JPH07273692A - Crosstalk prevention method and signal transmission device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a novel method for preventing crosstalk when transmitting a high-energy signal, and a signal transmission device having high reliability. [Construction] A converter is controlled by a transmission circuit 3 having transmission circuits 22-1 to 6 of AVR2 and reception circuits 12-1 to 12-6 of thyristor board 1 and core wire pairs 31-1 to 6 connecting a reciprocal path therebetween. The pulse signal is transmitted. Each core wire pair 3
1 includes an individual shield 33 that electrostatically shields each other, and this shield 33 is connected to the constant potential position 331 of the transmission circuit 22, that is, the power source 24 of the transmission circuit 22 or the + side output end of the transmission circuit 22. Even if the voltage of the return path (L ₁₂ ) of the core wire pair 33-1 is reduced by turning on the Tr _23-1 , the PS 33-1 is charged from the constant potential point 331-1 almost at the same time, and the potential is kept constant. Therefore, crosstalk is not generated in the core wires 33-6 of the other phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise countermeasure in a signal transmission device, and more particularly to a crosstalk prevention system for a transmission cable in the field of power electronics having a high energy signal.

[0002]

2. Description of the Related Art As a method of preventing crosstalk, for example, as described in Kenichi Ito, "Earth circuit-this way electronic circuit works correctly-NDC549", published by Nikkan Kogyo Shimbun, a pair of signal lines is used. There are known ones that are used, grounded at a single point by using a shielded cable, or that form an equilibrium circuit by providing an insulating transformer between the circuit and the cable.

[0003]

As described above, the conventional crosstalk preventing method is often effective in the case of weak electric power that requires a small signal energy, such as in the electronics field where only signals are transmitted, such as computers and communications. .
However, in recent years, the field of power electronics often requires a large amount of signal power beyond the boundary of conventional weak electric power.

FIG. 4 shows an example of such a power converter.
The gate pulse signal from the automatic voltage regulator (AVR) 2 is transmitted to the thyristor board 1 by the cable 3. The gate pulse that controls the SCR 11 of the thyristor board 1 is S
It requires a certain amount of electric power (current) corresponding to the capacity of CR11.

The cable 3 shields six sets of core wires 31 from a pair with a shield 36 and grounds the casing of the thyristor board 1. One of the core wires of each pair has a + side of the output of the transmission circuit 22 of the AVR 2 and a + side of the reception circuit 12 of the thyristor board 1.
Side (gate side) is connected, and the other of the core wires is the receiving circuit 12
The − side (cathode side) of − and the − side of the transmission circuit 22 are connected. The + side of the output of the transmission circuit 22 is connected to the positive power supply, and the − side is connected to the negative power supply via the transistor 23.

When such an output of the thyristor board 1 is used as the field voltage of the generator, the cable length connecting the AVR 2 in the central operation room and the thyristor board 1 reaches 500 m one way.

Well-known DC conversion is performed by sequentially turning on each of the SCRs 11-1 to 6 for a partial period of one cycle (2π) of three-phase AC. In this case, the output of the pulse generation circuit 21 of the AVR 2 causes the transistor 2 of the transmission circuit 22 to
Each of 3-1 to 6 is turned on / off to generate a pulse signal to be given to the gate of the SCR 11.

FIG. 6 shows a time waveform diagram of a gate pulse signal in this device. S1 is a main pulse and S2 is an auxiliary pulse, which is a regular control signal.
Noise may be superimposed, which may cause false firing of the SCR 11.

The cause of noise is mainly crosstalk that causes electrical coupling via stray capacitance between each phase.
That is, when the transmitter circuit is operated to superimpose a signal on a pair of core wires, the voltage between the core wires changes, so a charging current flows from the core wires of other phases to this stray capacitance, and this becomes noise in other phases. .

It is well known that each phase is electrostatically shielded and grounded in order to prevent electrical coupling due to stray capacitance between core wires of each phase. However, in the case of this example, it was not possible to obtain a sufficient effect by such conventional measures. This is because the influence of the charging / discharging time cannot be ignored when the signal power is high and the cable is long, as will be described later.

An object of the present invention is to provide a novel method for preventing crosstalk when transmitting a high energy signal based on the understanding of the phenomenon of electrical coupling due to the high energy signal.
Therefore, it is to provide a highly reliable signal transmission device.

[0012]

The above-mentioned object of the present invention is to provide a device for transmitting a pulse signal by a transmission cable having a plurality of transmitting circuits and receiving circuits and a plurality of core wires connecting the transmitting circuits and the receiving circuits. A predetermined constant potential of the transmission circuit corresponding to the individual shield (PS), the individual shield (PS) electrostatically shielding between a core wire pair connecting the transmitter circuit and the receiver circuit and another core wire pair. It is achieved by connecting to a position.

The constant potential position is the power supply or the + side output end of the transmission circuit. Alternatively, in the vicinity of the signal transmission position of the transmission circuit, with respect to the stray capacitance between the core wire and the individual shield (PS), when passing through the individual shield (PS) from the constant potential position, and the potential of the transmission circuit. It is characterized in that the distances are set so as to be substantially equidistant when passing through a core wire that undergoes fluctuation.

[0014]

According to the structure of the present invention, the potential at the constant potential position is the charge current to the stray capacitance between the core wire on the potential fluctuation side and the individual shield (PS) during the operation of the transmission circuit. Since the potential fluctuation of the individual shield (PS) can be suppressed by giving it without delay from the individual shield (PS), the crosstalk can be prevented without exerting the influence of the potential fluctuation on the core wire outside the individual shield.

As an operation of another aspect of the present invention, by connecting each individual shield (PS) near the signal source, the charge current to the stray capacitance between the core wires changes after the potential of one core wire changes. Since the path to the flow is sufficiently shorter than the charging path from the core wire outside the individual shield (PS), the potential fluctuation of the individual shield (PS) is instantaneously restored.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a power converter that preferably implements the pulse signal transmission method of the present invention. The power converter includes a thyristor board 1 for converting an AC power supply into a DC power supply, an AVR 2 for controlling the operation of the thyristor board, and a cable 3 for connecting the thyristor board 1 and the AVR 2 and transmitting a control signal.

The thyristor board 1 has three phases and six poles (UP, W
N, VP, UN, WP, VN) Thyristor 11-of each phase
A bridge circuit is composed of 1 to 11-6, and each thyristor is sequentially fired at every π / 3 to convert a three-phase alternating current into a direct current power source. Each thyristor 11 receives the gate signal via the receiving circuit 12.

The AVR 2 is composed of a pulse generation circuit 21 and pulse amplification circuits 22-1 to 22-6. Each pulse amplification circuit 22 is connected between a positive power supply 24 and a negative power supply 25,
A transistor 23 that operates according to a signal supplied from the pulse generation circuit 21 is provided to form a signal transmission circuit. Each of the pulse amplification circuits 22 fires the corresponding thyristor 11 every π / 3.

FIG. 2 is a time waveform diagram of a pulse signal output from the pulse generating circuit 21 to each pulse amplifying circuit 22 every one cycle (2π). The pulse signals of s1 and s2 generated in the period of π / 3 of one cycle are sequentially given to the transistor 23 of each pulse amplification circuit 22 every π / 3. From the positive power supply 24 to the cable 3 while the transistor 23 is turned on by the pulses s1 and s2 (300 μs)
A current flows through the receiving circuit 12 through the
A pulse signal with a current of about 1 A is transmitted to the receiver circuit 12, and the receiver circuit 12 increases the current to about several A (the voltage is 1 / several).
It is applied to the gate G to turn on the thyristor 11.

FIG. 3 is a sectional view of the cable 3 used in this embodiment. Conductor 3 that is covered with the insulator 32 and serves as a core wire
1 is an individual shield (P
It is shielded by S) 33 and further covered by an insulator 34. Six individual cables 30 are arranged in a circumferential shape and are collectively shielded by a common shield (CS) 36.
Covered with 7. The gap 35 in the cable is filled with inclusions 35.

In this embodiment, as a measure against crosstalk, as shown in FIG. 1, an individual shield (PS) of the cable 3 is used.
Each of the 33 is connected to the + side (+ side of the pulse amplification circuit 22) position 331 of the output of the AVR 2.

FIG. 5 shows a time waveform diagram of the gate pulse signal according to this embodiment. As shown in the figure, the normal control signals of the main pulse S1 and the auxiliary pulse S2 are kept normal and only noise is sufficiently reduced, so that there is no fear of causing false firing of the SCR.

Next, the reason why the crosstalk between the parallel cables can be reduced by the structure of the present embodiment will be described in comparison with the conventional structure.

FIG. 7 is an equivalent circuit diagram of the conventional configuration shown in FIG. For simplicity of explanation, only the UP phase and the VN phase are shown, and when Tr ₆ of the pulse amplification circuit 22 of the VN phase is turned on and a current is passed through the load Z ₆ on the receiving side, the UP state in the off state is shown.
The cause of causing crosstalk in the phase load Z ₁ will be described.

In the figure, L ₁₁ and L ₁₂ are UP phases, L ₆₁ and L ₆₂
Indicates the reciprocating core wires of the VN phase. C ₁₂ is L ₁₁ and L
₁₂ , C ₁₆ is a stray capacitance between L ₁₁ and L ₆₂ , and C ₆₁ is a stray capacitance between L ₁₂ and L ₆₂ . The DSW is a simulated switch that represents the delay caused by the cable length when the current flows from L ₁₁ to L ₁₂ .

In this circuit, when Tr ₆ is turned on, the voltage of L ₆₂ drops and a current flows from Z ₆₁ to Z ₆ . At this time,
L ₁₁ → Z ₁ → L ₁₂ → C ₆₁ → L ₆₂ → Tr ₆ and charging current i _c1 flow. However, assuming that the cable lengths of L ₁₁ and L ₆₂ are each about 500 m, it takes about 5 μs until the current i _c1 reaches C ₆₁ . That is, during this period, the current i
_Seen from _c1 , it is equivalent to the DSW being in the OFF state.

Therefore, the time of about 5 μs is L ₁₁ and L
Through C ₁₂ between ₁₂ the charging current i _c2 flows into the C _61, the charge of C ₁₂ the current i _c1 is L ₁₂ reach stops. After this, the charged charge of C ₁₂ begins to discharge to Z ₁ .

Charging current i _c1 and discharging current i _d1 flowing through Z ₁
Is one-time crosstalk. Discharge current i _d1
The value of is much larger than i _c1 because it is mainly determined by the voltage applied to C ₁₂ and the impedance of Z ₁ . The discharge time depends on the cable length and the impedance of the discharge loop.

FIG. 8 is an equivalent circuit diagram of a conventional example in which an individual shield PS is provided between each phase and is connected to the ground point E of the housing. The middle point of the ± V power sources and the ground point E are electrically connected as indicated by the dotted line.

With this configuration, when the voltage of L ₆₂ is lowered by turning on Tr ₆ , the potential of PS provided between the phases is suppressed to the ground potential, and the charging current to C ₁₂ → C _PS6-2 is generated. Is to prevent.

However, since the cable is long and the connection point between the power source V and the ground E is separated, it takes time for the charging current from the power source V to reach E → PS → C _PS62, and the EDSW A delay time of several μs equivalently shown by the switch occurs. Therefore, as in the case of FIG. 6, a charging current flows to C _PS6-2 via C ₁₂ during this delay time, and then crosstalk occurs due to discharging from C ₁₂ .

FIG. 9 is an equivalent circuit of the present embodiment shown in FIG. 1. PS _i provided for each phase is connected to a constant potential point (+ V side) near the signal source of each transmission circuit. Has been done.
According to this, the starting point of the signal current flowing through Z ₆ and the charging current flowing through PS ₆ are the same, and when Tr ₆ is turned on, the voltage of L ₆₂ decreases and at the same time the charging current changes from PS _{6 to} C _PS6-2. Therefore, the potential of PS _{6 and} the potential of C _PS hardly change. The constant potential point in the figure is actually the power supply (+ V) or the + side output end of the transmission circuit.

FIG. 10 shows the stray capacitance of FIG. 9 as a distribution constant at the same intervals. Assuming that the cable length is 500 m, the 100 m interval points between PS ₆ and L ₆₂ are a, b, c,
Let d, e and a ', b', c ', d', e '. In this case, a, b, c, d, from the power source V via PS ₆
Each point of e and a ′, b ′, from the power source V via Tr ₆
The points c ', d', and e'are almost equidistant.

Therefore, at the moment when the voltage of L _{62 drops} from the Tr ₆ side, the charging current from PS ₆ becomes C _PS6-2 (1 to
Since 4) is charged, the potentials at points a, b, c, d, and e hardly change. Therefore, since there is no change in the charging potential of the stray capacitance C _PS between PS ₁ and PS _6, the charging current does not flow through the one-phase inter-core stray capacitance C ₁₂ and the discharge of C ₁₂ leads to Z ₁ . No crosstalk current is generated.

FIG. 11 is an equivalent circuit diagram according to the modification of FIG. 1, in which the individual shields PS ₁ and PS ₆ are connected to the negative side of the power source. This can also achieve the same effect.

That is, in the figure, when Tr ₆ is off, the power supply voltage V is applied to the CPS 6-1 and CPS 6-2 to charge them. If Tr ₆ turns on in this state, L
Since _{the 62} potential of is the same as the PS _6, PS ₆ tries S'Agaro by the amount of charge potential. However, CPS6-1, CPS
Since 6-2 charge is discharged immediately in a loop of _{L 62, Tr 6, PS 6} , the potential of the potential or C _PS of PS ₆ hardly changes, and generates crosstalk Z ₁ of one phase There is no such thing.

As described above, when a plurality of closed circuits for transmitting a signal are formed by a transmission cable having a plurality of core wire pairs serving as a reciprocating path of a transmitting circuit and a receiving circuit, the transmitting circuit operates. When the potential of the core wire connected to the negative side of the output drops sharply, a charging current flows from the core wire or shield of another phase in an attempt to maintain the charging voltage of the stray capacitance between the core wires or between the core wire and the shield, and this This may cause crosstalk.

However, in the present embodiment, since the individual shield (PS) is provided for each core wire pair and is connected to the constant potential position of the transmission circuit (+ side of the output terminal or ± power supply), it is close to the transmission circuit. Can instantly react to the change in the potential of the core wire, and the charging current is passed through the stray capacitance between the core wire and the PS via its own PS to suppress the potential fluctuation of the PS.

That is, the potential fluctuation of the core wire of its own phase hardly reaches the core wires of other phases outside the individual shield (PS). As a result, the charging current generated in the closed circuit of the other phase is significantly reduced, and crosstalk can be prevented.

FIG. 12 shows the test results of the crosstalk countermeasure according to the conventional example and the present example. The test was carried out by applying a three-phase AC 220v to the thyristor board 1, 110v (+ 50v, -50v) in the DC power source of the transmission circuit 22, a cable length of about 500m between transmission and reception, and a gate pulse signal of 10v / 300μs.

(A) is a collective shield (CS) system,
(B) is an individual shield (PS) grounding method, both of which are conventional examples. (C) is a power supply side connection method of the individual shield (PS) according to the present embodiment. (D) is a common side (voltage fluctuation side) connection method of the individual shield (PS).
The test result shows that the noise value seen between G and K of SCR is
(A) 3.1v, (b) 0.36v, (c) 0.05
v, (d) 1.5v. Incidentally, the threshold value of the ignition signal of the thyristor used in this test is 0.1 v / several μs.

As described above, it is recognized that the noise according to the present embodiment is reduced by one to two orders of magnitude as compared with the conventional case, and the false ignition can be prevented. In the case of the (d) method in which the PS potential varies, it is inferior to the conventional grounding method of the individual shield (PS). This is because the potential fluctuation of PS due to (d) is due to the charging delay due to the long path including the power supply V and the ground point E, which is an example of the other side showing the validity of the configuration of the present embodiment.

FIG. 12 shows the configuration of another embodiment. As a measure against crosstalk, as in FIG. 1, each of the individual shields (PS) 34 of the cable 3 is connected to the + side (+ side of the pulse amplification circuit 22) 341 of the output circuit of the AVR 2. Along with this, a common shield (CS) 36 for collectively shielding each phase is provided and grounded.

According to this, each P of the previous embodiment and this embodiment is
When a potential is applied to S, CS is grounded so that no electric field is generated around the cable. Further, CS is grounded to the housing on the side where the external noise source is high. In the case of this example, in order to reduce the influence of the electromagnetic induction by the current from the anode of the thyristor to the cathode and the induction by the AC voltage, it is grounded to the casing of the thyristor board 1.

According to the present embodiment, it is possible to prevent crosstalk in the cable, and reduce the electrostatic field around the cable and noise due to external induction.

The noise countermeasure system according to the present invention is not limited to the above-mentioned embodiment, and various modifications can be made. For example,
As shown in FIG. 3, the individual shields PS are covered with an insulating material 34 to insulate the PSs from each other and have an independent shielding structure for each pair, so that even if the potential of the PSs is slightly changed, other PS Avoid the effect on the core wire.

Further, in the present embodiment, the power generation equipment in which the AVR is the transmitting side and the thyristor board is the receiving side is targeted, but two or more transmission / reception are performed by using a cable having a plurality of core wires or a group of similar parallel transmission lines. When a closed circuit for use is constructed, it can be widely applied as a measure against noise between these closed circuits.

[0049]

According to the crosstalk prevention method of the present invention, a constant potential on the transmitting side is applied to the individual shield that electrostatically shields the signal transmission paths to suppress the potential fluctuation due to the operation on the transmitting side. The effect of potential fluctuations in the signal transmission path does not extend to the outside of the individual shield, and crosstalk can be prevented.

According to the signal transmission device of the present invention, a cable having a plurality of core wire pairs individually shielded into an integral structure is used, and this shield is connected to a constant potential position near the signal output end on the transmission side. , It is possible to prevent crosstalk in the cable and improve reliability.

[Brief description of drawings]

FIG. 1 is a schematic connection diagram of a power converter including an automatic voltage regulator (AVR) connected by a cable and a thyristor panel, showing an embodiment of a signal transmission device of the present invention.

FIG. 2 is a waveform diagram of a pulse signal for one phase output from an AVR pulse generator.

FIG. 3 is a schematic sectional view of a transmission cable used in this embodiment.

FIG. 4 is a schematic connection diagram of a conventional power converter.

FIG. 5 is a time waveform diagram of a gate pulse signal of the receiving circuit according to the present embodiment.

FIG. 6 is a time waveform diagram of a gate pulse signal of a receiving circuit in a conventional example.

FIG. 7 is an equivalent circuit diagram of the conventional configuration shown in FIG.

FIG. 8 is an equivalent circuit diagram of another conventional configuration.

FIG. 9 is an equivalent circuit diagram of the present embodiment shown in FIG.

FIG. 10 is an equivalent circuit diagram showing FIG. 9 in a distributed constant system.

FIG. 11 is an equivalent circuit diagram showing a modified example of FIG.

FIG. 12 is an explanatory diagram showing test results of measures against crosstalk according to the related art and the present embodiment.

FIG. 13 is a schematic connection diagram of a power converter according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Thyristor board, 2 ... Automatic voltage regulator (AVR),
3 ... Transmission cable, 11 (1-6) ... Thyristor (SC
R), 12 (1-6) ... Receiving circuit, 21 ... Pulse generating circuit, 22 (1-6) ... Transmitting circuit, 23 (1-6) ... Transistor (Tr), 31 (1-6) ... Core wire ( Pair), 32
(1-6) ... Individual shield (PS), 33 ... Common shield (CS), 34, ... 35 Insulator, 37 ... Sheath, V ...
Power source of transmitter circuit, E ... Shield ground point, Z _i ... i phase receiver circuit impedance, L _i1 , L _{i 2} ... i phase forward core wire,
Return core wire, C ₁₂ ... stray capacitance between one-phase core wires (L ₁₁ , L ₁₂ ), C _ij ... stray capacitance between i-phase and j-phase core wires, C _iPS ... stray capacitance between i-phase core wire and PS, C _{iPS P Sij} ... _Stray capacitance between i-phase PS and j-phase core wire, C _PS ... Stray capacitance between _PS , DSW, EDS
W ... Delay simulation switch.

Claims (8)

[Claims] 1. A method for transmitting a pulse signal by a plurality of transmitting circuits and a receiving circuit, and a plurality of adjacent transmission lines connecting these circuits, wherein a shield is provided along the transmission line and electrostatically shields the transmission lines from each other. A method for preventing crosstalk, characterized in that a predetermined potential is applied from the side of the transmission circuit. 2. The crosstalk prevention method according to claim 1, wherein the predetermined potential is a power supply voltage of the transmission circuit or an output voltage that does not fluctuate during the operation of the transmission circuit. 3. The individual shield (1) according to claim 1 or 2, wherein the predetermined potential is a charge current to a stray capacitance between the transmission line and the individual shield (PS) whose potential varies during operation of the transmission circuit. A crosstalk prevention method characterized in that the potential fluctuation of the individual shield (PS) is suppressed by giving it from PS) without delay. 4. An apparatus for transmitting a pulse signal by a transmission cable having a plurality of transmission circuits and reception circuits and a plurality of core wires connecting the transmission circuits and the reception circuits, wherein the transmission cable includes a core wire pair connecting the transmission circuit and the reception circuit. A signal transmission device comprising an individual shield (PS) for electrostatically shielding between another core wire pair, and connecting the individual shield (PS) to a constant potential position of the corresponding transmission circuit. 5. The power source of the transmission circuit (+ side or −) according to claim 4,
Side) or a plus side output terminal. 6. The constant potential position according to claim 4 or 5, with respect to a stray capacitance between the core wire and the individual shield (PS), near the signal transmission position of the transmission circuit. A signal transmission device, which is set so as to be substantially equidistant when passing through an individual shield (PS) and when passing through a core wire which receives a potential fluctuation of the transmission circuit. 7. The transmission cable according to claim 4, 5 or 6, wherein the individual shield (PS) is provided on an outer periphery of the core wire pair, and a common shield is provided on an outer periphery of the core wire pair with an insulating material interposed therebetween. (CS) is provided, and the common shield (CS) is grounded to the high noise source side of either the transmission circuit or the reception circuit. 8. A converter that includes a bridge circuit of a plurality of thyristors to convert a three-phase alternating current into a direct current, and a voltage regulator (AVR) that includes a plurality of transmission circuits that generate pulse signals for controlling the thyristors. In a power device comprising a transmission cable having a plurality of core wires for transmitting a pulse signal from a transmitter circuit to a receiver circuit directly connected to a gate of each thyristor, the transmission cable is a core wire pair connecting a round trip path between the transmitter circuit and the receiver circuit. An electric power device characterized in that an electrostatic shield individual shield (PS) is provided on the outer periphery of each of them, and the individual shield (PS) is connected to a power source or a constant potential output terminal of the corresponding transmission circuit.