JPS60212058A - Power supply circuit of telephone set - Google Patents

Abstract

PURPOSE:To save the wear of a backup battery and to improve noise immunity of a control circuit by connecting a Zener diode as a voltage limiter to an input of a diode extracting a station power supply voltage and activating the control circuit with a negative power supply voltage. CONSTITUTION:The Zener diodes 25A, 25B as the voltage limiter are connected to the input of diodes 21, 23 extracting the station power supply voltage. Moreover, since the circuit is constituted to extract the negative station power supply voltage, transistors (TRs) of dial pulse transmission circuit 7 have different polarity different from a conventional circuit. Though the constitution above, since the output of the backup battery 26 is in opposite direction to the conducting direction of diodes 21, 23, 30 and 31, the current from the battery 26 is leaked via the Zener diodes 25A, 25B. As a result, the wear of the battery 26 is saved.

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, a control circuit is operated using the central power supply voltage extracted from the central office line terminal, 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, where 1 and 2 are central 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 circuit 4 side as shown in the figure. When an incoming call signal arrives, the incoming call signal is sent to the incoming call circuit 4, and the sounder 5 generates a ring tone. Conversely, when making a 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 telephone is input to the telephone circuit 8 via the diode bridge 6 and the dial pulse sending circuit 7. The signal is input to the handset 9 or the receiving monitor speaker 10 via the telephone circuit 8 and is output as voice. Reference numeral 11 denotes a control circuit for controlling the dialing operation and the calling operation, and receives the output of the hook switch contact 12 linked to the hook switch 3 and the output of the dial key pad 13, and controls the dial pulse sending operation of the dial sending circuit 7. together with the telephone circuit 8
◎In a telephone with such a configuration, the power supply for the operation of the control circuit 11 is ensured. Conventionally, the second
A power supply circuit as shown in the figure is used. That is,
A first diode 21 is connected to the output of the diode bridge 6 via a resistor 20 to extract the local power supply voltage during a call, and a resistor 22 is also connected to the output of the dial pulse sending circuit 7.
A second diode 23 is connected through the diodes 21 and 23, and the station power supply voltage is taken out through the dial pulse sending circuit 7 during dial pulse transmission and during a call, and these station power supply voltages are combined at the output side of the diode 21 and 23. The combined voltage is smoothed by a smoothing capacitor 24 and regulated to a constant voltage by a Zener diode 25 as a voltage limiter before being supplied to the control circuit 11. In this case, in order to back up the memory in the control circuit 11, the output voltage of the backup battery 26 is also combined via the diode 27 with the output of the diode 21.23.

Further, a power supply circuit as shown in FIG. 3 may be used. That is, diodes 17 and 18 resistor 19,
A constant current local power supply voltage is taken out via a diode 21 by a constant current circuit consisting of a transistor 16, the output voltage of a backup battery 26 is combined with the output of this diode 21 via a diode 27, and the combined voltage is connected to a smoothing capacitor. In this case, the backup battery 26 is stored in the memory section built into the control circuit 11. This is provided to prevent data such as speed dial numbers from being lost.

[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 one battery 26 is Even if the output voltage was almost the same as the Zener voltage, there was a problem in that a minute Zener current from the battery 26 would flow through the Zener diode 25 in the region below the breakdown point, causing the battery 26 to be exhausted quickly. .

Furthermore, since the first control circuit 11 operates on a positive power supply voltage with the ground potential on the low potential side, if disturbance noise occurs on the positive potential side, this disturbance noise will cause the chip enable to the main parts that make up the control circuit 11. There is a problem in that it adversely affects signals and read/write signals and destroys data such as speed dial numbers.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a telephone power supply circuit that can eliminate the above-mentioned problems, suppress consumption of a backup battery, and improve the noise resistance of a control circuit.

[Summary of the invention]

In the present invention, a Zener diode as a voltage limiter is connected to the input side of a diode for taking out the local power supply voltage, and the control circuit is configured to operate with a negative power supply voltage.

[Embodiments of the invention]

FIG. 4 is a circuit diagram showing an embodiment of the present invention, in which the power supply voltages of the control section 111 and the memory section 110 constituting the control circuit 11 are separated and taken out separately, and the negative station power supply voltage is taken out from the station line. It is configured to take out the voltage. That is,
The negative local power supply voltage is taken out by a first diode 21, 23 whose cathode is connected to the local line side, and is smoothed by a capacitor 33 before being supplied to the control unit 111, and the negative local power supply voltage is supplied to the memory. For the section 110, the negative local power supply voltage is taken out by a first diode 30, 31 whose cathode is connected to the local line side, and is supplied to the capacitor 34 after being smoothed. . Further, a negative battery voltage is added to the anode sides of the diodes ao and ai from the backup battery 26 via a resistor 35 and a diode 32. Further, a negative voltage obtained by current-limiting the voltage of the battery 26 by a current limiter circuit 28 is added to the anode side of the diodes 21 and 23 via a diode 29, which is a second diode. In this case, current limiter circuit 28 is connected to resistor 280
and 281. Zener diode 28z, diode 283, )2 transistor 284. It is constituted by a smoothing capacitor 285, and the current limit value is determined by the Zener voltage of the Zener diode 282.

Note that 35 is a current limiting resistor for preventing double-up of the memory section 110. On the other hand, ``Zener diode as a voltage limiter''
*, 2sB is the diode 21.23 that takes out the local power supply voltage.
connected to the input side of the

In addition, since the configuration is such that the negative local power supply voltage is taken out, the transistor of the dial pulse sending circuit 7 has a different polarity from that shown in Figures 2 and 3. In this configuration, the backup Since the output of the battery 26 is in the opposite direction to the conduction direction of the diodes 21, 23, 30, and 31, the current of the battery 26 does not leak through the Zener diodes 25A and 25B. As a result, consumption of the battery 26 can be suppressed. In addition, the line 36 to which the resistor 20 is connected is supplied with a DC voltage of 48 V to 100'7 at the initial stage of line connection and at the time of dial pulse transmission, and the line 37 to which the resistor 22 is connected is supplied with a DC voltage of 48 V to 100'7.
The DC voltage of 1K 24 V to IOV is high.
By providing the resistors 20 and 31 separately on the input side, leakage of local power supply current in the region below the breakdown point of each Zener diode 25A125B can be suppressed by appropriately selecting the value of the resistor 20.22. @ Also, since the control circuit 11 is supplied with power by a negative power supply voltage with the ground potential on the high potential side, the chip enable signal "■" and the read/write signal R to the memory section 110 are
/W becomes 1 meaningless when disturbance noise occurs (i.e., 1 terminal becomes 1H# and the chip is selected, and the R/W terminal becomes @H" and R
◎) Improves noise resistance. Furthermore, the control unit 1
11 and the memory section 110 are separated, so even if the power supply voltage for the control section 111 is lower than or at the same potential as the memory holding voltage, the memory section 1
10 will not be adversely affected, and data such as speed dial numbers stored internally will be retained without being destroyed.

Furthermore, since the voltage from the battery 26 to the control unit 111 is limited to a few μ by the current limiter circuit 28, abnormal consumption of the battery 26 is further suppressed (several 100 μA to several As degrees). be able to.

Here, by using a Zener diode in the current limiter circuit, the forward leakage current of the Zener diode is smaller than the forward leakage current of a normal diode, and this can be used to reduce the current consumption to about a few μA. I can do it.

Figure IA5 is a circuit diagram showing another embodiment of the present invention,
A positive power supply voltage is supplied to the control section 111, and the memory section 11
0 is supplied with a negative power supply voltage, and the station power supply voltage is directly taken out from the input side of the diode bridge 6 in order to compensate for the drop in power supply voltage due to the voltage drop of the diode bridge 6.

That is, the positive local power supply voltage is taken out by the resistor 20, the Zener diode 25, and the first diode 21, and the positive local power supply voltage is taken out directly by the diodes 40 and 41 connected to the input side of the diode bridge 60. This voltage is combined with the output voltage of the diode 21 via the transistor 42 and the resistor 43, and the combined voltage is regulated to a constant voltage by the Zener diode 45 and then supplied as the power supply voltage to the control unit 111. Further, the output voltage of the backup battery 26 is determined by a diode 46, a Zener diode 48. It is input to a second diode, diode 47, through a current limiter circuit consisting of a transistor 49 and a resistor 50, and further K l! I The configuration is such that the voltage is applied to the leg portion 111. Further, diodes 51 and 52 and a resistor 53 are directly connected between the ground potential and the negative terminal of the battery 26, a negative voltage is taken out from the connection point of the diodes 51 and 52, and this negative voltage is connected to the capacitor 54. The voltage is smoothed by the following steps and then supplied as the power supply voltage of the memory section 110.

Note that the transistor 42 is turned on when the transistor 44 is turned on, and the transistor 44 is turned on when the dial pulse is sent. Furthermore, the Zener diode 45 is connected to the ground potential via a transistor 4G that is turned on when a dial pulse is sent. Therefore, the local power supply voltage through the diodes 40 and 41 is taken out only when dial pulses are sent out, and is regulated to a constant voltage by the Zener diode 45, which functions effectively at this time, and is combined with the output voltage of the diode 21.

According to this configuration, since the local power supply voltage is also taken out from the input side of the diode bridge 6, it is possible to compensate for the low voltage of the power supply corresponding to the voltage drop of the diode bridge. Since it operates with m'a pressure, even if disturbance noise occurs, take notes! Chip enable signal “I” and read/write signal “R” for JglllO
/W is influenced to the side of ``1 meaningless'' @ Therefore, data such as stored speed dial numbers can be retained without being destroyed. Also, the Zener diode 25 as a voltage limiter is connected to the diode 21. Since it is connected to the input side, consumption of the battery 26 can be suppressed. In the above embodiment, an example was explained in which the station power supply voltage is taken out even when dial pulses are sent out, but a configuration in which this path is deleted may also be used. good.

〔Effect of the invention〕

As explained above, the present invention connects the voltage limiter to the input side of the diode that extracts the local power supply voltage so that it is combined with the output voltage of the backup battery, and *1+ The control circuit is operated with a negative power supply voltage. Because of this configuration, it is possible to significantly suppress the consumption of the backup battery, and furthermore, it is possible to improve the noise resistance of the control circuit.

[Brief explanation of drawings]

Figure 1 is a diagram showing the general configuration of a central power supply type telephone.
2 and 3 are diagrams showing conventional power supply circuits, FIG. 4 is a circuit diagram showing one embodiment of the present invention, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. 1, 2-...Station line terminal, 6...Diode connector,
7--Dial pulse sending circuit, 8--Telephone circuit, 11--Control circuit, 20.22--Resistor, 21,2
3゜30~32.40~42-...diode, 251
25 to 125B-... Zener diode, 26...
Backup battery, 110--Memory section, 111-
・Control unit, 28...Current limiter circuit, 282, 48
--Takahisa Kimura, Zener diode agent patent attorney tW Figure 4

Claims (3)

[Claims] (1) A first diode that takes out the station's source voltage, a second diode that joins the output voltage of the backup source to the output of the first diode, and a connection between these first and second diodes. In the above-mentioned telephone power supply circuit, the telephone power supply circuit includes a voltage limiter circuit that regulates the confluence voltage to a constant voltage and supplies the output voltage as a power supply voltage to a control circuit comprising a memory section and a control section that control dialing operations and telephone conversation operations. A telephone set, characterized in that a voltage limiter circuit is connected to the input side of the first diode, and the first and second diodes are connected to take out a negative station power supply voltage and a negative backup battery voltage. Power supply circuit〇 (2) A first diode that takes out the local power supply voltage, a second diode that merges the output voltage of the backup battery with the output of the first diode, and a second diode that
The combined voltage by the diode is regulated to a constant voltage,
A telephone power supply circuit including a voltage limiter circuit that supplies the output voltage as a power supply voltage to a control circuit comprising a memory section and a control section that control dialing operations and telephone conversation operations, wherein the voltage limiter circuit is connected to the first diode. A current limiter circuit for limiting the amount of incoming radio waves is connected to the input side of the second diode, and a negative power supply voltage is formed from the combined voltage of the first and second diodes. A third diode, a resistor, and a capacitor are provided, and the control unit is supplied with the combined voltage, and the memory unit is supplied with the negative power supply voltage of IW. Telephone power circuit. (3) A patent characterized in that the current limiter circuit consists of a transistor in which the output voltage of the backup battery is applied to the base terminal via a Zener diode and a diode, and the output voltage is applied to the emitter terminal via a resistor. A telephone power supply circuit according to claim (2).