JPS60182844A - Power supply circuit for telephone set - Google Patents

Abstract

PURPOSE:To supply a stable voltage to a control circuit by constituting a series connecting part comprising transistors (TRs) and diodes with TRs only so as to extract directly a station power supply voltage from a trunk line terminal thereby decreasing the loss of the station power supply voltage. CONSTITUTION:The station power supply voltage is rectified by a diode bridge 6, a power supply is fed to a control section 11 via a resistor 20 and a diode 21, and a Zener diode 25 as a voltage limiter is connected to a connecting point between the resistor 20 and the diode 21. The station power supply voltage at dial pulse transmission is extracted by an exclusive TR30 and the voltage is added to the output of the diode 21 via the resistor 32. The Zener diode 36 is connected to the connecting point between the resistor 32 and the diode 21 in order to make the station power supply voltage extracted dialing constant and the TR37 is operated only at dialing and talking. The TR30 is conductive by a TR33 only at dialing and talking. Thus, the loss of the station power supply voltage is decreased and a stable power supply voltage is applied to the control circuit 11.

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 A showing the structure of such a telephone, in which 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 call circuit 4 as shown, and when an incoming call signal arrives, the hook switch 3 sends the incoming signal to the incoming call circuit 4 and causes the sounder 5 to generate a ring tone. Conversely, when making a dial call or making a call, the hook switch 3 is connected to the diode bridge 6, and the call signal from the other party's telephone is sent to the telephone circuit via the diode bridge 6 and the dial pulse 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 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 keypad 13, and controls the dialing/gurus sending operation of the dial sending circuit 7. It also performs operations such as operations in the telephone circuit 8 during a call, switching between the handset 9 and the reception monitor speaker 10, and controls to prevent excessive sound from being heard when transmitting dial noise.

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
The first diode 21 is fully connected to the output of the dial pulse sending circuit 7 through a resistor 20 to extract the local power supply voltage during a call, and the second diode 23 is also connected to the output of the dial pulse sending circuit 7 through a resistor 22. At the time of sending out Noyalus and during a call, the local power supply voltage is taken out through the dial pulse sending circuit 7, these local power supply voltages are combined at the output side of the diode 21, 23, and the combined voltage is smoothed by the smoothing capacitor 24, and the voltage is The configuration is such that the Zener diode 25 serving as a limiter regulates the voltage so that it does not exceed a certain voltage before supplying it 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 source voltage is taken out via a diode 21 by a constant current circuit consisting of a transistor 31, 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 The control circuit 11 is smoothed by a smoothing capacitor 24 and further regulated to a constant voltage by a Zener diode 25.
The configuration is such that it is supplied as the power supply voltage.

[Problems with background technology]

However, in the power supply circuit shown in Figure 2, the second route,
In other words, the transistor 70 of the dial pulse sending circuit 7 and the diode 23 are connected to the route passing through the diode 23.
Since two elements are involved, the transistor 70 has approximately 0
．． 2 V, a voltage drop of about 0.7 V occurs at the diode 23, and there is a drawback that the local power supply voltage cannot be used effectively. On the other hand, in the power supply circuit shown in FIG.
1 and diode 21 are connected in series, a total voltage drop of 0.9 V occurs here as well, and a voltage drop of approximately 0.7 V occurs due to the circuit on the side of transistor 310, which lowers the local power supply voltage. It has drawbacks such as not being able to be used effectively or being unable to supply a sufficiently stable power supply voltage to the control circuit 11.

[Purpose of the invention]

The present invention eliminates the above drawbacks, suppresses loss of local power supply voltage,
An object of the present invention is to provide a telephone power supply circuit that can supply a stable power supply voltage to a control circuit.

[Summary of the invention]

The present invention achieves the above object by configuring the serially connected portion of a transistor and a diode to consist only of transistors, and by configuring the system so that the local power supply voltage can be taken out directly from the local line terminal as required.

[Embodiments of the invention]

FIG. 4 is a circuit diagram showing one embodiment of the present invention.

In the same figure, the difference from the conventional circuit in FIG. 3 is that the Zener diode 2 connected to the output side of the diode 21
5 is connected to the input side of the diode 21, and the transistor 3 is dedicated to the local power supply voltage when transmitting the dial pulse.
0 and is connected to the output of the diode 21 via the resistor 32. In addition, in order to regulate the local power supply voltage taken out at the time of dial transmission to a constant voltage, a second Zener diode 36 is connected to the connection point between the resistor 32 and the diode 21, and this Zener diode 36 is connected by a transistor 37 when dial pulses are transmitted. And, it was made to operate only when making a call. In this case, the transistor 30 is turned on by the transistor 33 when the dial dial pulse is transmitted and during a call. Note that 31.34°35.38.39 is a resistance.

According to this configuration, the path passing through the diode 21 has approximately 0
．． There is only a 7V voltage drop, and the path through transistor 30 is only about 0.2V. Therefore, loss of the local power supply voltage can be reduced, and a stable power supply voltage can be supplied to the control circuit 11. Further, in the conventional circuit shown in FIG. 3, the output of the backup battery 26 is always applied to the Zener diode 25, whereas in this embodiment, the output is blocked by the diode 21, and moreover, the output of the backup battery 26 is applied to the Zener diode 25. diode 3
6 also operates only when making a dial call or making a call, so the output of the backup battery 26 is not applied to the Zener diode 36 all the time. As a result, in the region below the breakdown point of the Zener diodes 25,36, the battery 2
6, no minute current flows, and consumption of the battery 26 can also be suppressed.

Note that the Zener diode 36 may be connected to the emitter side of the transistor 30.

FIG. 5 is a circuit diagram showing another embodiment of the present invention, in which the emitter of the transistor 30 in FIG. This eliminates the loss of the corresponding local power supply voltage.

In addition, only the memory section 110 is configured with a negative power supply so that the chip enable signal CE and read/write signal R/W to the memory section 110 of the control circuit 11 act on the "meaningless" side when disturbance noise occurs. Voltage is supplied to the section 110 through the diode 42, and voltage is supplied to the control section 111 from the output side of the Zener diode 36. Furthermore, in order to suppress consumption of the battery 26, the ground side of the control section 111 is supplied with voltage. A current limiter consisting of a Zener diode 43, diodes F'' 44 and 45, a transistor 46, and a resistor 47 is added between the power supply terminal and the negative side of the battery 26. As a result, the current supply from the battery 26 to the control unit 111 is restricted, and data such as speed dial numbers stored in the memory unit 110 is stably retained, and the stored data is also lost due to disturbance noise. It is also prevented that

〔Effect of the invention〕

As explained above, in the present invention, the series connection part of a transistor and a diode is composed only of transistors, and the station power supply voltage is taken out directly from the station line terminal as necessary, so that the loss of the station power supply voltage can be reduced and the control A stable power supply voltage can be supplied to the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the general configuration of a central power supply type telephone, and FIGS. 2 and 3 are diagrams showing conventional power supply circuits. FIG. 4 is a diagram showing one embodiment of the invention, and FIG. 5 is a diagram showing another embodiment of the invention. 1.2... Office line terminal, 6... Diode bridge,
7...Dial number 4 pulse sending circuit, 8...Telephone circuit, 11-...Control circuit, 21, 27, 40, 4
7-...Diode, 25.36 Zener diode, 30°33.39...Transistor, 11o...
Memo IJ section, 111...control section. Figure 2 7

Claims (1)

[Claims] A diode that derives the local power supply voltage through the diode 1'f during a call, a transistor that conducts during a call and when dial pulses are sent out to derive the local power supply voltage, and an input voltage of the diode that does not exceed a constant voltage. a first voltage limiter circuit that regulates the input voltage or the output voltage of the transistor so that it does not exceed a certain voltage; A telephone power supply circuit that supplies the power supply voltage to the control circuit that controls dialing and calling operations.