JPH0422086A - Protection circuit against surge voltage - Google Patents

Abstract

PURPOSE:To reduce cost with a power source device miniaturized and the need for a protecting member such as a surge killer eliminated by forming discharge gaps between the input and the output sides of a line filter with patterns of printed boards. CONSTITUTION:Discharging gaps 22 and 23 are formed between the input and the output sides of a line filter 4 with patterns 18-21 of printed boards. When surge voltage is applied between input terminals 14 and 15 and ground, back electromotive voltage is generated in a line filter 4, but it is discharged when reaches discharge voltage, and only voltage, in which the discharge voltage in the line filter 4 is added to applied surge voltage, is generated between a rectification smoothing circuit and the ground. Consequently a creeping distance between the rectification smoothing circuit and the ground can be shortened compared with a case when a discharge gap is unprovided. This can minimize a power source device and eliminate the need for a protecting member such as a surge killer, and thereby reduce cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surge voltage protection circuit at an input section of a power supply circuit.

[Prior Art] As an input section of a conventional power supply circuit, there is one shown in FIG. 5, for example.

In FIG. 5, 1.2 is an input terminal to which alternating current is input, and a line filter (common moat choke coil) 4 is connected to the input terminal 1.2 via a capacitor 3. A capacitor 5.6 is connected to the line filter 4, and the line filter 4 and the capacitor 5.6 form a circuit for removing common mode noise.

7 is a rectifier circuit made of a diode, 8 is a smoothing capacitor, and these rectifier circuit 7 and smoothing capacitor 8 collectively constitute a rectifier and smoothing circuit 9. In addition,
10 is a transformer, 11 is a ground terminal, and as shown by arrow A, a surge voltage is applied between the input terminal 2 and the ground terminal.

The line filter 4 includes a lead wire 1 as shown in FIG.
Input terminals 14.15 of 2.13 are soldered to patterns 18.19 of the printed circuit board, respectively, and output terminals 16.13 are soldered to patterns 18.19 of the printed circuit board, respectively.
17 are soldered to patterns 20 and 21 of the printed circuit board, respectively.

When a surge voltage is applied between the input terminal 2 where AC is input and the ground side terminal 11, a back electromotive voltage is generated in the line filter 4 when the surge current flowing through the capacitors 5 and 6 stops. Therefore, a high voltage higher than the surge voltage applied between the input terminal 2 and the ground is generated between the rectifying and smoothing circuit 9 and the ground.

Therefore, the creepage distance between the rectifying and smoothing circuit 9 and the ground is set at the input terminal 2 in order to prevent the discharge of surge voltage.
It needed to be longer than the distance between the ground and the ground.

[Problems to be Solved by the Invention] However, in the input section of a conventional power supply circuit, it is necessary to increase the distance between the rectifier and smoothing circuit and the ground in order to protect against surge voltage. It is difficult to miniaturize the device, and protective parts such as surge killers are required, which increases costs.

The present invention has been made in view of these conventional problems, and it is an object of the present invention to downsize a power supply device by forming a discharge gap between the input and output of a line filter using a pattern on a printed circuit board. The purpose of the present invention is to provide a surge voltage protection circuit that can reduce costs by eliminating the need for protective components such as surge killers.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an input section of a power supply circuit having a line filter into which alternating current is input and a rectifying and smoothing circuit connected to the line filter. A discharge gap is provided between the input side and the output side of the circuit board to protect against surge voltage using a printed circuit board pattern.

[Effect: Since a discharge gap is formed between the input and output sides of the colline filter by the printed circuit board pattern, when a surge voltage is applied between the input terminal and ground,
If a back electromotive voltage is generated in the line filter, the back electromotive voltage will be discharged when it reaches the discharge voltage, and the discharge voltage of the line filter will be added to the surge voltage applied between the rectifier and smoothing circuit and the ground. Only a certain voltage is generated.

Therefore, the creepage distance between the rectifying and smoothing circuit and the ground can be made shorter than when no discharge gap is provided.

As a result, the power supply device can be downsized, and protective parts such as surge killers are not required, so costs can be reduced.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.

In Fig. 1, 4 is a line filter consisting of a common malt choke coil, one end of the line filter 4 is connected to an input terminal for inputting AC, and the other end is connected to a noise removal capacitor and rectifier. It is connected to a smoothing circuit (see Figure 5).

The line filter 4 and the rectifying and smoothing circuit constitute an input section of the power supply circuit.

14.15 is an input terminal connected to the input side of the line filter 4 via the lead wire 12.13, and the input terminal 1
4.15 are soldered to patterns 18 and 19 on the printed circuit board, respectively. Output terminals 16 and 17 are soldered to patterns 20 and 21 of the printed circuit board, respectively.

The resist is removed from the tip portions 18A to 21A of the patterns 18 to 21, and the conductor portions 18B to 21B are exposed, respectively. The conductor portions 18B to 21B are each formed in a sawtooth shape, and form a discharge gap 22 on one side of the conductor portion 18B and the conductor portion 20B, and a discharge gap 23 on the other side of the conductor portion 19B and the conductor portion 21B. ing. The distance between these discharge gaps 22 and 23 is set to a distance that suppresses generation of reverse voltage in the line filter 4.

When a surge voltage is applied between the input terminal to which alternating current is input and the ground, a back electromotive voltage is generated in the line filter 4. In this case, since the discharge gaps 22 and 23 are formed between the input side and the output side of the line filter 4, the back electromotive voltage is discharged when it reaches the discharge voltage of the discharge gaps 22 and 23.

Therefore, only the voltage that is the sum of the applied surge voltage and the discharge voltage of the line filter 4 is generated between the rectifier and smoothing circuit 9 (see FIG. 5) and the ground.

Therefore, the creepage distance between the rectifying and smoothing circuit 9 and the ground can be shortened compared to the case where the discharge gaps 22 and 23 are not provided.

As a result, the power supply device can be downsized.

Furthermore, since protective parts such as surge killers are not required, costs can be reduced.

Note that, as shown in FIG. 2, when two line filters 4°24 are connected in two stages (see the dotted line on the left side), the first Provide a discharge gap as shown in the figure. Furthermore, even in the case of three or more line filters, discharge gaps are provided in all line filters. As a result, the voltage generated between the rectifying and smoothing circuit 9 and the ground can be reduced, and the effects described above can be obtained. In addition,
In FIG. 2, 25 to 27 are capacitors.

Next, FIGS. 3 and 4 are diagrams showing other embodiments of the present invention.

This embodiment is an example in which a discharge gap is added between the input side and output side of the line filter and the ground.

In FIG. 4, 28.29 is a protrusion formed on the pattern 19°21, and 30.31 is a protrusion formed on the ground pattern 32.The resist is removed from these protrusions 28-31. The conductor portions 28A to 31A are formed to be exposed. The conductor portion 28A and the conductor portion 30A form one discharge gap 33 between the input side of the line filter 4 and the ground, and the conductor portion 29A and the conductor portion 31A form one side between the output side of the line filter 4 and the ground. A discharge gap 34 is formed respectively.

Further, as shown in FIG. 3, the other discharge gap 35 is provided between the input side of the line filter 4 and the ground, and the other discharge gap 36 is provided between the output side of the line filter 4 and the ground. formed respectively.

The distance between the discharge gaps 33 to 36 is set to be equal to or longer than the creepage distance specified by safety standards. If the surge voltage applied between the input terminal 2 that inputs the alternating current and the ground is higher than the discharge voltage of the discharge gaps 33 to 36, a discharge occurs. The discharge current at this time is from the discharge gap 33 to
36 and the ground, so the rectifier and smoothing circuit 9
will not cause any damage. In addition, since a voltage higher than the discharge voltage is not applied between the rectifier and smoothing circuit 9 and the ground,
Between the rectifying and smoothing circuit 9 and ground and between the rectifying and smoothing circuits 9 and 2
The creepage distance of the next circuit can be shorter than that in the case where the discharge gaps 33 to 36 are not provided.

[Effects of the Invention] As described above, according to the present invention, the creepage distance between the rectifying and smoothing circuit and the ground can be shortened, so that the power supply device can be downsized.

Furthermore, since protective parts such as surge killers are not required, costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of main parts showing one embodiment of the present invention, Fig. 2 is a circuit diagram of a two-stage line filter, Fig. 3 is a circuit diagram showing another embodiment of the invention, and Fig. 4 is an essential part diagram. FIG. 5 is a circuit diagram showing a conventional example, and FIG. 6 is an explanatory diagram of main parts of the conventional example. In the figure, 1.2... Input terminal, 3... Capacitor, 4... Line filter, 5.6... Capacitor, 7... Rectifier circuit, 8... Capacitor, 9... Rectifier and smoothing circuit, 10...Transformer, 11...Ground terminal, 12.13...Lead wire, 14.15...Input terminal, 16.17...Output terminal, 18-21... Pattern, 18A-21A...Tip portion, 8B-21B...Conductor portion, 2.23...Discharge gap, 4...Line filter, 5-27...Capacitor, 8-31...・Protruding portion, 8A to 31A...Conductor portion, 2...Ground pattern, 3 to 36...Gap for discharge.

Claims (2)

[Claims] (1) At the input section of a power supply circuit that has a line filter into which alternating current is input and a rectifier and smoothing circuit connected to the line filter, surge voltage is protected by a printed circuit board pattern between the input side and output side of the line filter. A surge voltage protection circuit characterized by providing a discharge gap. (2) A discharge gap for protecting surge voltage is additionally provided between the input side of the line filter and the ground and between the output side and the ground using a printed circuit board pattern. Surge voltage protection circuit.