JPS60182845A - Power supply circuit for telephone set - Google Patents

Abstract

PURPOSE:To decrease the wear of a battery and the loss of station power supply current by arranging a voltage limiter circuit to the input stage of a diode summing a station power supply voltage and the output voltage of a backup battery. CONSTITUTION:The station power supply voltage is rectified by the diode bridge 6, a power supply is applied to a control circuit 11 via a resistor 20 and a diode 21, and the station power supply voltage is extracted via a dial pulse transmission circuit even at dialing and talking. Zener diodes 25A, 25B as the voltage limiter are connected to a connecting point between a resistor 20 and a diode 21 and a connecting point between a resistor 22 and a diode 23. Thus, an output of the backup battery 26 is opposite in the conducting direction of the diodes 21, 23 and the current of the battery 26 does not flow via the Zener diodes 25A, 25B. Moreover, the Zener diodes 25A, 25B are provided separately, the resistors 20, 22 are selected properly and the leakage of the power supply current below the breakdown voltage of the Zener diodes is reduced.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a power supply circuit for a central office power type telephone equipped with a control circuit that uses power from a central office to control dialing operations, etc. .

[Technical background of the invention]

Conventionally, in telephones powered by central office power, the central power supply voltage extracted from the central office line terminal is used to operate a control circuit, and this control circuit controls dialing operations, dial key input processing, and communication path formation operations. ing.

FIG. 1 is a block diagram showing the configuration of such a telephone, in which 1 and 2 are office line terminals, and 3 is a hook switch. When the hook switch 3 is waiting for an incoming call, it is connected to the incoming call circuit 4 as shown, and when an incoming call signal arrives, the hook switch 3 transmits the incoming signal to the incoming call circuit 4 and causes the sounder 5 to generate a ring tone. On the other hand, when making a one-dial call or making a call, the hook switch 3 is connected to the diode bridge 6 side, and the call signal from the other party's phone is sent to the telephone circuit via the diode bridge 6 and the dial/home signal sending circuit 7. 8, and is inputted via this telephone circuit 8 to a handset 9 or a reception monitor speaker 10, and is produced as voice. Reference numeral 11 is a control circuit that controls dialing and calling operations, and a hook switch 3.
The dial sending circuit 7 receives the output of the hook switch contact 12 which is linked with the
It also controls the operation of the telephone circuit 8 during a call, switches between the handset 9 and the receiving monitor speaker IO, and controls the prevention of excessive sound when transmitting dial/-P pulses.

In a telephone set having such a configuration, a power supply circuit as shown in FIG. 2 has conventionally been used in order to secure power for operation of the control circuit 11. That is, diode bridge 6
A first diode 21 is connected to the output of the dial via a resistor 20 to extract the local power supply voltage during a call, and a second diode 23 is also connected via a resistor 22 to the output of the dial/main line sending circuit 7. , the station power supply voltage is taken out through the dial/buses sending circuit 7 during dial/buses sending out and during a call, and the station power supply voltages are connected to the diode 21.2.
3, the combined voltage is smoothed by a smoothing capacitor 24, and regulated by a Zener diode 25 as a voltage limiter so as not to exceed a constant voltage, and then supplied to the control circuit 11K.

By the way, the control circuit li is composed of a control section such as a microconverter and a memory section for storing data such as speed dial numbers. The output voltage from the backup battery 26 is approximately the same as the Zener voltage of the Zener diode 25 to the output of the diode 2.
It is further merged via 7. The structure is taken.

[Problems with background technology]

However, in a power supply circuit with such a configuration, the output voltage of the backup battery 26 is always applied to the Zener diode 25 provided to regulate the local power supply voltage to a constant voltage, so the output voltage of the battery 26 is Even if the Zener voltage is approximately the same as the Zener voltage, a small amount of Zener current from the battery 26 flows through the Zener diode 25 in a region below the breakdown point, causing the battery 26 to be quickly consumed.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a telephone power supply circuit capable of eliminating the above-mentioned problems and suppressing consumption of a backup battery.

[Summary of the invention]

The present invention achieves the above object by connecting a Zener diode as a voltage limiter to the input side of a diode that takes out the local power supply voltage.

[Embodiments of the invention]

FIG. 3 is a circuit diagram showing one embodiment of the present invention.

In the same figure, the difference from the conventional circuit shown in FIG. 2 is that Zener diodes 25A and 25B, which act as voltage limiters that regulate the local power supply voltage so that it does not exceed a constant voltage, are installed on the input sides of diodes 21 and 23, respectively. This is what we have set up. By doing so, the output of the backup battery 26 is in the opposite direction to the conduction direction of the diodes 2i and 23, so that the current of the battery 26 does not leak through the Zener diodes 25A and 25B. As a result, unnecessary consumption of the battery 26 can be suppressed. In addition, the line 26 to which the resistor 20 is connected has a voltage of 48V to 100V at the initial stage of line connection and at the time of dialing/system transmission.
A DC voltage of 24V to lOv is applied to the wire 27 to which the resistor 22 is connected during a call, but the Zener diodes -25A and 25B are connected to the diode 21.2.
Since the resistor 20.22 is provided separately on the input side of 3.
By appropriately choosing the value of each Zener diode 2
Leakage of local power supply current in the region below the breakdown point of 5A and 25B can also be suppressed to a small level. Note that in FIG. 3, all parts that are the same as those in FIG. 2 are represented by the same symbols.

FIG. 4 is a circuit diagram showing another embodiment of the present invention, in which the control circuit 1
This is to improve the noise resistance of the memory section constituting the device. In this embodiment, the chizo enable signal CE and read/write signal R/w to the memory section 110 of the control circuit 11 have no meaning when disturbance noise occurs.
This is basically different from the configuration shown in FIG. 3 in that the negative power source is configured so as to work toward the side of . For this reason, the diodes 21, 22 and Zener diodes 25A, 2
The polarities of the polarized elements such as 58 are all reversed.

Furthermore, in order to prevent the power supply voltage of the memory section 110 from being adversely affected even if the power supply voltage of the control section 111 constituting the control circuit 11 drops abnormally, the power supply systems of the control section 111 and the memory section 11O are separated. ing. That is, the control unit 111 receives the voltage combined by the diodes 21 and 23,
The voltage of the battery 26 is limited by a current limiter circuit 28, and then the voltage is supplied through a diode 29. Zener diodes 25A, 2 are connected to the memory section 11O.
A voltage obtained by merging the output voltages of 5B through diodes 30 and 31 and an output voltage from the battery 26 through a diode 32 are supplied. In this case, current limiter circuit 28 includes resistors 280 and 281, Zener diode 2
82, diode-P2S5, transistor 284, flat i:
The current limit value is determined according to the Zener voltage of the Zener diode 282. Note that 33 and 34 are smoothing capacitors, and 35 is a current limiting resistor for preventing the memory section 1xoti>lasotiazo.

Therefore, in such a configuration, the control circuit 11 operates with a negative power supply voltage with the ground potential on the high potential side.
Since the power supply voltage systems for the control section 1to and the memory section 110 are separated, even if the power supply voltage for the control section 111 becomes low, the memory section 1to will not be adversely affected, and data such as speed dial numbers stored inside will be destroyed. Can be held without any problems. Further, even if disturbance noise occurs, the chip select signal CE and the read/write signal R/W change in one sense to the significant side, so that noise resistance can be improved. Further, the current limiter circuit 28 causes the battery 26 to
consumption can be further reduced.

In the above embodiment, the local power supply voltage is also taken out through the dial/receiver sending circuit 7, but it goes without saying that a configuration in which this route is omitted can be applied in exactly the same manner.

〔Effect of the invention〕

As explained above, the present invention provides a local voltage limiter circuit.
#Lf! ! Since it is placed in the input stage of the diode that combines the voltage and the output voltage of the backup battery, it has the effect of suppressing the consumption of the backup battery and further preventing the leakage of the local power supply current.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the general configuration of a central power supply type telephone, Fig. 2 is a diagram showing a conventional power supply circuit, Fig. 3 is a diagram showing an embodiment of the present invention, and Fig. 4 is a diagram showing an embodiment of the present invention. It is a figure which shows another Example. 1.2...Station line terminal, 6...Diode buritsuno,
7... Dial/9 pulse sending circuit, 8... Telephone circuit, 11... Control circuit, 20.22... Resistor, 21
, 23°29.30, 31.32...diode,
25.25A. 25B... Zener diode, 26... Backup battery, 24... Capacitor, 110... Memory section, 111... Control section. Figure 1

Claims (1)

[Claims] A first diode for deriving the local power supply voltage, a second diode for deriving the output voltage of the backup battery, and a first diode for deriving the output voltage of the backup battery. and a voltage limiter that regulates the voltage supply so that it does not exceed a constant voltage in a telephone power supply circuit that is supplied with a confluence voltage of the output voltages of the second diode and includes a control circuit that controls dialing and talking operations. A telephone power supply circuit, characterized in that the circuit is placed on the input side of the first diode.