KR101066496B1 - backlight unit - Google Patents

Abstract

In order to provide a backlight unit that can correct a plurality of fluorescent lamps with a small number of current balancers and to reduce production costs, the backlight unit for achieving the above object includes a lamp unit in which a plurality of fluorescent lamps are arranged; First and second current balancer portions disposed at both ends of the lamp portion, each of which comprises a plurality of current balancers each having Y sub-transformers having primary to (Y + 1) secondary windings; A protection circuit unit which receives a current from the first and second current balancer units and outputs a lighting state of each fluorescent lamp of the lamp units; A controller configured to receive an output signal of the protection circuit unit, sense an abnormality of the lamp unit configured by the fluorescent lamp, and control a flow of current applied to the fluorescent lamp; First and second switching units configured to control an on / off time of a MOSFET or a transistor by the controller to convert a DC voltage into an AC pulse wave and output the AC voltage; And a first transformer and a second transformer configured to output a voltage boosted to each fluorescent lamp of the lamp unit through the first and second current balancer units.

Current Balancer, Closed Loop, Fluorescent Lamp

Description

Backlight unit

1 is a layout plan view of a backlight unit according to the prior art

2 is a layout plan view of a backlight unit according to another conventional technology

3 is a layout plan view of a backlight unit according to an embodiment of the present invention;

4A to 4D are various exemplary views of winding directions of the current balancer of FIG. 3.

Explanation of symbols on the main parts of the drawings

30: lamp unit 31a. 31b: first and second electrodes

32 fluorescent lamp 33a, 33b 1st, 2nd power supply lead wire

40 and 41: first current balancer 50: protection circuit

60: controller 70, 71: first and second switching unit

80, 90: first and second transformer

The present invention relates to a backlight unit, and more particularly to a backlight unit suitable for reducing the current deviation between lamps with a minimum current balancer.

CRT (Cathode Ray Tube), one of the commonly used display devices, is mainly used for monitors such as TVs, measuring devices, and information terminal devices.However, due to the weight and size of the CRT itself, We couldn't respond actively to demands.

Therefore, in the trend of miniaturization and light weight of various electronic products, CRT has a certain limit in weight and size.

It is expected that the CRT will be replaced by a liquid crystal display (LCD) using an electro-optical effect, a plasma display device (PDP) using a gas discharge, and an EL display device using an electroluminescent effect ( Electro Luminescence Display (ELD) and the like, among them, research on liquid crystal display (LCD) is being actively conducted.

In order to replace the CRT, liquid crystal display devices having advantages such as small size, light weight, and low power consumption have been actively developed. Recently, the liquid crystal display device has been developed enough to perform a role as a flat panel display device. As it is used for a monitor of a desktop computer and a large information display device, the demand for a liquid crystal display device is continuously increasing.

Since most of the liquid crystal display devices are light-receiving devices that display an image by controlling the amount of light coming from the outside, a separate light source for irradiating light to the liquid crystal panel, that is, a back light unit is necessary. .

In general, a backlight unit used as a light source of a liquid crystal display device is a method of disposing a cylindrical light emitting lamp, and is divided into an edge method and a direct method.

The edge method is that the lamp unit is installed on the side of the light guide plate for guiding the light, the lamp unit is inserted into both ends of the lamp to emit light, the lamp holder to protect the lamp and the outer peripheral surface of the lamp and one side is It is provided with a lamp reflector plate fitted to the side of the light guide plate to reflect the light emitted from the lamp toward the light guide plate.

The edge method in which the lamp unit is installed on the side of the light guide plate is applied to a relatively small liquid crystal display device such as a monitor of a laptop computer and a desktop computer, and has good uniformity of light and a long service life. It is advantageous to thin the liquid crystal display device.

On the other hand, the direct method began to be developed mainly as the size of the liquid crystal display device became larger than 20 inches. will be.

The direct method is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

Hereinafter, a conventional backlight unit will be described with reference to the accompanying drawings.

1 is a layout plan view of a backlight unit according to the prior art, Figure 2 is a layout plan view of a backlight unit according to another conventional technology.

First, as shown in FIG. 1, the backlight unit according to the related art is used to individually drive lamps, and includes a plurality of fluorescent lights in which first and second electrodes 11a and 11b are provided inside both ends of a tube. The lamps 10 are arranged at regular intervals, and the first and second power lead wires 12a and 12b for transmitting power to the first and second electrodes 11a and 11b on both sides of the fluorescent lamp 10. Is connected.

In addition, first and second transformers 13a and 13b are connected to the first and second power lead wires 12a of the fluorescent lamp 10, respectively, and the first and second transformers 13a and 13b. The first and second controllers 15a and 15b respectively control the amount of current applied to the fluorescent lamp 10 by receiving a voltage feedback from the first and second MOSFETs 15a and 15b. Alternatively, each of the first and second switching units 14a and 14b adjusts the on / off time of the transistor to convert the DC voltage into an AC pulse wave.

In the above, the first and second transformers 13a and 13b receive a pulse wave from the first and second switching units 14a and 14b as primary windings, and the first and second transformers of the fluorescent lamp 10 through the secondary windings. The voltage boosted by the second power lead wires 12a and 12b is output.

As described above, the backlight unit is provided with a transformer, a switching unit, and a controller separately at both ends of each fluorescent lamp to individually drive the fluorescent lamps 10.

Next, a backlight unit according to another conventional technology is for driving a lamp in parallel, and as shown in FIG. 2, a plurality of first and second electrodes 21a and 21b are provided inside both ends of a tube. Two fluorescent lamps 20 are arranged at regular intervals, and the first and second power lead wires 22a and 12 for transmitting power to the first and second electrodes 21a and 21b on both sides of the fluorescent lamp 20. 22b) are connected, and first and second capacitors 23a and 23b are connected to the first and second power lead wires 22a and 22b of the fluorescent lamp 20, respectively. 23a are commonly connected to the first output power line of the first transformer 24a, and the second capacitors 23b are commonly connected to the first output power line of the second transformer 24b.

And a controller 26 disposed at both ends of the plurality of fluorescent lamps 20 to control and output an amount of current applied to the fluorescent lamp 20, and the controller 26 turns on a MOSFET or a transistor. The first and second switching units 25a connected to the primary windings of the first and second transformers 24a and 24b disposed across the fluorescent lamp 20 to change the DC voltage to AC pulse waves by adjusting the on / off time. 25b).

In the above, the first and second transformers 24a and 24b receive pulse waves from the first and second switching units 24a and 25b as the first and second input side windings, and receive fluorescent lamps 20 through the first output side windings. The boosted voltage is output to the first and second capacitors 23a and 23b connected to the first and second power supply leads 22a and 22b.

The second output power lines of the first and second transformers 24a and 24b are grounded.

The first and second capacitors 23a and 23b serve as safety capacitors to prevent a sharp increase in discharge current when driving lamps individually, and evenly distribute a plurality of lamps in parallel so that currents are uniformly distributed when driven by a single power supply. It serves to keep the brightness of the lamp uniform.

However, in the backlight unit according to another technique of the related art described above, when each capacitor is applied to the large screen backlight unit, it is difficult to reduce the current deviation between the lamps due to the impedance difference of each lamp.

If you want to design independent of each lamp's impedance difference, you can increase the impedance of each capacitor, but the output voltage of the transformer will be considerably higher to deliver the desired current to each lamp. As such, when the output voltage of the transformer is increased, power lost due to the formation of a strong electric field due to a high voltage may be generated, which may lower the efficiency of the backlight unit and may cause a problem in driving safety due to heat generation.

The present invention has been made to solve the above problems, and in particular, it is an object of the present invention to provide a backlight unit suitable for correcting a plurality of fluorescent lamps with a few current balancers and reducing production costs.

The backlight unit according to the present invention for achieving the above object comprises a lamp unit in which a plurality of fluorescent lamps are arranged; First and second current balancer portions disposed at both ends of the lamp portion, each of which comprises a plurality of current balancers each having Y sub-transformers having primary to (Y + 1) secondary windings; A protection circuit unit which receives a current from the first and second current balancer units and outputs a lighting state of each fluorescent lamp of the lamp units; A controller configured to receive an output signal of the protection circuit unit, sense an abnormality of the lamp unit configured by the fluorescent lamp, and control a flow of current applied to the fluorescent lamp; First and second switching units configured to control an on / off time of a MOSFET or a transistor by the controller to convert a DC voltage into an AC pulse wave and output the AC voltage; And a first transformer and a second transformer configured to output a voltage boosted to each fluorescent lamp of the lamp unit through the first and second current balancer units.

The lamp unit includes a plurality of fluorescent lamps having first and second electrodes disposed at both ends of a tube at regular intervals, and a first for transmitting power to the first and second electrodes on both sides of the fluorescent lamp. The second power lead wire is connected.

The first and second transformers are characterized in that the first and second input side windings are connected to the first and second switching units, and the second output power lines are grounded.

The first current balancer is composed of first to nth current balancers 40-1 and 40-n in which 'X' or more fluorescent lamps are bundled into one unit, and the second current balancer is also configured as the lamp. And first to nth current balancers 41-1 and 41-n in which negative 'X' or more fluorescent lamps are bundled into one unit.

The primary to Y primary windings of the sub-transformers have the same turns ratio and are characterized by having the same inductance.

The (Y + 1) secondary windings, which are the last windings of the sub-transformer, form a closed loop.

Each of the sub-transformers having the primary side to the (Y + 1) side windings is connected to Y lamps, and each current balancer is configured by using a fluorescent lamp of 2Y as a unit.

When the sub-transformer is composed of 1, 2, and 3 secondary windings, 4 fluorescent lamps are bundled and driven in one unit, and 1, 2, 3 secondary windings are provided in each current balancer of the first and second current balancer units. First and second sub-transformers are provided, and two fluorescent lamps are connected to the first and second sub-transformers, respectively, and the tertiary windings of the first and second sub-transformers form a closed loop. Characterized in forming.

When each sub-transformer of each current balancer is composed of 1, 2 and 3 windings (Y = 2), the portion adjacent to the fluorescent lamp of each winding is the first stage and the portion not adjacent to the fluorescent lamp is In summary, the winding start point of the primary, secondary, and tertiary windings is located at the first end.

The winding start point of the primary and tertiary windings is located in the first end, the winding start point of the secondary windings is characterized in that it further comprises located in the second end.

The winding start point of the primary and tertiary windings is located in the second end, the winding start point of the secondary windings is characterized in that it further comprises located in the first end.

The starting point of the winding of the primary, secondary, and tertiary windings is further characterized in that it is located in the second end.

The winding start point of the primary and secondary windings is located in the first end, the winding start point of the third winding is characterized in that it further comprises located in the second end.

The winding start point of the primary winding is located in the second end, and the winding start point of the secondary, tertiary winding is further characterized in that it is located in the second end.

The winding start point of the primary and secondary windings is located in the second end, the winding start point of the third winding is characterized in that it further comprises located in the first end.

The winding start point of the primary winding is located in the first end, and the winding start point of the secondary, tertiary winding is further characterized in that it is located in the second end.

Referring to the accompanying drawings, a backlight unit according to an embodiment of the present invention will be described.

3 is a layout plan view of a backlight unit according to an exemplary embodiment of the present invention, and FIGS. 4A to 4D are various exemplary views of a winding direction of a winding of the current balancer of FIG. 3.

In the backlight unit according to the exemplary embodiment of the present invention, as illustrated in FIG. 3, the lamp unit 30 in which a plurality of fluorescent lamps are arranged is equal to the current transmitted to each fluorescent lamp of the lamp unit 30. In order to maintain the lamp unit 30, current is fed back from the first and second current balancer units 40 and 41 disposed at both ends of the lamp unit 30 and the first and second current balancer units 40 and 41. The protection circuit unit 50 for outputting the lighting state of each fluorescent lamp of the) and the detection of the abnormality of the lamp unit 30 composed of the fluorescent lamp by receiving the output signal of the protection circuit unit 50, the current applied to the fluorescent lamp Controller 60 for controlling the flow of the first and second switching unit 70 for controlling the on / off time of the MOSFET (MOSFET) or transistor by the controller 60 to convert the DC voltage into an AC pulse wave and output it. , 71, and the first and second current balancer units 40 and 41. The first and second transformers 80 and 90 output voltages boosted by the fluorescent lamps of the lamp unit 30.

In the lamp unit 30, a plurality of fluorescent lamps 32 including first and second electrodes 31a and 31b are arranged at regular intervals in both ends of a tube, and the fluorescent lamp 32 The first and second power lead wires 33a and 33b for transmitting power are connected to the first and second electrodes 31a and 31b on both sides of.

The first and second transformers 80 and 90 receive pulse waves from the first and second switching units 70 and 71 as the first and second input side windings, and the first and second windings connected to the first output side. The voltage boosted to the fluorescent lamps 32 is output through the two current balancer units 40 and 41.

Second output power lines of the first and second transformers 80 and 90 are grounded.

In addition, the first and second current balancer parts 40 and 41 are provided to reduce the occurrence of the deviation of the tube current between the fluorescent lamps 32, and the first current balancer part 40 is provided in the lamp part 30. The first to nth current balancers 40-1 and 40-n which combine 'X' or more fluorescent lamps 32 into one unit, and the second current balancer 41 also includes a lamp unit 30. ) Is composed of first to nth current balancers 41-1 and 41-n in which 'X' or more fluorescent lamps 32 are bundled into one unit.

Each current balancer of the first and second current balancer portions 40 and 41 is composed of Y sub-transformers having a primary side to a (Y + 1) side winding.

In the above, the primary to Y primary windings of the sub-transformers have the same turns ratio and have the same inductance.

The (Y + 1) secondary windings, which are the last windings of each sub-transformer, form a closed loop, so that the same current always flows, so that the current flowing through each fluorescent lamp can be equally corrected.

As described above, each sub-transformer having primary to (Y + 1) primary windings is connected to Y lamps, and each current balancer drives 2Y fluorescent lamps as a unit.

For example, the case where the sub-transformer is composed of the first, second and third windings will be described as follows.

First, when four fluorescent lamps are driven in a unit, each current balancer includes first and second sub-transformers having first and second sub-transformers having first and second windings, and first and second sub-transformers. Two fluorescent lamps are connected to each other, and the tertiary windings of the first and second sub-transformers form a closed loop.

When the six fluorescent lamps are driven in a unit, each current balancer includes first, second and third sub-transformers having first, second and third windings. Two fluorescent lamps are connected to the third sub-transformer, respectively, and the tertiary windings of the first, second, and third sub-transformers form a closed loop.

That is, when the sub-transformer is composed of 1, 2, and 3 secondary windings, and the 2m fluorescent lamps are driven in a unit, the current balancer of each current balancer unit has 1, 2, 3, 3, 4, 4, 4, 3, 3, 4, 3 The m-th sub-transformer is provided, and two fluorescent lamps are connected to the first-m-th sub-transformers, respectively, and the tertiary windings of the first-m-th sub-transformers form a closed loop.

In FIG. 3, four fluorescent lamps are bundled to one current balancer as a unit.

Referring to FIG. 3, each current balancer of the first and second current balancer units will be described below.

Since the first and second current balancer parts 40 and 41 are symmetrically configured, and each current balancer has the same configuration, the first current balancer 40-1 of the first current balancer part 40 is here. The configuration of) will be described.

As shown in FIG. 3, the first current balancer 40-1 includes a first sub-transformer provided by winding primary, secondary, and tertiary windings on both ends of the first and second fluorescent lamps, respectively. And a second sub-transformer provided by winding primary, secondary and tertiary side windings on both ends of the third and fourth fluorescent lamps.

At this time, the primary and secondary windings of the first and second sub-transformers are wound to have the same number of turns and have the same inductance. And the tertiary winding is less wound than the primary and secondary windings, and therefore the inductance is small. In addition, the tertiary windings of the first and second sub-transformers are connected to each other to form a closed loop.

In the above, the primary and secondary windings of each current balancer of the first current balancer unit 40 receive a voltage from the first transformer 80 and supply the voltage to the fluorescent lamp. Each current of the second current balancer unit 41 is supplied. The primary and secondary windings of the balancer receive the voltage from the second transformer 90 and supply it to the fluorescent lamp.

The impedance values of the primary and secondary windings of each of the first and second sub-transformers of the first current balancer 40-1 may be measured by the impedance values of the first and second fluorescent lamps and the second and fourth fluorescent lamps. Greater than impedance As described above, since the impedance deviation of the primary and secondary windings is greater than the impedance deviation of the two fluorescent lamps connected to the primary and secondary windings, the currents flowing through the two fluorescent lamps are the same.

In addition, since the tertiary winding forms a closed loop, the current flowing in the closed circuit is the same. Therefore, since the current induced in the primary and secondary windings of each current balancer is the same, the current flowing through each fluorescent lamp is also the same.

Thus, two sub-transformers of each current balancer can be used to allow four fluorescent lamps to flow completely the same current.

When the sub-transformer of each current balancer is configured with the first and second windings, the respective windings may be configured by different winding start points (expressed as '●') of the windings.

In this case, a portion adjacent to the fluorescent lamp of each winding is described as the first stage, and a portion not adjacent to the fluorescent lamp is described as the second stage.

First, as shown in FIGS. 3 and 4A, the winding start point of the winding may be located at a first end adjacent to each fluorescent lamp.

As shown in FIG. 4B, the winding start point of the winding may be located at the first end and the third side winding at the first end adjacent to the fluorescent lamp, and the secondary side winding may be located at the second end.

As shown in FIG. 4C, the winding start point of the winding may be located at the primary and tertiary windings at the second end, and the secondary winding may be located at the first end.

And as shown in Figure 4d, the starting point of the winding of the winding of the primary, secondary, and tertiary side winding can be located in the second stage not adjacent to the fluorescent lamp.

In addition to the above, although not shown in the drawings, the winding start point of the winding may be positioned at the first end and the secondary winding at the first end, and the third winding may be located at the second end, and the winding starting point of the winding may be located at the first end. In the second stage, the secondary and tertiary windings may be located in the second stage, the winding starting point of the windings may be located in the primary stage, the secondary winding in the second stage, and the tertiary winding may be located in the first stage. The winding starting point may be such that the primary winding is located at the first end and the secondary and tertiary windings are located at the second end.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention.

Therefore, the technical scope of the present invention is not limited to the contents described in the above embodiments, but may be modified within the scope obvious to those skilled in the art.

The backlight unit according to the present invention as described above has the following effects.

By configuring the last winding as a closed loop in each current balancer and having a sub-transformer such that the remaining plurality of windings have the same number of windings, the plurality of lamps can be corrected with a few current balancers. Therefore, the production cost can be reduced by simplifying the configuration of the backlight unit.

Claims (16)

A lamp unit in which a plurality of fluorescent lamps are arranged; First and second current balancer portions disposed at both ends of the lamp portion, each of which comprises a plurality of current balancers each having Y sub-transformers having primary to (Y + 1) secondary windings; A protection circuit unit which receives a current from the first and second current balancer units and outputs a lighting state of each fluorescent lamp of the lamp units; A controller configured to receive an output signal of the protection circuit unit, sense an abnormality of the lamp unit configured by the fluorescent lamp, and control a flow of current applied to the fluorescent lamp; First and second switching units configured to control an on / off time of a MOSFET or a transistor by the controller to convert a DC voltage into an AC pulse wave and output the AC voltage; And a first transformer and a second transformer configured to output a voltage boosted to each fluorescent lamp of the lamp unit through the first and second current balancer units. The method of claim 1, The lamp unit includes a plurality of fluorescent lamps provided with first and second electrodes in both ends of the tube at regular intervals, And first and second power lead wires for transmitting power to the first and second electrodes on both sides of the fluorescent lamp. The method of claim 1, And the first and second transformers have first and second input side windings connected to the first and second switching units, and the second output power lines are grounded. The method of claim 1, The first current balancer is composed of first to nth current balancers 40-1 and 40-n in which at least 'X' fluorescent lamps are bundled into one unit. And the second current balancer is also composed of first to nth current balancers (41-1, 41-n) in which at least 'X' fluorescent lamps are bundled into one unit. The method of claim 1, The first to Y-th order windings of the sub-transformer have the same turns ratio and have the same inductance. The method of claim 1, And (Y + 1) secondary windings, which are the last windings of the sub-transformer, form a closed loop. The method of claim 1, And each sub-transformer having the primary to (Y + 1) secondary windings is connected to Y lamps, and each current balancer is configured by using a fluorescent lamp of 2Y as a unit. The method of claim 1, When the sub-transformer is composed of 1, 2, and 3 secondary windings, 4 fluorescent lamps are bundled and driven in units, and 1, 2, 3 secondary windings are provided in each current balancer of the first and second current balancer units. The first and second sub-transformers are provided, and two fluorescent lamps are connected to the first and second sub-transformers, respectively, and the tertiary windings of the first and second sub-transformers form a closed loop. Backlight unit, characterized in that. The method of claim 1, When each sub-transformer of each current balancer is composed of 1, 2 and 3 windings (Y = 2), the portion adjacent to the fluorescent lamp of each winding is the first stage and the portion not adjacent to the fluorescent lamp is In the second stage, And a winding starting point of the primary, secondary, and tertiary windings is located at a first end. The method of claim 9, And a winding start point of the primary and tertiary windings is located at a first end, and a winding start point of the secondary windings is located at a second end. The method of claim 9, And the winding start point of the primary and tertiary windings is located at a second end, and the winding starting point of the secondary winding is further located at a first end. The method of claim 9, And the winding start point of the primary, secondary, and tertiary windings is further positioned at a second end. The method of claim 9, And the winding start point of the primary and secondary windings is located at a first end, and the winding start point of the tertiary winding is further located at a second end. The method of claim 9, And a winding starting point of the primary winding is located at a second end, and a winding starting point of the secondary and tertiary windings is further located at a second end. The method of claim 9, And the winding start point of the primary and secondary windings is located at a second end, and the winding start point of the tertiary winding is further located at a first end. The method of claim 9, And the winding start point of the primary winding is located at the first end, and the winding start point of the secondary and tertiary windings is further located at the second end.

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