JP2002151706A - Electric apparatus comprising light-receiving unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric apparatus comprising a light-receiving unit wherein the receptible range is not shortened even if the electrostatic breakdown strength of the light-receiving unit is improved. SOLUTION: A light-receiving unit 1 is provided which comprises a photodiode, an integrated circuit which processes the output signal of the photodiode, a shield case 12 comprising a conductive member which prevents the external electromagnetic noise from entering the integrated circuit, and a ground terminal 13 which inputs a ground electric potential to the integrated circuit. Here, the shield case 12 is connected to the ground terminal 13 through a resistor R2. If an opening part provided to the place facing the photodiode of the shield case 12 is mesh, the value of the resistor R2 is 1 kΩ or below while that of the resistor R2 is 10 kΩ or below if it is a single hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various electric devices such as a TV (television), VTR (video tape recorder), and audio component having a light receiving unit for receiving an infrared signal transmitted from a remote controller. . In particular, the present invention relates to improvement of electrostatic withstand voltage of a remote control light receiving unit.

[0002]

2. Description of the Related Art Various electronic devices such as TVs, VTRs, and audio components usually have a light receiving unit for receiving an infrared signal transmitted from a remote controller. First, the configuration of the light receiving unit will be described below.

An integrated circuit section including an amplifier, a photodiode, a chip resistor, and a chip capacitor are mounted on a lead frame by die bonding and wire bonding. The resin frame is formed by molding the lead frame on which the various elements are mounted with a translucent resin. This resin mold body has a hemispherical lens portion at the light receiving portion facing the photodiode. With this lens unit, an infrared signal transmitted from the remote controller can be received at a wide angle. Further, the entire resin molded body except the lens portion is covered with a shield case made of a metal plate. That is, the shield case is provided with a substantially circular opening that fits with the lens unit. The shield case protects the integrated circuit section including the amplifier from external electromagnetic noise.

FIG. 7A shows a front view of such a light receiving unit, and FIG. 7B shows a right side view thereof.
The lens portion 11 of the resin mold body is provided on the front of the light receiving unit. Locking portions 12a and 12a 'are provided below the shield case 12. Locking portion 12a,
By providing 12a ', mounting when the light receiving unit is erected on the printed circuit board is facilitated. The lead frame has a ground terminal 13, a drive terminal 14, an output terminal 15
The ground voltage is input from the ground terminal 13 to various elements mounted on the lead frame. In addition, a drive voltage is input from the drive terminal 14 to various elements mounted on the lead frame. Also, an output voltage is output to the output terminal 15 from an element mounted on the lead frame.

[0005] Some light receiving units have openings formed in a shield case in a mesh shape in order to improve shield characteristics. FIG. 7C shows a front view of the appearance of such a light receiving unit, and FIG. 7D shows a right side view thereof. Note that the same parts as those of the light receiving unit in FIGS. 7A and 7B are denoted by the same reference numerals, and description thereof will be omitted. By forming the opening provided in the shield case in a mesh shape, external electromagnetic noise that enters the light receiving unit from the lens unit 11 can be reduced.

[0006] As described above, the light receiving unit has a mesh-shaped opening provided at a portion of the shield means facing the photodiode (hereinafter, referred to as a mesh light receiving unit), and is provided at a location of the shield means facing the photodiode. Those whose openings consist of one perforation (hereinafter referred to as
A non-mesh light receiving unit).

Next, a printed circuit board on which a light receiving unit is mounted will be described. In the printed circuit board, a copper foil conductive path having a required pattern such as a ground potential line, a drive voltage supply line, and an output signal line is formed on a glass epoxy substrate. As shown in FIG. 8, the ground terminal 13 of the light receiving unit 1 is connected to one end of the ground potential line 2a of the printed circuit board 2. The drive terminal 14 of the light receiving unit 1 is connected to one end of the drive voltage supply line 2b. The output terminal 15 of the light receiving unit 1 is
It is connected to one end of the output signal line 2c. further,
The other end of the ground potential line 2a is grounded. The other end of the drive voltage supply line 2b is connected to the constant voltage source 7. The other end of the output signal line 2c is connected to a control circuit 8 for controlling the operation of the electric device.

The drive voltage supply line 2b is provided with a resistor R1, and the ground potential line 2a and the drive voltage supply line 2b are connected via a capacitor C1. Since a low-pass filter is formed by the resistor R1 and the capacitor C1, high-frequency noise is removed from the drive voltage supply line 2b, and only the constant voltage Vcc is input to the drive terminal 14 from the drive voltage supply line 2b.

Generally, the amplifier included in the integrated circuit in the light receiving unit is a high gain amplifier. For this reason, the reception distance of the light receiving unit becomes short unless electromagnetic noise from the outside is shielded. Therefore, in the conventional light receiving unit, the shield case 12 and the ground terminal 13 are connected, and the shield case 12 is grounded by grounding the ground potential line 2a. This prevents external electromagnetic noise from entering the light receiving unit.

A plurality of mounting holes (not shown) are formed in the printed circuit board. Each of the mounting holes has a ground terminal 13, a drive terminal 14, an output terminal 15, and a shield case locking portion 12a. , 12a 'are engaged and fixed with a solder dip or the like, whereby the light receiving unit 1 is erected on the printed circuit board 2 (see FIG. 9).

[0011]

Generally, a light receiving unit is installed near a front portion of an electric device. For example, when the electric device is a TV, the outline of the internal structure is as shown in FIG. An infrared signal transmitted from a remote controller (not shown) is transmitted to a front panel 4 of the television 3.
The light-receiving unit 1 is illuminated by passing through a light-receiving window 5 provided in the light receiving unit 5, passing through a cylindrical light guide 6 provided in a horizontal state between the light-receiving window 5 and the light-receiving unit 1. . The lens section of the light receiving unit 1 faces the end face of the light guide 6. The infrared signal that has passed through the light guide 6 is applied to a lens unit of the light receiving unit 1 and received by a photodiode inside the light receiving unit 1.

In addition to the light receiving window 5, a push button switch for a main power supply (not shown) is also provided on the front panel 4. Since the push button switch of the main power supply is operated by a human hand, the human hand may approach the light receiving unit 1. At this time, static electricity may be discharged from a human hand to the shield case of the light receiving unit 1.
Since the shield case and the ground terminal of the light receiving unit 1 are directly connected as shown in FIG. 8, when static electricity is discharged to the shield case, the static electricity enters the integrated circuit in the light receiving unit 1 from the ground terminal, In the worst case, the light receiving unit 1 may be broken.

For this reason, in a conventional electric device having a light receiving unit, as shown in FIG. 10, the shield case 12 is grounded independently without being connected to the ground terminal 13, thereby preventing damage to the light receiving unit due to static electricity. Was. In FIG. 10, the same portions as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.

However, in such a structure, since the shield case 12 and the ground terminal 13 are not connected, the potential of the shield case 12 and the potential of the ground terminal 13 may be different. In such a case, the shield case 12 cannot sufficiently shield the external electromagnetic noise, so that the receiving distance of the light receiving unit has been shortened.

The present invention has been made in view of the above problems, and has as its object to provide an electric apparatus including a light receiving unit having a good electrostatic withstand voltage. In addition, the present invention, in view of the above problems,
An object of the present invention is to provide an electric device including a light receiving unit that does not shorten the receiving distance even when the electrostatic withstand voltage of the light receiving unit is improved.

[0016]

In order to achieve the above object, in an electric apparatus according to the present invention, a photodiode, an integrated circuit for processing an output signal of the photodiode, and electromagnetic noise from the outside are provided. A shielding unit comprising a conductive member for preventing entry into an integrated circuit, a ground terminal for inputting a ground potential to the integrated circuit, a light receiving unit, and a circuit board on which the light receiving unit is mounted, and The shield means is connected to the ground terminal via a resistor. Further, from the viewpoint of cost reduction, the resistor may be a wiring provided on the circuit board. In addition, from the viewpoint of not deteriorating the reception distance performance, when the shield means has a mesh-shaped opening at a position facing the photodiode, the resistance value of the resistor is set to 1 kΩ or less, and the shield means is connected to the photodiode. In the case where there is an opening composed of one perforation at the opposing portion, the resistance value of the resistor may be set to 10 kΩ or less. Further, from the viewpoint of further improving the electrostatic withstand voltage, the shield means may be connected to the ground via a capacitor.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. When the present invention is applied to a TV, T
The outline of the internal structure of V is the same as that of the conventional TV shown in FIG. The electric equipment (T
FIG. 1 shows the configuration of the light receiving unit and the printed circuit board included in V). The same parts as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. The shield case 12 is connected to the ground terminal 13 via the resistor R2. When a mesh light receiving unit as shown in FIGS. 7 (c) and 7 (d) is used as the light receiving unit 1, the electrostatic withstand voltage E1 shown in FIG. 2 is obtained. Further, when a meshless light receiving unit as shown in FIGS. 7A and 7B is used as the light receiving unit 1, the electrostatic breakdown voltage becomes E2 shown in FIG. The electrostatic withstand voltages E1 and E2 include the resistance value of the resistor R2 of zero, that is, the electrostatic withstand voltage of the light receiving unit in the conventional TV without the resistor R2 as shown in FIG.

The electrostatic withstand voltages E1 and E1 of the light receiving unit
It is understood from FIG. 2 that the provision of the resistor R2 improves the electrostatic breakdown voltage of the light receiving unit, and that the larger the resistance value of the resistor R2, the higher the electrostatic breakdown voltage of the light receiving unit. The reason why the provision of the resistor R2 improves the electrostatic withstand voltage of the light receiving unit is that when the static electricity is discharged to the shield case 12, the static electricity is consumed by the resistor R2 and the static electricity hardly reaches the ground terminal 13. Because. The reason that the larger the resistance value of the resistor R2 is, the higher the electrostatic breakdown voltage of the light receiving unit is, because the larger the resistance value of the resistor R2 is, the larger the amount of static electricity that can be consumed by the resistor R2 is.

Next, the receiving distance of the light receiving unit 1 will be described. When a mesh light receiving unit as shown in FIGS. 7C and 7D is used as the light receiving unit 1, a state in which electromagnetic noise is small (an electromagnetic wave is generated around the light receiving unit 1 without operating a CRT of a TV or the like). No state)
In FIG. 3, the reception distance becomes L1 shown in FIG. 3 and there is much electromagnetic noise (the distance between the CRT of the TV and the light receiving unit is 1 cm and the CRT of the TV is operated).
In this case, the reception distance becomes like L1 'shown in FIG. The reception distances L1 and L1 'include the resistance value of the resistor R2 of zero, that is, the reception distance of the light receiving unit in the conventional TV without the resistor R2 as shown in FIG.

In a state where the electromagnetic noise is small, a reception distance equivalent to a state where the resistance value of the resistor R2 is 100 kΩ or less and the resistor R2 is not provided can be obtained. In a state where the electromagnetic noise is large, when the resistance value of the resistor R2 is 1 kΩ or less,
, It is possible to obtain a reception distance equivalent to a state in which no is provided.
Therefore, the light receiving unit 1 provided in the electric device (TV) of the first embodiment is a mesh light receiving unit and the resistance value of the resistor R2 is set to 1 kΩ or less, whereby the resistance R
2, the receiving distance of the light receiving unit 1 is equal, and the electrostatic withstand voltage of the light receiving unit 1 can be improved. Since the electrostatic withstand voltage increases as the resistance value of the resistor R2 increases, the resistance value of the resistor R2 is preferably set to 100Ω or more.

When a non-mesh light receiving unit as shown in FIGS. 7A and 7B is used for the light receiving unit 1, a state in which electromagnetic noise is small (an electromagnetic wave is generated around the light receiving unit 1 without operating a cathode ray tube of a TV or the like). In the state where there is nothing to be generated), the reception distance becomes L2 shown in FIG. 3, and when the electromagnetic noise is large (the distance between the CRT of the TV and the light receiving unit is 1 cm and the CRT of the TV is operated). The reception distance is like L2 'shown in FIG.
The reception distances L2 and L2 'include the resistance value of the resistor R2 of zero, that is, the reception distance of the light receiving unit in the conventional TV without the resistor R2 as shown in FIG.

When a mesh-free light receiving unit is used as the light receiving unit 1, more electromagnetic noise enters through the opening of the shield case than when a mesh light receiving unit is used. Comparing the values with the same value, the reception distance L2 'is equal to the reception distance L
It is shorter than 1 '.

In a state where the electromagnetic noise is small, it is possible to obtain a reception distance equivalent to a state where the resistance value of the resistor R2 is 100 kΩ or less and the resistor R2 is not provided. In a state where the electromagnetic noise is large, when the resistance value of the resistor R2 is
A reception distance equivalent to a state where no 2 is provided can be obtained. Therefore, the light receiving unit 1 provided in the electric device (TV) of the first embodiment is a meshless light receiving unit, and the resistance value of the resistor R2 is set to 10 kΩ or less, so that the resistance value of the resistor R2 is lower than that of the conventional TV without the resistor R2. In addition, the receiving distance of the light receiving unit 1 is equal, and the electrostatic withstand voltage of the light receiving unit 1 can be improved. Since the electrostatic withstand voltage increases as the resistance value of the resistor R2 increases, the resistance value of the resistor R2 is preferably set to 100Ω or more.

Further, as shown in FIG. 4, the side of the resistor R2 that is not connected to the ground terminal 13 may be grounded via the capacitor C2. As a result, the static electricity generated in the shield case 12 can be consumed not only by the resistor R2 but also by the capacitor 2, so that it is more difficult for the static electricity to reach the ground terminal 13, and the electrostatic withstand voltage of the light receiving unit 1 is further reduced. improves. Since the capacitor C2 may be provided between the shield case 12 and the ground, the capacitor C2 may be provided not between the resistor R2 and the ground but between the ground potential line 2a and the ground.

Next, the structure of the light receiving unit and the printed circuit board included in the electric apparatus (TV) of the second embodiment is shown in FIG.
Shown in The same parts as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. The shield case 12 is connected to a ground potential line 2a via a wiring 2d provided on the printed circuit board 2. When the light receiving unit 1 is a mesh light receiving unit, the length and width of the wiring 2d are set so that the line resistance of the wiring 2d is 1 kΩ or less.
Is a meshless light receiving unit, the length and width of the wiring 2d are set so that the line resistance of the wiring 2d is 10 kΩ or less. As a result, the shield case 12 is connected to the ground terminal 13 via the resistor. Therefore, when the static electricity is discharged to the shield case 12, the static electricity is consumed by the wiring 2d, so that the static electricity hardly reaches the ground terminal 13, and the electrostatic withstand voltage of the light receiving unit 1 is improved.

The present invention is not limited to this embodiment. For example, the terminal of the ground potential line 2a to which the connection terminal 13 is connected and one end of the wiring 2d may be common.

The wiring 2d may be grounded via a capacitor C2 as shown in FIG. Thereby, not only the static electricity discharged to the shield case 12 can be consumed by the wiring 2d but also charged by the capacitor C2, so that the static electricity hardly reaches the ground terminal 13 and the electrostatic withstand voltage of the light receiving unit 1 is further reduced. improves.
Since the capacitor C2 may be provided between the shield case 12 and the ground, the capacitor C2 may be provided not between the wiring 2d and the ground but between the ground potential line 2a and the ground.

In the electric equipment (TV) of the first and second embodiments described above, the light receiving unit shown in FIG. 9 is used. However, the present invention is not limited to this. A light receiving unit having a shield means can also be applied to a light receiving unit configured to mount an integrated circuit section including an amplifier circuit on a printed circuit board, a photodiode, a chip resistor, and a chip capacitor. Further, the light receiving unit provided in the electric device according to the present invention may have a configuration in which the photodiode is included in the integrated circuit.

However, in a light receiving unit having a configuration in which the shield means includes a ground terminal, the present invention cannot be applied since static electricity is discharged to the ground terminal as the shield means. As such a light receiving unit, for example, a lead frame disclosed in Japanese Patent Application Laid-Open No. H10-74962 is bent in a U-shape so that a part of the lead frame is opposed to various elements mounted on the lead frame. A shield plate is arranged so as to face a light receiving unit using a frame as a shield means, or various elements mounted on a lead frame disclosed in Japanese Patent Application Laid-Open No. 11-121770, and the lead frame and the shield plate are used as shield means. A light receiving unit may be used.

[0030]

According to the present invention, since the shield means is connected to the ground terminal via the resistor, it is difficult for static electricity discharged to the shield case to enter the integrated circuit inside the light receiving unit from the ground terminal. Thereby, the electrostatic withstand voltage characteristic of the light receiving unit is improved, and the light receiving unit is not damaged by static electricity.

Further, according to the present invention, since the resistor provided between the shield means and the ground terminal is a wire provided on the circuit board, it is only necessary to change the settings such as the width and length of the wire. . Thus, the cost can be reduced as compared with the case where a chip resistor or the like is used as a resistor provided between the shield means and the ground terminal.

Further, according to the present invention, since the shielding means has a mesh-shaped opening at a position facing the photodiode, penetration of electromagnetic noise from the opening can be reduced, and the shielding effect can be enhanced. Thereby, the receiving distance of the light receiving unit becomes longer than when the opening is not in the mesh shape. Further, since the resistance value of the resistor provided between the shield means and the ground terminal is 1 kΩ or less, the receiving distance of the light receiving unit can be made equal to the case where no resistor is provided.

Further, according to the present invention, the shield means has an opening formed by a single hole at a position facing the photodiode, and the resistance value of a resistor provided between the shield means and the ground terminal is 10 kΩ or less. Therefore, the receiving distance of the light receiving unit can be made equal to the case where no resistor is provided.

Further, according to the present invention, since the shield means is connected to the ground via the capacitor, not only the static electricity discharged to the shield means can be consumed by the resistor but also charged by the capacitor. This further improves the electrostatic withstand voltage of the light receiving unit.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an electric device (T) according to a first embodiment of the present invention.
FIG. 5 is a diagram illustrating a configuration of a light receiving unit and a printed circuit board included in V).

FIG. 2 is a diagram showing an electrostatic withstand characteristic of the light receiving unit of FIG. 1;

FIG. 3 is a diagram showing a receiving distance characteristic of the light receiving unit of FIG. 1;

FIG. 4 is a diagram illustrating a configuration in which a capacitor is added to the light receiving unit and the printed circuit board of FIG. 1;

FIG. 5 shows an electric device (T) according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating a configuration of a light receiving unit and a printed circuit board included in V).

6 is a diagram showing a configuration in which a capacitor is added to the light receiving unit and the printed circuit board of FIG.

FIG. 7 is a diagram illustrating an appearance of a light receiving unit.

FIG. 8 is a diagram illustrating a configuration of a light receiving unit and a printed circuit board included in a conventional electric device.

FIG. 9 is a view schematically showing an internal structure of a TV provided with a light receiving unit.

FIG. 10 is a diagram illustrating a configuration of a light receiving unit and a printed circuit board included in a conventional electric device that has taken a countermeasure against static electricity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light receiving unit 2 Printed circuit board 2d Wiring 3 TV 12 Shield case 13 Ground terminal 14 Drive terminal 15 Output terminal C1, C2 Capacitor R1, R2 Resistance

Claims (5)

[Claims] An integrated circuit for processing an output signal of the photodiode; a shielding means comprising a conductive member for preventing external electromagnetic noise from entering the integrated circuit; and a grounding means for the integrated circuit. A light receiving unit having a ground terminal for inputting a potential, and a circuit board on which the light receiving unit is mounted, wherein the shield means is connected to the ground terminal via a resistor. Electrical equipment. 2. The electric device according to claim 1, wherein the resistor is a wiring provided on the circuit board. 3. The electric device according to claim 1, wherein the shielding means has a mesh-shaped opening at a position facing the photodiode, and a resistance value of the resistor is 1 kΩ or less. 4. The electric device according to claim 1, wherein the shield means has an opening formed by a single hole at a position facing the photodiode, and the resistance value of the resistor is 10 kΩ or less. . 5. The electric device according to claim 1, wherein said shield means is connected to ground via a capacitor.