JPH0145815B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a surge protection circuit that protects a repeater from surges, and particularly relates to a surge protection circuit for a repeater for a relay transmission system that operates by distant power supply from a terminal device, etc. The present invention relates to surge protection circuits.

(b) Prior art and problems Figure 1 is a diagram showing an example of the conventional technology. In Figure 1, 1 is a surge protection circuit, 2 is a main signal circuit of a repeater, and 3 is a main signal circuit. Zener diode for supplying voltage power, 4 and 4' are
Coil, 5 is arrester (varistor), A,
B is a terminal for power supply.

In conventional repeaters, the main signal circuit is mainly composed of individual components (transistors, diodes, resistors, capacitors, etc.), and a surge protection circuit as shown in FIG. 1 is used.

In Figure 1, the power supply to the repeater is at terminal A.
is positive, terminal B is negative polarity, and is applied between terminals A and B.
Zener diode 3, Chiyoke coil 4',
Flows in the order of terminal B. At this time, the terminal voltage of the Zener diode 3 becomes the power supply voltage for the repeater, and supplies the load current to the repeater.

In this case, when the power supply includes a surge voltage, that is, when a surge voltage is applied between terminals A and B, the chiyoke coils 4 and 4' block the surge voltage,
The arrester (varistor) 5 connected between terminals A and B short-circuits the surge voltage, thereby preventing the surge voltage from being applied to the repeater side, that is, the main signal circuit 2.

However, in recent years, the shift to monolithic IC circuits has progressed,
In particular, in the case of monolithic ICs for high-speed signals, their resistance to surges in the opposite direction is weak, and conventional surge protection circuits are no longer able to perform their functions satisfactorily, resulting in damage to the main signal circuit of the repeater due to surges. This has led to the disadvantage of being exposed.

(c) Purpose of the Invention The purpose of the present invention is to eliminate the drawbacks of the prior art as described above and to provide a surge protection circuit suitable for a new monolithic IC repeater.

(d) Structure of the Invention According to the present invention, in a repeater for a relay transmission system operated by distant power supply from a terminal device, etc., the above object is to provide a power supply unit between input and output terminals A and B of the power supply section of the repeater. A circuit consisting of a first Chiyoke coil, a forward first diode, a first Zener diode, a forward second diode, and a second Chiyoke coil connected in series is connected to the A second Zener diode connects the connection point between the first Chiyoke coil and the first diode and the connection point between the second diode and the second Chiyoke coil, and To provide a surge protection circuit, characterized in that an arrester is connected between power supply input/output terminals A and B, and the terminal voltage of the first Zener diode is output to the main signal circuit of the repeater. This is achieved by

(e) Embodiments of the Invention The present invention utilizes the operating characteristics of diodes to prevent reverse surges from entering the main signal circuit of a repeater.

FIG. 2 is a diagram showing an embodiment of the present invention.
5 are the same as in FIG. 1, 6 is a reverse surge protection diode of the present invention, and 7 is a Zener diode. The Zener voltage of the Zener diode 7 is higher than that of the Zener diode 3.

The details of the present invention will be explained below with reference to FIG.

As shown in FIG. 2, surges applied in the forward direction are handled by the action of the choke coils 4, 4' and the arrester (varistor) 5, similar to the conventional surge protection circuit shown in FIG. The main signal circuit 2 is protected from surges by bypassing the voltage.

Next, the protection function against surges entering from the opposite direction, which is the main focus of the present invention, will be described.

The diodes 6, 6' are biased in the opposite direction against a surge that enters from the opposite direction, resulting in an apparent high impedance. On the other hand, the Zener diode 7 is biased in the forward direction against surges entering from the opposite direction, and has an apparent low impedance. Therefore, diodes 6, 6' and Zener
Due to the function of the diode 7, surges entering from the opposite direction are bypassed by the Zener diode 7, so that it is possible to prevent surges from entering the main signal circuit 2 in the reverse direction.

The functions of the choke coils 4, 4' and the arrester (varistor) 5 are similar to those described in the conventional example shown in FIG. can be protected from surges.

Therefore, by employing such a protection circuit, it is possible to almost completely prevent the invasion of surges, and the protection effect is tremendous.

FIG. 3 shows another embodiment of the present invention,
All numbers used are the same as in Figures 1 and 2.

Even when a plurality of main signal circuits 2 are connected in series as shown in FIG. 3, the same protection function as described above can be achieved.

Note that the diodes 6, 6' can be replaced by Zener diodes with a suitable Zener voltage.

Furthermore, in FIG. 3, two diodes 6,
6' is used, but the number of main signal circuits 2 used,
The number of diodes used can be increased or decreased depending on the surge application conditions.

Further, the surge protection function can be further enhanced by connecting the Zener diodes 7 to 7 separately for each main signal circuit 2 as shown in FIG.

(f) Effects of the Invention As explained in detail above, according to the present invention, it is possible to almost completely block surges entering from the opposite direction, which is a particular problem in monolithic IC repeaters. Therefore, it has a very large effect in terms of surge protection.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of a conventional embodiment. In Fig. 1, 1 is a surge protection circuit, 2 is a main signal circuit of a repeater, and 3 is a zener for supplying constant voltage power to the main signal circuit.・Diode, 4, 4' are chiyoke ・
The coil 5 is an arrester (varistor), and power is supplied in the direction from terminal A to terminal B. FIG. 2 is a diagram showing an embodiment of the present invention.
5 are the same as in FIG. 1, 6 and 6' are reverse surge protection diodes of the present invention, and 7 is a Zener diode. FIG. 3 shows another embodiment of the present invention,
FIG. 4 is a diagram for explaining a modification of FIG. 3.

Claims (1)

[Claims] 1. In a relay transmission system repeater that operates by distant power supply from a terminal device, etc., a first chiyoke coil,
Connect a circuit in which a first diode in the forward direction, a first Zener diode, a second diode in the forward direction, and a second Chiyoke coil are connected in series, and the first Chiyoke coil and the Chiyoke coil are connected in series. A second Zener diode connects the connection point with the first diode and the connection point between the second diode and the second chiyoke coil, and connects the power supply input/output terminals A and B of the repeater. 1. A surge protection circuit, characterized in that an arrester is connected between the first Zener diode and the terminal voltage of the first Zener diode as output to the main signal circuit of the repeater.