KR20050114010A - Apparatus and method for lamp driving of liquid crystal display device - Google Patents

Abstract

The present invention relates to a lamp driving device and a method of a liquid crystal display device.

Lamp driving apparatus of the liquid crystal display device according to an embodiment of the present invention is a lamp for irradiating light to the liquid crystal panel, an inverter that receives a direct current power from an external power source to convert an AC waveform to supply the lamp, and both ends of the lamp At least two transformers independently boosting the supplied AC waveform, and at least four switching elements connected in parallel to the transformer.

Description

Lamp driving device and method of liquid crystal display device {APPARATUS AND METHOD FOR LAMP DRIVING OF LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a lamp driving device and a lamp driving method of the liquid crystal display device, and more particularly, to a lamp driving device and method of the liquid crystal display device to reduce the heat generated in the inverter circuit of the lamp driving unit to stably drive the lamp. It is about.

In general, liquid crystal displays (hereinafter referred to as "LCDs") have tended to be increasingly wider in application due to features such as light weight, thinness, and low power consumption. According to this trend, LCDs are used for office automation equipment, audio / video equipment, and the like. On the other hand, the LCD is controlled to display the desired image on the screen by adjusting the transmission amount of the light beam according to the image signal applied to the plurality of control switches arranged in a matrix form.

Since the LCD is not a self-luminous display device, a light source such as a back light is required. Such LCD backlight has a direct type and an edge type. In the edge type system, a lamp is installed outside the flat plate, and light is incident from the lamp onto the entire surface of the liquid crystal panel using a transparent light guide plate. The direct type places several lamps in the plane. A diffusion plate is installed between the lamp and the liquid crystal panel to maintain a constant space between the liquid crystal panel and the lamp.

1 is a view showing a lamp driver of a conventional liquid crystal display device.

Referring to FIG. 1, the lamp driver 60 of each liquid crystal display device is connected to one or more lamps 2 for generating light and one end of each lamp 2 to be supplied to the lamp 2, or a lamp ( A feedback circuit 42 for detecting the voltage and current output from 2), a controller 44 connected to one end of the feedback circuit 42 and receiving a feedback signal, and the other end of the controller 44; A plurality of inverter circuit circuits 46, which are connected and supplied with a DC power supply from a power supply unit (not shown), to generate a high-voltage AC power, and transformers 48 connected to each of the inverter circuits 46, are provided.

Each of the plurality of lamps 2 is composed of a glass tube, inert gases inside the glass tube, and a cathode and an anode installed at both ends of the glass tube. Inert gas is filled in the glass tube, and phosphor is coated on the inner wall of the glass tube.

Each of the plurality of lamps 2 has a high pressure AC waveform supplied from the inverter circuit 46 to the high voltage electrode and the low pressure electrode, and electrons are emitted from the low pressure electrode to collide with the inert gases inside the glass tube to form a geometric shape. The amount of electrons increases in series. As the current flows inside the glass tube by the increased electrons, ultraviolet rays are emitted as the inert gas is excited by the electrons. This ultraviolet light impinges on the luminescent phosphor applied to the inner wall of the glass tube to emit visible light. At this time, the plurality of lamps (2) is continuously supplied with a high-pressure AC waveform is always lit.

The feedback circuit 42 detects an alternating high voltage generated from the inverter circuit 46 and supplied to the lamp 2 to generate a feedback voltage. The feedback circuit 42 may be located at the output terminal of the lamp 2 and, when located at the output terminal, detects an output value output from the lamp 2.

The controller 44 receives the feedback voltage F / B generated from the feedback circuit 42 to control the switch element included in the inverter circuit 46. In detail, when the feedback voltage F / B is greater than a predetermined reference value, the controller 44 causes the switching device to transmit a voltage less than the reference voltage. In other words, the amount of power becomes smaller, and the current passing through the lamp 2 becomes smaller. On the contrary, when the feedback voltage F / B is smaller than the predetermined reference value, the controller 44 causes the switching element to transmit more voltage than the reference voltage. That is, the amount of voltage increases, and the current passing through the lamp 2 increases.

The plurality of inverter circuits 46 receive DC power from an external power source and convert the DC power into an AC signal by switching using a switch element included in the inverter circuit 46.

Each of the transformers 48 is induced by an AC voltage generated in the primary winding 51 by switching of the primary winding 51, the auxiliary winding 52, and a switch element included in the inverter circuit 46. It is provided with a secondary winding 53 for generating a secondary winding 52 disposed between the primary winding 51 and the secondary winding 53.

Let us look at the connection of the transformer 48 and the lamp (3).

Typically, the connection between the transformer 48 and the lamp 2 is a high-low method and a high-high method divided by the type of voltage supplied to one end and the other end of the lamp 2. Depends on.

In the high-low method, as shown in FIG. 2A, a high voltage AC waveform is applied to one end of the lamp 2, while a ground voltage GND is applied to the other end.

On the other hand, as shown in Figure 2b, a high voltage AC waveform (for example, + 700Vac) is applied to one end of the lamp 2, and the other end of the lamp 2 is supplied to one end of the lamp 2, as shown in FIG. In contrast to the high voltage AC waveform, a high voltage AC waveform (for example, -700 Vac) having an opposite direction is applied. In the lamp 2 using this high-high method, a virtual ground GND is formed at approximately an intermediate point in the overall length of the lamp 2.

3 is a diagram relating to the connection between the transformer 48 and the lamp 2 of the inverter circuit 46 using the conventional high-high method.

Referring to FIG. 3, the connection of the transformer 48 and the lamp 2 using the conventional high-high method is connected to the secondary winding 53 of the hydrostatic transformer 58 at one end of the lamp 2, and at the other end thereof. The secondary winding 63 of the negative pressure transformer 68 is connected. Each end of the primary winding 51 for inducing a voltage to the secondary winding 53 of the positive pressure transformer 58 is connected to each other of the ends of the primary winding 61 of the negative pressure transformer 68 and is connected to each other. Switching elements S1 and S4 are connected in parallel to one end of the primary winding 51 of the positive pressure transformer 58, and switching elements S3 and S2 are connected in parallel to the other end of the primary winding 61 of the negative pressure transformer 68. do.

In the hi-high method having such a structure, the amount of current flowing through each of the switching elements S1 to S4 is increased so that heat generated from each of the switching elements S1 to S4 is a reference value (for example, 35 ° at room temperature). Will occur higher. Accordingly, in order to reduce heat generated in each of the switching elements S1 to S4, heat reducing switching elements S1 ′ to S4 ′ are connected in parallel to each of the switching elements S1 to S4. However, in this connection method, since the amount of current dispersed in S1 'to S4' is not large, the effect of reducing heat generated in each of the switching elements S1 to S4 is not large. Accordingly, the heat generated in each of the switching elements S1 to S4 still causes a problem of being generated higher than the reference temperature, thereby reducing the lifetime of each of the switching elements S1 to S4 as well as deteriorating the liquid crystal display device. .

Accordingly, it is an object of the present invention to provide a lamp driving device and method of the liquid crystal display device which can stably drive the lamp by reducing the heat generated in the lamp driver of the liquid crystal display device.

In order to achieve the above object, the lamp driving device of the liquid crystal display device according to an embodiment of the present invention and a plurality of lamps for irradiating light to the liquid crystal panel; A plurality of inverters which convert DC power from the outside into AC power and supply the respective lamps; And a first boosting unit and a second boosting unit for independently boosting AC power supplied from the respective inverters to both ends of the lamps.

The lamp is at least one of a cold cathode tube lamp type and an external electrode lamp type.

At least one of the first and second boosting units includes at least two switching elements connected in parallel between one end of each boosting unit and a power supply, and at least two switching connected in parallel between the other end of each of the boosting units and a ground voltage. An element is provided.

The switching element is a MOS-FET.

Lamp driving method of the liquid crystal display device according to an embodiment of the present invention comprises the steps of converting into an AC waveform by receiving a DC power from an external power source; Boosting the AC waveform to an AC waveform having different directions through a first boosting unit and a second boosting unit, and supplying the AC waveform to each end of a lamp; And distributing a current by using a plurality of switching elements connected in parallel to the first and second connection circuits formed independently of the lamp and the first and second boosting units, respectively.

The step of boosting the AC waveform to an AC waveform having different directions through the first boosting unit and the second boosting unit and supplying the AC waveform to each stage of the lamp may include supplying a positive pressure AC waveform to one end of the lamp by boosting the AC waveform. ; And boosting and supplying a negative pressure AC waveform to the other end of the lamp.

Distributing the current by using a plurality of switching elements connected in parallel with each other in a connection circuit formed independently of the lamp and the first and second boosting units may include: outputting the current output from the first connection circuit to the first boost; Distributing a current by using at least two switching elements connected in parallel to one end and the other end of the unit, and at least two currents connected from the second connection circuit to one end and the other end of the second booster in parallel, respectively. Distributing the current using the switching element.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 6.

4 is a view illustrating a lamp driver of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the lamp driver 160 of the liquid crystal display according to the exemplary embodiment of the present invention is connected to a plurality of lamps 102 and one end of each lamp 102 to be supplied to the lamp 102 or to the lamp. A feedback circuit 142 for detecting the voltage and current output from the 102, a control unit 144 connected to one end of the feedback circuit and receiving a feedback signal, and the other end of the control unit 144; And a plurality of inverter circuits 146 for generating AC power by receiving DC power from the power supply unit, and transformers 148 connected to the plurality of inverter circuits 146 to boost AC power.

Each of the plurality of lamps 102 includes a glass tube, inert gases inside the glass tube, and a cathode and an anode installed at both ends of the glass tube. Inert gas is filled in the glass tube, and phosphor is coated on the inner wall of the glass tube.

Each of the plurality of lamps 102 has an exponential exponential force when high-pressure AC waveforms from the inverter circuit 146 are applied to the high-pressure electrode and the low-pressure electrode, and electrons are emitted from the low-pressure electrode to collide with inert gases in the glass tube. This increases the amount of electrons. As the current flows inside the glass tube by the increased electrons, ultraviolet rays are emitted as the inert gas is excited by the electrons. This ultraviolet light impinges on the luminescent phosphor applied to the inner wall of the glass tube to emit visible light. At this time, the plurality of lamps 102 are continuously supplied with a high-voltage AC waveform is constantly lit.

The feedback circuit 142 detects an alternating high voltage generated from the inverter circuit 146 and supplied to the lamp 102 to generate a feedback voltage. The feedback circuit 142 may be located at the output terminal of the lamp 102 and, when located at the output terminal, detects an output value output from the lamp 102.

The controller 144 receives the feedback voltage F / B generated from the feedback circuit 142 to control the switch element included in the inverter circuit 146. In detail, when the feedback voltage F / B is greater than a predetermined reference value, the controller 144 controls the switching device to transmit a voltage less than the reference voltage. In other words, the amount of power becomes small so that the current passing through the lamp 102 becomes smaller. On the contrary, when the feedback voltage F / B is smaller than the predetermined reference value, the controller 144 causes the switching element to transmit more voltage than the reference voltage. That is, the amount of voltage increases, and the current passing through the lamp 102 increases.

The plurality of inverter circuits 146 connected to the plurality of lamps receive DC power from an external power source and convert the DC power into an AC signal by switching using a switch element included in the inverter circuit 146.

Each of the transformers 148 is generated in the primary windings 151 and 161 by the switching of the primary windings 151 and 161, the auxiliary windings 152 and 162, and the switch elements included in the inverter circuit 146. Secondary windings 153 and 163 induced by voltage to generate an AC high voltage, and auxiliary windings 152 and 162 disposed between the primary windings 151 and 161 and the secondary windings 153 and 163 are provided.

Here, the driving method of the inverter circuit 146 and the transformer 148 will be described.

In the drive of the inverter circuit 146 and the transformer 148, first, an AC voltage is generated in the primary windings 151 and 161 by switching of the switch elements included in the inverter circuit 146. Thereafter, the secondary windings 153 and 163 are induced by an AC voltage generated in the primary windings 151 and 161 to generate an AC high voltage. The AC high voltage generated in this manner is input to the feedback circuit 142 and the lamp 102 connected to both sides of the secondary windings 153 and 163.

Let us look at in detail the wiring method of the transformer 148 and the lamp 102 according to an embodiment of the present invention having such a structure.

5 is a diagram illustrating a wiring method of a transformer 148 and a lamp 102 according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the connection between the transformer 148 and the lamp 102 according to an embodiment of the present invention includes a high voltage transformer connection unit 180 and a lamp 102 connected to the high pressure of the lamp 102. Low voltage transformer connection unit 190 is connected to the low pressure (Low) end.

The high voltage transformer connection unit 180 is disposed between one end of the lamp 102 and the ground voltage GND, and is supplied from the secondary winding 151 for applying a high voltage AC waveform to the lamp 102 and the inverter circuit 146. The primary winding 151 for inducing the received AC waveform to the secondary winding 153 is disposed facing the secondary winding 153. One end of the switching element S1 and S4 is connected in parallel to one end of the primary winding 151, and one end of the switching element S2 and S3 is connected in parallel to the other end of the primary winding 151. Here, the other ends of the switching elements S1 and S3 are connected to the inverter circuit 146, and the other ends of S4 and S2 are connected to the ground voltage.

The low voltage transformer connection unit 190 is also disposed between the other end of the lamp 102 and the ground voltage GND, and the secondary winding 161 for applying a high voltage AC waveform to the lamp 102 from the inverter circuit 146. The primary winding 151 for inducing the supplied AC waveform to the secondary winding 163 is disposed facing the secondary winding 163. Since each switching element S1 ′ through S4 ′ disposed in the low voltage transformer connection unit 190 is disposed at the same position as each switching element disposed in the high voltage transformer connection unit 190, the description thereof will be omitted.

On the other hand, the lamp 102 is a cold cathode tube lamp ("CCFL") method of supplying power by inserting the electrodes at both ends of the glass tube of the lamp 102 as shown in Figure 6a, and FIG. As shown in 6b, there is an External Electrode Fluorescent Lighting (“EEFL”) method for supplying power to an electrode part surrounding both ends of the glass tube of the lamp 102 with a metal material. The connection method of the transformer of the inverter circuit and the lamp among the lamp driver of the liquid crystal display according to the present invention can be applied regardless of the type of lamp, that is, CCFL and EEFL.

As described above, the transformer of the inverter circuit of the lamp driver of the liquid crystal display according to the embodiment of the present invention acts independently of each stage of the lamp. Accordingly, the transformer connection unit, which is divided into high and low pressure forms, dissipates heat by switching elements disposed in each connection unit, and thus operates while maintaining a temperature within a reference temperature. As a result, it is possible to maintain stable driving of the lamp driver and to prevent deterioration of the liquid crystal display device due to heat.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a view showing a lamp driver of a conventional liquid crystal display device.

2A and 2B are diagrams illustrating lamp driving of a high low and a high high system.

3 is a diagram illustrating a connection between a conventional transformer and a lamp.

4 is a view illustrating a lamp driver of a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a connection between a transformer and a lamp according to an exemplary embodiment of the present invention.

6A and 6B show a cold cathode tube lamp and an external electrode lamp.

<Description of Symbols for Main Parts of Drawings>

2, 102 lamp 42, 142 feedback circuit

44, 144 control unit 46, 146 inverter

48, 148: transformer 61, 51, 151: primary winding

52, 152: secondary winding 63, 53, 153: secondary winding

58: positive pressure transformer 68: negative pressure transformer

60, 160: lamp drive unit 180: high voltage transformer connection unit

190: low voltage transformer connection unit

Claims (7)

A plurality of lamps for irradiating light onto the liquid crystal panel; A plurality of inverters which convert DC power from the outside into AC power and supply the respective lamps; And a first boosting section and a second boosting section for independently boosting AC power supplied from the respective inverters to the both ends of the lamps. The method of claim 1, The lamp is And at least one of a cold cathode tube lamp type and an external electrode lamp type. The method of claim 1, At least one of the first and second boosting unit At least two switching elements connected in parallel between one end of each booster and a power source, And at least two switching elements connected in parallel between the other end of each boosting section and a ground voltage. The method of claim 3, wherein The switching device is a lamp driving device of the liquid crystal display device characterized in that the MOS-FET. Converting into an AC waveform by receiving a DC power from an external power source; Boosting the AC waveform to an AC waveform having different directions through a first boosting unit and a second boosting unit, and supplying the AC waveform to each end of a lamp; And distributing a current by using a plurality of switching elements connected in parallel to the first and second connection circuits formed independently of the lamp and the first and second boosting units, respectively. How to drive the lamp. The method of claim 5, The step of boosting the AC waveform to the AC waveform having a different direction through the first boosting unit and the second boosting unit to supply to each stage of the lamp, Boosting and supplying a positive AC waveform to one end of the lamp; And boosting and supplying a negative pressure AC waveform to the other end of the lamp. The method of claim 6, Distributing a current by using a plurality of switching elements connected in parallel in a connection circuit formed independently of the lamp and the first and second boosting units, Distributing the current using at least two switching elements connected in parallel with one end of the first booster and the other end of the current output from the first connection circuit; And distributing the current output from the second connection circuit by using at least two switching elements connected in parallel to one end and the other end of the second boosting unit, respectively. .