JP2659874B2 - Power supply control circuit - Google Patents

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 that can provide services such as telephone, data, and facsimile by one communication network including a digital exchange and a digital transmission line.

When such an ISDN is used in a home wiring system, for example, a connection form shown in FIG. 4 can be considered. In FIG. 4, a plurality of terminal devices are connected to a home terminal unit (DSU (Digital Service Unit)) or a (network terminator) connected to an exchange, and transmission and reception are performed. As the number of terminal devices, for example, in the case of a basic interface of 2B + D,
Up to eight units can be connected to the line terminator. here,
If the local power supply to the terminal device stops supplying power, and the so-called phantom power supply from the line terminating device to the terminal device enters the limited power supply state, it is necessary to minimize the power consumption in 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 respectively connected to a signal output terminal DR and a signal input terminal RE via transformers T1 and T2.

[0005] The lines L1 and L2 also serve as power supply lines, so that power can be obtained from a middle point on the primary side of the transformers T1 and T2. A polarity detection circuit 10 is connected to the power supply. The polarity detection circuit 10 detects a power supply state from the polarity of phantom power supply, and sends a signal to the operation state control unit 2. From this operation state control unit 2, a signal PSW for controlling phantom power supply is transmitted.

On the other hand, the middle point of each of the primary sides of the transformers T1 and T2 is connected to one input terminal B of the DC / DC converter 4 via a diode D1 and a hook switch HS.
1 and the other is connected to the other input terminal B2 of the DC / DC converter 4. The input side of the reception waveform control unit 11 is connected to the primary side of the transformer T2. The reception waveform control unit 11 is supplied with power by a resistor R6, and analyzes a waveform of a signal input from a line.

[0007] One end of a resistor R5 is connected to the cathode side of the diode D1. The other end of the resistor R5 is connected to a signal output unit of the reception waveform control unit 11. On the other hand, the emitter and the collector of a transistor Q1 are connected in parallel to the hook switch HS, and the 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.

[0008] The collector of the transistor Q1 is connected to the base of the transistor Q2 via a resistor R1. The base of the transistor Q2 is connected to a signal output unit of the reception waveform control unit 11 via a resistor R4. The emitter of the transistor Q2 is connected to the transformer T
1 and the other input terminal B2.

One input terminal B of the DC / DC converter 4
A capacitor C is connected between the input terminal 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 an output terminal of the operation state control unit 2. The output terminal 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 connected to +5 through a resistor R7.
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 specific operation in this configuration will be briefly described. When the line is connected and the terminal is in operation, the capacitor C is connected to the power supply from the line.
It is charged to about V. When the communication is completed here, the operation state control unit 2 is operated to pull the cathode of the light emitting diode in the photocoupler P to a low level. Then, a potential difference occurs 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 terminal 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 call waiting state.

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 2 MΩ, it is necessary to maintain the output of the operation state control unit 2 at the low level for 2 seconds before the capacitor C is completely discharged.

[0014]

However, in the above-mentioned conventional device, it takes several seconds for the terminal device to transition from the full current power supply mode to the current non-power supply mode. If there is an incoming call immediately, it takes a long time to enter the call waiting state, as described above, so that the incoming call cannot be made and the call loss rate increases.

Further, there is a possibility that the operation of the circuit may become unstable due to the voltage being unstable for several seconds. Also, as a problem inherent to ISDN due to the fact that the switching time takes several seconds, when a terminal in a stopped state receives INFO2, frame synchronization is established and the INFO is set within 100 ms.
3 cannot be satisfied.

The present invention has been made in view of the above-mentioned problems, and has a full current 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 of the present invention to provide a power supply control circuit capable of performing a transition from an activation state to a stop state in a short time in a limited power supply state, in addition to being able to switch appropriately.

[0017]

SUMMARY OF THE INVENTION The present invention, in order to solve the above technical problem, is an ISDN terminal device in which limited power supply is performed by phantom power supply from a network.

First, a full current supply mode in which the current supplied from the network is supplied to the terminal in a limited manner to supply the entire current when the terminal device is operating, and a current for stopping the current supply when the terminal device is not operating. A current control unit 1 having a non-power supply mode, an operation state control unit 2 for controlling whether a terminal is in an operation state or a stop state, and a current control unit 2 provided in the current control unit 1 A switching unit 3 that switches a power supply to the terminal to the current non-power supply mode when the terminal shifts from the operation state to the stop state in response to the signal, and a DC / DC converter 4 for voltage conversion. The power supply 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, a bypass path 5 is provided between the input terminals of the DC / DC converter 4 so as to be able to be switched on and off by a signal from the operation state control unit 2 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. The resistor R8 is provided for controlling a discharge current. The diode D2 is for preventing backflow, and the switching element P is for starting discharge of the capacitor C.

[0021]

When a signal indicating the end of communication is sent from the operation state control unit 2, the switching unit 3 switches to the current non-feed 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 completely shifts from the operating state to the stopped state. As the discharging speed of the capacitor C is increased, 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.

This power supply control section supplies the current supplied from the network connected via the lines L1 and L2 to the terminal device T in a limited manner, and supplies the total current for supplying the total current when the terminal device T is operating. The current control unit 1 includes a power supply mode and a current non-power supply mode in which current supply is stopped when the terminal device T is not operating. As the current value, the total current supply mode for supplying the total current during the operation of the terminal device T, the terminal device T
And a current control unit 1 having a current non-feeding mode in which current supply is stopped when the device is not operating.

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

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

The operation 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 into the terminal device T to the current non-power supply mode when the terminal device T shifts from the operating state to the stop state. doing.

The output of the current control section 1 is connected to a DC / DC converter 4 for voltage conversion. This DC
A capacitor C is connected to the input terminal 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, L2
Are signal output terminals DR and signal input terminals RE via transformers T1 and T2, respectively, and are connected to the communication unit S.

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

On the other hand, the middle point of each of the primary sides of the transformers T1 and T2 is connected to one input terminal B of the DC / DC converter 4 via a diode D1 and a hook switch HS.
1 and the other is connected to the other input terminal B2 of the DC / DC converter 4. The input side of the reception waveform control unit 11 is connected to the primary side of the transformer T2. The reception waveform control unit 11 is supplied with power by a resistor R6, and analyzes a waveform of a signal input from a line.

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

The collector of the transistor Q1 is connected to a transistor 3 as a switching unit 3 through a resistor R1.
Connected to the base. The base of the transistor 3 is connected to the signal output unit of the reception waveform control unit 11 via a resistor R4. The emitter of the transistor 3 is connected to the middle point on the primary side of the transformer T1 and to 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. Further, one input terminal B of the DC / DC converter 4
Between the first input terminal 1 and the other input terminal B2, there is provided a bypass path 5 which can be interrupted by a signal from the operation state control section 2.

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

The output terminal of the operation state control unit 2 is connected to the cathode side of the diode in the photocoupler P, and the anode side is connected to a + 5V power supply via a resistor R7. On the other hand, the collector of the phototransistor of the photocoupler P is connected to the base of the transistor 3 by a diode D3.
And 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 a call arrives, the reception waveform control unit 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 a high level, and is turned on.
Then, the voltage of one input terminal B1 rises and passes through the resistor R1 to raise the base voltage of the transistor 3. Then, the transistor 3 is kept on.

In this state, the DC / DC converter 4
A voltage of about V is applied, and the capacitor C is also charged to about 40V. End communication here (Hook switch H
When S is placed), 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 a low level. Then, a potential difference is generated between the cathode of the diode in the photocoupler P and this operates.

Then, the resistance between the collector and the emitter of the phototransistor of the photocoupler P decreases, and one end of the resistor R1 is grounded to the other input terminal B2. Then, the DC /
One input terminal B1 of the DC converter 4 is connected to the DC / D through a resistor R8, a diode D2, and a phototransistor.
The C converter 4 is connected to the other input terminal B2. As a result, the capacitor C is short-circuited via the bypass path 5 and immediately discharged to turn off the input power of the DC / DC converter 4. At the same time, the base voltage of the transistor 3 flows from the diode D3 and 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 operation state control unit 2 is 3 ms, 3 × 10 ⁻³ = 1 × 10 ⁻⁶ × R R = 3 × 10 ⁻³ × 10 ⁶ results in ³ KΩ.

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

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

FIG. 3 is a schematic block diagram of a system to which the present invention is applied, where T is a terminal device, U is a line termination device,
V indicates exchanges.

[0044]

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

Therefore, the switching from the end of the communication to the waiting for the 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 the drawings]

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

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

FIG. 3 is a schematic configuration diagram of a system to which the present invention is applied;

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

[Explanation of symbols]

 1. Current control unit, 2. Operation state control unit, 3. Switching unit, 4. DC / DC converter, 5. Bypass path, C. Capacitor, R8. Resistor D2. Diode P A switching element, 3a a control signal input terminal, D3 a second diode, and a terminal device.

Claims (3)

(57) [Claims] 1. An ISDN terminal device in which limited power supply is performed by phantom power supply from a network, wherein a current supplied from the network is limitedly supplied to the terminal, and a total current is supplied when the terminal device operates. Current control unit (1) having a full current power supply mode to perform power supply and a current non-power supply mode to stop current supply when the terminal device is not in operation, and an operation state to control whether the terminal is in an operation state or a stop state A control unit (2), which is provided in the current control unit (1) and receives power from the operation state control unit (2) to supply power to the terminal when the terminal transitions from an operating state to a stopped state; A switching unit (3) for switching to a current non-feed mode and a DC / DC converter (4) for voltage conversion are provided.
In a power supply control circuit in which a capacitor (C) is connected to an input terminal of a C converter (4), a resistor (R) is connected between input terminals of the DC / DC converter.
8), first diode (D2) and switching element (P)
Are connected in series, and a bypass path (5) is provided, which can be switched on and off by a signal from the operation state control unit (2). 2. The power supply control circuit according to claim 1, wherein said switching element is a photocoupler. 3. The control unit according to claim 1, wherein said switching unit is a control signal input terminal.
(3a) and the control signal input terminal (3
a), the diode (D2) and the switching element (P)
2. The power supply control circuit according to claim 1, wherein a second diode (D3) is connected between the power supply control point and the connection point.