JP2001119732A - Subscriber circuit feeding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subscriber circuit feeding system capable of feeding power by switching an analog terminal system to/from a digital terminal system with an economical configuration. SOLUTION: The feed control is switched by an analog/digital switching control signal and in the case of the analog terminal system, a VCE (voltage between collector and emitter) of an output transistor of the feeding circuit is measured to control a DC-DC converter, and in the case of the digital terminal system, measuring a current flowing to a subscriber line controls the DC-DC converter. Thus, the feeding in both systems can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber circuit power supply system, and more particularly to a subscriber circuit power supply system using a DC-DC converter capable of supplying power in both an analog terminal system and a digital terminal system.

[0002]

2. Description of the Related Art Power supply methods for subscriber terminals such as telephones include:
There are an analog terminal system and a digital terminal system. Conventionally, analog terminal power supply and digital terminal power supply have been realized using different circuits because required power supply characteristics are significantly different. Next, each power supply method will be described.

FIG. 2 shows a block diagram of a power supply circuit in the analog terminal system. The power supply 1 is connected to the DC-DC converter 9 and supplies power to the power supply circuit 2. An output transistor 3 (3a, 3b) is connected to the power supply circuit 2,
The output is connected to a current / voltage detection circuit 7 for detecting the current flowing through the subscriber line and the voltage between the subscriber lines.

The output of the current / voltage conversion circuit 7 is D
It is input to the power supply controller 6 that controls the C-DC converter 9. The output of the feed circuit 2 is a subscriber line resistance 12
(12a, 12b), it connects to the subscriber terminal 11. Let the value of the subscriber line resistance 12 be RL.

The power supply circuit 2 has a difference between the output voltage Vout of the DC-DC converter 9 and the voltage drop of the subscriber line load (the product of the current IL flowing through the subscriber line and the value RL of the subscriber line resistance 12). Voltage drop (Vout-IL / RL)
Occurs.

However, the power supply circuit 2 is constituted by an electronic circuit, and does not necessarily require a large voltage drop.
It is sufficient to supply a minimum voltage drop (VCEM) such that the output transistor 3 does not saturate (Vout = RL ·
IL + VCEM).

The result of detection by the current / voltage detection circuit 7 is input to the power supply control controller 6 to control the output of the DC-DC converter. These control operations are described in JP-A-57-12.
No. 4,962, and detailed description is omitted.

Next, power supply characteristics are shown in FIG. The current IL flowing through the subscriber circuit in the analog terminal type power supply is represented by the following equation.

IL = VBB / (RL + Rin) where VBB is a power supply voltage, RL is a subscriber line resistance, and R
in is the internal resistance of the power supply circuit, and generally VBB = −
48V, RL = 0 to 1720Ω, and Rin = 440Ω.

FIG. 4 shows a block diagram of a power supply circuit in the digital terminal system. The power supply 1 is connected to the DC-DC converter 9, and the current detection circuit 13 connected to the output of the DC-DC converter 9 outputs the detection output to the power supply controller 6.
To enter. The power supply controller 6 controls the DC-DC converter so that the current value flowing through the subscriber terminal 11 becomes a constant current value (for example, 39 mA). FIG. 5 shows the power supply characteristics.

[0011]

As shown in FIGS. 3 and 5, the analog terminal system requires a constant resistance power supply characteristic, and the digital terminal system requires a constant current power supply characteristic. Providing independent circuits for each of the power supply of the analog terminal system and the digital terminal system is disadvantageous in terms of reduction in mounting area and economy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a subscriber circuit power supply system capable of realizing both an analog terminal system and a digital terminal system in which the mounting area is reduced in size and economical.

[0013]

An object of the present invention is to share a DC-DC converter between an analog terminal power supply and a digital terminal power supply, and to supply power to a subscriber terminal via a power supply circuit in the case of an analog terminal power supply. However, in the case of the digital terminal type power supply system, the power supply circuit is bypassed, switching control is performed so that power is supplied, and power supply characteristics suitable for each power supply are provided.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 is a block diagram showing an example of a subscriber circuit power supply system according to the present invention. As shown, the power supply 1 is connected to a DC-DC converter 9 and a DC-DC converter
The output of the converter 9 is connected to the current / voltage detection circuit 7. The detection output of the current / voltage detection circuit 7 is input to a power supply controller 6 and the analog / digital switching control signal 5 determines whether power is supplied in an analog terminal system or a digital terminal system, so that desired power supply characteristics are obtained. To control the DC-DC converter 9. The current / voltage detection circuit 7 directly feeds the subscriber line in the case of digital terminal type power supply, and the power supply circuit 2 in the case of analog terminal type power supply.
To the switch 4 (4a, 4b) which is switched to connect to the subscriber line via. The power supply circuit 2 is connected to an output transistor 3 (3a, 3b). The output transistor 3 (3a, 3b) has a VCE (collector-emitter voltage) detection circuit 8 (8a, 8b).
And the detection result is the power supply controller 6
Enter

FIG. 6 shows a block diagram of the power supply controller 6. The power supply control controller 6 includes an output of the current / voltage conversion unit 15 that converts the current detection result of the current / voltage detection circuit 7 connected to the output of the DC-DC converter 9 into a voltage, and an output of the current / voltage detection circuit 7. A maximum value selection circuit 16 which compares the outputs of the voltage detectors and selects and outputs a larger value.
And the output of the voltage detection unit of the current / voltage detection circuit 7 and the output of the VCE detection circuit 8 for detecting the VCE of the output transistors 3a and 3b of the power supply circuit 2 in FIG. 1 to select and output a small value. According to the minimum value selection circuit 17 and the analog / digital control signal 5, the output of the maximum value selection circuit 16 is supplied in the case of the digital terminal type power supply, and the output of the minimum value comparison circuit 17 is supplied in the case of the analog terminal type power supply. The output of the power supply control controller 6 is input to the DC-DC converter 9 by an error amplifier 18 having a reference voltage Vref.

FIG. 7 shows an example of an embodiment of the DC-DC converter 9. The DC-DC converter 9 is a PW that outputs the output of the power supply control controller 6 after pulse width modulation.
An M generating circuit 19, a transistor 21 for receiving and switching the output of the PWM generating circuit 19, and one of the transistors 21 is connected to a primary winding of a switching transformer 22, and a secondary winding output of the switching transformer is rectified. Is connected to a diode 23 and a capacitor 24, and is output via a filter constituted by a coil 25 and a capacitor 26.

Next, referring to FIGS. 1, 6 and 7, a description will be given of the power supply mechanism in the digital terminal system and the analog terminal system.

First, digital power supply will be described. In FIG. 1, the analog / digital switching control signal 5
Sends a signal for the digital terminal system, and switches the changeover switch 4 (4a, 4b) to the D side. In the case of the digital terminal system, the current detecting section of the current / voltage detecting circuit 7 detects the current flowing through the subscriber line, and the voltage detecting section detects the voltage generated between the subscriber lines. The current detected by the current detection unit of the current / voltage detection circuit 7 is converted into a voltage by the current / voltage conversion unit 15 shown in FIG. Let the detected value be Vid. The detected value detected by the voltage detecting section of the current / voltage detecting circuit 7 is represented by V
vd. Angle characteristics of the power supply characteristics shown in FIG. 5 (IL = 3
Adjustment is made so that Vid = Vvd when 9 mA, VL = 60 V). Constant current region (IL = 39 mA), that is, 0
When <VL <60V, Vvd <Vid, and the maximum value selection circuit 16 selects Vid. Vid is input to the error amplifier 18 and outputs an error from Vref to the DC-DC converter 9. Here, when Vid <Vref, that is, when the current value is smaller than a desired value (for example, 39 mA), the output from the error amplifier 18 is received and P
The WM generation circuit 19 increases the output of the DC-DC converter 9 by increasing the on-time of the transistor 21, and conversely, when Vid> Vref, the transistor 2
A constant current characteristic is realized by reducing the output of the DC-DC converter 9 by shortening the on-time of 1.
In addition, a constant voltage region (VL = 60 V), that is, 0 <IL <3
At 9 mA, Vvd> Vid, so the maximum value selection circuit 16 shown in FIG. 6 selects Vvd. The DC-DC converter 9 realizes the constant voltage characteristic in the same manner as when Vid is selected.

Next, an analog terminal type power supply will be described. First, in FIG. 1, when the analog / digital switching control signal 5 sends out a signal for using the analog terminal system, the changeover switches 4a and 4b are switched to the A side. In the case of the analog terminal system, the output of the DC-DC converter 9 is connected to the power supply circuit 2. In addition, it is used as a non-floating circuit by being grounded to VBB or ground by a ground switch. Output transistors 3a, 3 of the power supply circuit 2
The detection result VCE of the VCE detection circuits 8a and 8b for detecting the VCE of b and the output Vvd of the voltage detection unit of the current / voltage detection circuit 7 are input to the minimum value selection circuit 17 shown in FIG. The signal is input to the error amplifier 18. VCE <V
In the case of vd, in other words, if the load resistance on the subscriber line side is large, the value of VCE is selected, and the minimum VCE value (referred to as VCEM) required for the transistor to operate
Is input to the error amplifier 18 as Vref. The output of the error amplifier 18 is input to the DC-DC converter 9 and is controlled so that VCE = VCEM. (DC-DC
The operation of converter 9 is the same as that of the digital terminal system. ) When VCE> Vvd, in other words, when the load resistance on the subscriber line side is small, the output voltage from the DC-DC converter becomes low, and the power supply circuit 2 may not operate. In this case, the output of the voltage detector of the current / voltage detector 7 is selected by the minimum value selector 17 so that
This is a subscriber circuit power supply control method that can control the voltage required for the operation of the power supply circuit 2 to be generated from the output of the DC-DC converter 9.

[0021]

As described above, the subscriber circuit power supply system according to the present invention uses one DC-DC converter instead of the conventional one in which the power supply of the analog terminal system and the power supply of the digital terminal system are realized by separate circuits. Can be realized by
It is possible to provide an economical subscriber circuit power supply system with low power consumption and mounting area.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional analog terminal type power supply circuit.

FIG. 3 shows power supply characteristics of a conventional analog terminal system.

FIG. 4 is a block diagram of a power supply circuit of a conventional digital terminal system.

FIG. 5 shows a power supply characteristic of a conventional digital terminal system.

FIG. 6 is a block diagram of a power supply control controller.

FIG. 7 is a circuit diagram showing an embodiment of a DC-DC converter.

[Explanation of symbols]

 1: power supply 3: output transistor 4: analog / digital switch 10: conventional analog terminal type power supply block 11: subscriber terminal 12: subscriber line resistance 14: conventional digital terminal type power supply block 21: transistor 22: switching transformer 23: Diode 24: Capacitor 25: Coil 26: Capacitor

Continued on the front page (72) Inventor Kaoru Arita 5-22-1, Kamimizuhoncho, Kodaira-shi, Tokyo F-term in Hitachi Super LSI Systems, Ltd. (reference) 5K037 AA12 AB01 AC05 AD01 AD04 BA01 BA03 DA04 5K050 AA19 BB06 BB11 BB12 DD21 DD30 EE02 FF06 FF15 FF17 FF19 GG02 GG12

Claims (3)

[Claims] In a subscriber circuit power supply system for supplying power to a subscriber terminal such as a telephone, a DC-connected power supply is connected.
A DC converter, a current / voltage detection circuit connected to an output side of the DC-DC converter and detecting an output current / voltage, a power supply circuit for supplying power to the subscriber terminal,
A power supply controller connected to a DC converter and the current / voltage detection circuit for controlling power supply characteristics of the converter, and a power supply controller provided between the output of the current / voltage detection circuit and the power supply circuit; A switch unit that switches between an analog terminal power supply system side that guides the output of the detection circuit to the power supply circuit and a digital terminal power supply system side that bypasses the power supply circuit and guides the subscriber terminal; and the switch unit and the power supply control controller. And a control unit for controlling power supply to the subscriber to one of an analog terminal power supply system side and a digital terminal power supply system side, wherein when the switch unit is switched to the analog terminal power supply system side, constant resistance power supply is performed. DC-DC converter so as to have the characteristics of constant current power supply when switching to the digital terminal power supply system side. SLIC power supply system the data has been characterized by being configured to control with at the feeding controller. An output transistor provided on an output side of the power supply circuit, and for the analog terminal type power supply, a voltage between a collector and an emitter of the output transistor of the power supply circuit is detected; 2. The subscriber circuit power supply system according to claim 1, wherein said DC-DC converter is controlled via a power supply, and a power supply voltage for supplying said collector-emitter voltage required for power supply is supplied to said power supply circuit. 3. In the case of the digital terminal type power supply, a current flowing through a subscriber line is detected by the current / voltage detection circuit, and the detected output is supplied to the D terminal via the power supply control controller.
2. The subscriber circuit power supply system according to claim 1, wherein a C-DC converter is controlled to realize the constant current power supply characteristic.