JP3048368B2 - Power supply circuit for terminal equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a power supply circuit for a terminal which operates using a call signal (16 Hz 75 V) of a telephone line as a power source.

(Prior Art) FIG. 3 is a diagram showing an example of this type of conventional power supply circuit for a terminal, wherein L1 and L2 are terminals connected to a telephone line, and 1 is a MOD.
EM (modulator / demodulator), DTMF dialer, transmission / reception circuit such as receiver, etc., 4 is a closed circuit that creates a telephone off-hook state, 3
Is a control circuit for controlling the transmitting / receiving circuit 1 and the closing circuit 4; 7 is an outlet plug for connecting an AC power supply; 6 is a converter for converting an AC voltage input from the outlet plug 7 into a DC voltage for an internal circuit; It is a power supply device for operating a dialer, a receiver, and the like.

(Problems to be Solved by the Invention) When the power supply circuit for a terminal shown in FIG. 3 is used, there are the following disadvantages.

(1) An AC power supply for operating the internal circuit is required.

(2) The power supply device 6 includes a transformer, a capacitor, a capacitor, a regulator, and the like, has a large volume, and is expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply circuit for a terminal which does not require an AC power supply for operating an internal circuit, has a small volume, has a small number of parts, and is connected to a low-cost telephone line.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a first terminal connected to one of a telephone line on which a DC signal and an AC bell ringing signal are superimposed. And a power storage element connected between a second terminal connected to the other side of the telephone line; and a serial connection between the first terminal and one terminal of the power storage element, for bell ringing. Having a Zener voltage greater than the DC voltage appearing on the communication line in the call signal,
When a voltage equal to or higher than the Zener voltage is applied, the Zener diode converts the voltage signal into a current signal and supplies the current signal to the power storage element. A Zener diode is connected between the Zener diode and one terminal of the power storage element in a forward direction. A diode for rectifying the voltage of the bell ringing call signal and applying the rectified voltage to the power storage element, and preventing a backflow of the charge stored in the power storage element; and detecting the power storage amount of the power storage element, Power storage amount detection means that outputs a detection signal when is greater than or equal to a certain value, and the electric charge stored in the power storage element is supplied as a power source to a transmission / reception circuit of the telephone line terminal, and the power storage amount detection means And a control means for controlling the transmission / reception circuit and starting communication when the detection signal is input.

(Operation) According to the present invention, as a power supply for the internal circuit, the call signal on the telephone line is stored in the storage element through the Zener diode and the diode, and the stored amount of electricity is used. An AC power supply for operation is not required, and a terminal power supply circuit having a small volume, a small number of parts, and a low cost can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention.
1, L2 is the first and second terminals connected to the telephone line, 1
Is a transmission / reception circuit for transmitting / receiving a dial tone or FSK (frequency shift keying) modulation signal, etc., C1 is a power storage element, for example, a capacitor connected to terminals L1 and L2, and is connected in parallel to the transmission / reception circuit 1 and has a telephone line described later The battery is charged by the rectified voltage based on the ringing signal for ringing the AC bell inside.

ZD1 is connected between one terminal (electrode) of the capacitor C1 and the terminal L2, and has a Zener voltage higher than the DC voltage (48V) appearing on the communication line in the ringing signal for bell ringing (16Hz 75V), When a voltage higher than the voltage is applied, the voltage signal is converted into a current signal and the
Zener diode supplied to C1.

D1 is a diode, the second terminal L2 and the capacitor C1
When the terminal L2 is positive, that is, when the telephone line is in communication, the voltage of the AC bell ringing signal output from the Zener diode ZD1 is rectified when the terminal L2 is positive, and this rectified voltage To charge the capacitor C1 and prevent the electric charge stored in the capacitor C1 from flowing backward.

Reference numeral 2 denotes a control circuit which detects the voltage of the capacitor C1 and notifies a control means such as a control circuit 3 when the voltage becomes equal to or higher than a predetermined voltage, for example, a voltage detector, and 3 a control circuit which controls the closing circuit 4 and the transmission / reception circuit 1. The closing circuit 4 is controlled by the control circuit 3 and closes the terminals L1 and L2 to create an off-hook state.

The feature of the embodiment described above is that the call signal on the telephone line is charged to the capacitor C1 through the Zener diode ZD1 and the diode D1, and the capacitor C1 is used as a power supply for the internal circuit.
(In FIG. 1, the charge of the capacitor C1 is used as the power source of the transmission / reception circuit 1).

In the non-communication state, the terminal L1 is positive and the terminal L2 is negative in the telephone line, but when a call comes in to this terminal,
A DC voltage signal (48V) appears with the terminal L1 negative and the terminal L2 positive. When this DC voltage signal is used as a terminal power supply,
Since the terminals L1 and L2 are closed, signal transmission starts and cannot be used.

Next, a bell ringing call signal is superimposed on the previous DC voltage signal between the terminals L2 and L1 to call the terminal. The Zener diode ZD1 outputs only the voltage of the superimposed calling signal, and outputs the output voltage to the diode D1.
And stored in the capacitor C1. Therefore, the Zener voltage of the Zener diode ZD1 must not be less than 48V.

The voltage detector 2 outputs a signal to the control circuit 3 when a constant charge is stored in the capacitor C1. After that, the control circuit 3
By turning on the closing circuit 4 and controlling the transmission / reception circuit 1, data transmission can be performed. In this case, the data signal such as a weighing value from the telephone line is an analog signal having a voltage sufficiently lower than the Zener voltage, and this analog signal is superimposed on the DC voltage signal, and the superimposed signal is in an off-hook state. Is completed, that is, the DC voltage signal and the superimposed signal of the calling signal can be distinguished from each other, so that data can be transmitted normally. The voltage charged in the capacitor C1 is (75
V × √2) minus the Zener voltage (48V). The power supply of the internal circuit of this type of terminal is about 3 to 5 V, so that the voltage charged in the capacitor C1 can be sufficiently used as the power supply of the internal circuit.

Since the use of the embodiment of the present invention described above does not require an AC power supply, it can be used even in a place without an AC outlet plug and can be used at the time of a power failure.

Further, since a large power supply component such as a transformer is not used, the volume is small and the cost is low.

 The embodiment described above can be modified and implemented as follows.

(A) The procedure of starting communication after detecting the voltage of the capacitor C1 of FIG. 1 and the detected value reaches a certain level was performed, but the number of ringing signals (for bell: 16 Hz 75 V) was counted and kept constant. After the number of times, communication may be started.

(B) In FIG. 1, power is stored using the capacitor C1, but a rechargeable battery such as a NiCd battery can be used instead of the capacitor C1.

(C) It is also possible to provide a time constant for charging the capacitor C1 by using a resistor.

(D) As shown in FIG. 2, a call signal (16 Hz 75 V) to the telephone 8 can be stored in the terminal 9 branched to the telephone 8 by using the present invention.

[Effects of the Invention] According to the present invention described above, as a power supply for an internal circuit,
The call signal on the telephone line is stored in the storage element through a Zener diode and diode, and the stored amount of electricity is used.Therefore, there is no need for an AC power supply to operate the internal circuit, and the volume is small. A low-cost, low-cost terminal power supply circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of a power supply circuit for a terminal according to the present invention, FIG. 2 is a block diagram for explaining a modification of the present invention, and FIG. FIG. 4 is a block diagram for explaining an example of the first embodiment. L1, L2 terminals, 1 transmission / reception circuit, 2 voltage detector, 3 control circuit, 4 closed circuit, ZD1 Zener diode, D1 diode, C1 capacitor.

Claims (1)

(57) [Claims] A first terminal connected to one side of a telephone line on which a DC signal and an AC bell ringing signal are superimposed, and a second terminal connected to the other side of the telephone line. The connected storage element, which is connected in series between the first terminal and one terminal of the storage element, has a Zener voltage higher than a DC voltage appearing on a communication line in the ringing signal for ringing the bell, When a voltage equal to or higher than the Zener voltage is applied, a Zener diode that converts the voltage signal into a current signal and supplies the current signal to the power storage element, and is connected in a forward direction between the Zener diode and one terminal of the power storage element; A diode for rectifying the voltage of the bell ringing call signal and applying the rectified voltage to the power storage element, and preventing a backflow of the electric charge stored in the power storage element, and detecting a stored amount of the power storage element, A storage amount detection unit that outputs a detection signal when the storage amount is equal to or more than a predetermined value; and a charge stored in the storage element is supplied as a power supply to a transmission / reception circuit included in the telephone line terminal, and the storage amount detection is performed. Control means for controlling the transmission / reception circuit and starting communication when a detection signal is input from the means.