JP2997630B2 - Switching control circuit and DC signal detection circuit used for switching control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching control circuit for switching equipment such as a terminal device from a communication line in accordance with a DC signal which is a control signal, and a DC signal for performing a fault diagnosis of a communication line system by a loop test. The present invention relates to a DC signal detection circuit for detecting.

[0002]

2. Description of the Related Art In a switching control circuit of this type, a switching control is usually performed using a DC signal coming from a communication line. Detecting the DC signal is an important function in discriminating between the AC signal for communication and the electric charge stored in the external capacitor. As an example of realizing this function, there is Japanese Patent Application Laid-Open No. Hei 3-226151 by the present applicant.

FIG. 2 shows the configuration of a switching control circuit according to the above publication.
FIG. 2 is a circuit diagram schematically showing a circuit in which 21 is a voltage;
A determination circuit that outputs an input signal exceeding a first threshold, 22
Is an input signal whose voltage exceeds a second threshold higher than the first threshold
Is a decision circuit that outputs a resistance value and a resistance value represented by Rd and Tr.
Discharge circuit composed of the transistors shown, C
L ₁, CL_TwoIs a line constituting a communication line, L₁, L_TwoIs
Track CL₁, CL_TwoNot shown external control device connected to
Side terminal, I₁, I_TwoIs the track CL₁, CL_TwoConnected to
FIL is a low-pass filter (not shown).
And SD are turned on and off according to the judgment result of the judgment circuit 22.
Switch element, RL is the switch on.
Or a relay that is driven in response to off, rl₁, Rl_TwoIs
A relay contact that switches the contact according to the drive of the ray RL,
Co is terminal L₁, L_TwoMore connected to the external control device side
External capacitors are shown respectively.

As described above, the switching control circuit, as shown in FIG. 2, connects the output of the low-pass filter FIL to the decision circuits 21 and 22 independently, and causes one of the decision circuits 21 to decide whether or not discharge is possible. The other determination circuit 22 determines whether the switch can be switched, and the two determination circuits 21 and 22 are used.
Constitutes a DC signal detection circuit.

Next, the operation will be described. In the switching control circuit shown in FIG. 2, when a DC signal, which is a control signal, is transmitted from the communication line, the output voltage of the low-pass filter FIL rises and reaches the first threshold value of the determination circuit 21. An output voltage is generated at 21. This output voltage turns on the transistor Tr of the discharge circuit 23 to turn on the transistor Tr, thereby conducting between the collector and the emitter and lowering the potential by the resistor Rd.

However, since the internal impedance of the external control signal generation source is low, an output voltage is generated when the voltage of the control signal further increases and reaches the second threshold value of the determination circuit 22. This output voltage turns on the switch element SD, drives the relay RL, and sets the relay contacts rl ₁ ,
Switching of rl ₂ is performed.

If a residual voltage is accumulated in the external capacitor Co when a ringing signal is input, an output voltage is generated in the determination circuit 21 as described above, and the transistor T
When r is turned on, discharging by the resistor Rd is performed. As a result, the voltage between the terminals L ₁ and L ₂ decreases and the judgment circuit 22
Does not reach the second threshold value, so that the switching element SD does not need to shift to the ON operation, so that malfunction of the switching element SD can be prevented.

Therefore, in the switching control circuit shown in FIG. 2, a reliable relay drive can be realized by accurately capturing the DC signal arriving from the communication line, whereby a stable switching control circuit free from malfunctions can be realized. Can be realized.

Incidentally, as this kind of prior art, for example,
JP-A-3-226154 and 2 of the present applicant.
Nos. 26155, 229556 and 2295
Nos. 57, 229558 and 4-12094
No. 8 publication.

[0010]

However, the conventional switching control circuit shown in FIG.
Since the determination is made by the two determination circuits 21 and 22, an increase in the number of components used for the determination causes the circuit to be complicated and expensive, and further research is needed to improve these. there were.

Accordingly, the present invention focuses on the problems of the prior art described above, and reduces the number of elements for detecting a DC signal to the minimum necessary without deteriorating the performance required of the circuit, thereby providing a simple and inexpensive switching control circuit. And a DC signal detection circuit used for a switching control circuit.

Another object of the present invention is to provide a switching control circuit capable of cutting noise flowing into a switching element and preventing malfunction of the circuit, and a DC signal detecting circuit used in the switching control circuit. I do.

Another object of the present invention is to provide a switching control circuit capable of preventing the malfunction of the circuit by increasing the stability of the switching element, and a DC signal detecting circuit used in the switching control circuit.

[0014]

According to a first aspect of the present invention, there is provided a switching control circuit for controlling a terminal device or the like connected to a communication line in accordance with an operation of a relay driving unit having a switching element. In a switching control circuit for separating devices, between two lines constituting the communication line,
First current passing means for passing a current when an input voltage exceeding one voltage value is applied between two lines, and an input voltage exceeding another voltage value higher than the one voltage value is applied between the two lines. And a second current passing means for passing a current is connected in series from the upstream side to the downstream side, and an output of the first current passing means is connected to a discharging means and the second current passing means is connected to the second current passing means.
The output of the current passing means is connected to the switch element of the relay driving means, the one voltage value is set lower than the maximum value of the voltage remaining in the communication line, and the other voltage value remains in the communication line. The voltage is set to be higher than the voltage value lowered by the discharge of the applied voltage and lower than the voltage value of the DC signal applied between the two lines.

According to a second aspect of the present invention, in the switching control circuit according to the first aspect, the first current passing means and the second current passing means have a first Zener diode and a second Zener diode, respectively. It is a feature.

According to a third aspect of the present invention, in the switching control circuit according to the second aspect, the first current passing means connects a low-pass filter upstream of the first zener diode. Is what you do.

A switching control circuit according to a fourth aspect of the present invention is the switching control circuit according to the second aspect of the present invention, wherein the second current passing means connects a shunt section downstream of the second zener diode. It is.

A switching control circuit according to a fifth aspect of the present invention is the switching control circuit according to the fourth aspect of the present invention, wherein the second current passing means connects a low-pass filter downstream of the shunt section. It is.

According to a sixth aspect of the present invention, there is provided a DC signal detecting circuit used in the switching control circuit, wherein a DC signal detecting circuit is connected between two lines constituting a communication line, and the communication line is controlled by the DC signal detecting circuit. Operating a switch element connected downstream when detecting a DC signal arriving via
In a DC signal detection circuit used for a switching control circuit for operating a discharging means when a residual voltage arriving via the communication line is detected, the DC signal detection circuit is connected to a line having an input voltage exceeding one voltage value. A first zener diode that allows a current to pass when applied between the two lines, and a second zener diode that allows a current to pass when an input voltage exceeding another voltage value higher than the one voltage value is applied between the two lines. The first zener diode is connected in series from the side to the downstream side, and the output of the first zener diode is connected to the discharging means, and the output of the second zener diode is connected to the switch element. The other voltage value is set lower than the maximum value of the voltage remaining in the communication line, and the other voltage value decreases due to the discharge of the voltage remaining in the communication line. Higher than the value, and is characterized in that is set lower than the voltage value of the DC signal applied between the two lines.

According to a seventh aspect of the present invention, there is provided a DC signal detecting circuit used in the switching control circuit, wherein a shunt portion is connected downstream of the second Zener diode. .

According to an eighth aspect of the present invention, in the DC signal detecting circuit used in the switching control circuit according to the seventh aspect of the present invention, a low-pass filter is connected to a downstream side of the branching section. .

[0022]

According to the first aspect of the present invention, the switching control circuit comprises:
In the current passing means, the voltage value for flowing the current is set lower than the maximum value of the voltage remaining in the communication line, and in the second current passing means, the voltage value for flowing the current is set lower than the voltage value of the DC signal. This is the configuration. Therefore, when the input from the communication line is a residual voltage, the output voltage of the first current passing unit is input to the discharging unit, and is discharged to reduce the voltage value.
When the input from the communication line is a DC signal, the first
Even when the output voltage from the current passing means is discharged, the voltage does not decrease since the external control signal source sets the current value to a large value. The current passing requirement is satisfied, and the output current of the second current passing unit is input to the relay driving unit as a DC signal. As a result, the relay driving means operates, and the equipment such as the terminal device is separated from the communication line.

According to a second aspect of the present invention, the switching control circuit comprises:
According to the first aspect of the present invention, since the first current passing means and the second current passing means are provided with the first Zener diode and the second Zener diode, respectively, the current flows according to the voltage value set to each Zener diode. And simplification of the circuit.

According to a third aspect of the present invention, the switching control circuit comprises:
According to the second aspect of the present invention, since the low-pass filter is connected to the upstream side of the first Zener diode,
The current passing means can remove the AC component of the signal at the time of input.

According to a fourth aspect of the present invention, the switching control circuit comprises:
According to the second aspect of the present invention, since the shunt portion is connected to the downstream side of the second Zener diode, the shunt current from the shunt portion is output to the relay driving means as a DC signal.

According to a fifth aspect of the present invention, the switching control circuit comprises:
According to the fourth aspect of the present invention, since a low-pass filter is connected to the downstream side of the branching section, the DC signal is output to the relay driving means after noise is removed by the low-pass filter.

The DC signal detecting circuit used in the switching control circuit according to the sixth aspect of the present invention has a configuration in which the DC signal detecting circuit is connected in series with the first Zener diode and the second Zener diode. Whether it is based on a voltage or a DC signal can be detected according to the tendency of the voltage.

The direct current signal detection circuit used in the switching control circuit according to the seventh aspect of the present invention has a configuration in which a shunt section is connected to the downstream side of the second Zener diode in the sixth aspect of the present invention. Is output to the switch element as a DC signal.

The direct current signal detecting circuit used in the switching control circuit according to the eighth aspect of the present invention has a configuration in which a low pass filter is connected to the downstream side of the shunt section in the seventh aspect of the present invention. After the noise is removed by the filter, the signal is output to the switch element.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a switching control circuit and a DC signal detection circuit according to the present invention. In the drawing, reference numeral 1 denotes a DC signal detection circuit. The DC signal detection circuit 1 includes a pair of Zener diodes 12 and 14, a shunt 16, and a low-pass filter 1.
8 is connected in series from the upstream side to the downstream side between the lines CL ₁ and CL ₂ .

The Zener diode 12 has an input connected downstream of the low-pass filter FIL, one of the outputs connected to the Zener diode 14, and the other connected to the discharge circuit 20. Diverter 16 is constituted by resistors, thereby connecting the other to the line CL ₂ with connecting the one output to the low-pass filter 18. The low-pass filter 18 is configured to pass a low-frequency component of a signal. One of the outputs is connected to a switch element SD of a relay drive unit RD including a relay RL and a switch element SD, and the other is connected to a line CL _2. Connected to The low-pass filter FIL is for removing an AC component from a signal arriving via a communication line to prevent a malfunction in a separating operation.

The discharge circuit 20 is composed of a transistor and a resistor, for example, like the discharge circuit 22 shown in FIG.

The DC signal detection circuit 1 determines whether to output the output voltage to the discharge circuit 20 or to output the output current to the switch element SD at the same time, based on the voltage values set in the Zener diodes 12 and 14, respectively. This is a circuit that is performed according to the magnitude relation. Therefore, the set voltage value of one Zener diode 12 is set to be lower than the maximum value of the residual voltage due to the capacitor Co, and the other Zener diode 14 is set to discharge the residual voltage by summing the voltage value of the Zener diode 12 with the residual voltage. Is set to be higher than the voltage value lowered and lower than the voltage value of the DC signal.

For example, when the set voltage value of the Zener diode 12 is set to V ₁ volt and the set voltage value of the Zener diode 14 is set to V ₂ volt, the voltage input through the low-pass filter FIL Exceeds V ₁ volts, an output voltage is generated from the Zener diode 12, current flows through the discharge circuit 20 and the Zener diode 14, and when the voltage further rises and exceeds V ₁ + V ₂ volts, the Zener diode An output voltage is generated from 14, and a current flows to the shunting section 16 in the subsequent stage. This is obtained by connecting the Zener diodes 12 and 14 in series and utilizing the voltage characteristics in the series circuit.

Next, the operation will be described. In switching control circuit shown in FIG. 1, when the DC signal from the communication line is a control signal arrives, the output voltage of the low-pass filter FIL has exceeded the rise to the above-mentioned set voltage value V ₁ volts, the Zener diode The current starts to flow through 12. This current is input to the discharge circuit 20 on the downstream side, is amplified by a transistor (not shown), and becomes a collector current as a line CL ₁ ,
It is discharged to the CL _2.

In a control signal generation source (not shown), since the internal impedance is usually low, the voltage of the incoming control signal is further increased. Therefore, the Zener diode 1
The voltage of the control signal input to ₂ rises to a voltage value exceeding V ₁ + V ₂ volts, and even after flowing through the Zener diode 12, sufficiently exceeds the set voltage value of the Zener diode 14. As a result, a DC signal is output downstream from the Zener diode 14.

This DC signal is split by the splitter 16 at the subsequent stage, and the noise component is removed by the low-pass filter 18 before being input to the switch element SD. Switch element S
D is turned on according to the input DC signal, and the relay R
L is driven. The relay contacts rl ₁ and rl ₂ are switched in response to the driving of the relay RL, and devices such as terminals are disconnected from the communication line.

Also, when a residual voltage is accumulated in the external capacitor Co at the time of input of the ringing signal, a current flows through the Zener diode 12 via the communication line and the low-pass filter FIL as described above. When the discharge is performed by the discharge circuit 20, the voltage between the lines CL ₁ and CL ₂ decreases and the residual voltage does not reach a voltage value exceeding V ₁ + V ₂ volts. It is not necessary to flow into the switch element SD through the diode 14.

As described above, according to the present embodiment, in the case of a residual voltage, the output voltage of the Zener diode 12 is input to the discharge circuit 20 and discharged there to reduce the voltage value. In this case, even if the output voltage from the Zener diode 12 is discharged, the current value of the external control signal generation source is set to a large value, so that the voltage does not decrease. 1
4 is satisfied and the Zener diode 14
Is supplied to the switch element SD as a DC signal. As a result, the switch element SD operates to disconnect a device such as a terminal from the communication line. Accordingly, a simple and inexpensive circuit can be provided by minimizing the elements for detecting a DC signal as the Zener diodes 12 and 14 without reducing the performance required for the switching control circuit and the DC signal detection circuit. Can be.

Further, since the shunt section 16 is connected to the downstream side of the Zener diode 14 and the shunt current from the shunt section 16 is output to the switch element SD as a DC signal, the operation of the switch element SD can be stabilized. This can prevent a malfunction in the separation operation.

Furthermore, a low-pass filter 18 is connected to the downstream side of the branching section 16, and the switch element SD is driven by a DC signal from which a noise component has been removed by the low-pass filter 18, so that malfunction of the switch element is prevented. Thus, the separating operation can be performed reliably.

As described above, the internal configuration of the discharge circuit 20 may be a current limiting type using a resistor,
A constant current method using a constant current element may be used.

[0043]

As described above, according to the first aspect of the present invention, the voltage value for flowing the current is set to be lower than the maximum value of the voltage remaining in the communication line in the first current passing means. (2) Since the current passing means has a configuration in which the voltage value for flowing the current is set lower than the voltage value of the DC signal, in the case of a residual voltage, the output voltage of the first current passing means is input to the discharging means and discharged. Although the voltage value decreases, in the case of a DC signal, even if the output voltage from the first current passing means is discharged, the voltage value decreases because the current value of the external control signal generation source is set to a large value. No, on the contrary, the voltage rises and the second
The requirement of the current passing means is satisfied, and the output current of the second current passing means is input to the relay driving means as a DC signal, whereby the relay driving means operates to disconnect the terminal or other device from the communication line. Therefore, by minimizing the number of elements for detecting a DC signal without reducing the performance required of the circuit, a simple and inexpensive switching control circuit can be provided.

According to the second aspect of the present invention, in the first aspect of the present invention, the first current passing means and the second current passing means are provided with the first Zener diode and the second Zener diode, respectively. Current can flow in accordance with the voltage value set in the above, and therefore, a simple and inexpensive supply is possible as compared with the conventional configuration in which two determination circuits are applied.

According to the third aspect of the present invention, in the second aspect of the present invention, a low-pass filter is connected upstream of the first Zener diode. AC components can be removed,
Therefore, it is possible to prevent a malfunction in the separation operation.

According to the fourth aspect of the present invention, in the second aspect of the present invention, since the shunt portion is connected to the downstream side of the second Zener diode, the shunt current from the shunt portion is supplied to the relay drive means as a DC signal. It is output, so that the separating operation can be stabilized.

According to the fifth aspect of the present invention, in the fourth aspect of the present invention, since a low-pass filter is connected to the downstream side of the branching section, the DC signal is removed after noise is removed by the low-pass filter. Output to the relay drive means,
It is possible to prevent a malfunction in the separation operation.

According to the sixth aspect of the present invention, since the first Zener diode and the second Zener diode are connected in series, it is determined whether the voltage coming from the communication line is a residual voltage or a DC signal. Therefore, there is an effect that a simple and inexpensive DC signal detection circuit can be provided.

According to the seventh aspect of the present invention, in the sixth aspect of the present invention, since the shunt section is connected downstream of the second Zener diode, the shunt current from the shunt section is output to the switch element as a DC signal. Therefore, the operation of the switch element can be stabilized.

According to the invention of claim 8, in the invention of claim 7, since a low-pass filter is connected to the downstream side of the branching section, the DC signal is removed after the noise is removed by the low-pass filter. The signal is output to the switch element, so that a malfunction in operation of the switch element can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a switching control circuit and a DC signal detection circuit thereof according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a switching control circuit according to a conventional example.

[Explanation of symbols]

12. Zener diode (first Zener diode,
(First current passing means) 14 Zener diode (second Zener diode,
(Second current passing means) 16 Shunt section (second current passing means) 18 low pass filter (second current passing means) 20 discharge circuit (discharge means) CL ₁ , CL ₂ line FIL low pass filter (first current Passing means) RD Relay drive unit (relay drive means) SD switch element

──────────────────────────────────────────────────続 き Continuing on the front page (73) Patent holder 391009442 Nisshin Electric Manufacturing Co., Ltd. 108-3 Oyama Sayamagahara, Iruma-shi, Saitama (72) Inventor Nobuteru Fujioka 3--18-14 Takada, Toshima-ku, Tokyo Inside the Hakusan Works, Ltd. (72) Hideo Miura, Inventor 3-18-14 Takada, Toshima-ku, Tokyo Inside the Hakusan Works, Ltd. Inside (72) Inventor Toshinori Yuki 1-30-13, Narimasu, Itabashi-ku, Tokyo Within Sanritz Co., Ltd. (72) Inventor Toshiro Sekido 3-12-15, Chuo, Warabi-shi, Saitama Pref. Nikko Electric Works, Ltd. (72) Inventor Tomoji Ogata 108-3 Sayamagahara, Iruma-shi, Saitama Pref. Nisatsu Electric Works, Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) H04M 1/24 H04M 1/00 H04M 3/30

Claims (8)

(57) [Claims] 1. A switching control circuit for separating a device such as a terminal connected to a communication line in accordance with an operation of a relay driving means having a switch element, wherein a switching control circuit is provided between two lines constituting the communication line. First current passing means for passing a current when an input voltage exceeding a voltage value is applied between two lines, and when an input voltage exceeding another voltage value higher than the one voltage value is applied between the two lines. And a second current passing means for passing an electric current in series from the upstream side to the downstream side, and an output of the first current passing means is connected to a discharging means, and an output of the second current passing means is connected to the discharge means. Connected to the switch element of the relay driving means, one voltage value is set lower than the maximum value of the voltage remaining in the communication line, and the other voltage value is lowered by discharging the voltage remaining in the communication line. Higher than the voltage value, and switching control circuit, characterized in that it is set lower than the voltage value of the DC signal applied between the two lines. 2. The switching control circuit according to claim 1, wherein said first current passing means and said second current passing means have a first Zener diode and a second Zener diode, respectively. 3. The switching control circuit according to claim 2, wherein said first current passing means connects a low-pass filter upstream of said first Zener diode. 4. The switching control circuit according to claim 2, wherein said second current passing means has a shunt portion connected downstream of said second Zener diode. 5. The switching control circuit according to claim 4, wherein said second current passing means has a low-pass filter connected downstream of said branching portion. 6. A DC signal detection circuit is connected between two lines constituting a communication line, and the DC signal detection circuit
A switching control circuit that operates a switch element connected downstream when detecting a DC signal arriving via the communication line, and operates a discharging unit when detecting a residual voltage arriving via the communication line. In the DC signal detection circuit used, a first Zener diode that passes a current when an input voltage exceeding one voltage value is applied between two lines, and another voltage higher than the one voltage value. And a second Zener diode that allows a current to pass when an input voltage exceeding the value is applied between the two lines, is formed in series from the upstream side to the downstream side, and the output of the first Zener diode is discharged. Means and the output of the second Zener diode is connected to the switch element so that the one voltage value is smaller than the maximum value of the voltage remaining in the communication line. And the other voltage value is set higher than the voltage value reduced by the discharge of the voltage remaining in the communication line and lower than the voltage value of the DC signal applied between the two lines. A DC signal detection circuit used for a switching control circuit. 7. The DC signal detecting circuit according to claim 6, wherein a shunt section is connected downstream of the second Zener diode. 8. The DC signal detection circuit used in the switching control circuit according to claim 7, wherein a low-pass filter is connected to a downstream side of said branching section.