JPH01149646A - Wave detecting circuit with level fluctuation correcting function - Google Patents

Abstract

PURPOSE:To reduce the deterioration in rising and falling times and distortion of detection output signals by detecting the fluctuation of the level of input signals and, in accordance with the level fluctuation, changing the level of reference signals which slice rectifying signals. CONSTITUTION:In case where non-modulated ON-OFF signals are inputted to a receiving input IN, the output (a) of a full-wave rectifying circuit 2 becomes DC signals which take the envelope of the inputted ON-OFF signals and is given to the input terminal A of a comparator 3. On the other hand, the mean value of the DC signals of the full-wave rectifying output is outputted at a low-pass filter 4 and given to the input terminal of a reference voltage controlling circuit 5. At the circuit 5, the output (c) of the said circuit 5 is usually controlled by using the value of the DC-level signals of an input (b). Therefore, when the slicing level of the comparator 3 is always set at the mean value of the input signal level, fluctuation of the incoming call level can be coped with.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention detects level fluctuations due to changes in transmission loss of a power transmission line in a detection circuit of a non-modulated 0N-OFF communication system using a power transmission line as a transmission path. This invention relates to a detection circuit with a correction function. The present invention particularly relates to a detection circuit with a level fluctuation correction function suitable for a power line carrier protection relay device.

(Prior art) Conventionally, the method of detecting this type of non-modulated 0N-OFF signal is to amplify and full-wave rectify the input signal, and compare this full-wave rectified signal with a reference voltage to determine the presence or absence of the signal input. A method of making a determination and outputting a detected signal is known.

(Problem to be solved by the invention) However, when a power transmission line is used as a transmission path using the non-modulated 0N-OFF signal detection method, it is difficult to The transmission loss of the power transmission line increases or decreases, and the incoming signal wave level changes.

Conventional detection circuits have the disadvantage that when the incoming signal level changes, a certain reference value remains constant, so the output is affected by time changes in rising and falling edges and deterioration of distortion.

The present invention eliminates such drawbacks and detects incoming level fluctuations due to changes in transmission loss of power transmission lines and changes the level at which the rectified signal is sliced, thereby eliminating time changes in the rise and fall of the detected output and deterioration of distortion. The object of the present invention is to provide a detection circuit that can reduce the amount of noise.

(Means for solving the problem) The detection circuit with a level fluctuation correction function of the present invention has a non-modulated 0N
- In a circuit that detects an OFF signal input, a means is provided for detecting a change in the input signal level and changing the reference signal level for slicing the rectified signal to reduce the rise and fall times and deterioration of distortion of the detected output signal. It is something to be prepared for.

(Example) Next, the present invention will be explained by way of example with reference to the drawings.

FIG. 1 is a block diagram of a detection circuit with a level fluctuation correction function according to an embodiment of the present invention. Also, Fig. 2(a), (
b) is a time chart diagram showing an example of the operation timing in the embodiment shown in FIG.
b) is a diagram showing the operation timing of the detection output with respect to the rectified waveform in the case of the method according to the present invention and the conventional method. Referring to FIG. 1, the output side of an amplifier circuit 1 is connected to the input side of a full-wave rectifier circuit 2, and a reception input IN is input to the amplifier circuit 1. The output a of the full-wave rectifier circuit 2 is connected to the input terminal A of the comparator 3 and the input terminal of the low-pass filter 4, and the output d of the comparator 3 is connected to the input side of the duty ratio detection circuit 6, and is also connected to the input terminal of the low-pass filter 4. The output of the device 4 and the output e of the duty ratio detection circuit are:
Each of them is connected to a respective input terminal of a reference voltage control circuit 5, and an output C of this reference voltage control circuit 5 is further connected to an input terminal B of a comparator 3.

To explain the present invention in detail with reference to FIGS. 1 to 3, first, when a non-modulated 0N-OFF signal is input to the receiving input IN of FIG. 1, the output of the full-wave rectifier circuit 2 A becomes a DC signal obtained by taking the radial line of the input ON-OFF signal and is applied to the input terminal A of the comparator 3. On the other hand, since the low-pass filter 4 has a cutoff frequency lower than the 0N-OFF period of the carrier wave, its output is the average value of the DC signal of the full-wave rectified output a, and the reference It is applied to the input terminal of the voltage control circuit 5. The reference voltage control circuit 5 normally controls the output C of the control circuit 5 based on the value of the DC level signal (ie, the average value of the input signal level) of the input signal. Therefore, by always setting the slice level of comparator 3 to the average value of the input signal level,
This makes it possible to respond to changes in the level of incoming calls. Note that the duty ratio detection circuit 6 monitors the duty ratio of the output d of the comparator 3, and when it detects continuous incoming calls or continuous disconnection, it passes a control signal to the reference voltage control circuit 5, and outputs the output of the control circuit 5. It has the function of fixing C to a certain value.

(Effects of the Invention) As explained above, the present invention includes a circuit that smoothes a full-wave rectified signal to control the reference voltage of the comparator and a circuit that monitors the duty ratio of the detection output, thereby tracking changes in the receiving input level. By changing the level at which the rectified signal is sliced, it is possible to suppress temporal changes in the rise and fall of the detected output and deterioration of distortion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a detection circuit with a level fluctuation correction function according to an embodiment of the present invention, and FIG. 2(a). (b) is a time chart diagram showing an example of operation timing in the embodiment shown in FIG. 1, and FIGS. 3(a) and (b)
) is a diagram showing the operation timing of the detection output with respect to the rectified waveform in the case of the method according to the present invention and the conventional method. DESCRIPTION OF SYMBOLS 1... Amplifier circuit, 2... Full wave rectifier circuit, 3... Comparator, 4... Low pass filter, 5... Reference voltage control circuit, 6... Duty ratio detection circuit. Agent Patent Attorney Toshikichi Somekawa Diagram 1 Renkyo-layer Reverse Biography

Claims (1)

[Claims] In a reception detection circuit of a signal terminal station device for a carrier protection relay device using a different frequency direction comparison method or a phase comparison method that uses a power line as a transmission path, the reception detection circuit has means for detecting level fluctuations in the reception input and changing the slice level. A detection circuit with a level fluctuation correction function.