JPH05153295A - Power feeding control circuit - Google Patents

Abstract

PURPOSE:To transit from a starting state to a stop state in a restricted power feeding state in a short time by providing a by-pass line between terminals on the input side of a DC/DC converter. CONSTITUTION:Current supplied from a network is supplied in an ISDN terminal which is restricted-power-supplied by phantom power feed from the network. A current control part 1 is provided with the by-pass line 5 which can be connected/disconnected with a signal from an operation state control part 2 between the terminals of the input side of the DC/DC converter 4. The by-pass 5 is constituted by serially connecting a resistance R8, a diode D2 and a switching element P. When the signal of finishing communication is sent from the operation state control part 2, at the same time when a switching part 3 is switched into a current no-feeding part, the by-pass line 5 short-circuits a capacitic. Thus, the discharge of a capacitor D is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control circuit, and more particularly to a terminal device connected to an ISDN.

[0002]

2. Description of the Related Art As is well known, ISDN is a data communication network capable of compositely providing services such as telephone, data, facsimile, etc. by one communication network composed of a digital exchange and a digital transmission line.

When such an ISDN is used in a home wiring system, for example, the connection configuration shown in FIG. 4 can be considered. In FIG. 4, a plurality of terminal devices are connected to a home line terminating device (DSU (digital service unit)) or (network terminator) connected to the exchange, and transmission / reception is performed. As for the number of terminal devices, for example, in the case of a 2B + D basic interface,
Up to 8 units can be connected to the line terminating equipment. here,
When the local power supply that supplies power to the terminal device is stopped and the so-called phantom power supply that supplies power to the terminal device from the line terminating device enters the limited power supply state, it is necessary to minimize the power consumption of the terminal device. is there.

A specific example of such a power supply control circuit will be described with reference to FIG. L1 and L2 indicate lines, which are a signal output terminal DR and a signal input terminal RE via transformers T1 and T2, respectively.

The lines L1 and L2 also serve as power supply lines, and power can be obtained from the midpoint of the primary side of the transformers T1 and T2. A polarity detection circuit 10 is connected to this power source, and the polarity detection circuit 10 detects the power supply state from the polarity of the phantom power supply and sends a signal to the operation state control unit 2. A signal PSW for controlling the phantom power supply is sent from the operation state control unit 2.

On the other hand, one of the midpoints of the transformers T1 and T2 on the primary side is one input terminal B of the DC / DC converter 4 via the diode D1 and the hook switch HS.
1 and the other is connected to the other input terminal B2 of the DC / DC converter 4. The input end of the reception waveform control unit 11 is connected to the primary side of the transformer T2. Power is supplied to the reception waveform control unit 11 by the resistor R6, and the waveform of the signal input from the line is analyzed.

One end of a resistor R5 is connected to the cathode side of the diode D1, and the other end of the resistor R5 is connected to the signal output unit of the reception waveform control unit 11. On the other hand, an emitter and a collector of a transistor Q1 are connected in parallel to the hook switch HS, and a base of the transistor Q1 is connected to the emitter via a resistor R2. Further, the base of the transistor Q1 is connected to the collector of the transistor Q2 via the resistor R3.

The collector of the transistor Q1 is connected to the base of the transistor Q2 via the resistor R1. The base of the transistor Q2 is connected to the signal output section of the reception waveform control section 11 via the resistor R4. The emitter of the transistor Q2 is the transformer T
It is connected to the middle point of the primary side of 1 and the other input terminal B2.

One input terminal B of the DC / DC converter 4
A capacitor C is connected between 1 and the other input terminal B2 so that the input power of the DC / DC converter 4 is smoothed.

A photocoupler P is connected to the output terminal of the operation state control unit 2. The output side of the operating state control unit 2 is connected to the cathode side of the light emitting diode in the photocoupler P, and the anode side is +5 via the resistor R7.
It is connected to the V power supply. On the other hand, the collector of the phototransistor of the photocoupler P is connected to the base of the transistor Q2, and the emitter of the phototransistor is connected to the other input terminal B2 of the DC / DC converter 4.

A concrete operation in this configuration will be briefly described. When the line is connected and the terminal is in operation, the capacitor C is 40
It is charged to about V. When the communication is finished here, the operation state control unit 2 is operated to pull the cathode of the light emitting diode in the photocoupler P to the low level. Then, a potential difference is generated between the cathode of the light emitting diode in the photocoupler P and this operates.

Then, the collector-emitter resistance of the phototransistor of the photocoupler P decreases and one end of the resistor R1 is grounded to the other input end B2. As a result, the capacitor C is short-circuited via the resistor R1, and the input power of the DC / DC converter 4 is turned off.
That is, the terminal can be placed in a waiting state for incoming calls.

However, in order to reduce the power consumption, the value of the resistor R1 must be set to a large value.
It takes several seconds to discharge the capacitor C.
Here, as a practical circuit, the capacitor C is 1 μF and the resistor R is
When 1 is set to 2 MΩ, it is necessary to maintain the output of the operation state control unit 2 at the low level for 2 seconds until the capacitor C is completely discharged.

[0014]

However, in the above-mentioned conventional device, since it takes several seconds for the terminal device to shift from the full-current feeding mode to the current non-feeding mode, after the communication is completed. When there is an incoming call immediately, as described above, it takes a long time to enter the call waiting state, so that the incoming call is disabled and the call loss rate is increased.

Further, the operation of the circuit may become unstable if the voltage is unstable for several seconds. Also, as a problem unique to ISDN due to the switching time of several seconds, when a terminal in a stopped state receives INFO2, frame synchronization is established and INFO is set within 100 ms.
However, there is a problem that the condition of transmitting data in No. 3 cannot be satisfied.

The present invention has been made in view of the above matters, and includes a full-current power supply mode for supplying a total current when the terminal device is operating and a current non-power supply mode for stopping the current supply when the terminal device is not operating. It is a technical object to provide a power supply control circuit which can be appropriately switched, and of course, can switch from a start state to a stop state in a short time in a limited power supply state.

[0017]

In order to solve the above technical problems, the present invention is an ISDN terminal device in which limited power supply is performed by phantom power supply from a network.

First, the current supplied from the network is supplied to the terminal in a limited manner to supply the total current when the terminal device is in operation, and the current which stops the current supply when the terminal device is not in operation. A current control unit 1 having a non-power supply mode, an operation state control unit 2 for controlling whether the terminal is in an operating state or a stopped state, and an operation state control unit 2 provided in the current control unit 1 It is provided with a switching unit 3 for switching the power supply into the terminal to a current non-power supply mode when the terminal receives a signal and shifts from the operating state to the stopped state, and a DC / DC converter 4 for voltage conversion, The power feeding control circuit in which the capacitor C is connected to the input terminal of the DC / DC converter 4 has the following configuration.

That is, the bypass path 5 which can be connected and disconnected by the signal from the operation state control section 2 is provided between the input side terminals of the DC / DC converter 4 so that the discharge of the capacitor C can be promoted.

The bypass path 5 is formed by connecting a resistor R8, a first diode D2 and a switching element P in series, and the resistor R8 is provided to control the discharge current. The diode D2 is for preventing backflow, and the switching element P is for activating the discharge of the capacitor C.

[0021]

When the signal indicating that the communication is completed is sent from the operating state control unit 2, the switching unit 3 switches to the current non-power supply mode, and at the same time, the bypass path 5 short-circuits the capacitor C.

As a result, the discharge of the capacitor C is promoted, and the terminal is completely shifted from the operating state to the stopped state. By speeding up the discharge of the capacitor C, the time during which the voltage is unstable becomes shorter and the operation of the circuit is stabilized.

[0023]

[Embodiment 1] An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a power supply control unit in an ISDN terminal device in which limited power supply is performed by phantom power supply from a network.

The power supply control unit restrictively supplies the current supplied from the network connected through the lines L1 and L2 into the terminal device T, and supplies the total current when the terminal device T is in operation. The current control unit 1 has a power supply mode and a current non-power supply mode in which the current supply is stopped when the terminal device T is not operating. As for the current value, the full-current power supply mode for supplying the full current when the terminal device T is in operation, and the terminal device T
The current control unit 1 has a current non-power supply mode in which the current supply is stopped when the device is not in operation.

The terminal device T represents the entire terminal device including the communication section S, and the total power consumption when the terminal device T is in operation (in the current supply mode) is 380 mW, and the power supplied from the line at this time is 400 mW. Is. The total power consumption in the current non-power supply mode is 25 mW.

In the terminal device T, an operation state control unit 2 for controlling whether the terminal device T is in an operating state or in a stopped state.
Is provided. The operating state control unit 2 is adapted to operate by the signal received from the line L2 and the signal from the polarity detection circuit 10.

The operating state control unit 2 is for switching the switching unit 3 provided in the current control unit 1.
The switching unit 3 has a function of receiving a signal from the operation state control unit 2 and switching the power supply to the terminal device T to the current non-power supply mode when the terminal device T shifts from the operating state to the stopped state. is doing.

The output of the current controller 1 is connected to a DC / DC converter 4 for voltage conversion. This DC
A capacitor C is connected to the input end of the / DC converter 4 so that the power supply can be smoothed.

The above is the basic configuration of the present invention. Hereinafter, each part will be further described. The lines L1 and L2
Is a signal output terminal DR and a signal input terminal RE via transformers T1 and T2, respectively, and is connected to the communication section S.

The lines L1 and L2 also serve as power supply lines, and power can be obtained from the midpoint of the primary side of the transformers T1 and T2. A polarity detection circuit 10 is connected to this power source, and the polarity detection circuit 10 detects the power supply state from the polarity of the phantom power supply and sends a signal to the operation state control unit 2. A signal PSW for controlling the phantom power supply is sent from the operation state control unit 2.

On the other hand, one of the middle points on the primary side of the transformers T1 and T2 is one input terminal B of the DC / DC converter 4 via the diode D1 and the hook switch HS.
1 and the other is connected to the other input terminal B2 of the DC / DC converter 4. The input end of the reception waveform control unit 11 is connected to the primary side of the transformer T2. Power is supplied to the reception waveform control unit 11 by the resistor R6, and the waveform of the signal input from the line is analyzed.

One end of a resistor R5 is connected to the cathode side of the diode D1, and the other end of the resistor R5 is connected to the signal output unit of the reception waveform control unit 11. On the other hand, an emitter and a collector of a transistor Q1 are connected in parallel to the hook switch HS, and a base of the transistor Q1 is connected to the emitter via a resistor R2. Furthermore, the base of the transistor Q1 is connected to the collector of the transistor 3 via the resistor R3.

The collector of the transistor Q1 is connected to the transistor 3 which is the switching unit 3 via the resistor R1.
Connected to the base of. The base of the transistor 3 is connected to the signal output section of the reception waveform control section 11 via the resistor R4. The emitter of the transistor 3 is connected to the middle point of the primary side of the transformer T1 and the other input terminal B2.

One input terminal B of the DC / DC converter 4
A capacitor C is connected between 1 and the other input terminal B2. Furthermore, one input terminal B of this DC / DC converter 4
A bypass path 5 is provided between 1 and the other input terminal B2 so that the signal can be interrupted by a signal from the operation state control section 2.

This bypass path 5 is for accelerating the discharge of the capacitor C, and includes a resistor R8 and a first diode D.
2 and a photocoupler P as a switching element are connected in series. The resistor R8 is provided to control the discharge current, and includes the first diode D2.
Is a photocoupler for preventing backflow, and the switching element P is a photocoupler for activating the discharge of the capacitor C.

The output terminal of the operating state control section 2 is connected to the cathode side of the diode in the photocoupler P, and the anode side is connected to the + 5V power source via the resistor R7. On the other hand, the collector of the phototransistor of the photocoupler P has a diode D3 at the base of the transistor 3.
The emitter of the phototransistor is connected to the other input terminal B2 of the DC / DC converter 4. The cathode of the diode D2 is further connected to the collector of the phototransistor. A specific operation in this configuration will be described.

First, when an incoming call arrives, the received waveform control section 11
Detects this, the base of the transistor 3 becomes high level, and the transistor 3 is turned on. Then, the base of the transistor Q1 becomes high level and is turned on.
Then, the voltage of the one input terminal B1 rises and the base voltage of the transistor 3 rises through the resistor R1. Then, the transistor 3 is held in the ON state.

In this state, the DC / DC converter 4 has 40
A voltage of about V is applied and the capacitor C is also charged to about 40V. Communication ends here (hook switch H
When S is set), the operation state control unit 2 is operated according to the condition of the polarity detection circuit 10 and the cathode of the diode in the photocoupler P is pulled to the low level. Then, a potential difference occurs between the cathode of the diode in the photocoupler P and this operates.

Then, the collector-emitter resistance of the phototransistor of the photocoupler P decreases, and one end of the resistor R1 is grounded to the other input end B2. Then DC /
One input terminal B1 of the DC converter 4 passes through the resistor R8, the diode D2 and the phototransistor, and the DC / D
It will be connected to the other input terminal B2 of the C converter 4. As a result, the capacitor C is short-circuited via the bypass path 5, and is immediately discharged to turn off the input power source of the DC / DC converter 4. At the same time, the base voltage of the transistor 3 flows from the diode D3, the phototransistor to the other input terminal B2, and the voltage drops,
The transistor 3 is turned on.

Here, when the value of the resistor R8 is calculated when the capacitor C is 1 μF and the signal PSW output from the operating state control unit 2 is 3 ms, 3 × 10 ⁻³ = 1 × 10 ⁻⁶ × R From R = 3 × 10 ⁻³ × 10 ⁶ , it becomes ³ KΩ.

Since the capacitor C is discharged through the dedicated bypass path as described above, there is no problem even if the value of the resistor R1 is set large, and the power consumption can be reduced.

Further, since the capacitor C can be instantly discharged, the sending time of the signal PSW output from the operation state control unit 2 can be extremely short. In addition, when the terminal in the stopped state receives INFO2, which is a problem unique to ISDN due to the drastic reduction in power supply switching time, the condition that frame synchronization is established and INFO3 is transmitted within 100 ms is required. Can be satisfied.

FIG. 3 is a schematic configuration diagram of a system to which the present invention is applied. T is a terminal device, U is a line terminal device,
V indicates an exchange, respectively.

[0044]

According to the present invention, the resistor (R8) and the first diode (D) are provided between the input side terminals of the DC / DC converter.
Since the bypass path (5) formed by connecting 2) and the switching element (P) in series is provided, the transition from the starting state to the stopping state can be performed in a short time in the limited power supply state.

Therefore, switching from the end of communication to waiting for a call becomes quick, and the call loss rate can be reduced.
Further, unlike the conventional case, the voltage does not become unstable, so that the operation of the circuit can be further stabilized.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a system targeted by the present invention.

FIG. 4 is a circuit diagram of a conventional example.

[Explanation of symbols]

 1 ... Current control section, 2 ... Operating state control section, 3 ... Switching section, 4 ... DC / DC converter, 5 ... Bypass path, C ... Capacitor, R8 ... Resistor D2 ... Diode P ..Switching element, 3a..Control signal input terminal, D3..Second diode, T..Terminal device.

Claims (3)

[Claims] 1. An ISDN terminal device in which limited power supply is performed by phantom power supply from a network, wherein the current supplied from the network is supplied to the terminal in a restricted manner, and the entire current when the terminal device is in operation is supplied. Current control unit (1) having a full-current power supply mode for controlling the terminal device and a current non-power supply mode for stopping current supply when the terminal device is not in operation, and an operating state for controlling whether the terminal is in the operating state or in the stopped state. Power supply to the inside of the terminal when the terminal shifts from the operating state to the stopped state by receiving a signal from the operating state control unit (2) provided in the control unit (2) and the current control unit (1). It is equipped with a switching unit (3) for switching to the current non-power supply mode and a DC / DC converter (4) for voltage conversion.
In the power feeding control circuit in which the capacitor (C) is connected to the input terminal of the C converter (4), a resistor (R
8), first diode (D2) and switching element (P)
2. A power supply control circuit comprising a bypass path (5), which is connected in series and which can be intermittently operated by a signal from the operation state control section (2). 2. The power supply control circuit according to claim 1, wherein the switching element (P) is a photocoupler. 3. The switching unit (3) is a control signal input terminal.
In addition to having (3a), this control signal input terminal (3
a), the diode (D2) and the switching element (P)
2. The power feeding control circuit according to claim 1, wherein a second diode (D3) is connected between the connection point and the connection point.