JPH08248383A - Backlight device for liquid crystal display and liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain almost uniform backlight lighting with simple work, to unnecessitate preparing a backlight substrate in accordance with kinds of power source conventionally, and to reduce a manufacturing cost more by simplifying a manufacturing process. CONSTITUTION: Light emitting diodes D1-D8 are provided in parallel between a power source side and a ground side, opening and closing sections WW1, SW3, SW5 are provided between light emitting diodes placed at a first stage to this side of the final stage and a ground side, cathodes of light emitting diodes of the preceding stage are connected to anodes of light emitting diodes of the succeeding stage by opening and closing sections SW7-SW9, light emitting diodes from the next of the first stage to the final stage are connected to a power source side through opening and closing sections SW2, SW4, SW6, each opening and closing section SW1-SW9 is selected and connected in accordance with power sources.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display backlight device and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art It is known that a liquid crystal display device has a backlight system in which a liquid crystal display body is illuminated from its back side.

By the way, as a backlight of, for example, a 4-digit liquid crystal display, there is known a backlight device for liquid crystal display which is used according to the size of an external power supply as shown in FIGS.

When the external power supply is + 9V, eight light emitting diodes D1 are provided between the power supply side and the ground side as shown in FIG.
Every two D8 to D8 are connected in parallel in the same polarity direction, and the first digit and D are paired with D1 and D2 according to the 4-digit liquid crystal display.
Placed on the backlight substrate as the backlight of the liquid crystal display of the second digit in the pair of 3, D4, the third digit in the pair of D5 and D6, and the fourth digit in the pair of D7 and D8. There is a liquid crystal display body that can be backlit with uniform brightness.

When the external power supply is + 12V, the light emitting diode D is provided between the power supply side and the ground side as shown in FIG.
1 to D8 every four D1 to D4; two of D5 to D8 series connection circuits are connected in parallel, and liquid crystal display of each digit is backlit with substantially uniform brightness in the same manner as described above. I am able to do it.

Further, when the externally supplied power source is +24 V, all the light emitting diodes D1 to D8 are connected in series between the power source side and the ground side as shown in FIG. The backlight is illuminated with a substantially uniform brightness.

In this way, in the conventional liquid crystal display backlight device, even if the backlight illumination of the liquid crystal display body for four digits is used, if the size of the externally supplied power source is, for example, three, A substrate having three kinds of circuits as shown in FIGS. 5 to 7 was required.

[0008]

As described above, since the circuit configuration on the backlight substrate is different, the backlight substrate is conventionally required according to the external power supply, and such a backlight substrate can be manufactured. The cost and the management of the backlight substrate are troublesome.

Therefore, it is an object of the present invention to provide a backlight device for a liquid crystal display and a liquid crystal display device using the same so that a single backlight substrate can accommodate different sizes of external power supply. I am trying.

[0010]

In order to achieve such an object, in a liquid crystal display backlight device of the present invention, a first light emitting element having an input section connected to at least a power source side, and the first light emitting element are provided. A first connection circuit having a first opening / closing section connected between the output section of the first light emitting element and the ground side; and a second opening / closing section and an input section connected to at least the power source side of the second connection section. One or a plurality of second connection circuits each having a second light emitting element connected to the opening / closing section and a third opening / closing section connected between the output section of the second light emitting element and the ground side; One or a plurality of fourth elements connected between the output section of the light emitting element on the front side and the input section of the light emitting element on the rear side.
It is characterized in that it has an opening and closing part.

In the liquid crystal display backlight device of the present invention, preferably, further, at least a fifth opening / closing section connected to the power source side, the input section is the fifth opening / closing section, and the output section is the ground side. A third connection circuit having a third light emitting element connected to each of the third connection circuit, and an output section of the second light emitting element of the second connection circuit at the final stage and a third connection circuit of the third connection circuit. A sixth opening / closing part connected to the input part of the light emitting element may be provided.

In the liquid crystal display backlight device of the present invention, preferably, the opening / closing portion is formed in an electrically open state on the same substrate, and can be electrically short-circuited by soldering. Can also be

In the liquid crystal display backlight device of the present invention, power is externally supplied to the power source side, and each of the opening / closing sections is electrically opened or short-circuited according to the type of power supplied. It can also be characterized in that it is something that is called.

In the liquid crystal display device of the present invention, at least the first light emitting element having the input portion connected to the power source side and the first light emitting element connected between the output portion of the first light emitting element and the ground side. A first connection circuit having an opening / closing section, a second opening / closing section connected at least to the power source side, a second light emitting element having an input section connected to the second opening / closing section, and a second light emitting element One or a plurality of second connection circuits having a third opening / closing section connected between the output section and the ground side, an output section of the light emitting element on the front stage side and an input section of the light emitting element on the rear stage side. One or a plurality of fourth opening / closing sections connected to each other, at least a fifth opening / closing section connected to the power supply side, an input section to the fifth opening / closing section, and an output section to the ground side. A third connection circuit having a connected third light emitting element, and the second stage of the final stage. A sixth opening / closing part connected between the output part of the second light emitting element of the connection circuit and the input part of the third light emitting element of the third connection circuit, and these are on the same substrate. It is characterized in that each of the opening / closing sections is formed in an electrically open state on the substrate and can be electrically short-circuited by soldering.

[0015]

According to the liquid crystal display backlight device of the present invention, when the first external power supply is connected to the power supply side,
When the first to third opening / closing parts are short-circuited and the fourth opening / closing part is opened, the first and second light emitting elements respectively operate as backlights of the liquid crystal display body to illuminate the back. Also,
When a second external power supply larger than the first external power supply is connected, the first and second opening / closing sections are opened and the third and fourth opening / closing sections are short-circuited, so that both light emitting elements Is connected in series between the second external power supply and the ground side to backlight the liquid crystal display and illuminate the back. Therefore, the illumination of the backlight can be made substantially uniform regardless of which external power supply is connected.

In the liquid crystal display backlight device of the present invention, further, at least a fifth opening / closing section connected to the power source side, an input section is connected to the fifth opening / closing section, and an output section is connected to the ground side. A third connection circuit having a third light emitting element, the output section of the second light emitting element of the second connection circuit of the final stage, and the third light emitting element of the third connection circuit. And a sixth opening / closing unit connected to the input unit, the first to third opening / closing units and the fifth opening / closing unit when the first external power supply is connected to the power supply side.
By short-circuiting only the opening / closing part of the above, the first, second, and third light emitting elements respectively illuminate the back as a backlight of the liquid crystal display. Further, when a second external power supply that is larger than the first external power supply is connected, and when the number of the second connection circuits is two, for example, the first connection circuit and the first stage of the first stage are connected. A fourth opening / closing section between the second connecting circuit and the second connecting circuit, a third opening / closing section of the second connecting circuit in the first stage, and a second opening / closing section in the second stage.
When only the second opening / closing part of the connection circuit and the sixth opening / closing part of the third connection circuit are short-circuited, the respective light emitting elements of the first connection circuit and the second connection circuit of the first stage are powered. Side and the ground side, the respective light emitting elements of the second connection circuit and the third connection circuit in the next stage are connected in series between the power supply side and the ground side. When a third external power supply, which is larger than the second external power supply, is connected, the fourth,
When only the sixth opening / closing section is short-circuited, all the light emitting elements are connected in series to the external power supply, and the backlight of the liquid crystal display body is operated to illuminate the back. Therefore, the illumination of the backlight can be made substantially uniform regardless of which external power supply is connected.

In the liquid crystal display backlight device of the present invention, when the opening / closing portion is formed in an electrically open state on the same substrate and can be electrically short-circuited by soldering, the opening / closing can be easily performed. You can

In the liquid crystal display backlight device of the present invention, power is externally supplied to the power source side, and each of the opening / closing sections is electrically opened or short-circuited according to the type of power supplied. If so, they can be configured on the same substrate.

According to the liquid crystal display device of the present invention, even if different kinds of external power supplies are connected, the liquid crystal display backlight device corresponding to them can be simply attached to the same liquid crystal display substrate by soldering or the like. Therefore, it is not necessary to prepare a substrate for backlight illumination for each power source as in the conventional case, the manufacturing process thereof can be simplified, and the cost can be reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. As the control equipment in which the liquid crystal display backlight device is used, there are an electronic timer, an electronic counter, a temperature controller, etc., which are configured by a liquid crystal display device as a display portion for setting values or current values on the operation panel. ing.

FIG. 1 is a diagram showing a configuration of a liquid crystal display backlight device used in a liquid crystal display portion of an operation panel of such a control device. Referring to FIG. 1, this backlight device includes four connection circuits 1 to 4 connected in parallel between an external power supply unit and a ground unit in order to backlight a 4-digit liquid crystal display. ing. Each connection circuit 1 to 4
Respectively have light emitting diodes D1 to D8 of the same polarity in series with each other for backlighting the liquid crystal display body of each digit.

The anodes on the input side of the light emitting diodes D1 and D2 of the connection circuit 1 are connected to the power supply via the resistor R1, and the cathodes on the output side are the ground side switch S.
It is connected to the ground via W1. The anodes of the light emitting diodes D3 and D4 of the connection circuit 2 are connected to the power supply via the power supply side opening / closing section SW2 and the resistor R2, and the cathodes are connected to the ground section via the ground side opening / closing section SW3. The anodes of the light emitting diodes D5 and D6 of the connection circuit 3 are connected to the power source via the resistor R3 and the power source side opening / closing section SW4, and the cathodes are connected to the grounding section via the grounding side opening / closing section SW5. Light emitting diode D of connection circuit 4
The anodes of 7 and D8 are connected to the power source side via the power source side opening / closing section SW6 and the resistor R4, and the cathodes are directly connected to the ground section.

The cathodes of the light emitting diodes D1 and D2 of the connection circuit 1 and the anodes of the light emitting diodes D3 and D4 of the connection circuit 2 are a relay opening / closing unit 7, and the cathodes of the light emitting diodes D3 and D4 of the connection circuit 2 and the connection circuit 3 are connected. The anodes of the light emitting diodes D5 and D6 are relay opening / closing sections SW8 via the resistor R3, and the cathodes of the light emitting diodes D5 and D6 of the connecting circuit 3 and the anodes of the light emitting diodes D7 and D8 of the connecting circuit 4 are relay opening / closing section SW9. Each is connected.

Referring to FIG. 2, the light emitting diodes D1 to D8 having the above circuit configuration are mounted and arranged on the backlight substrate BPB. The backlight substrate BPB is arranged below the liquid crystal display substrate LPB at a position where the back of the liquid crystal display substrate LPB can be illuminated. Liquid crystal display substrate LP
B and the backlight substrate BPB will be described with reference to FIG. 2. The liquid crystal display substrate LPB is 4 in the left-right direction in the figure as shown in the plan view of FIG. 2A and the side view of FIG.
The liquid crystal displays LC1 to LC4 corresponding to the digits are provided. The liquid crystal display LC1 faces the light emitting diodes D1 and D2,
The liquid crystal display LC2 faces the light emitting diodes D3 and D4, the liquid crystal display LC3 faces the light emitting diodes D5 and D6, and the liquid crystal display LC4 faces the light emitting diodes D7 and D8.

In this way, a wiring pattern is formed on the backlight substrate BPB in accordance with the structure of FIG. 1, and the resistors R1 to R4 and the light emitting diode D are formed in the wiring pattern.
1 to D8 are arranged, and portions corresponding to the opening / closing sections SW1 to SW9 are formed by using the wiring pattern end portions as solder lands at a predetermined distance from each other and electrically opened to each other. Then, depending on the type of the external power supply, the solder lands are connected by using jumper wires and soldered, so that they can be electrically short-circuited to each other.

In such a structure, when an external power supply of, for example, + 9V, + 12V, + 24V is connected to the power supply side, each opening / closing section is soldered and short-circuited as shown in the following table. Here, the ∘ marks indicate that they are electrically short-circuited, and the X marks indicate that they are electrically open.

[0027]

[Table 1]

As is apparent from this table, when the external power supply is + 9V, the light emitting diode D of the connection circuit 1 is
1, D2, the light-emitting diodes D3 and D4 of the connection circuit 2, the light-emitting diodes D5 and D6 of the connection circuit 3, and the light-emitting diodes D7 and D8 of the connection circuit 4 are supplied with + 9V power in parallel to perform light-emission operation and each liquid crystal. Liquid crystal display L of display digit
Illuminate C1-LC4 from the back. When the external power supply is + 12V, the light emitting diodes D1 and D2 of the connection circuit 1 and the light emitting diodes D3 and D4 of the connection circuit 2 are connected in series to the power supply of + 12V, and the light emitting diodes D5 and D6 of the connection circuit 3 are connected. And the light emitting diode D of the connection circuit 4
When 7 and D8 are connected in series to the + 12V power source, the same current as that of the + 9V power source flows in each light emitting diode, and the liquid crystal of each liquid crystal display digit has substantially the same brightness as in the case of + 9V. The display bodies LC1 to LC4 are illuminated from the back. When the external power supply is + 24V, all the light emitting diodes D1 to D8 are connected in series to the + 24V power supply, so that a current substantially the same as that of the + 9V and + 12V power supplies flows and the brightness is substantially the same as the above. Then, the liquid crystal display bodies LC1 to LC4 of the respective liquid crystal display digits are illuminated from the back.

Therefore, even if the types of externally supplied power supply are different, it is possible to deal with any power supply by simply selecting the short circuit of the opening / closing section with the same backlight substrate PBP.

The resistors R1 to R4 and the light emitting diodes D1 to D8 are mounted on the backlight substrate PBP on which the wiring pattern is formed, and the opening / closing sections SW1 to SW9 are soldered by an automatic soldering machine according to the type of power source. Short circuit.

The light emitting diodes D1 to D shown in FIG.
8 is a liquid crystal display LC1 of each digit on the liquid crystal display substrate LPB
When only a part of LC4 is displayed as a liquid crystal, it should not be necessary to illuminate all the liquid crystal displays LC1 to LC4 with the backlight. Therefore, if the light emitting diodes D1 to D8 are driven so as to illuminate all the liquid crystal displays LC1 to LC4 with backlight, power is wasted. Therefore, in the present embodiment, as shown in FIG. 3, the light emitting diodes D1 and D2 are connected via the transistor TR1 to the light emitting diode D.
Transistor TR2 is used for D3 and D4, and transistor TR3 is used for light emitting diodes D5 and D6.
The light emitting diodes D7 and D8 are directly driven by the drive circuit DC via the drive circuit DC. For example, when only the liquid crystal display body LC1 is driven for liquid crystal display, only the liquid crystal display body LC1 needs to be the backlight of the liquid crystal display body LC1. , D8 are driven to emit light and the liquid crystal displays LC1 and LC2 are driven to drive liquid crystal display, the backlight may be the liquid crystal displays LC1 and LC2, so the drive circuit DC turns on only the transistor TR3,
The other transistors TR1 and TR2 output a drive signal to turn off, thereby driving the light emitting diodes D5, D6, D7 and D8 as the backlight to emit light.

[0032]

As described above, according to the backlight device for a liquid crystal display of the present invention, even if the external power supply is connected by selecting the opening / closing of the opening / closing portion, it has a single circuit configuration. Uniform backlight illumination can be obtained. Further, according to the liquid crystal display device of the present invention, even if different types of external power supplies are connected, a substantially uniform backlight can be obtained by a simple operation of soldering the corresponding opening / closing parts on the same backlight substrate. You can get lighting,
There is no need to prepare a backlight substrate according to the type of power source as in the conventional case, the manufacturing process is simplified, and the cost can be further reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a liquid crystal display backlight device according to an embodiment of the present invention.

FIG. 2 shows a liquid crystal display substrate of a liquid crystal display device which is backlit by a light emitting diode in the backlight circuit of FIG. 1 and a backlight substrate arranged below the liquid crystal display substrate,
(A) is a plan view of a liquid crystal display substrate, (b) is a side view of the liquid crystal display substrate, and (c) is a side view of a backlight substrate.

FIG. 3 is a circuit diagram of a driving circuit and a light emitting diode driven by the driving circuit.

FIG. 4 is a circuit diagram of a conventional backlight device.

FIG. 5 is a circuit diagram of another conventional backlight device.

FIG. 6 is a circuit diagram of still another conventional backlight device.

[Explanation of symbols]

 D1 to D8 Light emitting diodes SW1 to SW8 Opening / closing part LPB Liquid crystal display substrate BPB backlight substrate

Claims (5)

[Claims] 1. A first light emitting element having an input portion connected to at least a power source side, and a first opening / closing portion connected between an output portion of the first light emitting element and a ground side. A second switching element connected to at least the power supply side, a second light-emitting element having an input section connected to the second switching section, and
One or a plurality of second connection circuits having a third opening / closing part connected between the output part of the light emitting element and the ground side, and the output part of the light emitting element on the front side and the light emitting element on the rear side. A backlight device for a liquid crystal display, comprising: one or a plurality of fourth opening / closing sections which are respectively connected to an input section. 2. A third light emitting element having at least a fifth opening / closing section connected to the power supply side, and an input section connected to the fifth opening / closing section and an output section connected to the ground side. A third connecting circuit connected between the output section of the second light emitting element of the second connecting circuit and the input section of the third light emitting element of the third connecting circuit. 6. The backlight device for a liquid crystal display according to claim 1, further comprising: an opening / closing part (6). 3. The liquid crystal display back according to claim 1, wherein the opening / closing portion is formed in an electrically open state on the same substrate and can be electrically short-circuited by soldering. Light device. 4. A power source is externally supplied to the power source side, and each of the opening / closing sections is electrically opened or short-circuited according to the type of the power source supplied. Item 4. A backlight device for liquid crystal display according to item 3. 5. A first light emitting element having an input section connected to at least a power supply side, and a first opening / closing section connected between an output section of the first light emitting element and a ground side. A second switching element connected to at least the power supply side, a second light-emitting element having an input section connected to the second switching section, and
One or a plurality of second connection circuits having a third opening / closing part connected between the output part of the light emitting element and the ground side, and the output part of the light emitting element on the front side and the light emitting element on the rear side. One or a plurality of fourth opening / closing sections respectively connected to the input section, a fifth opening / closing section connected to at least the power source side, and an input section in the fifth opening / closing section and an output section. A third connection circuit having a third light emitting element connected to the ground side, an output section of the second light emitting element of the second connection circuit at the final stage, and a third connection circuit of the third connection circuit. A sixth opening / closing section connected between the light emitting element and an input section of the light emitting element, the sixth opening / closing section being disposed on the same substrate, and each of the opening / closing sections being electrically open on the substrate. The liquid crystal display device is characterized in that it can be electrically short-circuited by soldering.