JP2589561Y2 - Power supply circuit at power failure - 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 circuit at the time of a power failure for supplying power from a telephone line to a control microcomputer provided in a telephone (home telephone) when a commercial power supply fails.

[0002]

2. Description of the Related Art Conventionally, FET (field effect transistor)
As shown in FIG. 2, when the hook switch 1 is turned on at the time of a commercial power outage, the power supply circuit at the time of a power failure of the telephone (home telephone) is provided between the telephone lines L1, L2 and the handset. The line switch PNP transistor 2 is turned on, and the control microcomputer 3 provided in the telephone (home telephone) is connected to the telephone lines L1, L2.
Power will be supplied from the side.

When such a power failure occurs, the PN for the line switch
As a gate bias voltage for keeping an FET (field effect transistor) 4 which is turned on to turn on the P transistor 2 and turned off when energized (when there is no power failure), 100 V AC of commercial power supply A voltage of −5 VDC is supplied. In addition,
5 is a diode bridge (polarity matching diode), and 6 is a speech network IC.

[0004]

In the prior art, as the gate bias voltage of the FET4, -DC5V generated from the commercial power supply of AC100V must be supplied only for the gate bias voltage, and the circuit configuration is complicated. Had the problem of becoming

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a control device provided in a telephone at the time of a commercial power failure in order to supply power from a telephone line side to a control device provided in the telephone. It is an object of the present invention to provide a power supply circuit at the time of a power failure which can control the FET for turning on / off the line switching transistor with the same single voltage as the DC voltage supplied to the control device.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention turns on a line switching transistor provided between a telephone line and a telephone by turning on an FET when a commercial power supply fails. A power supply circuit for supplying power from a telephone line to a control device provided in a telephone, wherein a DC power supply for supplying a positive voltage to the control device is connected to a source of the FET, and the FET
Connect the gate to earth and connect the hook switch to the FE
It is provided between the source of T and the ground.

[0007]

When the commercial power supply fails, the voltage between the source and the gate becomes 0 V, so that the FET is turned on, and the telephone line side sends the signal to the control device via the line switch transistor which is turned on by the FET being turned on. Power is supplied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a power supply circuit at the time of a power failure according to the present invention. The same components as those in the conventional technique shown in FIG. 2 are denoted by the same reference numerals.

In a power supply circuit for a telephone (home telephone) during a power failure shown in FIG. 1, telephone lines L1 and L2 are connected to a diode bridge 5,
The output terminal is connected to the emitter E of the line switch PNP transistor 2, and the other terminal is connected to the ground GND. The collector C of the line switch PNP transistor 2 is connected to the input terminal of the speech network IC 6 and to the power supply terminal of the control microcomputer 3 via the diode D1, and the base B is connected via the resistor R1. It is connected to the drain D of an FET (field effect transistor) 4. The power input terminal of the control microcomputer 3 is a diode D
+ DC made from AC100V of commercial power supply via 3
Connected to 5V power supply.

[0010] The source S of the FET4 is + DC5V generated from a commercial power supply of AC100V through a diode D2.
While being connected to a power supply, it is connected to one terminal 1a of the hook switch 1 via a resistor R2, and the terminal 1a is connected to an input terminal of the control microcomputer 3. The gate G of the FET 4 is connected via a resistor R3 to
The other terminal 1b of the hook switch 1 and the ground terminal of the control microcomputer 3 are connected to the ground GND.

The output terminal of the control microcomputer 3 is connected to the base B of the NPN transistor 7 via a resistor R4.
, The emitter E of the NPN transistor 7 is connected to the ground GND, and the collector C of the NPN transistor 7 is connected to the drain D of the FET 4.

The operation of the power supply circuit at the time of a power failure of the telephone (home telephone) configured as described above will be described.
First, when the commercial power supply is energized, the AC1
When the + DC5V generated from 00V is supplied via the diode D3, the control microcomputer 3 is operated by the + DC5V.

The source S of the FET 4 is connected to a +5 VDC power supply via a diode D2, and the gate G is connected to the ground GND via a resistor R3. This means that a bias voltage for turning off the FET 4 is applied.

Therefore, the hook switch 1 is disconnected from the base B of the line switch PNP transistor 2, so that even if the receiver is hooked off for an extension call and the hook switch 1 is turned on, PNP transistor 2 is never turned on.

In the case of an outside line call, a signal from the control microcomputer 3 turns on the NPN transistor 7, so that the PNP transistor 2 is turned on, and the telephone lines L1, L2 and the speech network IC6 are turned on. Is connected and you can talk.

Next, when the AC 100 V of the commercial power supply fails, the voltage of the + DC 5 V power supply also becomes 0 V. Then, FE
Since the voltage between the source S and the gate G of T4 is also 0 V,
The FET 4 is turned on.

At this time, when the hook switch 1 is turned on by lifting the receiver, the base B of the PNP transistor 2 is connected to the ground GND via the resistors R1, FET4 and R2, so that the PNP transistor 2 is turned on. In this state, power is supplied to the control microcomputer 3 from the telephone lines L1 and L2 via the diode D1.

Therefore, since the control microcomputer 3 operates, external line communication is possible. When the hook switch 1 is in the off state, a circuit through which the base current of the PNP transistor 2 flows is not formed even when the FET 4 is in the conducting state. Therefore, the PNP transistor 2 is not turned on, and the control microcomputer 3 and the like are not turned on. Is not supplied from the telephone lines L1 and L2.

[0019]

As described above, according to the present invention, a line switch transistor is turned on or off with a single voltage equal to a DC voltage for operating a control device provided in a telephone. Since the FET can be controlled, the configuration of the power supply circuit is simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a power supply circuit during a power failure according to the present invention;

FIG. 2 is a diagram illustrating a conventional power supply circuit during a power outage;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hook switch, 2 ... PNP transistor for line switch, 3 ... Control microcomputer (control device), 4 ... FET, 5 ... Diode bridge, 6 ... Speech network IC.

Claims (1)

(57) [Scope of request for utility model registration] A line switch transistor provided between a telephone line and a telephone at the time of a commercial power failure occurs.
In a power failure power supply circuit for supplying power from the telephone line side to a control device provided in the telephone from a telephone line side, turning on T to turn on T, a DC power supply for supplying a positive voltage to the source of the FET to the control device. A power supply circuit at the time of a power outage, wherein the power supply circuit is connected, the gate of the FET is connected to the ground, and a hook switch is provided between the source of the FET and the ground.