, and the high-accuracy signal transmission is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission device, and more particularly to a signal transmission device using an isolator used for mutually transmitting signals between systems having different drive potentials.

[0002]

2. Description of the Related Art An isolation amplifier using a photo coupler is often used when mutually transmitting an analog amount signal or a digital amount signal between signal processing systems having different drive potentials. In this isolation amplifier, the photo coupler is used in its dynamic range. The photocoupler used in this isolation amplifier has a structure in which a light emitting diode and a phototransistor are molded with a transparent electrically insulating resin.

By selecting different values for the power supply potential of the light emitting diode and the power supply potential of the phototransistor, it is possible to maintain electrical insulation between the signal processing systems having different drive potentials. , Signal transmission with signal level conversion can be performed.

[0004]

In the isolation amplifier for transmitting signals between the signal processing systems having different drive potentials, the conversion efficiency of the signal of the photocoupler used in the isolation amplifier varies. It is known that there is. Such variations in conversion efficiency cause variations in the output signal level of the isolation amplifier. Therefore, the conventional isolation amplifier has a problem that it is difficult to transmit signals with high accuracy.

An object of the present invention is to solve the above technical problems and to provide a signal transmission device capable of highly accurate signal transmission.

[0006]

According to another aspect of the signal transmitting apparatus of the present invention, a signal to be transmitted is input to a non-inverting input section, and the signal to be transmitted and the signal input to the inverting input section are included. From the differential amplifier input to the input terminal, and the differential amplifier that outputs a signal obtained by superimposing the signal to be transmitted on the deviation And a negative feedback path for negatively feeding back the output of the isolator to the inverting input section of the differential amplifier section. The purpose can be achieved.

In the invention of claim 1, another isolator may be provided in the feedback path.

[0008]

According to the invention of claim 1, the signal to be transmitted is input to the non-inverting input section of the differential amplifier section. The differential amplifier outputs a signal in which the signal to be transmitted is superimposed on the deviation between the signal to be transmitted and the signal input to the inverting input unit. The signal output from the differential amplifier is input to the input end of the isolator. The isolator has an input end and an output end electrically insulated from each other, and converts the signal level of a signal input to the input end and outputs the signal from the output end. The signal output from the output terminal is negatively fed back to the inverting input section of the differential amplification section by the feedback path.

Therefore, when there is a variation in signal conversion efficiency in the isolator, the signal output from the isolator including the variation of the signal due to this variation should be transmitted to the differential amplifier. A deviation between a signal and a signal including a variation of the signal input to the inverting input unit, that is, a signal in which the signal to be transmitted is superimposed on the variation is output. As a result, the signal output from the isolator converges to the signal converted by the isolator without the variation in the signal to be transmitted. As a result, variations in conversion efficiency of the isolator can be absorbed in the signal transmission device of the present invention, and highly accurate signal transmission can be performed.

In the signal transmission device according to the invention of claim 1,
When the feedback path is provided with another isolator, the input side and the output side of the feedback path are also electrically insulated, so that the electrical input and output sides of the signal of the signal transmission device are electrically connected. Insulation can be reliably achieved.

[0011]

1 is a circuit diagram showing the electrical construction of a signal transmission device according to an embodiment of the present invention. The present embodiment is a signal transmission device used when mutually transmitting an analog amount signal or a digital amount signal between signal processing systems having different drive potentials. In the signal transmission device 1 of this embodiment, the signal Vin to be transmitted is input to the non-inverting input unit 4 of the differential amplifier 3 via the input line 2. A signal via a negative feedback path of the signal transmission device 1 described later is input to the inverting input section 5 of the differential amplifier 2.

The output terminal 6 of the differential amplifier 3 is connected to the base of an NPN transistor 8 via a resistor 7. An operating power supply Vcc is connected to the collector of the transistor 8,
The emitter is connected to the anode of the photodiode 10 of the photocoupler 9. The cathode of the photodiode 10 is connected to the ground potential via the resistor 11. An operating power supply VDD different from the operating power supply Vcc is connected to the collector of the phototransistor 12 of the photocoupler 9. The emitter of the phototransistor 12 is connected to the common potential via the resistor 13 and is also connected to the output line 14 of the signal transmission device 1.

The output line 14 is also connected to the differential amplifier 1.
5 to the non-inverting input section 16. The output section 18 of the differential amplifier 15 is connected to the base of an NPN transistor 28 via a resistor 19. The operating power supply VDD is connected to the collector of the transistor 28, and the emitter is connected to the anode of the photodiode 21 of the photocoupler 20. The cathode of the photodiode 21 is connected to the common potential via the resistor 23 and is also connected to the inverting input section 17 of the differential amplifier 15. The operation power supply Vcc is connected to the collector of the phototransistor 22 of the photocoupler 20, the emitter is connected to the ground potential via the resistor 24, and is also connected to the inverting input section 5 of the differential amplifier 4.

An isolation amplifier 26 is constructed by including the differential amplifier 15 and the photocoupler 20, and a negative feedback path 29 of the signal transmission device 1 of this embodiment is constructed by including the isolation amplifier 26. . Further, the isolation amplifier 25 is configured by including the differential amplifier 3 and the photocoupler 9. In the isolation amplifiers 25 and 26 of this embodiment, the photocouplers 9 and 20
Is used in its dynamic range.

The operation of this embodiment will be described below.
The signal Vin to be transmitted is input to the non-inverting input unit 4 of the differential amplifier 3. In the differential amplifier 3, the signal V1 in which the deviation between the signal Vin to be transmitted and the signal input to the inverting input unit 5 and the signal Vin to be transmitted are superposed on each other.
Is output. The signal V1 output from the differential amplifier 3
Is input to the photocoupler 9. The photo coupler 9 is
The input end and the output end are electrically insulated from each other, and a signal based on the operating power supply Vcc input to the input end is converted into a signal level based on the operating power supply VDD and output. The signal Vout output from the photocoupler 9 becomes the output signal of the signal transmission device 1 of the present embodiment, and is output to the outside via the output line 14.

This output signal Vout is returned to the feedback path 29.
Thus, the negative feedback is input to the inverting input section 5 of the differential amplifier 3. At this time, the output signal Vout is input to the non-inverting input unit 16 of the differential amplifier 15, and the differential amplifier 1
The output unit 18 of 5 outputs the signal V2. Signal V
2 is converted into a signal having the maximum value VDD by the transistor 28 and input to the photocoupler 20. The output of the photodiode 21 of the photocoupler 20 is input as a signal V3 to the inverting input section 17 of the differential amplifier 15 by negative feedback. As a result, the output V2 converges on the signal Vout. The signal level of the signal V2 is converted by the photocoupler 20 into a signal level based on the operating power supply Vcc, and the signal V4 is inverted by the inverting input section 5 of the differential amplifier 3.
Negative feedback input to.

Here, it is assumed that there is a variation in the conversion efficiency of the photocoupler 9 and a deviation ΔV is present in the signal Vout. Output signal Vo including this deviation ΔV
The signal level of ut is converted by the photocoupler 20 as described above. The variation in conversion efficiency at the time of photoelectric conversion in the photodiode 21 of the photocoupler 20 is
As described above, it is absorbed by the differential amplifier 15 connected in the negative feedback. On the other hand, the output signal Vout including the deviation ΔV is converted into the signal V4 by the photocoupler 20 and input to the differential amplifier 3.

At this time, in the differential amplifier 3, the deviation between the signal Vin to be transmitted and the signal V4 including the deviation ΔV input to the inverting input section 5, that is, the deviation Δ.
The signal Vin to be transmitted is superimposed on V, and the signal V1
Is output as As a result, the signal Vout output from the photocoupler 9 is the signal Vi to be transmitted.
n converges on the signal converted by the photocoupler 9 without the variation.

As a result, variations in conversion efficiency of the photocoupler 9 can be absorbed in the signal transmission device 1 of this embodiment, and highly accurate signal transmission can be performed.

Further, in the present embodiment, since the negative feedback path 29 is provided with the isolation amplifier 26 described above, the input side and the output side of the negative feedback path 29 are also electrically insulated. Therefore, even when the negative feedback path 29 is provided between the input side and the output side of the signal of the signal transmission device 1, electrical insulation can be reliably achieved between the input side and the output side. .

[0021]

As described above, according to the invention of claim 1, when the signal conversion efficiency of the isolator varies, the signal output from the isolator including the variation of the signal due to the variation. However, in the differential amplifier, the deviation between the signal to be transmitted and the signal including the change in the signal input to the inverting input section, that is, the signal in which the signal to be transmitted is superimposed on the change is Is output. As a result, the signal output from the isolator converges to the signal converted by the isolator without the variation in the signal to be transmitted. As a result, variations in conversion efficiency of the isolator can be absorbed in the signal transmission device of the present invention, and highly accurate signal transmission can be performed.

In the signal transmission device according to the invention of claim 1,
When the feedback path is provided with another isolator, the input side and the output side of the feedback path are also electrically insulated, so that the electrical input and output sides of the signal of the signal transmission device are electrically connected. Insulation can be reliably achieved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an electrical configuration of a signal transmission device according to an exemplary embodiment of the present invention.

[Explanation of symbols]

 1 signal transmission device 2 input line 3,15 differential amplifier 4,16 non-inverting input section 5,17 inverting input section 6,18 output terminal 9,20 photocoupler 14 output line 25,26 isolation amplifier 29 negative feedback path S1 , S2, S3, S4 signal Vin signal to be transmitted Vcc, VDD operating power supply

Claims (2)

[Claims] 1. A signal to be transmitted is input to a non-inverting input unit, and a signal obtained by superposing the signal to be transmitted on a deviation between the signal to be transmitted and the signal input to the inverting input unit is provided. The differential amplifier that outputs the signal and the input end and the output end are electrically insulated from each other, and the signal from the differential amplifier that is input to the input end is converted in signal level and output from the output end. A signal transmission device comprising: an isolator; and a negative feedback path that negatively feeds back the output of the isolator to an inverting input section of the differential amplification section. 2. The signal transmission device according to claim 1, wherein another isolator is provided in the return path.