JPH05308443A - Feeding circuit for subscriber system transmitter - Google Patents

Abstract

PURPOSE:To quicken the response when a loop current is turned on/off in a way of a pulse by adopting the specific circuit configuration. CONSTITUTION:A rapid charging circuit 10 charges quickly a capacitor C of a CR filter FLT when the circuit 10 monitors a loop current monitor voltage VRDC to detect off-hook operation of a telephone set. When a rapid discharge circuit 20 monitors a difference between the loop current monitor voltage VRDC and a voltage across the capacitor C of the CR filter FLT charged by the rapid charging circuit 10 and detects the on-hook of the telephone set, the circuit 20 discharges forcibly and rapidly the voltage charged across the capacitor C. The CR filter FLT eliminates an AC component superimposed on an on-hook voltage and an off-hook voltage and eliminates a delay of response due to the changeover (by using a timing pulse) between the on-hook voltage and the off-hook voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feeder circuit for a subscriber transmission device, and more particularly to a feeder circuit for a subscriber line interface of a subscriber transmission device.

[0002] With the recent miniaturization of transmission devices, there is a demand for the LSI of the power feeding circuit of the subscriber transmission device. For this reason, various SLIC-LSIs have been provided.
When the IC detects the dial pulse by the power supply current, it is necessary to smooth the AC component, and such a power supply circuit has a function of supplying a constant DC loop current to the telephone and also has an AC component in the loop current. A CR filter to remove is needed.

[0003]

2. Description of the Related Art FIG. 8 shows a CR connected to a telephone TE for supplying a constant loop current to the telephone TE at the same time.
The feeder circuit BSH provided with the filter is shown, and the off / on hook operation from the subscriber (telephone TE) is performed by opening / closing the relay switch SW of the telephone TE, but the terminal voltage of this telephone TE. That is, the tip (TIP) -ring voltage is applied to the power supply circuit BSH during off-hook or on-hook.

In the power supply circuit BSH, the tip ring voltage is constantly monitored by the differential amplifier 11, and the input signal of the differential amplifier 11 is on the ring side when the relay switch SW is open and on hook. At 48V, the chip side becomes 0V and the relay switch SW closes off.
When hooked, the ring side is -4 due to the resistance R of the telephone TE.
The absolute value decreases from 8V, and it is 0V on the chip side. Therefore, the difference between the ring side voltage and the chip side voltage is output from the differential amplifier 11.

From the output voltage of the differential amplifier 11, it is possible to recognize the off / on hook operation of the subscriber.
Its output voltage via the arithmetic circuit 12, the output terminal RDC of the feeder circuit BSH, as shown in FIG. 9, at the time of on-hook by applying 0V, the (-V _P in the illustrated example) V _P at the time of off hook Apply.

However, the signal appearing at the output terminal RDC is shown in FIG.
As shown in Fig. 3, not only the DC loop current component but also the audio signal (this is
The analog (alternating current) component of (transmitted to the EC) also becomes the superimposed signal V _S. Therefore, from the power supply circuit BSH to the telephone set T
In order to give a constant loop current to E, control must be performed based on the signal component from which the above analog component has been removed.

Therefore, the output signal of the power supply circuit BSH is sent to the CR filter FLT which is composed of the resistors R _{1 and} R ₂ and the capacitor C, and the analog component is removed by the capacitor C therein, and the resistor R _1, The loop current value is determined by R _{2 and} applied to the I / V conversion circuit 15, so that the I / V conversion circuit 15 controls the constant current sources 13 and 14. As a result, 1000V from the constant current sources 13 and 14
A constant current of _P / (R ₁ + R ₂ ) is sent from the ring side to the chip side via the telephone TE.

[0008]

However, when a dial pulse is applied from the subscriber, the DC loop current signal is pulsed on / off (on-hook operation-off-hook operation) as shown in FIG. So CR filter FL
There is a problem in that the tip ring voltage has a delayed response due to the time constant of the capacitor C and the resistor R _{1 of} T, which causes malfunction.

Therefore, the present invention provides a loop current in a power supply circuit of a subscriber transmission apparatus having a CR filter for supplying a constant DC loop current to a telephone and eliminating an AC component in a monitoring voltage of the loop current. The purpose is to speed up the response when the pulse turns on and off.

[0010]

In order to achieve the above-mentioned object, a power supply circuit of a subscriber transmission apparatus according to the present invention is shown in FIG.
In principle, the CR filter FLT is
And a resistor R ₁ for smoothing an AC component, the loop current monitoring voltage V _RDC is monitored, and when the off-hook operation of the telephone is detected, the capacitor C of the CR filter FLT is rapidly charged. Circuit 10 for monitoring the voltage difference between the loop current monitoring voltage V _RDC and the charging voltage of the capacitor C, and when the on-hook operation of the telephone is detected, the charging voltage of the capacitor C is forcibly increased rapidly. And a circuit 20 for discharging.

Further, according to the present invention, as shown in FIG. 1, the rapid charging circuit 10 has a constant positive or negative polarity depending on whether the loop current monitoring voltage V _RDC is larger or smaller than the reference voltage V ₁ . A charging voltage detection circuit that outputs a voltage signal and the loop current monitoring voltage V _RDC are the reference voltage V ₁
A differentiating circuit that generates a trigger signal only during an off-hook operation that changes below, a switch circuit that is turned on by the trigger signal, and a charging voltage for the capacitor C without a resistor while the switch circuit is on. And a charging voltage supply circuit that supplies the charging voltage V _RDC and the charging voltage V _{RDC for the} loop current monitoring voltage V _RDC and the capacitor C.
_The voltage difference with _C is monitored, and the loop current monitoring voltage V
It is composed of a discharge voltage detector that detects a voltage change accompanying the on-hook operation of _RDC , and a switch circuit that is turned on by an output signal of the discharge voltage detector and forcibly discharges the charging voltage of the capacitor C. be able to.

[0012]

In FIG. 1, according to the present invention, a quick charging circuit 10 is provided.
_Turns off the telephone by monitoring the loop current monitoring voltage _VRDC.
When the hook operation is detected, the capacitor C of the CR filter FLT is rapidly charged, and the quick discharge circuit 20 monitors the difference voltage between the loop current monitoring voltage V _RDC and the voltage across the capacitor C charged by the quick charging circuit 10. When the on-hook operation of the telephone is detected, the charging voltage of the capacitor C is forcibly and rapidly discharged.

As a result, the CR filter FLT shown in FIG.
On hook voltage, as shown in the on-hook to remove the AC component V _S to be superimposed on (0V) and the off-hook voltage (V _P) - switching between off-hook (Timing Pulse) It is possible to eliminate the response delay due to (see FIG. 7).

Further, the operation when the quick charge circuit 10 and the quick discharge circuit 20 in the present invention are more specifically configured as described above will be described below with reference to FIGS.

First, the capacitor C of the CR filter FLT
In the charging mode, the quick charging circuit 10 operates, and the loop voltage monitoring voltage V _RDC is monitored by the charging voltage detector therein, and the loop current is compared with the reference voltage V ₁ (see FIGS. 1 and 2). When the monitoring voltage V _RDC is V _RDC > V ₁ , -V ₂ is sent to the differentiating circuit, and when V _RDC <V ₁ , + V ₂ is sent to the differentiating circuit (see FIG. 3).

In the differentiating circuit, the loop current monitoring voltage V
_{When the RDC} changes to the reference voltage V ₁ or less (in the direction of charging the capacitor C), the output signal V ₃ changes to + V ₂ → −V ₂ (that is, the off-hook operation). A positive differential voltage appears, which serves as a trigger signal for turning on the switch circuit. When the switch circuit turns on, the voltage V stored in the charging voltage supply circuit
₄ appears as the terminal voltage V _C of the capacitor C. In this case, since there is no resistor in the middle, the capacitor C
Is charged rapidly.

On the other hand, in the mode for discharging the capacitor C, the rapid discharge circuit 20 operates, and first, the discharge voltage detector detects the difference voltage _VRDC between the loop current monitoring voltage and the capacitor C.
-V _C is monitored, and when the loop current monitoring voltage V _RDC changes from V _{P to} 0 V as shown in FIG. 3 (that is, when the on-hook operation is performed), V _{C is} caused by a transient response.
Since <V _RDC , it is possible to forcibly discharge the charge charged in the capacitor C by turning on the switch circuit at that time.

[0018]

FIG. 5 shows an embodiment of a power supply circuit of a subscriber transmission apparatus according to the present invention. In this embodiment, FIG.
As shown in the waveform diagram of No. 3, when the loop current monitoring voltage V _RDC from the power supply circuit BSH (see FIG. 8) is off hook, V
An example of the circuit when _p = -2.5 V is shown, and
77.5K as the resistance R ₁ that constitutes the CR filter FLT
Ω, capacitor C 2.2 μF, resistance R ₂ 30K
Ω is used.

Further, in the rapid charging circuit 10, a comparator is used as the charging voltage detector, the loop current monitoring voltage V _RDC is input to its inverting input terminal, and -5 V is connected to the resistor r1 at its non-inverting input terminal. The reference voltage V ₁ obtained by dividing with r2 is input. Furthermore, a well-known combination of a capacitor C1 for inputting the output signal of the comparator and a resistor r3 is used as the differentiating circuit.
0.033 μF and 56KΩ are used as the resistance r3. Furthermore, a MOS-FET that inputs the terminal voltage of the resistor r3 to its gate is used as a switch circuit.
At the source terminal S of the resistor r that constitutes the charging voltage supply circuit
The voltage V ₄ obtained by dividing the voltage -5V is given by 4 (for example, 2 KΩ) and r5 (for example, 200 Ω), and the drain terminal D becomes the charging voltage V _{C of the} capacitor C.

Furthermore, in the rapid discharge circuit 20, a comparator is used as a discharge voltage detector, and the output signal of this comparator is a MOS circuit which constitutes a switch circuit.
-Given to the gate of the FET. The source terminal S-drain terminal D of the MOS-FET is connected across the resistor R ₁ via the resistor r6 (300Ω).

In the operation of such an embodiment, first, when the on-hook changes to the off-hook as shown in FIG. 6, the loop current monitoring voltage V _RDC is 0 V → −2.5.
It changes to V, but a comparator monitoring the loop current monitoring voltage V _RDC is, V _RDC reference voltage V ₁ = -1.16V
When it becomes the following, it changes from + 5V to -5V (see FIG. 3).

Only while the positive differential voltage V ₂ output by the output voltage of the comparator passing through the differentiating circuit exceeds the operating voltage of the MOS-FET, M
The OS-FET turns on, and the voltage V _{4 of the} charging voltage supply circuit
= -0.45 V is applied to the terminal voltage V _C of the capacitor C, and as shown in FIG. 7, rapid charging (solid line) is performed unlike the conventional case (dotted line). The reference voltage V ₁ is selected so as not to be detected by the AC signal V _S at the time of off-hook (see FIG. 6), and the charging voltage V ₄ is set to V ₄ in order to prevent discharge due to overcharge applied to the capacitor C. The value is set to a potential shallower than the steady voltage applied to the capacitor C during the pulse operation, that is, | V ₄ | <| V _P · R ₂ / (R ₁ + R ₂ ) |. That is, −
2.5V ・ 30KΩ / (77.5KΩ + 30KΩ) ＝-0.70V It is selected as a shallower potential.

The next time changes from off-hook to on-hook, between the loop current monitoring voltage V _{RD C} varies in -2.5 V → 0V, becomes V _C <V _RDC by transient response, V
_The comparator monitoring _RDC- V _C is + 5V
Send to the gate of MOS-FET to turn on MOS-FET. At this time, the resistor r6 is the resistor R ₁ of the CR filter FLT.
Is using 300Ω which has a relation of R ₁ >> r6,
Again, as shown in FIG. 7, the charge stored in the capacitor C can be forcibly discharged.

[0024]

As described above, according to the feeder circuit of the subscriber transmission apparatus of the present invention, the loop current monitoring voltage is provided between both ends of the resistor which constitutes the CR filter and smoothes the AC component. A circuit that rapidly charges the CR filter capacitor when it detects the off-hook operation of the telephone and monitors the difference voltage between the loop current monitoring voltage and the charging voltage of the capacitor to monitor the on-hook operation of the telephone. Since it is configured by a circuit for forcibly and rapidly discharging the charging voltage of the capacitor when detected, it becomes possible to give a pulse signal from the telephone as a waveform for loop current control without delay by the CR filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing in principle the configuration of a power supply circuit of a subscriber transmission device according to the present invention.

FIG. 2 is a waveform diagram of a loop current monitoring voltage in the power supply circuit of the subscriber transmission device according to the present invention.

FIG. 3 is an operation time chart diagram during charging in the power supply circuit of the subscriber transmission device according to the present invention.

FIG. 4 is an operation time chart diagram at the time of discharging in the power supply circuit of the subscriber transmission device according to the present invention.

FIG. 5 is a diagram showing an embodiment of a power supply circuit of a subscriber transmission device according to the present invention.

FIG. 6 is a waveform diagram showing an example of a loop current monitoring voltage in the power supply circuit of the subscriber transmission device according to the present invention.

FIG. 7 is a waveform diagram of a loop current control signal provided by a power supply circuit of the subscriber transmission device according to the present invention.

FIG. 8 is a circuit diagram showing a conventional example.

FIG. 9 is a waveform diagram of a loop current monitoring voltage for explaining the operation of the conventional example.

FIG. 10 is an operation waveform diagram of the telephone.

[Explanation of symbols]

BSH feeder circuit FLT CR filter C capacitors R _1, R ₂ resistor 10 rapid charging circuit 20 the rapid discharge circuit charging voltage detector differentiating circuit, in the switch circuit charging voltage supply circuit discharge voltage detector V _RDC loop current monitoring voltage diagram, the same reference numerals Indicates the same or a corresponding portion.

Claims (2)

[Claims] 1. A power supply circuit of a subscriber transmission apparatus having a CR filter (FLT) for supplying a constant DC loop current to a telephone and removing an AC component of a monitoring voltage ( _VRDC ) of the loop current. In the off-hook of the telephone, the loop current monitoring voltage ( _VRDC ) is monitored across the resistor (R ₁ ) that constitutes the CR filter (FLT) and smoothes the AC component. A circuit (10) for rapidly charging the capacitor (C) of the CR filter (FLT) when an operation is detected, and a voltage difference between the loop current monitoring voltage ( _VRDC ) and the charging voltage of the capacitor (C) is monitored. And a circuit (20) for forcibly and rapidly discharging the charging voltage of the capacitor (C) when the on-hook operation of the telephone is detected, and a power supply for a subscriber transmission device characterized by the following: circuit. 2. The quick charging circuit (10) is provided with a reference voltage (V ₁ ).
To the reference voltage, the charging voltage detection circuit () that outputs a positive or negative constant voltage signal depending on whether the loop current monitoring voltage (V _RDC ) is large or small, and the loop current monitoring voltage (V _RDC ) are the reference voltage. OFF that changes below the voltage (V ₁ )
A differentiating circuit () that generates a trigger signal only when hooked, a switch circuit () that is turned on by the trigger signal, and a capacitor (C) without a resistor while the switch circuit () is on. is composed out with the charging voltage supply circuit for applying a charging voltage (), the sudden speed discharge circuit (20), the loop current monitoring voltage charging voltage (V _C) and of (V _RDC) and the capacitor (C) A differential voltage is monitored, and a discharge voltage detector () that detects a voltage change accompanying the on-hook operation of the loop current monitoring voltage ( _VRDC ) and an ON signal by an output signal of the discharge voltage detector () 2. The power supply circuit for a subscriber transmission device according to claim 1, further comprising a switch circuit () for forcibly discharging the charging voltage of the capacitor (C).