JPH0638526Y2 - Telephone power circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a telephone having a memory in which a stored telephone number is protected by being constantly supplied with power, and particularly to a power supply circuit.

(B) Prior Art Recently, electronic telephones that electrically perform dial signal transmission operations have become widespread in place of mechanical telephones that mechanically perform dial signal transmission operations. Such an electronic telephone has a function generally called auto-dial, that is, a function of storing a telephone number in a memory and reading a telephone number stored in the memory by a simple operation to make a call. In a telephone having such a function incorporated therein, it is necessary to hold the telephone number stored in the memory, so it is necessary to constantly supply the memory holding power to the memory. There is one disclosed in Japanese Utility Model Laid-Open No. 59-27659.

(C) Problems to be Solved by the Invention In the technology of the above-mentioned publication, the telephone number stored in the memory is retained by the power supply from the battery during the on-hook operation, and the power obtained from the power line is supplied during the off-hook operation. It is configured to perform a memory holding operation of a telephone number. Such a technique has a problem that the battery life is shortened because the power from the battery is constantly supplied to the memory when in the on-hook state. As a method of solving such a problem, there is a method of using the voltage obtained from the telephone line for holding the memory in the on-hook state. However, with such a method, it is not possible to obtain a current larger than that of the telephone line. Therefore, when the voltage of the telephone line drops due to the off-hook of another telephone connected in parallel to the same telephone line, the memory is not retained. There is a problem that the applied voltage is insufficient. The present invention is intended to provide a power supply circuit that improves such a point.

(D) Means for Solving the Problem The power supply circuit of the present invention is designed so that the voltage obtained from the telephone line is first
A power supply circuit for supplying the memory through a resistor, a battery incorporated in the telephone and supplying a voltage to the memory when the voltage supplied from the power supply circuit is insufficient, and detecting a voltage drop in the telephone line. A voltage detection circuit that outputs a switching signal when a voltage drop is detected, and a voltage that is switched to a conductive state when the switching signal is output from the voltage detection circuit and that has a resistance value smaller than that of the first resistor is obtained from the telephone line. It is composed of a power supply transistor for supplying the memory through the second resistor that it has.

(E) Operation The present invention is provided with a power supply transistor which is turned on when the voltage of the telephone line is lowered, and the voltage obtained from the telephone line is supplied to the memory for storing data through the transistor. Is.

(F) Embodiment The illustrated circuit is an embodiment of the power supply circuit of the present invention.
(1) is the first connection terminal to the telephone line, (2) is the first connection terminal
The second connection terminal is connected in parallel to the connection terminal (1) and is connected to the telephone circuit (3) of the other telephone. (4) is a diode bridge circuit that determines the polarity of the voltage supplied from the telephone line, (5) is a battery built into the telephone, (6) is a dial operation button, and (7) is the voltage obtained from the telephone line. Is a bridge circuit (4), a first resistor (8) and a diode (9)
0) is a control circuit for controlling each operation of the telephone circuit while being supplied to a power supply terminal (11) through which a dial signal is generated in accordance with the operation of the dial operation button (6) and a telephone number is stored. Built-in memory. Reference numeral (12) is a diode for supplying the voltage obtained from the battery (5) to the power supply terminal (11) of the control circuit (7). (13) is a voltage detection circuit for detecting a DC voltage output from the diode bridge circuit (4), and a power supply terminal (14) is connected to a power supply terminal (11) of the control circuit (7). (15) is an input terminal to which the DC voltage from the diode bridge circuit (4) is input, (16) is a reference voltage input terminal to which the reference voltage set by the Zener diode (17) is input, and (18) is The voltage input to the input terminal (15) is the reference voltage input terminal (16)
It is a light emitting diode which is driven to blink when the voltage drops below the reference voltage input to. (19) is a switching signal terminal provided in the voltage detection circuit (13), and the voltage input to the input terminal (15) is a reference voltage input terminal (16).
H (high) when the voltage drops below the reference voltage input to
It is configured to output a level switching signal.
(20) The emitter is the diode bridge circuit (4)
A power supply transistor (23), which is connected to an output terminal of the control circuit and has a collector connected to a power supply terminal (11) of the control circuit (7) through a second resistor (21) and a diode (22). Is a control transistor whose collector is connected to its base through a resistor (24) and whose emitter is grounded so as to control the operation of the power supply transistor (20), and whose base is a resistor (25). Is connected to the switching signal output terminal (19) of the voltage detection circuit (13). In such a circuit,
The voltage value supplied from the battery (5) through the diode (12) to the power supply terminal (11) of the control circuit (7) is used for the memory holding operation of the memory incorporated in the control circuit (7). It is set so that the required voltage value can be obtained. In addition, the first resistor (8) that constitutes the power supply circuit ( 10 )
The resistance value of the power supply terminal (11) is the minimum voltage required to reverse bias the diode (12) when the voltage value of the telephone line is at a predetermined high voltage value, that is, when the other telephone is not used. ) Is set to the value to be supplied to. Then, when the voltage value of the telephone line is at a low voltage value, that is, when the other telephone is being used, the holding voltage is supplied to the power supply terminal (11) of the control circuit (7) by conduction of the power supply transistor (20). The resistance value of the second resistor (21) is set to be a value that reverse-biases the diode (12), that is, a value smaller than the resistance value of the first resistor (8). Further, the current value supplied from the power supply circuit ( 10 ) to the control circuit (7) and the like is set so as not to exceed the regulation regarding the use of the telephone line. In this embodiment, a ringer circuit for emitting a ringing signal, a closing circuit for closing a telephone line, a dial circuit for sending a dial signal, and a handset circuit for sending and receiving a voice signal are used. Was omitted. The power supply circuit of the present invention is configured as described above. Next, the operation of such a circuit will be described.

The DC voltage output to the output terminal of the diode bridge circuit (4) is at a predetermined high voltage value when the other telephone is not in use, that is, in the on-hook state.
Therefore, the telephone number stored in the memory is stored in the power supply terminal (11) of the control circuit (7) via the first resistor (8) and the diode (9) which form the power supply circuit ( 10 ). The necessary voltage is supplied to the voltage detection circuit (13) and the operating power is supplied to the voltage detection circuit (13). In such a state, since the voltage input to the input terminal (15) of the voltage detection circuit (13) is a high voltage, the blinking drive operation of the light emitting diode (18) is not performed and the switching signal is output. No switching signal of H level is output to the terminal (19). Therefore, the control transistor (23) is not biased and is in a non-operating state, and the power supply transistor (20) whose operation is controlled by the control transistor (23) is also in a non-conducting state. Further, in such a state, the diode (12) is reverse biased, so that the current of the battery (5) is not consumed. In such a state, when the other telephone is used, that is, when the telephone is off-hook, the DC voltage output to the output terminal of the bridge circuit (4) drops to a low voltage value. As a result, the voltage detection circuit (1
Since the operation of detecting the voltage drop of the telephone line by 3) is performed, the blinking drive operation of the light emitting diode (18) is performed and an H level switching signal is output to the switching signal output terminal (19). Therefore the user is the light emitting diode (18)
It is possible to recognize that the other telephone is being used by the blinking operation of and the telephone cannot be used. When an H level switching signal is output to the switching signal output terminal (19), the control transistor (23) is biased and inverted to the conductive state, and the power supply transistor (20) is turned on in accordance with the inversion. Flip to. When the power supply transistor (20) is turned on, the power supply terminal (11) of the control circuit (7) and the voltage detection circuit (between the emitter and collector, the second resistor (21) and the diode (22)) A predetermined voltage is supplied to the power supply terminal (14) of 13). Therefore, the memory holding operation of the memory incorporated in the control circuit (7) and the blinking drive operation of the light emitting diode (18) by the voltage detection circuit (13) are performed. Even in such a state, the diode (12) is reverse-biased and the current of the battery (5) is not consumed. And the current from the battery (5) is
The power supply terminal (11) and voltage of the control circuit (7) when the voltage of the telephone line drops slightly from the high voltage value to the low voltage value during the switching operation or in each state It is supplied to the power supply terminal (14) of the detection circuit (13).

(G) Effect of the device The power supply circuit of the present invention is provided with a power supply transistor that reverses to a conducting state when the voltage of the telephone line drops, and supplies the voltage obtained from the telephone line to the memory for storing data through the transistor. The memory storage operation is performed even if the telephones configured to obtain the power for memory storage from the telephone line are connected in parallel. Can be reliably performed, and the practical value of the present invention is extremely high.

[Brief description of drawings]

The circuit shown is an embodiment of the power supply circuit of the present invention. Description of main drawing numbers (4) …… Diode bridge circuit, (5) …… Battery,
(7) …… Control circuit, (8) …… First resistor, ( 10 ) …… Power supply circuit, (13) …… Voltage detection circuit, (20) …… Power supply transistor, (21) …… Second resistance, (23) ...
… Control transistor.

Claims (1)

[Scope of utility model registration request] 1. A telephone having a memory for holding a stored telephone number when power is always applied, and a power supply circuit for supplying a voltage obtained from a telephone line to the memory through a first resistor, and the telephone. A battery that is incorporated into the memory and supplies a voltage to the memory when the voltage supplied from the power supply circuit is insufficient,
A voltage detection circuit that detects a voltage drop in the telephone line and outputs a switching signal when a voltage drop is detected, and a voltage detection circuit that reverses the conductive state when the switching signal is output from the voltage detection circuit and that obtains the voltage from the telephone line A power supply circuit for a telephone set, comprising a power supply transistor for supplying to the memory through a second resistor having a resistance value smaller than that of the first resistor.