JPH04115727A - Pulse output circuit - Google Patents

Abstract

PURPOSE:To prevent distortion of a waveform of a signal received at a reception terminal of a transmission line by modifying a waveform at the rising and the falling of a pulse signal so as to cancel the waveform deformation caused in the transmission line by a waveform generating section. CONSTITUTION:A controller 9 changes over a switch 3 at a prescribed period to apply alternately a voltage E1 from a fixed power supply 1 and a voltage E2 from a variable power supply 2 to a tap of a primary coil 4a of a transformer 4 and controls switches 7,8 alternately to connect each terminal of a coil 4a to ground via resistors 5,6 at a prescribed period. Then a pulse signal having overshoot is induced positively and negatively into a secondary coil 4b and the DC component is cut off by a capacitor 10 and the result is sent to a transmission line 11 and fed to a load resistor 12. Since the pulse signal from the capacitor 10 has an overshoot, the waveform of the signal fed across a resistor 12 is made almost rectangular.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a pulse output circuit used in various industrial fields.

(Prior art) Pulse output circuits used in various industrial fields are usually
It includes an oscillation section that oscillates at a predetermined frequency and an amplification section that amplifies the pulse signal obtained by the oscillation section.
A pulse signal is generated by the oscillation operation and sent out onto a transmission path to be transmitted to a desired location.

(Problem to be Solved by the Invention) However, when transmitting a pulse signal obtained by a pulse output circuit via a transmission line, the high frequency component normally attenuates quickly, so depending on the type and length of the transmission line, The waveform of the pulse signal received at the receiving end is distorted.

In particular, when communicating by superimposing a pulse signal on an analog signal using a 4-20 mA DC output cable such as CVVS, the pulse signal is The rise/fall times are large, and the waveform distortion increases accordingly.

In this case, a comparator or the like is used at the receiving end to shape the waveform of the received pulse signal and perform reception processing to prevent malfunctions caused by waveform distortion.
Since such a method uses level discrimination processing using a comparator or the like, it is easily affected by noise, and waveform shaping cannot be performed correctly, often resulting in malfunction.

This is especially true when the distances range from several tens of meters to 2,000 meters in the transmission lines used to communicate between sensors with communication functions installed in various locations and hand belt communicators. Therefore, the waveform distortion of the pulse signal received at the receiving end becomes large, and this waveform distortion often makes communication impossible.

In view of the above circumstances, an object of the present invention is to provide a pulse output circuit that can prevent the waveform of a pulse signal received at the receiving end from being distorted even if high frequency components are attenuated in the transmission path. There is.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a pulse output circuit according to the present invention generates a pulse signal and sends it onto a transmission line, in which waveform distortion caused by the transmission line is canceled out. The present invention is characterized in that it includes a waveform forming section that transforms the waveform of the rising and falling portions of the pulse signal so as to cause the pulse signal to change.

(Function) In the above configuration, the waveform forming section transforms the waveform of the rising and falling portions of the pulse signal so as to cancel out the waveform distortion caused by the transmission path, and the waveform of the signal received at the receiving end of the transmission path is changed. Fix it.

(Embodiment) FIG. 1 is a block diagram showing a first embodiment of a pulse output circuit according to the present invention.

The pulse output circuit shown in this figure includes a fixed power supply 1, a variable power supply 2, a power supply changeover switch 3, a transformer 4, two resistors 5.6, two polarity changeover switches 7.8, a controller 9, The controller 9 switches the power supply selector switch 3 and each polarity selector switch 7.8 to generate a pulse signal with overshoot on the positive side and negative side, and transmits this via the capacitor 10. It is sent out to the line 11 and supplied to the resistor 12 which serves as a load.

The fixed power supply 1 generates a voltage of voltage value E1 and supplies it to the terminal 3a of the power supply changeover switch 3.

Further, the variable type W2 generates a voltage of a voltage value E2 specified within a preset range (where E2>El), and supplies this to the terminal 3b of the power source changeover switch 3.

The power supply changeover switch 3 selects the voltage value supplied to either one of the terminals 3a and 3b based on the control signal from the controller 9, outputs it from the common terminal 3c, and supplies it to the intermediate tap of the transformer 4. do.

The transformer 4 has an intermediate tap formed in the primary coil 4a, and supplies a signal induced in the secondary coil 4b to the capacitor 10 when voltage is supplied to the intermediate tap.

The capacitor 1o is provided for blocking DC current, and cuts the DC component of the signal supplied from the secondary coil 4b of the transformer 4 and sends it onto the transmission line 11.

Further, each resistor 5.6 is a current limiting resistor connected to each end of the primary coil 4a of the transformer 4 and each terminal of each polarity changeover switch 7.8, and each of the polarity changeover switches When each terminal of 7.8 is grounded, the value of the current output from each end of the primary coil 4a is limited to a predetermined value.

Each polarity selector switch 7.8 is a switch whose other end is grounded, and is opened and closed based on a control signal from the controller 9, and is connected to the primary coil 4a via one of the resistors 5.6. Ground either end of the

Further, the controller 9 operates the power source changeover switch 3 and each polarity changeover switch 7.8 at a preset period to generate a pulse signal having overshoot on the positive side and the negative side.

Next, the operation of this embodiment will be explained with reference to FIGS. 2(a) to 2(e).

First, the controller 9 switches the power source selector switch 3 at a predetermined period to alternately select a voltage value E1 outputted from the fixed power source 1 and a voltage value E2 outputted from the variable power source 2, so that the transformer 4 The signal shown in FIG. 2(a) is supplied to the intermediate tap of the primary coil 4a, and each polarity changeover switch 7.8 is operated alternately at the period shown in FIG. 2(b) and (c). Each end of the primary coil 4a is alternately grounded via each resistor 5.6.

As a result, the voltage supplied to the intermediate tap of the primary coil 4a of the transformer 4 causes the secondary coil 4b to be connected to the secondary coil 4b.
As shown in Figure (cl), a pulse signal with overshoot on the positive side and negative side is induced, and the DC component of this is cut by the capacitor 10, and the transmission line 1
1 and is supplied to a resistor 12 serving as a load.

In this case, even if high-frequency components are attenuated in the transmission line 11, the pulse signal output from the capacitor 10 has an overshoot, so the waveform of the signal applied to both ends of the resistor 12 is shown in FIG. As shown by the solid line in e), it can be made into a substantially rectangular shape, and as shown by the dotted line, it is possible to eliminate the rounding of the pulse signal that occurs when a rectangular pulse signal is transmitted.

As described above, in this embodiment, since the pulse signal sent onto the transmission line 11 has an overshoot in advance, the attenuation of the high frequency component in the transmission line 11 is applied to the resistor 12 serving as a load. The waveform of the pulse signal can be made substantially rectangular.

FIG. 3 is a block diagram showing a second embodiment of the pulse output circuit according to the present invention. In this figure, parts corresponding to those in FIG. 1 are given the same reference numerals.

The pulse output circuit shown in this figure differs from the circuit shown in FIG. 1 in that the fixed power supply 1 is on the voltage E1 side.

The power source selector switch 3 and the current limiting resistors 5 and 6 are eliminated, and the voltage output from the variable power source 2 is directly supplied to the intermediate tap of the transformer 4, and a variable capacitor 13 is provided in place of the capacitor 10. It is.

As described above, in this embodiment, a variable capacitor 13 is provided between the transformer 4 and the transmission line 11, and the value of the variable capacitor 13 is adjusted to adjust the differential amount of the pulse signal output from the transformer 4. Therefore, when the waveform of the pulse signal output from the transformer 4 is distorted by the transmission line 11, by adjusting the capacitance of the variable capacitor 13, the waveform of the pulse signal sent onto the transmission line 11 can be changed. Distortion can be corrected.

FIG. 4 is a block diagram showing a third embodiment of the pulse output circuit according to the present invention.

The pulse output circuit shown in this figure includes a voltage regulator 15, a fixed power supply 16, a power supply changeover switch 17, a transformer 18, a capacitor 19, and two polarity changeover switches 20.2.
1, a controller 22, and a feedback section 23, the feedback section 23 detects the output waveform, and the controller 22 switches the power supply while adjusting the voltage output from the voltage adjustment section 15 based on the detection result. switch 17
and each polarity switch 20 and 21 to generate a pulse signal with overshoot on the positive side and negative side,
This is sent to a transmission line 24 via a capacitor 19 and supplied to a resistor 25 serving as a load.

The voltage adjustment section 15 includes a transistor 26 for adjusting the output voltage and a resistor 27 that biases the transistor 26. value E2
generates a voltage of
7b.

Further, the fixed power supply is configured to generate a voltage having a voltage value E1, and supplies this voltage to the terminal 17a of the power supply changeover switch 17.

The power supply selector switch 17 selects the voltage supplied to either one of the terminals 17a, 17b based on the control signal from the controller 22, and transfers it to the common terminal 17c.
It is outputted from and supplied to the intermediate tap of the transformer 18.

The transformer 18 has an intermediate tap formed in the primary coil 18a, and when voltage is supplied to the intermediate tap,
The signal induced in the secondary coil 18b is transferred to the capacitor 19.
supply to.

The capacitor 19 is provided for blocking DC current, and cuts the DC component of the signal supplied from the secondary coil 18b of the transformer 18 and sends it onto the transmission line 24.

Further, each polarity changeover switch 20, 21 is a switch whose other end is grounded, and opens and closes based on a control signal from the controller 22 to ground one of the ends of the primary coil 18a.

The controller 22 also controls the power supply changeover switch 17 and each polarity changeover switch 2o, 2 at a preset period.
1 to generate a pulse signal with overshoot on the positive and negative sides.

Further, the feedback section 23 includes a bypass filter 30, a transformer 31, a rectifying and smoothing circuit 32, a reference power source 33, and a differential amplifier circuit 34, and the feedback section 23 has A corresponding control signal is generated to control the voltage (II!E2) output from the voltage regulator 15, and the waveform of the pulse signal sent onto the transmission line 24 is made into a rectangular shape.

The bypass filter 30 takes in the pulse signal sent onto the transmission line 24, extracts its high frequency component, and supplies it to the rectifying and smoothing circuit 32 via the transformer 31.

The rectifying and smoothing circuit 32 rectifies the signal supplied via the transformer 31, smoothes the signal, and supplies the smoothed signal to the inverting input terminal of the differential amplifier circuit 34.

Further, the reference power supply 33 generates a reference voltage of a preset value and supplies it to the non-inverting input terminal of the differential amplifier circuit 34. A difference signal between the voltage value and the value of the signal supplied from the rectifying and smoothing circuit 32 is extracted, and this difference signal is amplified to generate a control signal and supplied to the voltage adjustment section 15.

As described above, in this embodiment, the waveform of the pulse signal sent onto the transmission line 24 is detected by the feedback unit 23,
Based on this detection result, the value of the control signal is adjusted to control the magnitude of the voltage value E2 output from the voltage adjustment section 15, thereby controlling the magnitude of the overshoot of the pulse signal sent onto the transmission line 24. Therefore, when the rise or fall of the pulse signal sent out on the transmission line 24 is slow as shown in FIG. 5(a), the bypass filter 30 is When the value of the signal output from the voltage adjustment section 15 is small, the waveform of the pulse signal sent onto the transmission line 24 can be made rectangular by increasing the value E2 of the voltage output from the voltage adjustment section 15.

〔Effect of the invention〕

As explained above, according to the present invention, even if high frequency components are attenuated in the transmission path, the waveform of the pulse signal received at the receiving end side can be prevented from being distorted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the pulse output circuit according to the present invention, FIG. 2 is a waveform diagram showing an example of the operation of the pulse output circuit shown in FIG. 1, and FIG. 3 is a pulse output circuit according to the present invention. FIG. 4 is a block diagram showing a third embodiment of the pulse output circuit according to the present invention,
FIG. 5 is a waveform diagram showing an example of the operation of the pulse output circuit shown in FIG. 4. 1...Fixed power supply 2...Variable power supply 3...Power supply selector switch 3 4...Transformer 4 7.8...Polarity selector switch 9...Waveform forming section (controller) 11...Transmission Illustration of Hidekazu Miyoshi, a roadside speaker

Claims (1)

[Claims] (1) A pulse output circuit that generates a pulse signal and sends it out onto a transmission path, comprising a waveform forming section that transforms the waveform of rising and falling portions of the pulse signal so as to cancel out waveform distortion caused by the transmission path. A pulse output circuit characterized by: