JP2003298779A - Feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a feeder and reduce its cost. <P>SOLUTION: The feeder mounted on a balanced transmission line for feeding a current to a terminal connected to the balanced transmission line comprises an electronic inductance circuit constituted, as follows. Between input and output terminals, two uncontrolled terminals of a transistor are connected in series to a first resistor, and a second resistor and a capacitor are connected in series. A connecting point of the second resistor and the capacitor is connected to a control terminal of the transistor and also to a current source for determining its DC operating point. The electronic inductance circuit has a switching means for cutting off the capacitor from this circuit when specified pulse signals are transmitted in the circuit. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and is suitable for application to, for example, a power supply circuit of a subscriber circuit for supplying a call current to a subscriber terminal.

[0002]

2. Description of the Related Art Subscriber circuits have come to realize many circuit elements on a semiconductor substrate for the purpose of downsizing and cost reduction. For this reason, there is an electronic inductance circuit described in the following document 1 which does not use a coil as all or a part of the inductance element in the subscriber circuit.

Document 1: Japanese Patent Laid-Open No. 11-340786 The structure of this electronic inductance circuit is shown in FIG.

In FIG. 3, the computerized inductance circuit is composed of an NPN type computerized inductance circuit 13 shown in FIG. 3A and a PNP type computerized inductance circuit 12 shown in FIG. 3B. Here, FIG.
(A) NPN type electronic inductance circuit 13 and FIG.
The transistor type used in the PNP type electronic inductance circuit 12 of (B) is NPN type or PNP type.
Only the type is different, and the other points are the same in configuration and operation.

In the NPN type electronic inductance circuit 13 shown in FIG. 3A, the terminal AI is connected to the collector of the NPN type transistor Tr and one end of the resistor R1, and the emitter of the transistor Tr is connected to one end of the resistor R2. The other end of the resistor R2 is connected to the terminal AO and one end of the capacitor C1. The base of the transistor Tr is the resistor R3.
And a capacitor C2 connected in parallel to the filter. The connection point between the resistor R3 and the other end of the capacitor C2 is the other end of the resistor R1 and the other end of the capacitor C1 and the current source I1.
It is connected to the.

The current direction of the current source I1 is a direction in which a current flows from the connection point of the resistor R1 and the capacitor C1 to the current source I1.

Next, the computerized inductance circuit 13
The direct current (calling current) passing function of is described with reference to FIG. The direct current flows in the order of terminal AI → collector / emitter of NPN transistor → resistor R2 → terminal AO. When the DC operating point of the terminal AI (voltage drop between both terminals AI-AO) is obtained, if the DC current amplification factor hfe of the transistor Tr is sufficiently high and the base current is ignored, the voltage drop of the resistor R1 and Since it is the sum of the voltage drop VBE between the base and the emitter of the transistor Tr and the voltage drop of the resistor R2, it can be expressed by the following equation (1). Here, the voltage drop in the filter including the resistor R3 and the capacitor C2 is ignored.

[0008]     Voltage drop between AI and AO = R1 × I1 + VBE + R2 × IL (1) Next, the AC impedance will be described.

Since the resistance R1 is sufficiently larger than R2 and the hfe of the transistor Tr is sufficiently high, the resistance R1 is
1 can be ignored, and the AC impedance of the constant current source I1 can be ignored sufficiently higher than that of the resistors R1 and R2. Therefore, the AC impedance between AI and AO can be expressed by the following equation (2). Can be expressed as

[0010]   AC impedance between AI and AO = Jω ((1 / gm + R2) × C1 × R1) + 1 / gm + R2 (2)   gm: Transconductance of transistor Tr

[0011]

By the way, it is considered that the feeder circuit in the subscriber circuit formed by using the above-mentioned electronic inductance circuit has a structure as shown in FIG.

Here, the terminals AO and AI of the NPN type electronic inductance circuit shown in FIG.
Corresponding to O and AI, terminals BO and BI of the PNP type electronic inductance circuit shown in FIG. 3B are B in FIG.
Corresponds to O and BI.

In FIG. 2, normally, when supplying a call current to a subscriber terminal, the subscriber power supply 16 must have a high AC differential impedance with respect to the AC transmission circuit 8 in order to ensure AC characteristics. Therefore, a high inductance element is required.

Further, since this inductance element requires a large inductance value, the component shape becomes large with a simple inductance and the mounting area becomes strict. Therefore, a transistor, a resistor, and a capacitor are combined and an electronic inductance circuit as shown in FIG. 3 is used.

In the circuit shown in FIG. 2, the subscriber power supply 16 → current / voltage monitor circuit 15 → BI terminal of the PNP type electronic inductance circuit 12 → BO terminal → subscriber side → NPN type electronic inductance circuit. 13 AI terminal →
A call current flows through the route of AO terminal → current / voltage monitor circuit 15 → subscriber power supply 16. Here, the subscriber power supply 16 has a high impedance with respect to the AC signal handled by the AC transmission circuit 8 as shown in the above equation (2).

When a pulse signal such as a dial path (hereinafter referred to as "DP") is applied from the subscriber side, the detection of this pulse signal is usually detected by the current / voltage monitor circuit 15, and the detection is performed. The resulting output signal is the signal processing circuit 14
At, the signal is processed and sent to a host device (not shown).
However, if the computerized inductance circuit is left operating, charging and discharging of the capacitor C1 shown in FIG. 3 causes delay and distortion in detection, making it impossible to send an accurate signal to the host device. Therefore, when a pulse signal such as DP is applied, the delay and distortion can be eliminated by short-circuiting the electronic inductance circuits 12 and 13 with the short switches 10 and 11.

However, the short switches 10 and 1
In the subscriber line to which 1 is connected, a large current (maximum of about 130 mA even in a normal state as described later) flows,
Since a high voltage (for example, about 200 V) can be applied,
The short switches 10 and 11 located on the power supply route to the subscriber line are required to have electrical performance capable of withstanding such a large current and a high voltage and stably operating.

The parts that can meet this requirement are:
In practice, it is limited to special switch parts with high rated values. Examples of such special parts include some semiconductor switches and mechanical relays.

However, the semiconductor switch is expensive, and the mechanical relay has a large shape, so that in a subscriber circuit which is required to be miniaturized and multifunctional, if the number is large, the mounting area impact is too large. However, there is a drawback that it is difficult to meet the demand for miniaturization and multi-functionality.

Therefore, it is required to reduce the size and cost of the power supply circuit itself.

[0021]

In order to solve such a problem, according to the present invention, an input terminal and an output are provided in a power supply device arranged on a balanced transmission line and supplying a current to a terminal connected on the balanced transmission. A terminal, between the input terminal and the output terminal, the two non-controlled ends of the transistor and the first
And the second resistor and the capacitor are connected in series, and the connection point of the second resistor and the capacitor is connected to the control end of the transistor and the DC operating point. The computerized inductance circuit is also connected to a current source for determining, and when the computerized inductance circuit transmits a predetermined pulsed signal in the circuit, a disconnecting operation for disconnecting the capacitor from the circuit is performed. It is characterized in that it is provided with disconnection switch means for performing.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION (A) Embodiment Hereinafter, an embodiment of a power feeding device according to the present invention will be described.

The features common to the first to fourth embodiments are as follows.
By reducing the number of special switch parts corresponding to the element short-circuiting switches 10 and 11 described above, it is possible to provide a power supply circuit that can easily meet the demands for downsizing and multi-functionalization at low cost.

(A-1) Configuration of First Embodiment An example of the overall configuration of a power feeding circuit according to this embodiment is shown in Fig. 1. This power feeding circuit corresponds to the power feeding circuit shown in Fig. 2. .

In FIG. 1, the power feeding circuit is an AC transmission circuit 1, a PNP type electronic inductance circuit 3,
It is provided with an NPN type electronic inductance circuit 4, a signal processing circuit 5, a current / voltage monitor circuit 6, and a subscriber power supply 7.

Of these, the subscriber power supply 7 is connected to the current / voltage monitor circuit 6, and the current / voltage monitor circuit 6 is connected.
The detection result output signal DT of is sent to the signal processing circuit 5.

B of the PNP type electronic inductance circuit 3
This current / voltage monitor circuit 6 connected to the I terminal and the AO terminal of the NPN type electronic inductance circuit 4 detects the value of the call current IL and outputs the detection result as the detection result output signal DT. Is. When the pulse signal such as DP is applied from the subscriber side, this pulse signal is reflected in the change in the current value of the call current IL,
By inspecting the output signal DT, it is possible to detect the presence or absence of a pulse signal. It is the signal processing circuit 5 that receives the detection result signal DT that performs the inspection.

From the signal processing circuit 5, a control signal CS reflecting the result of the inspection is output to the host device.

The terminals of the PNP-type electronic inductance circuit 3 and the NPN-type electronic inductance circuit 4 are input terminals when "I" is added to the right side of the alphabet, and are added with "O". The thing shows an output terminal.
Therefore, AI and BI are input terminals, and AO and BO
Is an output terminal.

Further, the AC system transmission circuit 1 interposed between the subscriber lines A2 and B2 and the host device 2 is the subscriber line A.
2, a part for transmitting an AC signal between B2 and the upper device 2.

B of the PNP type electronic inductance circuit 3
AI of O terminal and NPN type computerized inductance circuit 4
The terminals are connected to the AC transmission circuit 1 and the subscriber lines A2 and B2.

The NPN type electronic inductance circuit 4
6A shows an example of the circuit configuration of FIG. 6A, and FIG. 6B shows an example of the circuit configuration of the PNP type electronic inductance circuit 3.

Since the inductance values required for the computerized inductance circuits 3 and 4 are considerably large, if the inductance values are simply realized by using a coil, the size is inevitably increased and the mounting becomes difficult. The disadvantage of.

Therefore, in order to avoid such a disadvantage, an active element such as a transistor and an OP amplifier and a passive element such as a capacitor and a resistor are combined to realize an equivalently required inductance value. It is an electronic inductance circuit.

(A-1-1) Configuration example of electronic inductance circuit NPN type electronic inductance circuit 4 shown in FIG. 6 (A)
In, the terminal AI is connected to the collector of the NPN transistor Tr and one end of the resistor R1, the emitter of the transistor Tr is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the terminal AO and the capacitor C1. The base of the transistor Tr is connected to a filter formed by a parallel circuit of a resistor R3 and a capacitor C2.

The connection point between the resistor R3 and the other end of the capacitor C2 is connected to the other end of the resistor R1 and a switch (ON / OF switch) S.
The switch SW1 is connected to the current source I1, and the other end of the switch SW1 is connected to the other end of the capacitor C1.

The current direction of the current source I1 is a direction in which a current flows out from the connection point of the resistor R1 and the capacitor C1 to the current source I1.

The switch SW1 is turned on or off by a control signal from the outside. Specifically, when the DP pulse signal is not applied, it is turned on.

By turning off the switch SW1 when the pulse signal of DP is applied, the capacitor C1 is disconnected from the computerized inductance circuit 4, so that the DP signal is delayed or distorted. Disappears.

The terminals AO and AI of the NPN type electronic inductance circuit 4 shown in FIG. 6A correspond to AO and AI shown in FIG.

On the other hand, the PN of this embodiment shown in FIG.
Compared with the NPN type electronic inductance circuit 4, the P type electronic inductance circuit 3 has a transistor type of N type.
It is provided with a symmetrical configuration in which only PN and PNP are replaced. That is, the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4 have a balanced type circuit configuration.

Therefore, the terminal BO and the terminal BI of the PNP type electronic inductance circuit 3 are the same as those shown in FIG.
Corresponds to BI.

In the above configuration, the power feeding circuit as a whole is 2
Will have two switches (two SW1),
There is no switch that can apply a large current of about 130 mA or a high voltage of about 200 V, and only a small current flows through the two switches SW1 and only a small voltage is applied. Because of this, the circuit does not become large in scale or expensive.

The operation of this embodiment having the above-mentioned structure will be described below.

(A-2) Operation of the First Embodiment First, the operation principle of the NPN type electronic inductance circuit 4 will be described. In the NPN type electronic inductance circuit 4, the direct current (call current) IL is changed to the terminal AI →
NPN transistor Tr collector, emitter → resistor R
It flows in the order of 2 → terminal AO. When the DC operating point of the terminal AI (voltage drop between both terminals AI-AO) is calculated, if the DC current amplification factor hfe of the transistor Tr is sufficiently high and the base current is ignored, the voltage drop of the resistor R1 and the transistor Since it is the sum of the voltage drop VBE between the base and the emitter of Tr and the voltage drop of the resistor R2, it can be expressed by the following equation (3) which is equal to the above equation (1).

Voltage drop between AI and AO = R1 × I1 + VBE + R2 × IL (3) It should be noted that the voltage drop in the filter formed by the resistor R3 and the capacitor C2 is neglected in obtaining the equation (3).

The value of the call current IL dynamically changes within a range of, for example, about 0 to 130 mA depending on the situation. Therefore, the maximum is 130 mA on the subscriber lines A2 and B2.
A large amount of current will flow.

Next, the AC impedance between AI and AO when the switch SW1 is in the ON state is such that the resistor R1 is sufficiently larger than the resistor R2 and the h of the transistor Tr is h.
If fe is sufficiently high, the AC current flowing through the resistor R1 can be ignored, and since the AC impedance of the constant power source I1 is sufficiently higher than that of the resistors R1 and R2, it can be ignored.
Therefore, it can be expressed by the following equation (4) which is equal to the above equation (2).

AC impedance between AI and AO = jω ((1 / gm + R2) × C1 × R1) + 1 / gm + R2 (4) gm: Transconductance of transistor Tr Symmetrical configuration with the NPN type electronic inductance circuit 4 It goes without saying that the PNP type electronic inductance circuit 3 having the same (the values of corresponding constants are also the same) performs the same (symmetrical) operation as the NPN type electronic inductance circuit 4.

Therefore, these NPN type computerized inductance circuit 4 and PNP type computerized inductance circuit 3
The operation of the entire power supply device of FIG. 1 including the above is as follows.

During normal power supply, the subscriber power supply 7 → current / voltage monitor circuit 6 → BI terminal of the PNP type electronic inductance circuit 3 → BO terminal → subscriber side → AI of the NPN type electronic inductance circuit 4 The call current IL flows through the route of terminal → AO terminal → current / voltage monitor circuit 6 → subscriber power supply 7. Here, by further turning on the switch SW1 shown in FIGS. 6A and 6B, the subscriber power supply 7 is handled by the AC transmission circuit 1 as shown in the equation (4). High impedance for AC signals.

Next, when a pulse signal such as a DP signal is applied from the subscriber side, the two switches SW1 are turned off in the power feeding route, so that the charging and discharging of the capacitor C1 disappears. Since the delay and distortion are eliminated, the DP signal and the like can be accurately detected by the current / voltage monitor circuit 6. As a result, the influence of the delay and the distortion is removed from the output signal DT to improve the accuracy, and thus the reliability of the control signal CS supplied from the signal processing circuit 5 to the host device in accordance with the output signal DT is also improved. .

(A-3) Effects of the First Embodiment As described above, according to the present embodiment, the electronic inductance circuit (3 and 4) does not have the configuration shown in FIG. Switch (SW1) to the condenser (C1) of
By disconnecting the computerized inductance circuit from the computerized inductance circuit, charging / discharging of the capacitor (C1) is eliminated even for a pulse signal such as a DP signal, so that accurate detection can be easily performed without delay and distortion. It is possible. In addition, because no special parts with large rated values that can withstand large currents and high voltages are used, the mounting area can be reduced, and the cost and size of the entire power supply circuit (and subscriber circuit) can be reduced. Can be achieved.

Here, a switch (SW) for disconnecting the capacitor (C1) from the computerized inductance circuit.
As described above, 1) does not serve as a route for supplying power to the subscriber line, and does not require a high breakdown voltage or a large current to flow. Therefore, general transistors, MOS-FETs, and other inexpensive and small parts can be used. Can be configured.

(B) Second Embodiment Hereinafter, only differences of the present embodiment from the first embodiment will be described.

The present embodiment provides a preferable implementation example regarding the control method of the switch SW1 which is not always clear in the first embodiment.

(B-1) Configuration and operation of the second embodiment The overall configuration of the power feeding circuit of the present embodiment may be basically the same as that of FIG. 1, but as shown in FIG. A control signal output from the processing circuit 5 (which can be regarded as corresponding to CS in the first embodiment, so in the present embodiment, C
SW1 control signal CS1 is S1).
The difference is that it is supplied to the control input terminal of W1. In this embodiment, the two switches SW1 are connected to the control signal C
Depending on S1, it is turned on or off.

In FIG. 7, the functions of the respective parts and the respective electric signals given the reference numerals corresponding to those of FIGS. 6 and 1 are basically the same as those of the first embodiment.

Therefore, in FIGS. 1 and 7, the DC operation and AC impedance of the computerized inductance circuits 3 and 4 are similar to those of the first embodiment.

When a pulse signal such as a DP signal is applied from the subscriber side, the call current IL fluctuates.
The current / voltage monitor circuit 6 monitors the call current IL, and supplies the call current detection result to the signal processing circuit 5 as a detection result output signal DT1. In the signal processing circuit 5, the call current IL is received according to the received detection result output signal DT1.
When it detects that the current value exceeds the certain threshold value, it turns on the switch SW1, and when it detects that it falls below the threshold value, it sends a control signal (SW1 control command) CS1 that turns off the switch SW1. To do.

That is, when the output signal DT1 of the current / voltage monitor circuit 6 indicates the presence of one pulse signal and the switch SW1 is turned off via the signal processing circuit 5,
During the period in which the 1-pulse signal is detected (that is, the duration of the pulse width of the 1-pulse), the signal processing circuit 5 continues to output the control signal CS1 designating the OFF state of the switch SW1. When the pulse signal is no longer detected, the control signal CS1 designating the ON state is output, and thereafter, the same operation is repeated each time a new pulse signal is detected.

The threshold used by the current / voltage monitor circuit 6 for detecting the pulse signal is, for example, 12 m.
It may be about A.

(B-2) Effect of Second Embodiment As described above, according to this embodiment, the same effect as that of the first embodiment can be obtained.

In addition, in this embodiment, the call current (I
SW1 control signal (CS1) for controlling the switch (SW1) from the signal processing circuit (8) by monitoring L)
Therefore, it is not necessary to receive a control signal from the outside, and the switch (SW1) can be autonomously switched only within the power feeding circuit.

This means that the delay and distortion relating to the pulse signal can be eliminated independently by only the feeding circuit. Further, since it does not depend on an external circuit, it is possible to simplify a specific circuit configuration.

(C) Third Embodiment Hereinafter, only differences of the present embodiment from the first embodiment will be described.

In this embodiment, the OF of the switch SW1 is
Even in the F state, charging (pre-charging) of the capacitor C1 improves the responsiveness of the computerized inductance circuit.

(C-1) Configuration and operation of the third embodiment The entire configuration of the power feeding circuit of this embodiment is different from the internal configuration of the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4. It is similar to FIG.

The PNP type electronic inductance circuit 3
The internal configuration of the NPN type electronic inductance circuit 4 may be that shown in FIG. 4 as an example.

In FIG. 4, the functions of the respective parts and the respective electric signals given the reference numerals corresponding to those of FIGS. 6 and 1 are basically the same as those of the first embodiment.

However, in FIG. 4, in addition to the configuration of the first embodiment, a Zener diode D1 having a function of precharging the capacitor C1 is connected in parallel to the capacitor C1, and the PNP type electronic inductance circuit 3
In the inside of the resistor, one end of the resistor R4 has a Zener diode D
1 is connected to the anode, the capacitor C1 and the switch SW1, and the other end of the resistor R4 is connected to the terminal AO outside the PNP type electronic inductance circuit 3.

In the NPN type electronic inductance circuit 4, one end of the resistor R4 has a cathode of the Zener diode D1, a capacitor C1 and a switch SW.
1 and the other end of the resistor R4 is connected to a terminal BI located outside the NPN type electronic inductance circuit 4.

The potential of the terminal BI is always higher than that of the terminal AO.

1 and 4, the DC operation and AC impedance of the computerized inductance circuits 3 and 4 are the same as in the first embodiment.

Even when a pulse signal such as a DP signal is applied from the subscriber side, the same as in the first embodiment, the current / voltage monitor circuit 6 is turned off by turning off the switch SW1 in FIG. The pulse signal (each pulse that is a constituent of DP) detected by the capacitor C
Since the current / voltage monitor circuit 6 is not affected by the charge / discharge of No. 1, the current / voltage monitor circuit 6 can perform highly accurate detection based on the pulse signal without delay and distortion.

Therefore, the reliability of the control signal CS transmitted to the higher-level device through the signal processing circuit 5 is enhanced.

Further, in this embodiment, PN in FIG.
The capacitor C1 of the P-type computerized inductance circuit 3 is
The charging is performed along the route through the resistor R4 connected to the capacitor C1 to the terminal AO, and the charging voltage is determined by the Zener diode D1. In contrast to this, the capacitor C1 of the NPN type electronic inductance circuit 4 is charged from the terminal BI through the resistor R4, and the charging voltage is determined by the Zener diode D1.

(C-2) Effect of Third Embodiment As described above, according to this embodiment, the same effect as that of the first embodiment can be obtained.

In addition, in this embodiment, the switch (SW
The capacitor (C1) can be charged (precharged) even when 1) is in the OFF state, and the switch (SW
By optimizing the voltage value of the Zener diode (D1) immediately after switching 1) to the ON state, it is possible to more quickly provide the function as the electronic inductance of each electronic inductance circuit (5 and 6). .

Further, since the precharge does not cause the capacitor (C1) to be rapidly charged immediately after the switch (SW1) is switched to the ON state, the rapid voltage fluctuation to the subscriber side is suppressed, and the telephone set Therefore, it is possible to reduce noise and the like heard by the telephone user.

(D) Fourth Embodiment Below, only the points of difference of this embodiment from the first and third embodiments will be explained.

The present embodiment is characterized in that the same effect as that of the third embodiment is obtained only by the internal configuration of each electronic inductance circuit.

(D-1) Configuration and Operation of Fourth Embodiment The entire configuration of the power feeding circuit of this embodiment is exactly the same as that of FIG. 1 except for the internal configuration of each electronic inductance circuit 3, 4.

The internal configuration of the computerized inductance circuits 3 and 4 of the present embodiment may be that shown in FIG. 5 as an example.

In FIG. 5, the functions of the respective parts and the respective electric signals given the reference numerals corresponding to those of FIGS. 6, 1 and 4 are as follows.
Basically, it is the same as the first and third embodiments.

However, in the circuit configuration of FIG. 5 showing the present embodiment, the resistor R4 used in FIG. 4 does not exist, and the current source I2 that does not exist in FIG. 4 exists. The current source I2 is
When the switch SW1 is in the OFF state, it is a current source that contributes to precharge for charging the capacitor C1 inside each of the computerized inductance circuits 3 and 4.

In FIG. 5A, the capacitor C1
Zener diode D1 is connected in parallel with
The cathode of the Zener diode D1 is further connected to the resistor R2 and the terminal BI, and the anode of the Zener diode D1 is also connected to the current source I2 and the switch SW1.
The current direction of the current source I2 is the direction in which current flows from the anode of the capacitor C1 and the Zener diode D1 to the current source I2 in FIG.
In (B), the capacitor C1 and the Zener diode D1
This is the direction in which an electric current is caused to flow into the cathode of.

1 and 5, the DC operation and AC impedance of the computerized inductance circuits 3 and 4 are the same as those in the first embodiment.

Even when a pulse signal such as a DP signal is applied from the subscriber side, it is similar to the first embodiment, and the current / voltage monitor circuit 6 is turned off by turning off the switch SW1 in FIG. Pulse signal (D
Since each pulse of P) is not affected by charging / discharging of the capacitor C1, the current / voltage monitor circuit 6 can perform highly accurate detection based on the pulse signal without delay and distortion.

Therefore, the reliability of the control signal CS transmitted to the host device through the signal processing circuit 5 is enhanced.

Further, in FIG. 5, the capacitor C1
Can be charged by the current source I2 even when the switch SW1 is in the OFF state, and the charging voltage at that time is determined by the Zener voltage of the Zener diode D1.

Therefore, in this embodiment, the switch SW
The capacitor C1 can be charged even when 1 is in the OFF state, and the voltage value of the Zener diode D1 immediately after the switch SW1 is switched to the ON state is optimized, so It is possible to provide the function as a variable inductance faster.

Further, when the switch SW1 is switched to the ON state, the capacitor C1 is not charged abruptly, so that abrupt voltage fluctuations to the subscriber side are suppressed, and the noise heard by the telephone user from the telephone is suppressed. It can be reduced.

(D-2) Effects of Fourth Embodiment As described above, according to this embodiment, the same effects as those of the first embodiment and the same effects as those of the third embodiment are obtained. be able to.

In addition, in this embodiment, it is not necessary to connect the resistance (R4) in the computerized inductance circuit to another computerized inductance circuit as in the third embodiment, so that the degree of freedom in design is increased. .

Further, since the current source (I2) newly added in this embodiment can be easily incorporated in the LSI, the number of parts can be reduced and the mounting area can be reduced.

(E) Other Embodiments In the first to fourth embodiments, the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4 shown in FIG. 1 may be replaced with each other. .

From the viewpoint of downsizing, etc., FIG.
It is preferable to use a semiconductor switch as the switch SW1 in 3, 4, and 5, but a mechanical relay can be used if necessary. In this sense, the present invention can be regarded as increasing the degree of freedom in design.

The internal structure of the computerized inductance circuits in FIGS. 2, 3, 4, and 5 is not limited to the illustrated structure as long as it has a similar effect.

Furthermore, since the features of the second embodiment are not in an exclusive relationship with the other embodiments, the features of the second embodiment can be implemented in the same power supply circuit in combination with the configurations of the other embodiments.

The control of turning the switch SW1 off when the SW1 control signal from the signal processing circuit 8 in the second embodiment exceeds a certain threshold value and turning the switch SW1 on when it falls below the threshold value may be reversed.

The Zener diode D1 shown in FIGS.
Can be replaced with a cascade-connected diode or the like as long as it has a voltage clamp operation.

[0103]

As described above, according to the present invention, it is possible to provide a small-sized and low-priced power supply device.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the overall configuration of a power supply circuit according to a first embodiment.

FIG. 2 is a schematic diagram showing a configuration example of a power supply circuit for explaining a problem to be solved by the invention.

FIG. 3 is a schematic diagram showing a configuration of a conventional computerized inductance circuit.

FIG. 4 is a schematic diagram showing a configuration example of an electronic inductance circuit according to a third embodiment.

FIG. 5 is a schematic diagram showing a configuration example of an electronic inductance circuit according to a fourth embodiment.

FIG. 6 is a schematic diagram showing a configuration example of an electronic inductance circuit according to the first embodiment.

FIG. 7 is a schematic diagram showing a configuration example of an electronic inductance circuit and its periphery according to a second embodiment.

[Explanation of Codes] 1 ... AC system transmission circuit, 2 ... Host device, 3 ... PNP type computerized inductance circuit, 4 ... NPN type computerized inductance circuit, 5 ... Signal processing circuit, 6 ... Current / voltage monitor circuit, 7 … Subscriber power supply, A2, B2… Subscriber line.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Takaya             1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric             Industry Co., Ltd. (72) Inventor Takashi Kato             1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric             Industry Co., Ltd. (72) Inventor Masao Kamio             1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric             Industry Co., Ltd. (72) Inventor Kazuhiko Akiyama             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F term (reference) 5K037 AA14 AB07 AC03 AD01 BA01                       BA06 DA03

Claims (3)

[Claims] 1. A power supply device which is arranged on a balanced transmission line and supplies a current to a terminal connected to the balanced transmission line. The power feeding device has an input terminal and an output terminal, and a transistor is provided between the input terminal and the output terminal. Two non-control ends and a first resistor are connected in series, a second resistor and a capacitor are connected in series, and the connection point of the second resistor and the capacitor controls the transistor. When the computerized inductance circuit transmits a predetermined pulsed signal in the circuit, the computerized inductance circuit is connected to the end and is also connected to a current source for determining a DC operating point. A power supply device comprising disconnection switch means for disconnecting the capacitor from the circuit. 2. The power supply device according to claim 1, wherein a change in a current value flowing through the balanced transmission line is monitored, and the pulsed signal transmitted through the balanced transmission line is detected based on the change in the current value. A power supply device, comprising: a pulse signal detection unit for controlling the cutting operation, and causing the cutting switch unit to perform the cutting operation when the pulse signal detection unit detects a pulsed signal. 3. The power supply device according to claim 1, wherein when the disconnection switch means is performing a disconnection operation,
A power supply device comprising a disconnection charging means for charging the capacitor.