JPH0336206Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a surge protection circuit, and in particular protects electronic equipment such as communication equipment connected to a transmission line from vertical voltage surges such as lightning surges induced in the transmission line and between the transmission lines. The present invention relates to a surge protection circuit that protects against lateral voltage surges.

Generally, electronic equipment such as communication equipment connected to a transmission line is composed of a large number of semiconductor components, and therefore, the withstand voltage of these electronic equipment is extremely low. Therefore, it is necessary to protect these electronic devices and the like from vertical voltages such as surges entering from transmission lines and lateral voltages induced between transmission lines.

For this reason, surge protection circuits for electronic equipment and the like are known, for example, as described in Japanese Patent Publication No. 52-17216. This conventional surge protection circuit is the first
For example, when a vertical voltage surge enters the transmission lines 1 and 2, the surge is discharged to the ground 9 via the diodes 3 and 4 and the overvoltage operating element 7 in the case of a positive surge. In the case of a negative polarity surge, the surge is discharged to the ground 9 via the diodes 5 and 6 and the overvoltage operating element 8 to protect electronic equipment, etc. connected to the transmission lines 1 and 2 from the vertical voltage surge. There is. This conventional surge protection circuit operates as described above, so if a vertical voltage surge is induced in the transmission line, it is immediately released to the ground, and the residual voltage between the transmission lines can be extremely low. It is possible to effectively protect electronic equipment etc. from surges.

However, in the surge protection circuit shown in FIG. 8 and the circuit leading to the transmission line 2 via the diode 6, or from the transmission line 2 to the transmission line 1 via the diode 4, the overvoltage operating elements 7 and 8, and the diode 5. Therefore, when a horizontal voltage surge is induced between transmission lines 1 and 2, unlike the case where a longitudinal voltage surge is induced, both overvoltage operating elements 7 and 8 operate in series, so that The operating voltage increases, which increases the residual voltage between transmission lines 1 and 2, so transmission line 1
This residual voltage may destroy electronic equipment connected between the circuit and the circuit 2, which has the drawback that it cannot be completely ensured as a surge protection circuit.

The present invention was proposed in view of the above circumstances, and the purpose is to provide a surge protection circuit that can reliably absorb both vertical voltage surges and horizontal voltage surges, and can extremely reduce residual voltage. It is something.

The surge protection circuit according to the present invention includes a first series circuit formed by connecting a plurality of diodes in a forward direction between transmission lines connected to electronic equipment, etc., and a first series circuit having a polarity opposite to that of the first series circuit between the transmission lines. A second series circuit formed by connecting a plurality of diodes in series, and an overvoltage operation connected between a short circuit part that shorts between the middle points of each series connection of the first series circuit and the second series circuit, and the ground. The device is characterized by comprising a device.

Next, one embodiment of the present invention will be described in detail based on the drawings. FIG. 2 is a circuit diagram showing a schematic configuration of an embodiment of the present invention, in which a plurality of diodes 13 and 14 (in FIG. a first series circuit 23 formed by connecting two diodes in series in the forward direction; Multiple diodes with opposite polarity 1
5 and 16 (as before, two diodes are shown in FIG. 2, but the number is not limited to two) connected in series, respectively. .

An overvoltage operating element 17 is provided between the ground 22 and the short circuit portion 18 that shorts the series connection midpoint 19 of the first series circuit 23 and the series connection midpoint 20 of the second series circuit 24.
is connected.

Next, the operation of the surge protection circuit shown in FIG. 2 will be explained. Transmission line 1 connected to electronic equipment, etc.
1 and 12, the positive polarity surge is transmitted from the transmission line 11 to the diode 13, the short circuit part 18, and the overvoltage operating element 17.
It is emitted from the transmission line 12 to the earth 22 through the diode 15, the short circuit 18, and the overvoltage operating element 17. Further, the negative polarity surge is discharged from the transmission line 11 to the ground 22 through the diode 16, the short circuit part 18, and the overvoltage operating element 17, and is discharged from the transmission line 12 to the diode 1.
4, the short circuit 18 and the overvoltage operating element 17 to the ground 22. As a result, transmission line 1
Electronic devices connected to terminals 1 and 12 are protected from vertical voltage surges.

Next, when a lateral voltage surge enters between the transmission lines 11 and 12, the lateral voltage surge is transferred from the transmission line 11 to the first series circuit 2 due to the polarity of the lateral voltage surge.
3 to the transmission line 12 or through the transmission line 12
flows through the second series circuit 24 to the transmission line 11 and is absorbed, so the residual voltage between the transmission lines 11 and 12 becomes low, and as a result, the residual voltage between the transmission lines 11 and 1
2 can be protected from horizontal voltage surges.

Note that in the embodiment of the present invention, the first series circuit 2
3 and the second series circuit 24, respectively, have been described using series circuits of two diodes, diodes 13 and 14 and diodes 15 and 16, respectively. However, as the first series circuit 23 and the second series circuit 24, Of course, the present invention is not limited to a series circuit of diodes, and any number of diodes may be stacked in accordance with the voltage used between the transmission lines 11 and 12. That is, by stacking and using a plurality of diodes, the forward voltage of the diodes can be increased, so that the surge protection circuit according to the present invention can be used even when the circuit voltage is high. Furthermore, by stacking multiple diodes like this,
Since the capacitance of the diode can be reduced, the surge protection circuit according to the present invention can be used even in a high frequency band.

Furthermore, in each of the series circuits of the first series circuit 23 and the second series circuit 24, by further connecting a plurality of stacked diodes in parallel, forward voltage, current withstand capacity, etc. can be set arbitrarily, so that any circuit can be used. A surge protection circuit suitable for the conditions can be obtained.

FIG. 3 is a circuit diagram showing a schematic configuration of another embodiment of the present invention, and the same parts as those in FIG. 2 are given the same reference numerals and their explanation will be omitted. In FIG. 3, a diode 13 and a diode 15 are connected in series with opposite polarity, and this connects the transmission lines 11 and 1 in parallel with the opposite polarity connection between the diode 16 and the diode 14.
This shows the case where it is connected between 2 and 2, but
Each of these series connection midpoints 19 and 20 is the short circuit part 1
8, so that the structure shown in FIG. 3 is substantially the same as that in FIG. That is, the first series circuit in FIG. 3 is composed of a series circuit of a diode 13, a short circuit part 18, and a diode 14, and the second series circuit is composed of a series circuit of a diode 15, a short circuit part 18, and a diode 16. It is. Therefore, it is clear that the embodiment shown in FIG. 3 has substantially the same functions and effects as the embodiment shown in FIG. 2, so a description thereof will be omitted.

In another embodiment of the present invention shown in FIG. 3, an overvoltage operating element 25, such as a varistor or a Zener diode, is further connected between the inner terminals of the surge protection circuit, so that a small amount of residual voltage that cannot be reduced by the surge protection circuit can be removed. Voltage overvoltage operation element 25
An example of a case where lower voltage withstand voltage equipment such as electronic equipment connected between the extension terminals is also reliably protected is shown. Furthermore, FIG. 3 shows an example in which the current capacity of the overvoltage operating element 25 is reduced by connecting resistors 26 and 27 in series with the transmission lines 11 and 12, respectively.

Since the present invention is constructed as described above, it can reliably absorb both vertical voltage surges and horizontal voltage surges that enter the transmission line, and by making the residual voltage extremely low, it can also be used in electronic equipment with low withstand voltage. Thus, a surge protection circuit capable of providing protection is obtained.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional surge protection circuit.
FIG. 2 is a circuit diagram showing a schematic structure of one embodiment of the present invention, and FIG. 3 is a circuit diagram showing a schematic structure of another embodiment of the present invention. 1, 2...Each transmission line, 3, 4, 5, 6...Each diode, 7, 8...Each overvoltage operating element, 9...
...Earth, 11, 12...Each transmission line, 13, 1
4, 15, 16... Each diode, 17... Overvoltage operating element, 18... Short circuit part, 19, 20... Midpoint of each series connection, 22... Ground, 23... First series circuit, 24... Second series circuit, 25... overvoltage operating element, 24... second series circuit, 25... overvoltage operating element, 26, 27... each resistor.

Claims (1)

[Claims for Utility Model Registration] A first series circuit formed by connecting a plurality of diodes in series in a forward direction between transmission lines connected to electronic equipment, etc.; and the first series circuit between the transmission lines. a second series circuit formed by connecting a plurality of diodes in series with opposite polarities; a short-circuit portion that shorts the middle points of the series connections of the first series circuit and the second series circuit; and a connection between the short-circuit portion and the ground. What is claimed is: 1. A surge protection circuit comprising: an overvoltage operating element connected between the surge protection circuit;