JPH0683263B2 - Terminal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a configuration of a terminal device which is supplied with a voltage from a line.

With the recent remarkable development of semiconductor integrated circuit technology, attempts have been made to integrate subscriber circuits in exchanges into integrated circuits, but in the conventional subscriber line signaling system, high-level amplitude signals are used as ringing signals and Haura signals. Therefore, it is necessary to increase the breakdown voltage of the constituent elements of the subscriber circuit, and it is difficult to realize the high breakdown voltage element in the integrated circuit, which is a major obstacle in realizing the integrated circuit.

Therefore, in order to facilitate the integration of the subscriber circuit into the integrated circuit, a subscriber signal system for realizing a subscriber line signal only by a DC signal without using a high-level amplitude signal is proposed by the same applicant as Japanese Patent Application No. 57-33412.
(Japanese Patent Application Laid-Open No. 58-151161) and Japanese Patent Application No. 57-33413.
(Japanese Patent Laid-Open No. 58-151162).

In this subscriber line signaling system, the call display from the exchange to the terminal equipment sends out only the reversing signal of the line current or the reversing pulse or the intermittent pulse in combination with the reversing signal, and only the above-mentioned reversal signal at the terminal equipment. Alternatively, a loop is formed in the subscriber line for the reversal signal and the repolarization pulse or the intermittent pulse.

An object of the present invention is to provide a terminal device adapted to a subscriber line signal system realized only by a DC signal.

The present invention will now be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, reference numerals 11, 12, 13, 14 denote diode elements, which are connected so as to perform full-wave rectification on the voltage applied between the connection terminals T1 and T2 for connection with the line. 21 and 22 are the high potential side and the low potential side of the line after full-wave rectification. Reference numeral 31 denotes a logic circuit which is provided in the control circuit 30 and monitors the connection terminals T1 and T2 with the line and the user circuit 40 to control the connection between the rectified lines 21 and 22 and the user circuit 40. A constant current element 50 limits the current flowing through the control circuit 30 to a certain constant value. 61 and 62 are NPN transistors, which are Darlington-connected and have a switching function. V _SC is a control voltage that controls switching of the transistors 61 and 62. A base current flows into the I _B transistor 61. 70 is a resistance element, a transistor
Limit the base current I _{B of} 61. 23 is the monitoring line for terminal T1, 24
Is a monitor line of the terminal T2, and 25 is a monitor line of the user circuit 40, which is drawn into the logic circuit 31 to monitor each state.

Next, a connection control operation between the user circuit 40 and the connection terminals T1 and T2 of the line will be described.

In the logic circuit 31, the line current flows in the direction from the terminal T1 to T2 (whether the terminal T1 has a high potential with respect to the terminal T2) or vice versa, or by the change of the flowing direction (change of the voltage polarity) or the flowing direction. The number of changes (the number of changes in voltage polarity) or a signal resulting from a combination of these to monitor the line state and further monitor the state of the user circuit 40 to connect the user circuit 40 to the connection terminals T1 and T2 of the line. Control the connection. When the logic circuit 31 determines that the connection between the user circuit 40 and the rectified lines 21 and 22 should be opened, the control voltage V
By outputting a voltage lower than the base voltage at which the transistors 61 and 62 are turned off to the line 22 through the _SC , the transistors 61 and 62 are turned off and the user circuit operating current I is stopped. Therefore, the connection between the user circuit 40 and the terminals T1 and T2 is disconnected. On the contrary, the logic circuit 31 and the user circuit 40 and the rectified lines 21, 2
If it is determined that the connection with 2 should be made, the logic circuit 31
Applies the control voltage V _SC to the line 22 in addition to the base voltage at which the Darlington connection transistors 61 and 62 turn on, and the base current I
A voltage higher than the voltage drop between _B and the resistance element 70 is output to turn on the Darlington transistors 61 and 62 so that the user circuit operating current I flows. Therefore, the user circuit 40 and the connection terminals T1 and T2 of the line are connected.

Next, the function of the constant current element 50 will be described.

Since the terminal device shown in FIG. 1 is supplied with a voltage via an external line (not shown), a voltage drop occurs due to the line resistance and the line current of the line on the way, and the connection terminal T1 with the line is connected. The voltage applied during T2 varies. That is,
The voltage between the terminals T1 and T2 and the rectified voltage between the lines 21 and 22 vary depending on the magnitude of the line current and the length of the line. Further, the signal current is superimposed on the line current. However, since the constant current element 50 absorbs this voltage fluctuation and keeps the current supplied to the control circuit 30 at a constant value, the voltage applied to the control circuit 30 can be set to a constant value and a stable operation terminal device is realized. be able to. The voltage fluctuations are particularly severe when the user circuit 40 is connected to the terminals T1 and T2 and when it is not, and the operating condition is the most severe, that is, the connection terminal with the line.
The voltage applied between T1 and T2 is the lowest when connected. However, even in this case, the user circuit 40
The voltage drop at is larger than the sum of the voltage required for the constant current element 50 to perform the constant current function (about 1V) and the voltage required for the control circuit 30 to operate (about 2V). As a result, the control circuit 30 operates sufficiently stably.

Next, the logic circuit 31 will be described.

By configuring the logic circuit 31 with CMOS elements, it is not necessary to hold the operating voltage within a strictly constant range (+ 5V ± 5% for TTL elements) unlike other logic elements (for example, TTL elements). That is, the operating voltage values of the logic circuit 31 do not have to be the same for each terminal device, and may be different. The control voltage V _SC can be set to the transistor 6 by using the CMOS device.
When 1,62 is turned on, a value almost equal to the operating voltage of the logic circuit 31 can be output, and when turned off, the line 22 is used.
It is possible to output a value approximately equal to the voltage of. Thus transistor be output or voltage value in consideration of the voltage drop of the operating voltage at the limiting resistor 70 by the base current I _B the saturation voltage between the base and emitter of the transistor 61, 62 61 and 62
The switching of can be controlled stably. Further, since the saturation voltage between the base and the emitter is about 0.7V per transistor, it can be controlled at a low operating voltage (about 2V). The operating voltage of the logic circuit is set low and the consumption of current is extremely low by using CMOS elements (about 1 μA per gate), and the base current I _B when connecting the user circuit 40 is extremely low by the Darlington connection method. It can be suppressed to a small current value (about 100 μA), and the control circuit 30 can consume very little power. Further, the constant current element 50 allows the control circuit 30 to have a high resistance to an AC signal.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In FIG. 2, the parts using the same symbols as in FIG. 1 have the same names and functions as in FIG. 32 is added to FIG. 1 to show the power storage circuit.

The operation is almost the same as that of the embodiment shown in FIG. 1. However, in this embodiment, the control circuit 30 is provided with a power storage circuit, which converts the voltage applied between the connection terminals T1 and T2 to the line. Since the power supply power is maintained within the instantaneous power interruption time that occurs at the extreme time, the operation can be further stabilized as compared with the first embodiment. Further, as described above, since the current consumption in the logic circuit 31 can be made extremely small, there is an advantage that the power storage circuit can be realized with an extremely simple configuration.
Specifically, a capacitor may be used, or if necessary, a Zener diode or a parallel connection of diodes or a combination circuit thereof may be connected in parallel with the capacitor to limit or stabilize the voltage applied to the logic circuit.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention. Parts in FIG. 3 using the same symbols as in FIG. 1 have the same names and functions as in FIG. In Figure 3
15a and 16a are diode elements 11 in the first and second embodiments,
A light emitting diode in the optocoupler instead of 12, which is combined with the diode elements 13 and 14 to connect terminals T1 and T to the line.
Full-wave rectify the voltage applied between 2. Reference numerals 15b and 16b are light receiving transistors in the optical coupling element, and together with the Darlington-connected transistors 15c and 16c, ON / OFF is controlled by the direction of the line current flowing through the light emitting diodes 15a and 16a, and the direction of the circuit current (voltage) is directed to the logic circuit 31. Inform.

The connection terminal T between the user circuit 40 and the line based on FIG. 3 below.
The connection control operation with 1, T2 will be described. The logic circuit 31 is connected to the user circuit 40 and the rectified lines 21, 22 via the optical coupling element.
If it is determined that the connection with the
The V _SC to line 22, by outputting a lower voltage than the base voltage transistors 61 and 62 is turned off, turns off the transistors 61 and 62, stopping the user circuit operation current I. Therefore, the connection between the user circuit 40 and the terminals T1 and T2 is disconnected. On the contrary, the logic circuit 31 and the user circuit 40 and the rectified lines 21, 2
If it is determined that the connection with 2 should be made, the logic circuit 31
The control voltage V _SC is added to the base voltage Darlington connected transistors 61 and 62 is turned on for the line 22, and outputs a higher voltage than the voltage drop of the base current I _B and the resistance element 70, Darlington transistors 61 and 62 Is turned on so that the user circuit operating current I flows. Therefore, the user circuit 40 and the connection terminals T1 and T2 of the line are connected.

By the way, since the line current is relatively large when the user circuit 40 is connected to the terminals T1 and T2 (about 10 mA to 50 mA) and extremely small when not connected (about several hundred μA), it fluctuates greatly. Therefore, the detection of the direction of the line current is most severe when the user circuit 40 in which the line current flowing through the light emitting diode in the optical coupling element has an extremely small value is not connected. However, if the current is amplified by using the Darlington connection method shown in FIG. 3, the direction detection operation of the line current can be stably performed even when the line current is extremely small. If necessary, a constant current circuit or a resistor may be connected between the terminals T1 and T2, or a resistor may be connected in parallel to the control circuit to ensure the minimum current value necessary for detecting the line current.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention. Parts in FIG. 4 using the same symbols as in FIG. 3 have the same names and functions as in FIG. In this embodiment, a power storage circuit 32 is added to FIG. The operation is almost the same as that of FIG. 3, but in the present embodiment, the power storage circuit 32 is provided in the control circuit 30. This power supply is generated when the voltage applied between the connection terminals T1 and T2 with the line is reversed. Since the power supply power is held within the instantaneous interruption time, the operation can be further stabilized as compared with the third embodiment. Further, as described in the first embodiment, the current consumption in the logic circuit 31 can be set to an extremely small value,
The power storage circuit 32 also has an advantage that it can be realized with an extremely simple configuration. Specifically, a capacitor may be used, and if necessary, a Zener diode or a diode may be connected in parallel in parallel with the capacitor, or a combination circuit thereof may be connected to limit or stabilize the voltage applied to the logic circuit 31. Good.

As described above, the switching element is the Darlington connection transistor in all of the first, second, third and fourth embodiments.
It is also possible to use a transistor. Since the input impedance of the gate of the FET transistor is extremely high,
The resistor 70 is unnecessary, and the gate current corresponding to the base current I _B can be extremely reduced. Also, the user circuit
40 Inside has a switching function by wiring logic etc.,
A configuration may be considered in which part or all of the state monitoring of the user circuit 40 is left to the user circuit side, and the present invention is applied regardless of the configuration of the user circuit. In this embodiment, the user circuit
The case where there is one 40 is explained, but the user circuit 40
The present invention also includes a configuration in which a plurality of are connected in parallel. In addition, the constant current function can be realized by a high resistance, and can be realized by a simple circuit.

As described above, according to the present invention, by arranging the logic circuit and the user circuit after the line current is rectified, the potential relationship between these circuits can be fixed and the switching element having polarity can be used. Becomes In addition, the voltage applied to both ends of the connection terminal with the line of the terminal device varies greatly depending on whether the user circuit is connected to the line after full-wave rectification or disconnected, although the voltage varies. It is possible to provide a terminal device which absorbs the constant current and has a high resistance of the control circuit with respect to the AC signal, and enables stable control without attenuation of the communication signal. The logic circuit is CMOS
Since the power storage circuit can be configured with a simple circuit such as a constant voltage generating element and a capacitor because the power consumption can be reduced by forming the element, the power supply power can be maintained when the voltage applied to the line is polarized. Furthermore, it is possible to provide a terminal device that consumes less power in an empty state in which the user circuit is disconnected from the line. When the logic circuit is composed of CMOS elements, the voltage value supplied to the logic circuit is
It is not necessary to hold within a certain range (+ 5V ± 5%) like L), and the voltage value in each terminal device may be slightly different, and ripples may exist, which is very economical. It is possible to provide various terminal devices.

In addition, the rectifying element of the line current is also used as the issuing diode in the optocoupler used to detect the direction of the line current. It is possible to provide an economical terminal device that can be separated and operates stably.

[Brief description of drawings]

1 to 4 are circuit diagrams showing first to fourth embodiments of the present invention, respectively. 11 to 14: diode element, 15a, 16a: light emitting diode in the optical coupling element, 15b, 16b: light receiving transistor in the optical coupling element, 15
c, 16c: Transistor, 21, 22: Line after rectification, 23: Terminal T1
Monitoring line, 24: terminal T2 monitoring line, 25: user circuit 40 monitoring line, 30: control circuit, 31: logic circuit, 32: power storage circuit, 40:
User circuit, 50: constant current element, 61, 62: NPN transistor,
70: resistive element, T1, T2: connection terminals of the circuit, V _SC: control voltage, I _B: The base current, I: user circuit operating current.

Claims (3)

[Claims] 1. A terminal device which receives a voltage supply from a line, which is connected in series to a full-wave rectification circuit connected to both ends of the line and rectifying the line current, and a user circuit which is supplied with power from the rectification circuit, A switching element that opens and closes the power supply to the user circuit, a constant current conversion unit that makes the output current from the rectifier circuit a constant value, and a current is supplied from the constant current unit to check the state of the line and A terminal device, comprising: a control circuit that monitors a state of a user circuit and that generates a control voltage that controls opening and closing of the switching element according to these states. 2. The full-wave rectifier circuit has a light emitting diode in an optical coupling element, and the control circuit has a light receiving element in the optical coupling element. The terminal device described. 3. The terminal device according to claim 1, wherein the control device includes power storage means.