KR920005051Y1 - A power supply circuit of subscribers systems - Google Patents

Abstract

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Description

Constant current power supply circuit in subscriber circuit of switching system

1 is a conventional circuit diagram.

2 is a circuit diagram according to the present invention.

* Explanation of symbols for main parts of the drawings

ZD1, ZD2: Zener Diodes Q11, Q12: Transistor

R11, R12, R13, R14, R15: Resistor C11, C12, C13: Capacitor

T11: Transformer

The present invention relates to a subscriber circuit of an exchange system, and more particularly to a circuit for supplying a constant current of direct current to a telephone set in a subscriber circuit of an exchange system.

In general, a telephone connected to a switching system operates by receiving a talk current from a subscriber circuit of the switching system to transmit a voice signal to the switching system.

1 is a power supply circuit diagram of a conventional subscriber circuit, and is composed of a transformer T1, resistors R1-R3, and capacitors C1-C2.

In FIG. 1, when the tip line T and the ring line R are connected to the telephone, the supply current limited to the resistors R1-R2 by the supply power (-48 V) is supplied to the telephone. Supplied. Therefore, the AC signal of the telephone is removed from the DC component by the capacitor C1 and transmitted to the network by the transformer T1. In addition, the resistor R3 and the capacitor C2 of the secondary side of the transformer perform a decoupling operation. On the other hand, such a circuit has a problem that a large transformer must be used to prevent saturation of the transformer T1. In addition, there is a problem that the loss of the AC signal by the circuit itself occurs.

Accordingly, an object of the present invention is to provide a constant current supply circuit that compensates for the loss of an AC signal and maintains a constant DC current supplied to a telephone by using a small transformer in a power supply circuit of a subscriber circuit for supplying current to a telephone. In providing.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a specific circuit diagram of the constant current supply circuit according to the present invention, the NPN type of the different types such that the constant current is supplied to the telephone by the power supply through the tip line (T) and the ring line (R) connected to the telephone Along with the zener diodes ZD1-ZD2 and the zener diodes ZD1-ZD2 which determine the direct current bias of the transistors Q11 and PNP transistor Q12, the NPN and PNP transistors Q11-Q12. Resistors R11 and R14 and resistors R12 and R13 for determining driving currents of the NPN and PNP transistors Q11 to Q12, the base of the NPN transistor Q11, and the PNP transistor Q12. A capacitor (C11) connected between the bases of the capacitors to block the direct current component so that the NPN and PNP transistors Q11-Q12 amplify and compensate for the loss caused by the circuit itself of the AC signal in the low frequency band, Via (T) and ring line (R) A capacitor C12 for removing the DC component of the AC signal inputted therein, a transformer T11 for transmitting the AC signal to the network, a resistor R15 for operating as a decoupling circuit, and a capacitor C13.

Hereinafter, an operation example of FIG. 2 according to the present invention will be described in detail.

Now, when tip line T and ring line R are hooked off to the telephone and hooked off, the tip line T and ring line R are looped and supply power (-48V). Current supply path connected to supply power (-48) → resistance (Rn) → transistor (Q11) → tip line (T) → ring line (R) → transistor (Q12) → resistance (R14) → contact Is configured so that the drive current is supplied to the phone via the tip line (T) and the ring line (R). In addition, the drive current is kept constant by the zener diodes ZD1-ZD2 and the resistors R11-R14.

On the other hand, the AC signals inputted through the tip line T and the ring line R cause loss by the circuit itself, and the transistors Q11 to Q12 having bases connected to each other by the capacitor C11 with respect to the AC signal. Since the circuit is configured to act as a push pull amplifier, the loss of the AC signal is amplified and compensated by the transistors Q11 to Q12. In addition, the direct current component is removed by the capacitor C2, and the pure AC signal is transmitted to the network as the transformer T11.

As described above, the present invention enables the use of a small transformer as a circuit for maintaining a constant DC current supplied to a telephone in the subscriber circuit of the switching system, thereby reducing the mounting area of the transformer and lowering the price.

In addition, the loss of the AC signal can be compensated by amplifying and transmitting the loss of the AC signal by the circuit itself.

Claims (2)

In the constant current power supply circuit in the subscriber circuit of the switching system, different types of NPN transistors are provided such that the constant current is supplied to the telephone by the supply power through the tip line T and the ring line R connected to the telephone. The NPN together with the zener diodes ZD1-ZD2 and the zener diodes ZD1-ZD2 which determine the direct current bias of the Q11) and PNP transistors Q12, the NPN and PNP transistors Q11-Q12. Resistors R11 and R14 and resistors R12 and R13 for determining the drive current of the transistor type and PNP transistors Q11 to Q12, the base of the NPN transistor Q11, and the base of the PNP transistor Q12. A capacitor C11 and a tip line T connected to each other to block a direct current component and to allow the NPN and PNP transistors Q11 to Q12 to amplify and compensate for a loss caused by a circuit itself of an AC signal in a low frequency band; ) And through the ring line (R) A capacitor (C12) for removing the direct current component of the output AC signal, and a transformer (T11) for transmitting the AC signal from which the direct current component has been removed to a network. . The base terminal of claim 1, wherein the base terminals are connected to each other by a capacitor C11 so that the NPN transistor Q11 and the PNP transistor Q12 operate as a push-pull amplifier to amplify and compensate for the loss of an AC signal. A constant current supply circuit in a subscriber circuit of an exchange system.