JPH0383483A - Received signal converting circuit - Google Patents

Abstract

PURPOSE:To execute the processing of a response signal by the circuit element of a generally using low voltage driving without using the special circuit element by shifting the level of the response signal, which is superimposed to the feeding line of a high voltage, to a grounding potential by a differential amplifier and a level shift circuit. CONSTITUTION:A voltage induced by a resistor 7 for current detection is amplified by a differential amplifier 8 and a collector current ic for a transistor in a level shift circuit 12 is controlled by the amplified voltage. A voltage proportional to the collector current ic can be obtained in the both ends of a resistor 13 provided in the rear step of the level shift circuit 12. The voltage is proportional to a response signal im and lowered. Thus, an amplifier 15 for level adjustment and a processing circuit 17 can be operated by the low voltage and composed of general circuit parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a received signal conversion circuit provided in a receiving device of a device composed of a terminal and a receiving device.

[Prior Art] FIG. 3(a) is a block diagram showing a conventional received signal conversion circuit.

There is a device in which data of a measurement target is converted into voltage or current magnitude by a terminal 30 installed in a remote location, and the data is directly transmitted to a receiving device 31.

Between the receiving device 31 and the terminal 30, there are power supply lines 32, 33 for operating power of the terminal 30, and a signal line 34 provided for other purposes. A predetermined voltage (R large number V) is applied between the power supply lines 32 and 33 by a power supply 35.

The data of the terminal 30 is transmitted to the power supply line 32 and the signal line 3.
4, a detection resistor 36 provided between them, and a differential amplifier 37 operated by a power supply 35 to detect changes in voltage or current amount.

Furthermore, as shown in FIG. 3(b), the feeder line 32 on which the data is superimposed is set to the earth's potential, and a differential amplifier 39 that operates from a separate power supply 38 with this as a reference is provided. .

Further, as shown in FIG. 3(C), an isolation amplifier 40 is used to acquire the data using a variation obtained by separating the DC component from the power supply voltage.

[Problems to be Solved by the Invention] However, according to the configuration shown in FIG. 3(a), since the power supply voltage is directly input to the differential amplifier 37 in the receiving device, data for changes must be taken into account. In this case, a device with a large dynamic range must be used, which is expensive and dangerous during maintenance due to this voltage.

Moreover, although the resistive ground setting shown in FIG. 3(b) allows the differential amplifier to operate near the ground potential, the power supply line itself is at a high voltage.

Furthermore, the isolation amplifier 40 shown in FIG. 3(C) is expensive.

Furthermore, since the power supply voltage at the end of the receiver 31 increases almost in proportion to the distance between the terminal 30 and the receiver 31, the power supply line itself has become dangerous to the human body.

The present invention has been made in view of the above problems, and includes:
It is an object of the present invention to provide a received signal conversion circuit that can detect a response signal superimposed on a high-voltage power supply line without using special circuit elements.

[Means for Solving the Problems] In order to achieve the above objects, the received signal conversion circuit of the present invention converts the response signal 1I transmitted between one line of the power supply line and the signal line.
The detection voltage of the current detection resistor that detects 11 is input,
The operating power supply is divided by a resistor, and the dividing point is connected to the power supply line.The output of the differential amplifier is supplied with the operating power, and one end is connected to the ground. The present invention is characterized by comprising: a level shift circuit that level-shifts a voltage to near a potential; and a processing circuit driven at a low voltage that performs processing corresponding to the response signal is based on the output of the level shift circuit.

[Operation] According to the above configuration, the response signal superimposed on the high-voltage power supply line is detected by the differential amplifier and then level-shifted to earth potential by the level shift circuit, thereby being driven to a low voltage. It will be processed in the subsequent circuit.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a received signal conversion circuit according to the present invention.

The terminal 1 is installed in a remote location (several tens of kilometers away) from the receiving device 2, and is composed of a detection circuit 1a that detects a measurement target and a response circuit 1b that sends data to the receiving device 2. There is.

A power supply line 4.5 and a signal line 6 are provided between the receiving device 2 and the terminal 1 for the operating power source of the terminal l.

A voltage of about 100 liters is applied to the earth's air by a power source 6 whose midpoint is set at the same potential as the earth's voltage. As a result, each power supply line 4.5 can be set to a voltage of ±special compared to the conventional one, and safety is increased.

A current detection resistor 7 is provided in series with the power supply line 4 and the signal line 6, and both ends of the current detection resistor 7 are connected to the input of a differential amplifier 8.

The power supply line for operation of the differential amplifier 8 is operated by a resistor 9.10 connected across the power supply line 4 and a power supply 11. By making the values of the resistors 9 and 10 the same, the differential amplifier 8 can be operated at the same voltage level as the power supply 11, and the direction in which the response signal All flows can be arbitrarily set. Here, the power supply 11 is set to a voltage that allows the dynamic range of the differential amplifier 8 to include iltI-Rm.

The output of this differential amplifier 8 is connected to the base of a transistor forming a level shift circuit 12. The emitter is connected to a power supply line 4, and the collector is connected via a resistor 13 to a ground terminal 14 which is at earth potential. By fixing the ground terminal 14 to the ground of the receiving device 2, the subsequent circuit can be constructed from low-voltage general-purpose elements.

Both ends of the resistor 13 are connected to the human power of the level adjustment amplifier 15. Furthermore, the dynamic range of the level adjustment amplifier 15 is determined by the collector current IC of the level shift circuit 12.
The value of the resistor 13 is set to cover the range of values of the X resistor 13.

The processing circuit 17 is composed of an A/D, a CPU, etc., receives the output from the level adjustment amplifier 15, processes data from the terminal 1, and digitally outputs the measurement result from the terminal 17.

These level adjustment amplifier 15 and processing circuit 17 are operated by a power supply 16.

Next, the operation of the above configuration will be explained.

The measurement in the detection circuit 1a of the terminal worker causes a current proportional to the measured value to flow in the response circuit lb as a response signal 1111.

This response signal i+m induces a voltage across the current detection resistor 7 that is proportional to the measured value. Here, since each power supply line 4.5 has a voltage of % of the maximum power supply voltage, safety can be improved.

Then, the differential amplifier 8 amplifies the voltage induced by the current detection resistor 7, and the level shift circuit 12 uses the amplified voltage.
The collector current IC of the transistor is current-controlled.

This differential amplifier 8 is fixed to the power supply l1i4 by resistors 9 and lO, and is operated across the potential of this power supply line 4, so that this differential amplifier 8 and power supply 11 are operated at a low voltage below the voltage of the power supply line. You can use anything that works, there is no need to use anything special.

A voltage proportional to the collector current IC is obtained across the resistor 13 provided at the subsequent stage of the level shift circuit 12, and this voltage is proportional to the response signals i and m and is a low voltage. It has become. Thereby, the level adjustment amplifier 15 and the processing circuit 17 can be driven with low voltage and can be constructed from general-purpose circuit components.

Next, FIG. 2 is a block diagram showing another embodiment of the received signal conversion circuit according to the present invention.

In the above embodiment, the signal line 6 for response signals is used, but in addition, as shown in FIG. A meeting line 20 may be used instead of the signal line 6 of the embodiment, and even in this case, the same effects as in the above embodiment can be obtained.

[Effects of the Invention] According to the present invention, the differential amplifier and the level shift circuit level shift the response signal superimposed on the high-voltage power supply line to the earth's potential. Response signals can be processed using commonly used low-voltage drive circuit elements, reducing costs and reducing voltage, improving safety during maintenance and other work. can.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a received signal conversion circuit of the present invention, Fig. 2 is a block diagram showing another example of the same circuit, Fig. 3(a),
(b) and (c) are circuit configuration diagrams each showing a conventional receiving device. l...terminal, la=detection circuit, ib-...response circuit, 2...receiving device, 4.5...power supply line, 6...signal line, 7...current detection resistor , 8... differential amplifier,
9゜lO...Resistor, 11...Power supply, 12...Level shift circuit, 13...Resistor, 14...Ground terminal,
15... Level adjustment amplifier, 16... Power supply, 17
...processing circuit.

Claims (1)

[Claims] A device provided on the receiving device side of a device that obtains a response signal from a terminal by a terminal provided at a remote location and a power supply line and a signal line for operating the terminal provided between the terminal and the receiving device. A reception signal conversion circuit that receives a detection voltage of a current detection resistor that detects a response signal im transmitted between one wire of a power supply line and a signal line, and that operates as an operating power source by a resistor connected to the power supply line. a divided differential amplifier; a level shift circuit to which the output of the differential amplifier is input and whose one end is connected to the ground to level shift the voltage to near the ground potential; and the output of the level shift circuit to A received signal conversion circuit comprising: a processing circuit that performs processing corresponding to a response signal im;