JP4079671B2 - Power supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply apparatus, and is suitably applied to, for example, a power supply circuit of a subscriber circuit that supplies a call current to a subscriber terminal.
[0002]
[Prior art]
Subscriber circuits have come to realize many circuit elements on a semiconductor substrate for miniaturization and cost reduction. For this reason, there is an electronic inductance circuit described in the following document 1 that does not use a coil as all or a part of the inductance elements in the subscriber circuit.
[0003]
Reference 1: Japanese Patent Application Laid-Open No. 11-340786
The configuration of this electronic inductance circuit is shown in FIG.
[0004]
In FIG. 3, the computerized inductance circuit includes an NPN type computerized inductance circuit 13 shown in FIG. 3A and a PNP type computerized inductance circuit 12 shown in FIG. 3B. Here, in the NPN type electronic inductance circuit 13 in FIG. 3A and the PNP type electronic inductance circuit 12 in FIG. 3B, whether the type of transistor used is an NPN type or a PNP type. However, the other points are the same, and the operation is the same.
[0005]
In the NPN type electronic inductance circuit 13 shown in FIG. 3A, the terminal AI is connected to the collector of the NPN 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 is connected to the terminal AO and one end of the capacitor C1. The base of the transistor Tr is connected to a filter composed of 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, the other end of the capacitor C1, and the current source I1.
[0006]
The current direction by the current source I1 is a direction in which current flows out from the connection point of the resistor R1 and the capacitor C1 to the current source I1.
[0007]
Next, the DC current (calling current) passing function of the electronic inductance circuit 13 will be described with reference to FIG. The direct current flows in the order of the terminal AI → the collector and emitter of the NPN transistor → the resistor R2 → the terminal AO. When the DC operating point of the terminal AI (voltage drop between both terminals AI and 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 is Since this is the sum of the voltage drop VBE between the base and emitter of the transistor Tr and the voltage drop across the resistor R2, it can be expressed by the following equation (1). Here, the voltage drop in the filter composed of the resistor R3 and the capacitor C2 is ignored.
[0008]
Voltage drop between AI and AO = R1 × I1 + VBE + R2 × IL (1)
Next, AC impedance will be described.
[0009]
The resistor R1 is sufficiently larger than R2 and the hfe of the transistor Tr is sufficiently high, so that the AC current flowing through the resistor R1 can be ignored, and the AC impedance of the constant current source I1 is sufficiently higher than those of the resistors R1 and R2. Since it can be ignored, the AC impedance between AI and AO can be expressed by the following equation (2).
[0010]
AC impedance between AI and AO
= Jω ((1 / gm + R2) × C1 × R1) + 1 / gm + R2 (2)
gm: mutual conductance of the transistor Tr
[0011]
[Problems to be solved by the invention]
By the way, it is considered that the power supply circuit in the subscriber circuit configured using the above-described electronic inductance circuit has a configuration as shown in FIG.
[0012]
Here, the terminal AO and the terminal AI of the NPN type electronic inductance circuit shown in FIG. 3A correspond to AO and AI of FIG. 2, and the terminal BO and the terminal BO of the PNP type electronic inductance circuit shown in FIG. The terminal BI corresponds to BO and BI in FIG.
[0013]
In FIG. 2, in general, when a call current is supplied to a subscriber terminal, the subscriber power supply 16 must have an AC differential impedance higher than that of the AC transmission circuit 8 in order to ensure AC characteristics. A high inductance element is required.
[0014]
In addition, since this inductance element requires a large inductance value, a simple inductance increases the component shape and the mounting area becomes severe. Therefore, an electronic inductance circuit as shown in FIG. 3 is used by combining transistors, resistors, and capacitors.
[0015]
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 → AI of the NPN type electronic inductance circuit 13 A call current flows in the route of terminal → 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 equation (2).
[0016]
When a pulse signal such as a dial path (hereinafter referred to as “DP”) is applied from the subscriber side, this pulse signal is normally detected by the current / voltage monitor circuit 15 and the detection result is output. The signal is processed by the signal processing circuit 14 and sent to a higher-level device (not shown). However, if the electronic inductance circuit is left operating, the detection and delay of the capacitor C1 shown in FIG. 3 cause delay and distortion, and an accurate signal cannot be sent to the host device. Therefore, when a pulse signal such as DP is applied, delay and distortion can be eliminated by short-circuiting the electronic inductance circuits 12 and 13 by the short switches 10 and 11.
[0017]
However, a high current (for example, about 200 V) flows through the subscriber line to which the short switches 10 and 11 are connected and a high current (for example, about 130 mA at the maximum is normal even when normal) as described later. Therefore, the short switches 10 and 11 located on the power supply route to the subscriber line are required to have electrical performance that can withstand such a large current and high voltage and operate stably. .
[0018]
The parts that can satisfy this requirement are practically limited to special switch parts having a large rated value. Examples of such special parts include some semiconductor switches and mechanical relays.
[0019]
However, the semiconductor switches are expensive, and the mechanical relays are large in shape. In subscriber circuits that require miniaturization and multi-functionality, the large number of subscriber circuits has a large impact on the mounting area, resulting in a reduction in size.・ There was a drawback that it was difficult to meet the demand for multi-functionality.
[0020]
For this reason, it is required to reduce the size and price of the power supply circuit itself.
[0021]
[Means for Solving the Problems]
In order to solve such a problem, in the present invention, in a power feeding device that is arranged on a balanced transmission line and supplies a current to a terminal connected on the balanced transmission, the power supply device has an input terminal and an output terminal. Between the output terminals, the two non-control terminals of the transistor and the first resistor are connected in series, and the second resistor and the capacitor are connected in series, and the second resistor and the capacitor are connected. An electronic inductance circuit having a point connected to the control terminal of the transistor and also connected to a current source for determining a DC operating point is provided, and the electronic inductance circuit has a predetermined pulse shape in the circuit. When transmitting a signal, it is provided with a disconnect switch means for disconnecting the capacitor from the circuit. And a disconnection charging means for charging the capacitor when the disconnect switch means is performing a disconnection operation. It is characterized by that.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
(A) Embodiment
Hereinafter, embodiments of a power feeding device according to the present invention will be described.
[0023]
A feature common to the first to fourth embodiments is that the number of special switch parts corresponding to the above-described element short switches 10 and 11 is reduced to meet the demand for downsizing and multi-functionality at a low price. It is to provide a power feeding circuit that is easy to handle.
[0024]
(A-1) Configuration of the first embodiment
An example of the overall configuration of the power feeding circuit according to this embodiment is shown in FIG. This power supply circuit corresponds to the power supply circuit shown in FIG.
[0025]
In FIG. 1, the power supply circuit includes an AC transmission circuit 1, a PNP type electronic inductance circuit 3, an NPN type electronic inductance circuit 4, a signal processing circuit 5, a current / voltage monitor circuit 6, and a subscriber. A power supply 7 is provided.
[0026]
Among these, the subscriber power supply 7 is connected to the current / voltage monitor circuit 6, and the detection result output signal DT of the current / voltage monitor circuit 6 is sent to the signal processing circuit 5.
[0027]
The current / voltage monitor circuit 6 connected to the BI terminal of the PNP type electronic inductance circuit 3 and the AO terminal of the NPN type electronic inductance circuit 4 detects the value of the call current IL, and detects the detection result. It is a circuit that outputs as a result output signal DT. When a 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, so the presence or absence of the pulse signal is detected by examining the output signal DT. It is possible. The inspection is performed by the signal processing circuit 5 that receives the detection result signal DT.
[0028]
From the signal processing circuit 5, a control signal CS reflecting the result of the inspection is output to the host device.
[0029]
As for each terminal of the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4, an “I” on the right side of the alphabet indicates an input terminal, and an “O” indicates an output. Indicates a terminal. Therefore, AI and BI are input terminals, and AO and BO are output terminals.
[0030]
The AC transmission circuit 1 interposed between the subscriber lines A2 and B2 and the host device 2 is a portion that transmits an AC signal between the subscriber lines A2 and B2 and the host device 2. .
[0031]
The BO terminal of the PNP type electronic inductance circuit 3 and the AI terminal of the NPN type electronic inductance circuit 4 are connected to the AC transmission circuit 1 and the subscriber lines A2 and B2.
[0032]
A circuit configuration example of the NPN electronic inductance circuit 4 is shown in FIG. 6A, and a circuit configuration example of the PNP electronic inductance circuit 3 is shown in FIG. 6B.
[0033]
Since the inductance value required for the electronic inductance circuits 3 and 4 is quite large, if the inductance value is simply realized by using a coil, the shape will inevitably become large and mounting will be difficult, and various disadvantages will occur. Occurs.
[0034]
Therefore, in order to avoid such disadvantages, it is this electronic inductance that realizes the required inductance value equivalently by combining active elements such as transistors and OP amplifiers and passive elements such as capacitors and resistors. Circuit.
[0035]
(A-1-1) Configuration example of an electronic inductance circuit
In the NPN type electronic inductance circuit 4 shown in FIG. 6A, 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 of the resistor R2 The end is connected to the terminal AO and the capacitor C1. The base of the transistor Tr is connected to a filter composed of a parallel circuit of a resistor R3 and a capacitor C2.
[0036]
The connection point of the other end of the resistor R3 and the capacitor C2 is connected to the other end of the resistor R1, the switch (ON / OF switch) SW1, and the current source I1, and the other end of the switch SW1 is connected to the other end of the capacitor C1. ing.
[0037]
The current direction by the current source I1 is a direction in which current flows out from the connection point of the resistor R1 and the capacitor C1 to the current source I1.
[0038]
The switch SW1 is turned on or off by an external control signal. Specifically, when the DP pulse signal is not applied, the signal is turned on.
[0039]
By turning off the switch SW1 when the DP pulse signal is applied, the capacitor C1 is disconnected from the computerized inductance circuit 4, so that the DP signal is not delayed or distorted.
[0040]
Note that 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.
[0041]
On the other hand, the PNP type computerized inductance circuit 3 of this embodiment shown in FIG. 6B has a symmetrical configuration in which the transistor type is replaced with NPN and PNP, compared to the NPN type computerized inductance circuit 4. I have. That is, the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4 have a balanced circuit configuration.
[0042]
Therefore, the terminal BO and the terminal BI of the PNP type electronic inductance circuit 3 correspond to BO and BI in FIG.
[0043]
In the above configuration, the power supply circuit as a whole has two switches (two SW1s). However, there is no switch that can flow a large current of about 130 mA or a high voltage of about 200 V, Since only a small amount of current flows through the two switches SW1 and only a small voltage is applied, the circuit is not enlarged or expensive because of the switch SW1.
[0044]
The operation of the present embodiment having the above configuration will be described below.
[0045]
(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, a direct current (talking current) IL flows in the order of the terminal AI → the collector of the NPN transistor Tr → the emitter → the resistor R2 → the terminal AO. When the DC operating point of the terminal AI (voltage drop between the terminals AI and 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 the transistor Since it is the sum of the voltage drop VBE between the Tr base and the emitter and the voltage drop across the resistor R2, it can be expressed by the following equation (3) equal to the equation (1).
[0046]
Voltage drop between AI and AO = R1 × I1 + VBE + R2 × IL (3)
Note that in obtaining the equation (3), the voltage drop in the filter composed of the resistor R3 and the capacitor C2 is ignored.
[0047]
The value of the call current IL dynamically changes within a range of about 0 to 130 mA, for example, depending on the situation. Therefore, a large current of about 130 mA at maximum flows on the subscriber lines A2 and B2.
[0048]
Next, when the switch SW1 is in the ON state, the AC impedance between AI and AO is sufficiently large compared to R2, and if the hfe of the transistor Tr is sufficiently high, the AC current flowing through the resistor R1 is Since the AC impedance of the constant power source I1 is sufficiently higher than the resistors R1 and R2, it can be ignored. Therefore, it can be expressed by the following equation (4) equal to the equation (2).
[0049]
AC impedance between AI and AO
= Jω ((1 / gm + R2) × C1 × R1) + 1 / gm + R2 (4)
gm: mutual conductance of the transistor Tr
The PNP-type electronic inductance circuit 3 having a symmetric configuration (the corresponding constant values are also the same) as the NPN-type electronic inductance circuit 4 is the same (symmetric) as the NPN-type electronic inductance circuit 4. It is natural to perform the operation.
[0050]
Therefore, the operation of the whole power feeding apparatus of FIG. 1 including these NPN type electronic inductance circuit 4 and PNP type electronic inductance circuit 3 is as follows.
[0051]
During normal power supply, subscriber power supply 7 → current / voltage monitor circuit 6 → BI terminal of PNP type electronic inductance circuit 3 → BO terminal → subscriber side → AI terminal of NPN type electronic inductance circuit 4 → AO The call current IL is passed through the route of the 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 to AC signal.
[0052]
Next, when a pulse signal such as a DP signal is applied from the subscriber side, charging and discharging of the capacitor C1 is eliminated by turning off the two switches SW1 in the power feeding route. Thus, the DP signal and the like can be accurately detected by the current / voltage monitor circuit 6. As a result, the influence of delay and distortion is also removed from the output signal DT and the accuracy is improved, so that the reliability of the control signal CS supplied from the signal processing circuit 5 to the host device according to the output signal DT is also improved. .
[0053]
(A-3) Effects of the first embodiment
As described above, according to the present embodiment, the configuration as shown in FIG. 2 is not adopted, and the capacitor (C1) in the digitized inductance circuit (3 and 4) is converted into the digitized state by the switch (SW1). By separating from the 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. In addition, since no special parts with large rated values that can withstand high voltages can be applied, the mounting area can be reduced, and the overall power supply circuit (and thus the subscriber circuit) can be reduced in price and scale. Can be achieved.
[0054]
Here, as described above, the switch (SW1) for separating the capacitor (C1) from the electronic inductance circuit is not a route for supplying power to the subscriber line, and it is necessary to flow a high breakdown voltage or a large current. Therefore, it can be constituted by inexpensive and small parts such as a general transistor and a MOS-FET.
[0055]
(B) Second embodiment
Below, only the point from which this embodiment is different from 1st Embodiment is demonstrated.
[0056]
The present embodiment provides a preferable implementation example with respect to the control method of the switch SW1, which is not necessarily clear in the first embodiment.
[0057]
(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. 7, a control signal output from the signal processing circuit 5 (the CS of the first embodiment). The SW1 control signal CS1, which is CS1 in this embodiment, is supplied to the control input terminal of the switch SW1. In the present embodiment, the two switches SW1 are turned on or turned off according to the control signal CS1.
[0058]
In FIG. 7, the function of each part and each electric signal to which the reference numerals corresponding to FIG. 6 and FIG.
[0059]
Therefore, in FIG. 1 and FIG. 7, the DC operation and AC impedance of the electronic inductance circuits 3 and 4 are the same as those in the first embodiment.
[0060]
When a pulse signal such as a DP signal is applied from the subscriber side, the call current IL fluctuates. Therefore, the call current IL is monitored by the current / voltage monitor circuit 6, and the call current detection result is detected as a detection result output signal. The signal is supplied to the signal processing circuit 5 as DT1. When the signal processing circuit 5 detects that the current value of the call current IL exceeds a certain threshold value according to the received detection result output signal DT1, the signal processing circuit 5 turns on the switch SW1 and detects that the value is below the threshold value. Then, a control signal (SW1 control house number) CS1 for turning off the switch SW1 is sent.
[0061]
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, the period during which the one pulse signal is detected (that is, When the pulse width of the one pulse lasts>, the signal processing circuit 5 continues to output the control signal CS1 designating the OFF state of the switch SW1, and when the one pulse signal is no longer detected, designates the ON state. After that, the control signal CS1 is output, and thereafter the same operation is repeated every time a new pulse signal is detected.
[0062]
The threshold value used by the current / voltage monitor circuit 6 for detection of the pulse signal may be, for example, about 12 mA.
[0063]
(B-2) Effects of the second embodiment
As described above, according to the present embodiment, it is possible to obtain the same effect as that of the first embodiment.
[0064]
In addition, in the present embodiment, the SW1 control signal (CS1) for controlling the switch (SW1) can be transmitted from the signal processing circuit (8) by monitoring the call current (IL). There is no need to receive a signal, and the switch (SW1) can be switched independently only within the power feeding circuit.
[0065]
This means that it is possible to eliminate the delay and distortion related to the pulse signal independently only by the power feeding circuit. In addition, since it does not depend on an external circuit, a specific circuit configuration can be simplified.
[0066]
(C) Third embodiment
Below, only the point from which this embodiment is different from 1st Embodiment is demonstrated.
[0067]
The present embodiment is characterized in that the responsiveness of the electronic inductance circuit is improved by charging (precharging) the capacitor C1 even in the OFF state of the switch SW1.
[0068]
(C-1) Configuration and operation of the third embodiment
The overall configuration of the power feeding circuit of the present embodiment is the same as that of FIG. 1 except for the internal configuration of the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4.
[0069]
The internal configuration of the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4 may be as shown in FIG. 4 as an example.
[0070]
In FIG. 4, the function of each part and each electric signal to which the reference numerals corresponding to those in FIG. 6 and FIG.
[0071]
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. One end of the resistor R4 is connected to the anode of the Zener diode D1, 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.
[0072]
In the NPN electronic inductance circuit 4, one end of the resistor R 4 is connected to the cathode of the Zener diode D 1, the capacitor C 1 and the switch SW 1, and the other end of the resistor R 4 is connected to the NPN electronic inductance circuit 4. It is connected to an external terminal BI.
[0073]
Note that the potential of the terminal BI is always higher than that of the terminal AO.
[0074]
1 and 4, the DC operation and AC impedance of the electronic inductance circuits 3 and 4 are the same as those in the first embodiment.
[0075]
Even when a pulse signal such as a DP signal is applied from the subscriber side, it is the same as in the first embodiment, and the current / voltage monitor circuit 6 detects by turning off the switch SW1 in FIG. Since the pulse signal (each pulse constituting the component of DP) is not affected by the charging / discharging of the capacitor C1, the current / voltage monitor circuit 6 is highly accurate based on the pulse signal without delay and distortion. Detection can be performed.
[0076]
For this reason, the reliability of the control signal CS transmitted to the host device through the signal processing circuit 5 is increased.
[0077]
Further, in the present embodiment, the capacitor C1 of the PNP type electronic inductance circuit 3 in FIG. 4 is charged through a route that leads to the terminal AO through the resistor R4 connected to the capacitor C1, and the charging voltage is applied to the Zener diode D1. Determined. In contrast to this, the capacitor C1 of the NPN electronic inductance circuit 4 is charged through the resistor R4 from the terminal BI, and the charging voltage is determined by the Zener diode D1.
[0078]
(C-2) Effects of the third embodiment
As described above, according to the present embodiment, an effect equivalent to that of the first embodiment can be obtained.
[0079]
In addition, in this embodiment, the capacitor (C1) can be charged (precharged) even when the switch (SW1) is in the OFF state, and the Zener diode (D1) immediately after the switch (SW1) is switched to the ON state. By optimizing the voltage value of), the function as the electronic inductance of each electronic inductance circuit (5 and 6) can be provided more quickly.
[0080]
In addition, since the precharge prevents the capacitor (C1) from being rapidly charged immediately after the switch (SW1) is switched to the ON state, a rapid voltage fluctuation to the subscriber side is suppressed, and the telephone can be changed from the telephone to the telephone. Noise and the like heard by the user can be reduced.
[0081]
(D) Fourth embodiment
Below, only the points in which this embodiment is different from the first and third embodiments will be described.
[0082]
This embodiment is characterized in that an effect equivalent to that of the third embodiment is obtained only by the internal configuration of each electronic inductance circuit.
[0083]
(D-1) Configuration and operation of the fourth embodiment
The overall configuration of the power supply circuit of this embodiment is exactly the same as that shown in FIG. 1 except for the internal configuration of each of the electronic inductance circuits 3 and 4.
[0084]
The internal configuration of the electronic inductance circuits 3 and 4 of the present embodiment may be as shown in FIG. 5 as an example.
[0085]
In FIG. 5, the function of each part and each electric signal to which the reference numerals corresponding to those in FIGS. 6, 1 and 4 are given is basically the same as in the first and third embodiments.
[0086]
However, in the circuit configuration of FIG. 5 showing this 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 a current source that contributes to precharging for charging the capacitor C1 inside each of the electronic inductance circuits 3 and 4 when the switch SW1 is in the OFF state.
[0087]
5A, a Zener diode D1 is connected in parallel to the capacitor C1, 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 connected to the current source I2 and the switch. It is also connected to SW1. The current direction by the current source I2 is a direction in which current flows from the capacitor C1 and the anode of the Zener diode D1 to the current source I2 in FIG. 5A, and in FIG. 5B, the capacitor C1 and the Zener diode. This is the direction in which current flows into the cathode of D1.
[0088]
1 and 5, the DC operation and AC impedance of the electronic inductance circuits 3 and 4 are the same as those in the first embodiment.
[0089]
Even when a pulse signal such as a DP signal is applied from the subscriber side, it is the same as in the first embodiment, and the current / voltage monitor circuit 6 detects by turning off the switch SW1 in FIG. Since the pulse signal (each pulse of DP) is not affected by the charging / discharging of the capacitor C1, the current / voltage monitor circuit 6 performs highly accurate detection based on the pulse signal without delay and distortion. Can do.
[0090]
For this reason, the reliability of the control signal CS transmitted to the host device through the signal processing circuit 5 is increased.
[0091]
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.
[0092]
Therefore, in the present embodiment, the capacitor C1 can be charged even when the switch SW1 is in the OFF state, and each electronic component is optimized by optimizing the voltage value of the Zener diode D1 immediately after the switch SW1 is switched to the ON state. The function as the electronic inductance of the inductance circuits 3 and 4 can be provided more quickly.
[0093]
Further, since the capacitor C1 is not charged suddenly when the switch SW1 is switched to the ON state, a rapid voltage fluctuation to the subscriber side is suppressed, and the noise heard by the telephone user from the telephone is reduced. Can do.
[0094]
(D-2) Effects of the fourth embodiment
As described above, according to this embodiment, it is possible to obtain the same effect as that of the first embodiment and the same effect as that of the third embodiment.
[0095]
In addition, in this embodiment, it is not necessary to connect the resistor (R4) in the digitized inductance circuit to another digitized inductance circuit as in the third embodiment, so that the degree of design freedom is increased.
[0096]
In addition, since the current source (I2) newly added in the present embodiment can be easily built in the LSI, the number of components can be reduced and the mounting area can be reduced.
[0097]
(E) Other embodiments
In the first to fourth embodiments, the arrangement of the PNP type electronic inductance circuit 3 and the NPN type electronic inductance circuit 4 shown in FIG. 1 may be mutually replaced.
[0098]
From the viewpoint of miniaturization and the like, the switch SW1 in FIGS. 2, 3, 4 and 5 is preferably a semiconductor switch, but if necessary, a mechanical relay can also be used. In this sense, the present invention can also be positioned as increasing the degree of design freedom.
[0099]
In addition, the internal configuration of the electronic inductance circuit in FIGS. 2, 3, 4 and 5 is not limited to the illustrated configuration as long as the circuit configuration has the same effect.
[0100]
Furthermore, since the features of the second embodiment are not in an exclusive relationship with the other embodiments, they can be mounted in the same power feeding circuit in combination with the configuration of the other embodiments.
[0101]
Note that the SW1 control signal from the signal processing circuit 8 in the second embodiment may be reverse to the control in which the switch SW1 is turned off when it exceeds a certain threshold value, and the switch SW1 is turned on when it falls below the threshold value.
[0102]
Also, the Zener diode D1 of FIGS. 4 and 5 can be replaced with a cascade-connected diode or the like as long as it has a voltage clamping operation.
[0103]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a small and low-priced power supply device.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of the overall configuration of a power feeding circuit according to a first embodiment.
FIG. 2 is a schematic diagram illustrating a configuration example of a power feeding circuit for explaining a problem to be solved by the invention.
FIG. 3 is a schematic diagram showing a configuration of a conventional electronic inductance circuit.
FIG. 4 is a schematic diagram illustrating a configuration example of an electronic inductance circuit according to a third embodiment.
FIG. 5 is a schematic diagram illustrating 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 an example of the configuration of an electronic inductance circuit and its periphery according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... AC system transmission circuit, 2 ... Host apparatus, 3 ... PNP type electronic inductance circuit, 4 ... NPN type electronic inductance circuit, 5 ... Signal processing circuit, 6 ... Current / voltage monitor circuit, 7 ... Subscriber supply Power supply, A2, B2 ... subscriber line.

Claims (2)

In a power feeding device that is arranged on a balanced transmission line and supplies a current to a terminal connected to the balanced transmission line,
An input terminal and an output terminal are provided. Between the input terminal and the output terminal, two non-control terminals of the transistor and a first resistor are connected in series, and a second resistor and a capacitor are connected in series. An electronic inductance circuit connected to the control terminal of the transistor and connected to a current source for determining a DC operating point, the connection point of the second resistor and the capacitor being connected,
When the computerized inductance circuit transmits a predetermined pulse signal in the circuit, the computerized inductance circuit includes a disconnect switch means for performing a disconnect operation for disconnecting the capacitor from the circuit ,
A power supply apparatus comprising: a disconnecting charging unit that charges the capacitor when the disconnecting switch unit is performing a disconnecting operation . In the electric power feeder of Claim 1,
A pulse signal detector that monitors a change in a current value flowing through the balanced transmission path and detects the pulse signal transmitted through the balanced transmission path based on the change in the current value;
When the pulse signal detection section detects a pulse signal, the power supply device causes the disconnection switch means to perform the disconnection operation.

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