JPH02303319A - Surge protective circuit - Google Patents

Abstract

PURPOSE:To suppress surges by providing a conductor gap, which causes spark discharge to high voltage applied, between power input lines. CONSTITUTION:A surge protective circuit 1 is provided between an AC power input terminal and a rectifier OB. The surge protective circuit 1 is the one where a conductor gap 4, which causes spark discharge, is formed in the power input line on the input side of a capacitor C and a resistor R is connected to the input side. The discharge gap 4 is formed by projecting triangular projections 5a, respectively, from the positive and negative copper foil patterns 5 in the power input line on a printed board. When surges occur, spark discharge occurs between the projections 5a, and the surges are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a surge protection circuit that protects a circuit from lightning surges superimposed on a power source.

[Conventional technology 1 Recent electricity 8! Semiconductors are increasingly being used in devices. However, semiconductors are susceptible to N# structural surges,
When a surge, especially a lightning surge, is applied, there is a problem that malfunction or destruction is likely to occur. In addition, the surge S is heavy on the power input line! FIG. 8 shows the power supply voltage waveform when the power supply voltage is turned off. Here, the voltage of the surge superimposed on the distribution Ml line is 2k
Surges of V or less are very common, but surges of 5.6 kV or more are sometimes observed.

Therefore, in order to protect circuits from such surges, a surge protection circuit 1 as shown in FIG. 6 has conventionally been used. This figure 6 shows a charger equipped with a surge protection circuit 1, in which protective resistors R are connected to both the positive and negative sides of the dark power input line between the commercial power supply AC and the input of the diode bridge DB. A capacitor CI and a ZnO varistor 2 are connected in parallel to the input amount.

Note that the charger block 3 is connected to the output of the diode Pritsuno DB. Here, the ZnO varistor 2 has the characteristics shown in Figure 7, and when a voltage higher than a predetermined voltage is applied to the power input line, the impedance decreases, current flows through the ZnO varistor 2, and surges are suppressed. be done. Further, the capacitor C3 is provided to store the residual energy when a surge is applied and to suppress the surge. In this surge protection circuit 1, since the capacitance of the capacitor C5 cannot be made sufficiently large due to space limitations, the voltage that cannot be suppressed by the capacitor C4 is clamped to a constant voltage by the ZnO varistor 2. Further, the capacitor C9 also serves as a filter that reduces noise output from the charger block 3 to the commercial power supply AC side.

[Problem to be solved by the invention] However, as in the surge protection circuit 1 described above, ZnO
If the varistor 2 is used, it is difficult to reduce the cost because the ZnO varistor 2 is expensive. Also, capacitors C1 and Z
Since nO varistor 2 is large, surge protection circuit 1
Moreover, when a large surge voltage higher than the varistor voltage is applied to the ZnO varistor 2, the impedance increases, and such a large surge cannot be sufficiently suppressed.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a surge protection circuit that is inexpensive, compact, and capable of good surge suppression.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention includes a conductor gap that causes a spark discharge in response to a high voltage applied to the power supply line.

"Effect 1 The present invention provides a conductive gap as described above.
When a surge is input to the power input line, the surge is suppressed by spark discharge to obtain a sufficient surge suppression effect, and by using a conductive gap, this conductive gap can be connected to the gi4ti pattern on the printed circuit board. It is made to be inexpensive and small in size.

[Example 1] An embodiment of the present invention is shown in FIGS. 1 to 4.

As shown in FIG. 1, the surge protection circuit 1 of this embodiment has the following features:
A conductor gap 4 is formed in the power input line on the input side of the capacitor C3 to cause spark discharge in response to high voltage. Note that the other configurations are the same as the circuit in FIG. 6. As shown in FIG. 2, the conductor gap 4 is formed by protruding triangular protrusions g5a from the positive and negative copper foil patterns 5 of the power input lines on the printed circuit board.

The distance between the needle-like pointed tips of the projections 5a is, for example, 2 to 3 cm. Then, no soldering resin is applied to the protrusion 5a, so that spark discharge in the conductive gap 4 is likely to occur.

Now, if a surge shown by the broken line of the third rj When reaching the conductive gap 4
Corona discharge begins. And then the conductive gap 4
The spark discharge starts at , the energy of the surge is absorbed by the spark discharge, and the voltage applied to the conductive gap 4 becomes
suppressed as shown in the figure. Therefore, the surge will not be propagated to the circuit after this conductive gap 4. As mentioned above, the conductive gap 4 is slightly opened before the spark discharge starts, but since this delayed opening of the spark discharge is short, the stress exerted on the subsequent circuit is small and is not a problem. Must not be.

The graph in FIG. 4 shows the relationship between spark discharge voltage and gap length. When the gap length is about 116I11, the spark discharge voltage is about 3 kV, and the conductive gap 4 can suppress surges exceeding the spark discharge voltage. Note that if a voltage lower than this spark discharge voltage is input to the power input fin, it is absorbed by the capacitor C1.

Furthermore, it is also effective to form the conductive gap 4 after the diode DB.

[Example 2] Another example of the present invention is shown in tIS5 diagram. In this embodiment, the present invention is applied to a charger that operates using a voltage obtained by half-wave rectification of commercial fiiAc as a power source. In this case, a conductive gap 41 and a capacitor C3 are provided after the rectifier diode D, and a conductive gap 4□ is provided at both ends of the rectifier diode D.

Now, if a surge in the positive direction of the commercial power supply AC is input to the power supply input line, in this case, the surge is suppressed by the conductive gap 41 and the capacitor C5 in the same way as in the first embodiment described above. Note that it is necessary to select a rectifier diode D that can withstand this surge.

Further, when a negative surge of the commercial Ml source AC is input to the power supply input line, the surge is suppressed by the conductive gap 4 and the capacitor CI. Here, if there is no conductive gap 42, if the surge has a voltage that exceeds the reverse breakdown voltage of the rectifier diode D, the rectifier diode D will fail! be done.

Therefore, a conductive gap 4□ is provided at both ends of the rectifier diode D, so that the voltage exceeding the reverse withstand voltage is connected to the rectifier diode °D.
Try not to get infected. In this case, the surge voltage is shared and limited by the conductive gap 41.4□.

[Effect of the Invention 1] As described above, the present invention includes a conductor gap that causes a spark discharge in response to a high voltage applied between the power input lines, so that when a surge is input to the power input line, Surges can be suppressed by spark discharge, and therefore, unlike in the case of ZnO varistors, impedance does not increase and surges cannot be suppressed sufficiently, and a good surno suppressing effect can be obtained. However, if it is a conductive gap, it can be formed with a copper foil pattern on a printed circuit board, making it inexpensive and compact.

[Brief explanation of drawings]

Figure 11111 is a circuit diagram of an embodiment of the present invention, Figure 2 is an explanatory diagram showing the structure of a conductive gap, Figure 3 is an explanatory diagram showing a surge suppression state by the conductive gap, and Figure 4 is the gap length of the conductive gap. Figure 5 is a circuit diagram of another embodiment, Figure 6 is a circuit diagram of a conventional example, Figure 7 is a characteristic diagram of a ZnO varistor, and Figure 8 is a graph showing the relationship between voltage and spark discharge voltage. FIG. 2 is a voltage waveform diagram of a commercial power source. 1 is a surge protection circuit, 4, 4. ．． 42 is a conductive gap. Agent Patent Attorney Ishi 1) Chief 7 Figure 2 Figure 3 Figure 4 Cape Gi 1. pu1j(rnrn Figure 5

Claims (1)

[Claims] (1) A surge protection circuit with a conductor gap that causes a spark discharge in response to a high voltage applied between power supply input lines.