JP2001085885A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a leakage of an inductive noise to the outside by connecting a circuit board which is supported by a part of an internal wall of a chassis with an each circuit board for a conductor with which an inductor is serially connected. SOLUTION: A terminal part 30a of a rigid printed wiring board 30 is supported by a supporting wall in a chassis. The wiring board 30 contains an earth wiring part 32 having a flag film state, and the earth wiring part 32 is made to locate by separating from an earth land 31. An inductor 100 is connected between both earth wiring parts 33 and 34 and is connected with the earth land 31. The inductor 100 has a little attenuation property in a low frequency range and has a large attenuation property in a high frequency range. When a high frequency noise flows through the chassis, the earth land 31, the inductor 100, the earth wire 111 and so on as a high frequency current, the high frequency current is attenuated and the inductive noise caused by the current is suppressed from leaking to the outside from the earth wire 111 of a wire harness 110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electronic device such as an EL display device.

[0002]

2. Description of the Related Art As this kind of electronic equipment, there is, for example, an EL display device as disclosed in Japanese Patent Application Laid-Open No. 5-283882. This EL display device has an EL
A panel is provided, and a drive circuit is mounted on a flexible printed wiring board extending from an end of the EL panel in a case.

In this EL display device, by wrapping a part of the wiring of the printed wiring board in a loop with a magnetically permeable conductive sheet, the current flowing through the wiring of the printed wiring board is controlled and the leakage of radiation noise is suppressed. Like that.

[0004]

However, in the above EL display device, when the radiated noise becomes high-frequency noise, the noise radiated from the driving circuit or the EL panel passes through the wiring of the printed wiring board to the external wiring harness. Causes increased inductive noise going. For this reason, in a vehicle, an aircraft, or the like that has particularly strict standards for electromagnetic waves, there is a problem that the above-described induction noise has an adverse effect on peripheral devices such as a radio.

[0005] In view of the above, an object of the present invention is to appropriately suppress the leakage of the induced noise to the outside in an electronic device in order to cope with the above.

[0006]

In order to solve the above-mentioned problems, an electronic apparatus according to the present invention is arranged in a conductive casing for electromagnetic shielding (10) or on a part (11) of a peripheral wall thereof. And a wiring board (30) supported in the housing, and electronic circuits (50 to 80) arranged on the wiring board and connected to the equipment main body.

In the electronic device, the wiring board is supported by a part (12) of the inner wall of the housing at a supporting end (30a), and the wiring board is connected to the supporting end. A conductor ground wiring portion (31, 33, 34) connected to a part of the inner wall of the housing via the housing, and an inductor (100) connected in series to the ground wiring portion.

Accordingly, if the housing is connected to the external earth wiring through the housing ground wiring portion of the wiring board and the inductor at a part of the peripheral wall, radiation noise generated from the wiring board and the device body is generated. Even if the high-frequency noise is incident on the housing, the high-frequency current caused by the incident noise is attenuated by the inductor when flowing out of the housing to the external ground wiring. Therefore, leakage of high-frequency noise as induction noise through the external ground wiring can be suppressed.

Here, according to the invention described in claim 2,
The electronic device according to claim 1, wherein the wiring board includes an electronic circuit ground wiring portion (32), and the housing ground wiring portion is an electronic circuit ground wiring portion with respect to the external ground wiring (111). Except for the ground end connected together with a part (32a) of the electronic circuit, it is located separately from the ground wiring for the electronic circuit.

Therefore, as described above, the high-frequency current does not flow to the external ground wiring via the electronic circuit ground wiring, and as a result, the induction noise caused by the high-frequency current flows from the external ground wiring to the outside. Can be more reliably suppressed.

According to the third aspect of the present invention, in the electronic device according to the first or second aspect, the inductor has a frequency characteristic for reducing high-frequency noise. Thereby, the operation and effect of the invention described in claim 1 or 2 can be more reliably achieved.

According to the fourth aspect of the present invention, in the electronic device according to the second or third aspect, the device main body includes:
The electronic circuit is a circuit for driving and controlling the EL panel, and the wiring board includes a connector (90) having a ground terminal connected to an external ground wiring. The ground wiring portion for the housing is connected to the ground terminal of the connector together with a part of the ground wiring portion for the electronic circuit at the ground end.

As described above, even if the main body of the device is an EL panel and the electronic circuit is a circuit for driving and controlling the EL panel, the high-frequency current generated in the housing is properly attenuated by the damping action of the inductor. Accordingly, the same function and effect as the invention described in claim 2 or 3 can be achieved.

The reference numerals in the parentheses of the above means indicate the correspondence with the specific means described in the embodiments described later.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an automotive EL display device according to the present invention. This EL display device includes an electromagnetic shielding casing 10, and this casing 10 is provided in a low frequency band (AM radio frequency band in the range of 0 Hz to 2 MHz) from an EL panel 20 or an EL panel circuit described later. In order to reduce generated noise to peripheral devices such as radios, it is formed of a conductive material such as a nickel-plated steel plate or a copper foil so as to cover at least the EL panel circuit.

As shown in FIG. 1 or FIG. 2, the EL display device includes an EL panel 20 provided in an opening 11 of a housing 10 and a wiring board 30 supported in the housing 10.
A wiring board 40 for electrically connecting the EL panel 20 to the wiring board 30, a control circuit 50, a power supply circuit 60, a scan electrode driving circuit 70, a data electrode driving circuit 80, and a connector 90 provided on the wiring board 30. It has. The control circuit 50, the power supply circuit 60, the scan electrode drive circuit 70, and the data electrode drive circuit 80 are referred to as the EL panel 20 circuit.

The EL panel 20 has a light emitting layer sandwiched between both dielectric layers, a plurality of scanning electrodes formed on the surface of one dielectric layer, and a surface formed on the other dielectric layer. A plurality of data electrodes are formed so as to intersect with a plurality of scanning electrodes.

The wiring board 30 is made of a rigid printed wiring board. The wiring board 30 has a support wall 12 (from the above-described conductive material) extending from an inner wall of the housing 10 at an end 30a thereof. ) In parallel with the opening 11. In the present embodiment, the ground land 31 and the support wall 12 which are ground wiring portions formed at the end of the wiring board 30 are provided.
The wiring board 30 is supported by the support wall 12 by inserting the screw 13 through the through hole and fastening the nut 14 to the screw 13.

Further, the wiring board 30 has a built-in ground wiring portion 32 in the form of a flat film.
As shown by, it is located separately from the earth land 31. In the present embodiment, the ground wiring part 32 is
It is used as a ground wiring portion of the panel 20 circuit.

The wiring board 40 is made of a flexible printed wiring board. The wiring board 40 is electrically connected to the scanning electrodes and data electrodes of the EL panel 20 and the wiring board 30. However, in the present embodiment, as shown in FIG. 1, the wiring board 40 is positioned in an S-shape so as to be interposed between the EL panel 20 and the wiring board 30. Thereby, wiring board 40 plays a role of absorbing radiation noise between wiring board 30 and EL panel 20.

The connector 90 is provided on the other end of the wiring board 30. The connector 90 is connected to the grounding terminals 33, 34 of the wiring board 30 and the grounding wiring parts by the ground terminals. It is electrically connected to the earth land 31 via an inductor 100 connected between 33 and 34 (see FIG. 2). The connector 90 is connected to the connection terminal 3 of the ground wiring portion 32 of the wiring board 30 with the ground terminal.
2a, and to the ground wire 111 of the wire harness 110, which is an external wiring. Note that the wire harness 110 is grounded by the ground wire 111.

As shown in FIG. 3, the control circuit 50 receives display data and dimming data from the electronic control unit ECU mounted on the vehicle and drives and controls the scan electrode driving circuit 70 and the data electrode driving circuit 80. Clock, data, and control signals for Power supply circuit 60
Supplies the voltage VDDH2 to the scan electrode driving circuit 70 and supplies the voltage VDDH1 to the data electrode driving circuit 80. The power supply circuit 60 is provided with a switching transistor 61 and a transformer 62 (see FIG. 1), and supplies these voltages by driving them at about 30 kHz. Note that the above-described driving at about 30 kHz causes noise in the low frequency band.

The scanning electrode driving circuit 70 and the data electrode driving circuit 80 are connected to the power supply circuit 60 according to the output of the control circuit 50.
A driving voltage and a data voltage of a waveform formed based on the voltage from the EL panel 20 are applied to the scanning electrodes and the data electrodes of the EL panel 20 to drive the EL panel 20 in a matrix. Thus, the EL panel 20 performs a matrix display.

The inductor 100 has an impedance-frequency characteristic as shown in FIG. In FIG.
Symbol X indicates a characteristic of a reactance component of the impedance-frequency characteristics, symbol R indicates a characteristic of an effective resistance component of the impedance-frequency characteristics, and symbol Z indicates a combination of the two characteristics X and R, that is, And the impedance-frequency characteristics. Here, the impedance of the inductor 100 is small in a low frequency band, and is small in a high frequency band (74 MHz to 23 MHz which is an FM or TV frequency band).
0 MHz), it is large. In other words, the inductor 100 has a small attenuation characteristic in a low frequency band, and has a large attenuation characteristic in a high frequency band. In addition,
As the inductor 100, BLM1 manufactured by Murata Manufacturing Co., Ltd.
A 1B102S type inductor is employed.

In this embodiment constructed as described above, the circuit board 30 and the E
When radiation noise is generated from the L panel 20, the radiation noise is incident on the conductive casing 10 for shielding electromagnetic waves. Here, when this noise is high-frequency noise, the impedance of the inductor 100 connected between the ground wiring portions 33 and 34 is reduced as shown by the impedance-frequency characteristic shown in FIG. It takes a value in the range of 0.8 kΩ to 1.8 kΩ in the frequency range and becomes higher.

For this reason, high-frequency noise is transmitted as high-frequency current from the housing 10 to the support portion 12, the ground land 31, the ground wiring portion 34, the inductor 100, the ground wiring portion 33 and the ground terminal of the connector 90, and the wire harness 110.
This high-frequency current is sufficiently attenuated by the inductor 100 when the current flows to the side of the ground wire 111. Therefore, induction noise caused by the high-frequency current is generated by the ground wiring portion 33,
Leakage to the outside from the ground terminal of the connector 90 and the ground wire 111 of the wire harness 110 can be appropriately suppressed. Therefore, the electromagnetic shielding in the high frequency band is secured without causing any adverse effects on the peripheral devices due to the high frequency noise of the EL display device, and the present invention is suitable for a vehicle with strict electromagnetic wave regulations.

In this case, as described above, the ground wiring portions 33 and 34 of the wiring board 30 are connected only to the ground wiring portion 32 only at the ground terminal of the connector 90. The part 32 is separated. Accordingly, as described above, the high-frequency current flowing through the housing 10 is supplied to the wire harness 1 via the ground wiring portion 32.
As a result, the leakage of the induction noise due to the high-frequency current to the outside from the wire harness 110 can be more reliably suppressed.

If the noise incident on the housing 10 is low-frequency noise as described above, the inductor 100
Is reduced to about 10Ω in the frequency range of the low-frequency noise as shown by the impedance-frequency characteristic shown in FIG. For this reason, low-frequency noise is passed from the housing 10 to the support portion 12, the ground land 31, the ground wiring portion 34, the inductor 100, the ground wiring portion 33, and the ground terminal of the connector 90 as low-frequency current. Flows to the side. Thereby, electromagnetic shielding in a low frequency band with respect to a peripheral device such as a radio can be ensured.

By the way, when the attenuation effect is compared between the case where the inductor 100 is employed as in the present embodiment and the case where the inductor 100 is not employed, the result shown in FIG. 5 is obtained. Here, FIG. 5A shows the frequency characteristics of attenuation when the inductor 100 is used as in the present embodiment, and FIG. 5B shows the frequency characteristics of attenuation when the inductor 100 is not used. . FIG. 5 shows a comparison between the two.
It can be seen that the characteristic of (a) has a greater damping effect than the characteristic of FIG.

In practicing the present invention, the present invention is not limited to an EL display device, but may be applied to an electronic device that generates low-frequency noise or high-frequency noise. In this case, the electronic device has a device main body corresponding to the EL panel 20 and a circuit corresponding to the EL panel circuit.

In the above embodiment, the housing 10 is an EL
Although included in the display device, the housing 10 may not be included in the EL display device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 shows a wiring board of FIG.
It is a top view shown with the circuit for L, a connector, etc.

FIG. 3 is a block diagram of a circuit for driving and controlling the EL panel of FIG. 1;

FIG. 4 is a graph showing impedance-frequency characteristics of the inductor of FIG. 2;

FIG. 5A is a diagram showing a frequency characteristic of noise level attenuation when an inductor is employed, and FIG.
It is a figure which shows the frequency characteristic of the attenuation of a noise level when not using an inductor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Case, 11 ... Opening, 12 ... Support wall, 20 ... EL
Panel, 30, 40 ... Wiring board, 30a ... End, 32a ...
Connection end, 31 earth ground, 32, 33, 34 earth wiring, 50 control circuit, 60 power supply circuit, 70
Scan electrode drive circuit, 80 ... Data electrode drive circuit, 90 ...
Connector, 100: inductor, 110: wire harness, 111: ground wire.

Claims (4)

[Claims] 1. An apparatus body (20) disposed in an electromagnetic shielding conductive casing (10) or on a part (11) of a peripheral wall thereof.
An electronic device comprising: a wiring board (30) supported in the housing; and electronic circuits (50 to 80) arranged on the wiring board and connected to the device main body. The supporting end (30a) is supported on a part (12) of the inner wall of the housing, and the wiring board is connected to a part of the inner wall of the housing via the supporting end. Ground wiring for housing (31, 33, 3
4) and an inductor (100) connected in series in the ground wiring portion. 2. The wiring board includes the electronic circuit ground wiring section (32), and the housing ground wiring section includes an external ground wiring (111).
The electronic circuit ground wiring section is located separately from the electronic circuit ground wiring section, except for a ground end connected together with a part (32a) of the electronic circuit ground wiring section.
An electronic device according to claim 1. 3. The electronic device according to claim 1, wherein the inductor has a frequency characteristic for reducing high-frequency noise. 4. The device main body is an EL panel disposed on a part of a peripheral wall of the housing, the electronic circuit is a circuit for driving and controlling the EL panel, and the wiring board is an external device. A connector (90) having a ground terminal connected to a ground wire, wherein the housing ground wire portion is connected to a part of the electronic circuit ground wire portion together with a part of the electronic circuit ground wire portion at the ground end. 3. A terminal connected to a terminal.
Or the electronic device according to 3.