JPH062786U - EMI filter - Google Patents

Abstract

(57) [Summary] [Purpose] To cut off interference by mounting so as to penetrate through the hole of the shield. [Structure] A first inductor (3) having one terminal as an external terminal and the other terminal connected to one terminal of a capacitor (2) and one terminal of a second inductor (4), and one terminal as an external terminal A second inductor (4) connecting the other terminal to the one terminal of the capacitor (2) and the first inductor (3), and the other terminal for connecting to the ground potential to the ground terminal (8). And the capacitor (2) that operates.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement in the structure of a three-terminal EMI (electromagnetic interference noise) filter used in various electronic devices for the purpose of removing a noise signal superimposed on a signal.

[0002]

[Prior art]

 For example, when a MUSE signal demodulated by a BS tuner is input and digital signal processing is performed and then analog primary color signals are supplied to a high-definition monitor like a MUSE decoder in high-definition television, the analog primary color signals are digital. There is a clock signal mixed in in the process of signal processing. Therefore, in order to obtain a picture with good image quality without noise, the analog primary color signal and the like are supplied to the high-definition monitor without the clock signal that causes noise superimposed on the analog primary color signal and the like. There is a need. FIG. 3 is an example of noise suppression using a conventional EMI filter. In the figure, reference numeral 1 denotes a shield which is connected to the ground pattern 7 of the printed circuit board 10 and is provided so as to cover the entire circuit portion for outputting a signal on which noise and noise are superimposed. 3 is a first inductor connected to the circuit pattern A (5), 4 is a second inductor connected to the circuit pattern B (6), 20 is a capacitor connected to the ground pattern 7, and 3 4, 4 and 20 constitute an EMI filter for removing a noise component such as a clock signal which interferes with a circuit in the next stage. Reference numeral 5 is a circuit pattern A which is connected to the terminal of the first inductor 3 of the EMI filter and outputs a signal containing disturbing noise, and 6 is connected to the terminal of the second inductor 4 of the EMI filter. At the same time, it is a circuit pattern B for supplying only the signal from which noise has been removed to the next stage circuit or the like. However, the conventional noise suppression method using the EMI filter and the shield has problems due to the following reasons. Since the conventional EMI filter is mounted on the printed circuit board 10, it is installed inside the shield 1. Therefore, for circuit connection, the circuit pattern B (6) which should originally be placed outside the shield 1 is placed inside the shield. As a result, the circuit pattern A (5) and the circuit pattern B (6) are electromagnetically coupled, and a noise component is induced in the circuit pattern B (6). Therefore, ideal noise suppression could not be performed.

[0003]

[Problems to be solved by the device]

 The present invention has been made in view of the above problems, and it has a through terminal (ground) of a feedthrough capacitor at the center for circuit connection to a shield (earth potential) and one signal terminal on the other side. Three-terminal structure in which other signal terminals are provided on the side, they are fitted into the holes provided in the shield, mounted so as to penetrate, and connected to the circuit, and the internal circuit of the shield, the external circuit, and the shield are connected to the circuit. It aims at providing the EMI filter of.

[0004]

[Means for Solving the Problems]

 In order to achieve the above object, one signal terminal is provided on one side, the other signal terminal is provided on the other side, and a ground portion is provided around the center.

[0005]

[Action]

 Since it is configured as described above, it penetrates the shield provided so as to cover the noise and the circuit that generates the signal in which the noise is superimposed, and the central earth portion (the feedthrough terminal of the feedthrough capacitor) of the EMI filter according to the present invention Circuit connection to the shield, and one signal terminal provided on one side is connected to the circuit inside the shield, and the other signal terminal provided on the other side is connected to the circuit outside the shield. The shield prevents electromagnetic coupling between the internal circuit of the shield and the external circuit, and the noise (high frequency component) generated in the internal circuit is generated by the first inductor and the second inductor. It is blocked by a low-pass filter (EMI filter) consisting of a feedthrough capacitor, etc. and does not reach the external circuit.

[0006]

【Example】

 Hereinafter, the EMI filter according to the present invention will be described in detail with reference to the drawings. FIG. 2 is an assembly view (a) and an external perspective view (b) of the EMI filter according to the present invention. Reference numeral 2 is a feedthrough capacitor which connects the signal terminal to the first inductor 3 and the second inductor 4 and has a lead terminal 8 in the feedthrough terminal. Reference numeral 8 is a lead terminal provided in the feedthrough capacitor 2 which is made of metal or the like that can be soldered, and 9 is a signal terminal of the first inductor 3 or the second inductor 4.

The operation will be described. FIG. 1 is an enlarged view of a main part of a noise suppression circuit to which the EMI filter according to the present invention is applied. Signals and noise are present in circuit pattern A (5). The noise composed of the above-mentioned signal and a frequency component higher than the signal is EMI having a low-pass characteristic obtained by equivalently star-connecting the first inductor 3, the feedthrough capacitor 2, and the second inductor 4. After passing the filter, only the signal appears in the circuit pattern B (6). Further, since the shield 1 blocks the electromagnetic coupling between the inside and the outside of the shield 1, noise components such as the circuit pattern A (5) inside the shield are induced to the external circuit pattern B (6). Is prevented. When the EMI filter according to the present invention is mounted on the printed circuit board 10, the lead terminal 8 included in the feedthrough capacitor 2 is connected to the earth pattern 7 of the printed circuit board 10 to form a conventional EMI filter. Can also be used as

[0008]

[Effect of device]

 Since it is possible to realize a structure in which the shield is directly mounted on the shield while penetrating the shield, it is possible to provide an EMI filter that ideally prevents noise generated by a circuit in the shield from leaking to the outside. Therefore, for example, in a circuit that requires both analog and digital signal processing such as a video signal processing circuit, the EMI filter of the present invention is effective in order to prevent noise from being superimposed on a signal transmitted to the outside. Available.

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part of a noise suppression circuit to which an EMI filter according to the present invention is applied.

FIG. 2 is a component assembly view (a) and an external perspective view (b) of the EMI filter according to the present invention.

FIG. 3 is an example of noise suppression using a conventional EMI filter.

[Explanation of symbols]

 1 Shield 2 Feedthrough Capacitor 3 First Inductor 4 Second Inductor 5 Circuit Pattern A 6 Circuit Pattern B 7 Ground Pattern 8 Lead Terminal 9 Signal Terminal 10 Printed Circuit Board 20 Capacitor

Claims (3)

[Scope of utility model registration request] 1. An EMI filter comprising one signal terminal on one side, the other signal terminal on the other side, and a ground portion around the center. 2. A first inductor, wherein one terminal is an external terminal and the other terminal is connected to one signal terminal of a feedthrough capacitor and one terminal of a second inductor; and one terminal is an external terminal and the other terminal is a through terminal. A second inductor connected to the other signal terminal of the capacitor and the first inductor; and the one signal terminal connected to the first inductor and the other signal terminal to the second inductor, and The through capacitor, which is provided as a ground terminal for connecting the through terminal to the ground potential, is fitted so as to penetrate through a hole provided in a shield that electromagnetically shields an internal circuit and an external circuit, and a central portion Circuit-connecting the through terminal provided on the shield to the shield, connecting the terminal provided on one side to the internal circuit of the shield, and the terminal provided on the other side to the seal. An EMI filter having a structure that is mounted so as to be connected to an external circuit of a cable. 3. The EMI filter according to claim 1, wherein the feedthrough terminal of the feedthrough capacitor is provided with a terminal formed of a lead wire.