WO2013095055A1

WO2013095055A1 - Backlight module, method for driving same and display device using same

Info

Publication number: WO2013095055A1
Application number: PCT/KR2012/011289
Authority: WO
Inventors: 정혜만; 김오석; 강현구; 서일경; 양영은
Original assignee: 서울반도체 주식회사
Priority date: 2011-12-21
Filing date: 2012-12-21
Publication date: 2013-06-27

Abstract

The present invention relates to a backlight module, a method for driving the same and a display device using the same, in which a plurality of light-emitting diodes of a backlight unit can be efficiently driven using a pulsed rectified voltage and a power factor corrected voltage having a direct current component of a predetermined size or larger. A display device comprises: a power rectifying unit for rectifying alternating power and outputting a rectified voltage; a power factor correction unit for receiving the rectified voltage from the power rectifying unit, correcting the power factor of the alternating power and outputting a power factor corrected voltage containing a direct current voltage component having at least a predetermined size; a display module driven by the power factor corrected voltage; a backlight unit having a plurality of light-emitting diodes for providing backlighting to the display module; and a driving unit for a backlight unit for receiving the rectified voltage to generate a main driving voltage or a main driving current, supplying the main driving voltage or the main driving current to a backlight unit, receiving the power factor corrected voltage when the size of the rectified voltage is smaller than a preset threshold value to generate a supplementary driving voltage or a supplementary driving current, and supplying the generated supplementary driving voltage or supplementary driving current to the backlight unit.

Description

Backlight module, driving method thereof, and display device using same

The present invention relates to a backlight module, a method of driving the same, and a display device using the same. More specifically, the plurality of light emitting diodes of the backlight unit may be formed using a rectified voltage in the form of a pulse current and a power factor correction voltage having a DC component of a predetermined magnitude or more. The present invention relates to a backlight module that can be driven efficiently, a driving method thereof, and a display device using the same.

Recently, flat panel display devices have been widely used not only for mobile devices requiring miniaturization and low power, but also for large digital TVs that need to reduce weight and thickness due to their various applications. Among them, the liquid crystal display device is the most widely used method, and since the liquid crystal panel does not emit light by itself, a light source called a backlight unit (BLU) is required on the back of the liquid crystal panel.

Since the light generated from the backlight unit passes through the liquid crystal layer, the color filter, and the like, the backlight unit has a significant effect on the performance of the liquid crystal display (LCD) device. For example, not only the screen quality of the liquid crystal display device but also the weight, design, lifespan, power consumption, etc. can be significantly affected by the backlight unit.

Recently used backlight module is composed of a backlight unit consisting of a plurality of LED (Light Emitting Diode) and a backlight unit driver for driving the backlight unit, the performance is determined according to the method of driving each LED backlight unit.

The backlight module used in the conventional liquid crystal display device drives a plurality of LEDs using a DC power supply. To this end, the liquid crystal display device has a burden of adding a separate converter circuit for generating a DC power required to drive the LED.

As described above, the conventional liquid crystal display device needs to further include a separate converter for driving the backlight module in addition to the converter necessary for driving the display module, thereby increasing power consumption and increasing power loss in the converter. .

The present invention is to solve the above problems, the backlight module according to the present invention and a driving method and a display device using the same, the rectified voltage in the form of a pulse current to remove the DC-DC converter for supplying driving power to the backlight module An object of the present invention is to efficiently drive a plurality of light emitting diodes of a backlight unit by using a power factor correction voltage having a DC component having a predetermined magnitude or more.

According to an embodiment of the present invention, a backlight module, a method of driving the same, and a display device using the same include a ratio generated during multi-stage driving of an LED backlight unit using a rectified voltage in the form of a pulse current and a power factor correction voltage having a DC component of a predetermined magnitude or more. It is another object of the present invention to ensure stable driving of the device and to improve the reliability of the device by replenishing the insufficient energy when the current level rises by the dimming signal while the light emission period is removed.

According to another embodiment of the present invention, a backlight module, a driving method thereof, and a display device using the same may be manufactured by removing a DC-DC converter used to supply driving power of an LED backlight unit of a liquid crystal display device. Reducing costs is another purpose.

In order to achieve the above object, a display device according to the present invention includes a power rectifier for rectifying AC power to output a rectified voltage; A power factor correction unit configured to receive the rectified voltage from the power rectifier and compensate the power factor of the AC power and output a power factor correction voltage including at least a predetermined DC voltage component; A display module driven by the power factor correction voltage; A backlight unit having a plurality of light emitting diodes for providing backlight illumination to the display module; And receiving the rectified voltage to generate the main driving voltage or the main driving current, and supply the main driving voltage or the main driving current to the backlight unit, and receiving the power factor correction voltage when the magnitude of the rectifying voltage is smaller than a preset threshold to compensate the driving. And a backlight unit driver configured to generate a voltage or supplemental drive current, and supply the generated supplemental drive voltage or supplemental drive current to the backlight unit.

In the display device according to the exemplary embodiment of the present invention, the backlight unit driver may include a supplementary driving voltage or a supplementary driving current when the magnitude of the main driving voltage from the rectified voltage is smaller than the minimum voltage for driving the at least one light emitting diode. It is characterized by supplying to the backlight unit.

In the display device according to another exemplary embodiment, the display module may generate a dimming signal for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current. Here, when the dimming signal is received, the backlight unit driver supplies the supplementary driving voltage to the backlight unit when the main driving voltage is less than the set dimming voltage, or the supplementary driving current to the backlight unit when the main driving current is less than the set dimming current. It is characterized by the supply.

According to another exemplary embodiment of the present invention, a display apparatus includes: a first wire connecting an output terminal of a power rectifying unit and a first input terminal of a backlight unit driving unit and transferring a rectified voltage from the power rectifying unit to the backlight unit driving unit; And a second wiring connecting the output terminal of the power factor compensator to the second input terminal of the backlight unit driver and transferring the power factor correction voltage from the power factor compensator to the backlight unit driver.

In the display device according to another embodiment of the present invention, the backlight unit driver emits light among the plurality of light emitting diodes as the magnitude of the rectified voltage increases based on the rectified voltage whose voltage varies periodically over time. As the number of s increases and the magnitude of the rectified voltage decreases, the backlight unit is controlled to reduce the number of light emitting diodes emitting light among the plurality of light emitting diodes.

In the display device according to another embodiment of the present invention, the backlight unit driving unit is connected between the output terminal of the plurality of LED groups each including at least one light emitting diode of the plurality of light emitting diodes, and the reference potential, respectively. A plurality of current controllers forming a current path between an output terminal of each LED group and a reference potential according to a control signal; And a control signal generator for applying a control signal for controlling the operations of the plurality of current controllers to the plurality of current controllers according to the magnitude of the main driving voltage.

In the display device according to another embodiment of the present invention, the backlight unit driver is disposed between an output terminal of the power factor correction unit and an input terminal of the backlight unit, and further includes a voltage compensator for controlling supply of the power factor correction voltage to the backlight unit. Characterized in that.

In the display device according to another embodiment of the present invention, the voltage compensator includes: a switching element having a first terminal connected to an output terminal of the power factor compensator; And a diode having an anode connected to the second terminal of the switching element and a cathode connected to the input terminal of the backlight unit. Here, the switching element is characterized in that the on or off operation by the control signal of the control signal generator.

In the display device according to another embodiment of the present invention, the backlight unit driving unit, when the magnitude of the rectified voltage is less than the minimum voltage for driving at least one LED group of the plurality of LED groups to the control unit to the voltage compensation unit It is characterized by supplying a supplementary drive voltage or supplemental drive current by the power factor correction voltage to the plurality of LED groups.

In the display device according to another embodiment of the present invention, when a dimming signal for controlling the backlight unit driver to generate the set dimming voltage or the set dimming current is received from the display module, the backlight unit driver is configured such that the main driving voltage is set dimming. The supplementary driving voltage is supplied to the backlight unit when the voltage is smaller than the voltage, or the supplementary driving current is supplied to the backlight unit when the main driving current is smaller than the set dimming current.

In the display device according to another exemplary embodiment of the present invention, the power rectifier includes: a first power rectifier disposed at an input terminal of the power factor corrector and configured to supply a rectified voltage rectified by AC power to the power factor corrector; And a second power rectifying unit provided in the backlight unit driving unit and supplying a rectified voltage obtained by rectifying AC power to the backlight unit.

In the display device according to another embodiment of the present invention, the power factor correction unit includes: an inductor having a first terminal connected to a high potential first terminal of an input capacitor connected in series with an output terminal of a power rectifier; A switch having a first terminal connected to the second terminal of the inductor, and a second terminal connected to the low potential second terminal of the input capacitor; A diode having an anode commonly coupled to a second terminal of the inductor and a first terminal of the switch, and a cathode coupled to the high potential first terminal of the output capacitor; And an output capacitor having a first terminal connected to the cathode of the diode, and a second terminal commonly connected with the second terminal side of the low potential side of the input capacitor and the second terminal side of the switch.

In the display device according to another embodiment of the present invention, the power factor correction unit has an interleaved boost converter type in which two power factor correction units each including an inductor, a switch, a diode, and an output capacitor are connected in parallel to each other. It is done.

In the display device according to another embodiment of the present invention, at least one of the power rectifier and the power factor correction unit is disposed in the form of a single integrated circuit with the backlight unit driver.

The backlight module according to the present invention comprises: a power factor correction unit configured to output a power factor correction power by compensating a power factor of an AC power source; A backlight unit including a plurality of light emitting diodes; And a backlight unit driver configured to drive the plurality of light emitting diodes according to the dimming signal. The backlight unit driver may be configured to selectively supply the AC power and the power factor correction power to the plurality of light emitting diodes according to the dimming signal and the magnitude of the AC power.

In the backlight module according to an embodiment of the present invention, the backlight unit includes a plurality of light emitting diodes connected in series, and the backlight unit driving unit includes: a power rectifying unit rectifying AC power to supply a rectified voltage to the backlight unit; A plurality of current controllers connected between one terminal of the light emitting diode (cathode) and the reference potential and forming a current path between the light emitting diode and the reference potential according to a control signal; And a control signal generator configured to generate a control signal for controlling the operations of the plurality of current controllers according to the dimming signal and the magnitude of the rectified voltage.

In the backlight module according to another embodiment of the present invention, the control signal generation unit may adjust the current value flowing through the backlight unit by controlling the operation state of the current controller according to the level of the dimming signal.

The backlight module according to another embodiment of the present invention may further include a voltage compensator for supplying a voltage output from the power factor compensator to the backlight unit according to the magnitude of the rectified voltage and the level of the dimming signal.

In the backlight module according to another embodiment of the present invention, the voltage compensator supplies a voltage output from the power factor compensator to the backlight unit during a period where the rectified voltage is less than or equal to the threshold.

In the backlight module according to another embodiment of the present invention, the voltage compensator includes a switching device that performs a switching operation according to a compensation control signal generated based on a dimming signal during a period where the rectified voltage is less than or equal to a threshold value. do. Here, the switching element is characterized in that for connecting the output terminal of the power factor correction unit to the backlight unit according to the compensation control signal.

In the backlight module according to another embodiment of the present invention, the voltage compensator further comprises a diode in which one terminal of the switching element and the anode are connected in series. Here, the other terminal of the switching element is connected to the output terminal of the power factor correction unit, and the cathode of the diode is connected to the node connected to the input terminal of the backlight unit and the power rectifier.

In the method of driving a backlight module according to the present invention, the backlight unit is driven by a backlight unit driver for driving a backlight unit including a plurality of light emitting diode (LED) groups each having at least one light emitting diode to provide lighting to a display module. A method of driving a module, comprising: a first step of rectifying an AC power source to generate a rectified voltage; Compensating the power factor of the AC power supply to generate a power factor correction voltage including a DC voltage component having at least a predetermined magnitude; Receiving a rectified voltage to generate a main driving voltage or a main driving current, and supplying the main driving voltage or the main driving current to the backlight unit; And supplying a supplementary driving voltage or supplementary driving current by the power factor correction voltage to the backlight unit when the magnitude of the rectified voltage is smaller than a preset threshold.

In a method of driving a backlight module according to an embodiment of the present invention, the third step is to emit light among the plurality of LED groups as the magnitude of the rectified voltage increases based on the rectified voltage whose voltage varies periodically with time. The operation of the backlight unit is controlled to increase the number of LED groups, and the operation of the backlight unit is controlled to reduce the number of LED groups emitting light among the plurality of LED groups as the size of the rectified voltage decreases.

In a method of driving a backlight module according to another embodiment of the present invention, the fourth step may include a power factor correction voltage when the magnitude of the rectified voltage is smaller than a minimum voltage for driving at least one LED group among the plurality of LED groups. The supplementary driving voltage or supplementary driving current is supplied to the plurality of LED groups.

The driving method of the backlight module according to another embodiment of the present invention further includes, before the fourth step, receiving a dimming signal from the display module for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current. It is characterized by. Here, the fourth step may be characterized in that the supplementary driving voltage is supplied to the backlight unit when the main driving voltage is smaller than the set dimming voltage, or the supplementary driving current is supplied to the backlight unit when the main driving current is smaller than the set dimming current. .

According to the above configuration, the backlight module, the driving method thereof, and the display device using the same according to the present invention remove a DC-DC converter for supplying driving power to the backlight module, and provide a rectified voltage in the form of a pulse current and a DC component of a predetermined size or more. The excitation power factor compensation voltage is used to efficiently drive a plurality of LEDs of the backlight unit.

According to an embodiment of the present invention, a backlight module, a method of driving the same, and a display device using the same include a ratio generated during multi-stage driving of an LED backlight unit using a rectified voltage in the form of a pulse current and a power factor correction voltage having a DC component of a predetermined magnitude or more. By eliminating the light emission period and supplementing the insufficient energy at the current level rise by the dimming signal with the supplementary driving current of the power factor correction voltage, it is possible to ensure the stable driving of the device and improve the reliability of the device.

According to another embodiment of the present invention, a backlight module, a driving method thereof, and a display device using the same may be manufactured by removing a DC-DC converter used to supply driving power of an LED backlight unit of a liquid crystal display device. It provides the effect of reducing costs.

1 is a schematic block diagram of a display device according to the present invention;

FIG. 2 is a circuit diagram of an AC-DC converter employable in the display device of FIG. 1. FIG.

3 is a block diagram of a backlight module employable in the display device of FIG.

4 is a waveform diagram illustrating an operating principle of a backlight module of the display device of FIG. 1.

5 and 6 are waveform diagrams for explaining the dimming principle that can be employed in the display device of FIG.

7 is a schematic block diagram of a display device according to an embodiment of the present invention.

8 is a circuit diagram of an AC-DC converter employable in the display device of FIG.

9 is a block diagram illustrating a power supply device of a display device according to another embodiment of the present invention.

FIG. 10 is a block diagram of a backlight module employable in the display device of FIG. 9. FIG.

FIG. 11 is a waveform diagram illustrating an operating principle of the display device of FIG. 9. FIG.

12 is a flowchart illustrating a method of driving a backlight module according to the present invention.

The terms or words used in this specification and claims are not to be construed as being limited to conventional or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention various that can be substituted for them at the time of the present application It should be understood that there may be equivalents and variations.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise.

EXAMPLE

1 is a schematic block diagram of a display device according to the present invention.

Referring to FIG. 1, a display apparatus according to the present invention includes a display module 101, a power rectifier 102, a power factor corrector 104, a backlight unit 120, and a backlight unit driver 130. The power current unit 102 and the power factor correction unit 104 may correspond to the AC-DC converter 101a disposed at the power input terminal of the display device to convert AC power into DC power. The backlight unit 120 and the backlight unit driver 130 may correspond to a backlight module that provides illumination to the screen display unit of the display module 101.

In the display device according to the present exemplary embodiment, the backlight module 140 receives the rectified power including the rectified voltage V _REC from the AC-DC converter 101a, and receives the power factor correction voltage from the AC-DC converter 101a. The main characteristic is to receive the power factor correction power supply including V _PFC and to remove the non-light emitting period in the multi-stage driving type backlight unit 120 using the received rectification power factor and the power factor correction power source.

Here, the rectified power including the rectified voltage V _REC is connected to the backlight unit at the power rectifying unit 102 through the first wiring 105a connecting the output terminal of the power rectifying unit 102 and the first input terminal of the backlight unit driver 130. It may be supplied to the driver 130. The power factor correction power supply including the power factor correction voltage V _PFC is connected to the power factor correction unit 104 through a second wiring 105b connecting the output terminal of the power factor correction unit 104 and the second input terminal of the backlight unit driver 130. ) May be supplied to the backlight unit driver 130. The first wiring 105a and the second wiring 105b may be implemented by a power cable, a conductive pattern of an integrated device, or the like.

That is, when the backlight module 140 according to the present invention drives the backlight unit 120 including the plurality of LED groups in a multi-stage driving scheme, the non-light emission period accompanying the multi-stage driving scheme is performed using a power factor correction voltage. Remove Here, in the multi-stage driving method, as the size of the driving voltage (corresponding to the rectified voltage) of the backlight unit 120 increases, the number of LED groups emitting from the backlight unit 120 increases, and the backlight decreases as the size of the driving voltage decreases. Refers to controlling the operation of the backlight unit 120 to reduce the number of LED groups emitting from the unit 120. As described above, the backlight module 140 according to the present invention removes the non-light emitting period generated when the backlight unit of the conventional multi-stage driving method is driven so that the backlight unit 120 flickers while driving, or the luminance thereof is changed by the user. You can prevent it from shaking so hard that you can feel it easily.

Meanwhile, depending on the implementation, the backlight module 140 may have a predetermined voltage Va or a predetermined signal for driving and controlling the backlight module from the display module 101 connected to the user of the display apparatus through a predetermined user interface. It can be implemented to receive.

FIG. 2 is a circuit diagram of an AC-DC converter employable in the display device of FIG. 1.

Referring to FIG. 2, the AC-DC converter 101a according to the present embodiment includes a first filter 102a, a power rectifier 102, a second filter 102b, an input capacitor Cin, and a power factor corrector ( 104).

The first filter 102a may be an electromagnetic interference (EMI) filter disposed at an input terminal of the power rectifier 102. In that case, the EMI filter operates to reduce the noise signal on the input AC power supply during normal operation of the display device or AC-DC converter 101a and to reduce the magnitude of the surge pulse during abnormal operation. Such an EMI filter may be implemented with a common mode choke capable of reducing noise on both power lines of an input AC power supply, and two capacitors C1 and C2 connected to both ends of the common mode choke. .

The power rectifying unit 102 is for rectifying the input AC power, and may be implemented as a bridge diode that full-wave rectifies the input AC power by four diodes.

The second filter 102b may be an LC filter by the capacitor C and the inductor L disposed at the output terminal of the power rectifier 102. When the second filter 102b is used, a resonant circuit is formed by a combination of a capacitor C through high frequency current and an inductor L through high frequency current, and the display device or AC The high frequency noise at the power input terminal of the DC converter 101a can be selectively removed.

The input capacitor Cin is disposed at the output end of the second filter 102b, that is, at the output end of the power rectifier 102, and operates to stabilize the rectified power applied to the power factor corrector 104.

In the present embodiment, the high potential side output terminal of the power rectifier 102 to which the first terminal of the input capacitor Cin is connected and the inductor L of the second filter 102b is connected is the AC-DC converter 101a of the display device. ) Corresponds to the first output terminal for outputting the rectified voltage V _REC .

The power factor correction unit 104 compensates for the power factor of the input AC power source based on the rectified power supply from the power supply rectifier, and includes an inductor L1, a switch S1, a diode D1, and an output capacitor ( It can be implemented as an active power factor correction circuit having a Cout).

In the power factor correction unit 104, the inductor L1 includes a first terminal commonly connected to the first terminal of the input capacitor Cin and the high potential output terminal of the power rectifier 102. The switch S1 comprises a field effect transistor having a first terminal, a second terminal, and a control terminal, etc., wherein the first terminal is connected to the second terminal of the inductor L1, and the second terminal is connected to the resistor R1. And are commonly connected to the second terminal and the reference potential of the input capacitor Cin. The control signal SC6 from a predetermined power factor correction (PFC) controller is applied to the control terminal of the switch S1. The PFC controller may be implemented as at least some functional units of the backlight unit driver of the backlight module (see 140 of FIG. 1) or at least some components of the backlight unit driver that performs functions corresponding to the functional units.

In addition, in the power factor correction unit 104, the anode of the diode D1 is commonly connected to the second terminal of the inductor L1 and the first terminal of the switch S1, and the cathode thereof is formed of the output capacitor Cout. 1 terminal is connected. The second terminal of the output capacitor Cout is commonly connected to the low potential side output terminal of the power rectifier 102, the second terminal of the input capacitor Cin, and the second terminal of the switch S1.

In this embodiment, the node to which the cathode of the diode D1 of the power factor correction unit 104 and the first terminal of the output capacitor Cout are connected is connected to the power factor correction voltage V _PFC in the AC-DC converter 101a of the display device. Corresponds to the second output terminal for outputting

When operating in the discontinuous current mode (DCM), the power factor correction unit 104 is turned on when the current flowing in the inductor L1 is zero, and is a voltage applied across the resistor R1 as a comparator. The operation of the switch S1 may be controlled to be turned off when the voltage applied to the negative input terminal and the rectifier voltage applied to the positive input terminal are the same according to the current flowing through the inductor L1. In this case, the power factor correction unit 104 can substantially make the power factor close to 1 by causing the average waveform of the current (corresponding to the rectified current) output from the power supply rectifier 102 to follow the waveform of the rectified voltage.

On the other hand, in the conventional backlight module, in order to minimize the ripple of the output voltage in the power factor correction circuit, it is common to consider a specific specification (low ESR capacitor, etc.) of the output capacitor. Since the rectified voltage and the power factor correction voltage are used as they are, the degree of freedom in design can be increased by increasing the selection range of the output capacitor of the power factor correction unit as compared to the conventional power factor correction circuit.

In addition, although not shown in the drawing, the AC-DC converter 101a may be disposed at an input terminal of the backlight unit 120 according to an implementation, and may include a ripple remover (not shown) to remove ripple of driving power supplied to the backlight unit 120. May be provided). The ripple removing unit may be included as a part of the backlight unit driver 130, or may be included as a part of the backlight module 140 including the backlight unit driver 130 and the backlight unit 120. The ripple remover removes at least a part of the AC component included in the power factor correction voltage V _PFC provided from the power factor correction unit 104, and then provides the power factor compensation voltage to which the AC component is partially removed to the backlight unit 120. If the ripple cancellation unit is used, the size of the AC component included in the power factor correction voltage is too large to reduce the power consumption by the ripple component, thereby facilitating the driving of the backlight unit 120. can do.

3 is a block diagram of a backlight module employable in the display device of FIG. 1.

Referring to FIG. 3, the backlight module 140 according to the present exemplary embodiment includes a backlight unit 120 and a backlight unit driver 130.

First, the backlight unit driver 130 includes a plurality of current controllers 131 to 134, a control signal generator 135, and a voltage compensator 138.

The plurality of current controllers 131 to 134 control paths and magnitudes of currents flowing through the first to

fourth LED groups

122, 124, 126, and 128 according to the switching control signals SC1 to SC4. Here, each LED group has at least one light emitting diode. Each LED group may have a plurality of light emitting diodes connected in series with each other.

In more detail, each of the plurality of current controllers 131 to 134 includes a switching element (not shown) and a feedback resistor (not shown). The switching element is connected between the output terminal (corresponding to the cathode side of the light emitting diode) of each LED group and one end of the feedback resistor, and is selectively turned on in accordance with the switching control signals SC1 to SC4. Here, the switching element may be a semiconductor switch such as a field effect transistor (FET), and controls the magnitude of the current flowing through each LED group by the switching control signal. The other end of the feedback resistor may be connected to a reference potential or ground.

The control signal generator 135 generates the switching control signals SC1 to SC4 and the compensating switching control signal SC5 according to the rectified voltage V _{REC in} which the magnitude of the voltage fluctuates periodically, and generates the current by the generated control signal. The controllers 131 to 134 and the voltage compensator 138 are provided.

For example, the control signal generator 135 detects a current flowing through each of the

light emitting diodes

122, 124, 126, and 128 through the current controllers 131 ˜ 134, and detects a current or a voltage corresponding to the current. Is compared with a preset reference value, and the switching control signals SC1 to SC4 are generated according to the comparison result. In addition, the control signal generator 135 compares the rectified voltage V _REC with a reference value and generates the compensation switching control signal SC5 according to the comparison result.

Here, the preset reference value is a voltage level corresponding to the minimum emission reference of the backlight unit 120 and a forward voltage (Vf) level of any one of the plurality of

light emitting diodes

122, 124, 126, and 128. It can be set based on either.

The voltage compensator 138 selectively supplies the power factor correction power supply (V _PFC, etc.) to the backlight unit 120 according to the compensation switching control signal SC5. The voltage compensator 138 may be formed as a series circuit of the switching element SW5 and the diode D5 connected between the output terminal of the power factor compensator 104 and the input terminal of the backlight unit 120.

The switching element SW5 may be implemented as a field effect transistor having a first terminal, a second terminal, and a control terminal, and the first terminal is connected to the output terminal of the power factor correction unit, and the second terminal is connected to the diode D5. It is connected to the anode and is selectively turned on according to the compensation switching control signal SC5. The cathode of the diode D5 is commonly connected to the output terminal side of the power rectifier and the input terminal of the backlight unit 120. The diode D5 prevents the rectified power supply V _REC from flowing back to the power factor correction unit 104 when the switching element SW5 is turned off.

Meanwhile, the backlight unit 120 includes one or more LED arrays in which a plurality of LED groups 122 to 128 each having at least one LED element are connected in series. The backlight unit 120 performs the multi-stage driving in the form of adjusting the lighting state of the light emitting diode according to the degree of the rising or falling of the voltage of the AC power source or the rectifying power source by the current control of the backlight unit driver 130.

That is, the backlight unit 120 may drive in multiple stages such that the number of LED groups emitting from the LED array increases as the size of the rectified voltage increases, and the number of LED groups emitting from the LED array decreases as the size of the rectified voltage decreases. Can be. In particular, the backlight unit 120 operates to receive at least one LED group by receiving the power factor correction voltage from the power factor correction unit in the non-light emitting period generated during the multi-stage driving so that the non-light emitting period is not formed during the multi-stage driving. Here, the non-light emitting period refers to a period in which the magnitude of the rectified voltage is smaller than the forward voltage of one LED group. In the non-light emitting period, all the LED groups of the backlight unit 120, that is, all the light emitting diodes are turned off. According to such an off state, the conventional backlight unit may cause a flicker phenomenon during multi-stage driving, but the backlight module of the present invention uses a power factor correction voltage to eliminate the non-light emitting period that causes the flickering problem. To improve.

In the foregoing detailed description with reference to FIG. 3, for convenience of description, the backlight unit 120 is illustrated as having four

LED groups

122, 124, 126, and 128 each represented by one light emitting diode. The number of light emitting diodes or the number of LED groups included in each LED group, the number of current controllers and their specific configurations may be changed in various forms. For example, the backlight unit 120 may include two or more LED groups connected in series or may include a plurality of LED groups connected in series or in parallel.

4 is a waveform diagram illustrating an operating principle of a backlight module of the display apparatus of FIG. 1.

As shown in FIG. 3, the backlight module of the display device according to the present exemplary embodiment includes a backlight unit 120 having a plurality of

LED groups

122, 124, 126, and 128, current controllers 131 to 134, A case in which the control signal generator 135 and the voltage compensator 138 are provided and the forward voltages of the plurality of

LED groups

122, 124, 126, and 128 are all predetermined voltages Vf will be described. Each LED group of the plurality of LED groups is referred to as a first LED group 122, a second LED group 124, a third LED group 126, and a fourth LED group 128 in the order described, and each LED The current controllers connected to the output terminals of the group are referred to as a first current controller 131, a second current controller 132, a third current controller 133, and a fourth current controller 134, respectively.

Referring to FIG. 4, first, the switching elements of each of the current controllers 131 to 134 maintain a turn-on state, and the switching element SW5 of the voltage compensator 138 maintains a turn-off state. In this state, when the rectified voltage V _REC is applied to the backlight module and the rectified voltage becomes equal to or greater than the first voltage Vf1 at a predetermined time t0, the first LED group 122 and the first current controller 131. The current path (Path) through the () is formed so that the first LED group 122 emits light. In this case, the first current controller 131 controls the magnitude of the current flowing in the first LED group 122 according to a preset current level based on the first voltage Vf1.

Meanwhile, the backlight module may be set to supply the power factor correction voltage V _PFC to the backlight unit 120 when the rectified voltage V _REC is smaller than the first voltage Vf1, in which case, according to the present embodiment The backlight module 140 backlights the power factor correction current I _PFC of the level set by the first current controller 131 during the hatched period from a certain time point before the predetermined time point t0 to the predetermined time point t0. Supply to unit 120.

Next, when the rectified voltage rises to reach the second voltage Vf2 at the first time point t1, the control signal generator 135 turns off the switching element of the first current controller 131. Then, a current path through the two

LED groups

122 and 124 and the second current controller 132 is formed, and the two

LED groups

122 and 124 emit light. In this case, the second current controller 132 controls the magnitude of the current I _REC flowing through the two

LED groups

122 and 124 in response to the magnitude of the rectified voltage.

Next, when the rectified voltage rises to reach the third voltage Vf3 at the second time t2, the control signal generator 135 switches the switching element and the second current controller 132 of the first current controller 131. Turn off the switching element. Then, a current path is formed through the three

LED groups

122, 124, and 126 and the third current controller 133, and the three

LED groups

122, 124, and 126 emit light. In this case, the third current controller 133 controls the magnitude of the current I _REC flowing through the three

LED groups

122, 124, and 126 in response to the magnitude of the rectified voltage.

Next, when the rectified voltage rises to reach the fourth voltage Vf4 at the third time point t3, the control signal generator 135 controls the switching elements of the first to third

current controllers

131, 132, and 133. Turn off. Then, a current path is formed through the four

LED groups

122, 124, 126, and 128 and the fourth current controller 134, and the four

LED groups

122, 124, 126, and 128 emit light. In this case, the fourth current controller 134 controls the magnitude of the current I _REC flowing through the four

LED groups

122, 124, 126, and 128 in response to the magnitude of the rectified voltage.

As described above, the control signal generator 135 multi-stages the plurality of

LED groups

122, 124, 126, and 128 so that the number of LED groups emitting from the backlight unit 120 increases as the size of the rectified voltage increases. Drive it.

Then, when the magnitude of the rectified voltage decreases, the control signal generator 135 turns off the LED group in the reverse order when the rectified voltage rises. That is, when the rectified voltage is lower than the fourth voltage Vf4 at the fourth time point t4, the control signal generator 135 drives the third current controller 133 to display the three

LED groups

122, 124, and 126. And a current path passing through the third current controller 133, thereby causing the three

LED groups

122, 124, and 126 to emit light. When the rectified voltage is lower than the third voltage Vf3 at the fifth time point t5, the control signal generator 135 drives the second current controller 132 to drive the two

LED groups

122 and 124 and the second current. A current path is formed through the control unit 132, thereby causing the two

LED groups

122 and 124 to emit light. When the rectified voltage is lower than the second voltage Vf2 at the sixth time point t6, the control signal generator 135 drives the first current controller 131 to drive the first LED group 122 and the first LED. The first LED group 122 emits light by forming a current path through the current controller 131.

Next, when the rectified voltage is smaller than the preset reference value, for example, the first voltage Vf1 at the seventh time point t7, the control signal generator 135 may determine the voltage compensator 138 at the seventh time point t7. Turns on the switching element SW5.

Since the power factor correction voltage V _PFC has a voltage level higher than the forward voltage Vf4 of the plurality of

LED groups

122, 124, 126, and 128, the control signal generator 135 may be connected to the seventh time point t7. The power factor correction current I _PFC may be supplied to the first LED group 122 through a current path through the first LED group 122 and the second current controller 131 during the period of the eighth time point t8. . Here, the interval between the seventh time point t7 and the eighth time point t8 corresponds to the non-light emitting period when the power factor correction voltage V _PFC is not supplied to the backlight unit 120 (comparative example).

When the rectified voltage V _REC becomes equal to or greater than a preset reference value, for example, the first voltage Vf1, at the eighth time point t8, the control signal generator 135 may generate a voltage compensator at the eighth time point t8. The switching element SW5 of 138 is turned off.

As described above, the backlight module 140 according to the present embodiment supplies the power factor correction voltage V _PFC to the backlight unit 120 when the rectified voltage V _REC is smaller than the first voltage Vf1. The power factor correction current I _PFC of a level preset by the first current controller 131 may be supplied to the backlight unit 120 in the hatched section (t7-t8, etc.), thereby removing the existing non-light emitting section. can do.

In the present embodiment, the rectified voltage V _REC corresponds to the driving voltage V _LED of the backlight unit 120, and the rectified current I _REC and the power factor correction voltage V _PFC by the rectified voltage V _REC . Corresponds to the driving current I _LED of the backlight unit 120 in combination with the power factor correction current I _PFC .

Meanwhile, the backlight module according to the present exemplary embodiment may receive a predetermined voltage Va or a predetermined signal from the display module 101 (refer to 101 of FIG. 1) to control brightness of the backlight unit 120. The predetermined voltage Va may be a reference voltage and the predetermined signal may be a dimming signal.

The following describes the operation principle of the backlight module when the backlight module receives a dimming signal (see V _DIMM of FIG. 10) from the signal processor of the display module. For convenience of description, it is assumed that the dimming signal is received during the multi-stage driving of the backlight module described above with reference to FIG. 4.

5 and 6 are waveform diagrams for describing a dimming principle that can be employed in the display device of FIG. 1.

First, a case in which the dimming signal maintains a voltage level corresponding to the minimum light emission reference of the backlight unit 120, for example, a luminance level corresponding to the first voltage Vf1 regardless of a change in brightness of an image signal, will be described. As follows.

Referring to FIG. 5, when a dimming signal is received from the signal processor of the display module during the multi-stage driving of the backlight unit 120, the backlight unit driving unit corresponds to a driving current corresponding to the voltage level (eg, the first voltage) designated by the dimming signal. (I _LED ) is operated to be supplied to the backlight unit 120.

Meanwhile, the conventional multi-stage driving unit of the backlight unit generates a non-emitting section corresponding to the hatched section during the dimming operation. The backlight module according to the present exemplary embodiment has a hatched section (P1, etc.) corresponding to the non-emitting section. By supplying the power factor correction voltage V _PFC and the power factor correction current having a predetermined magnitude by the first current controller 131 to the backlight unit, it is possible to prevent the non-light emitting period from occurring in the backlight unit during the dimming operation.

Next, an example in which the dimming signal is input to maintain the luminance level corresponding to the fourth voltage Vf4 at a predetermined time t3 will be described below.

Referring to FIG. 6, when a new dimming signal is received at a third time point t3 from the signal processing unit of the display module while the backlight unit 120 is dimming at the same voltage level as in FIG. The driving current I _LED corresponding to the voltage level (eg, the fourth voltage Vf4) designated by the dimming signal is operated to be supplied to the backlight unit 120.

On the other hand, the backlight unit of the conventional multi-stage driving method generates a non-light emitting period corresponding to the hatched division during the dimming operation due to the lack of driving energy due to the characteristics of the multi-stage driving method, the backlight module according to the present embodiment is a hatched section ( According to the operation of the fourth current controller 134 in P2, the power factor correction current corresponding to the level of the dimming signal may be supplied to the backlight unit so that the non-light emitting period may not occur in the backlight unit during the dimming operation.

As described above, according to the present invention, even when the level of the dimming signal increases from a low level to a high level, the non-emission period may be prevented from occurring in the backlight unit 120 using the power factor correction voltage V _PFC . have. That is, in the backlight module according to the present invention, the backlight unit 120 dimmes by supplementing energy to the backlight unit by using the power factor correction voltage output from the power factor correction unit 104 during a period corresponding to the existing non-light emitting period. It can be operated normally at high level of signal.

Meanwhile, in the present embodiment, for convenience of description, the conventional non-light emitting section formed during driving according to the dimming signal in the backlight module of the multi-stage driving method can be removed, but the present invention is not limited to such a configuration. When there is a non-light emitting section in which a backlight module which is not driven in multiple stages but driven by a pulse voltage, substantially all of the light emitting diodes of the backlight unit are not driven, all configurations using the power factor correction voltage to remove such non-light emitting sections are required. It may include.

In addition, the number of LEDs to be lit or the level of voltage to be compensated for may be changed according to a user's selection according to a reference brightness, a reference brightness required when driving the backlight unit 120. The waveform diagrams shown in FIGS. 5 and 6 are examples, and the number of LED groups turned on, the turn-on timing, etc. may be variously changed according to the configuration of the current controller. In addition, in a display device such as a liquid crystal display, a separate converter must be used to generate a DC power source for driving the backlight module. The backlight module and the display device using the same according to the present invention omit a DC-DC converter for the backlight unit. In addition, the backlight unit can be directly driven by an AC power supply, thereby miniaturizing the device and reducing manufacturing cost.

7 is a schematic block diagram of a display apparatus according to an embodiment of the present invention.

Referring to FIG. 7, the display device according to the present exemplary embodiment includes a power rectifier 102, a power factor correction unit 104, a converter 106, a signal processor 110, a display driver 112, and a screen display 114. And a backlight module 140A. The converter 106, the signal processor 110, the display driver 112, and the screen display 114 may correspond to the display module 101 of FIG. 1. The display device according to the present embodiment may further include a filter at an input terminal or an output terminal of the power rectifying unit 102 according to the implementation.

The power rectifier 102 rectifies and supplies the AC power to the power factor correction unit 104. For example, the power rectifying unit 102 may be implemented as a bridge diode for full-wave rectifying the sinusoidal AC power.

The power factor correction unit 104 outputs the power factor correction power by compensating the power factor of the AC power supply 10 based on the rectified power output from the power rectifier 102. The power factor correction power source has a DC voltage level. For example, when the AC power source 10 is 220V, the power factor correction power source may have a voltage magnitude of about 380 to 420V. The power factor correction unit 104 may be implemented using a plurality of passive elements or active elements. For example, it may include an active power factor correction circuit in the form of a boost converter.

The converter 106 receives the power factor correction power to generate a DC power having a level required to drive the signal processor 110 and the display driver 112. In detail, the DC power output from the converter 106 may be used to drive various processors included in the signal processor 110. In addition, the DC power is supplied to the gate line or the data line of the screen display unit 114 through the display driver 112, whereby a predetermined image is displayed on the screen display unit.

The signal processor 110 generates various control signals by processing various image signals input from the outside, and supplies the generated control signals to the display driver 112. For example, the signal processor 110 processes an image signal to generate a control signal for controlling a voltage to be applied to a data line of the screen display 114, or generates a control signal for controlling a voltage to be applied to a gate line. .

In addition, the signal processor 110 generates a control signal (hereinafter, referred to as a dimming signal) for controlling the brightness and the on / off timing of the backlight unit 120 and supplies it to the backlight unit driver 130. Here, the dimming signal may include a signal required for local dimming when the backlight unit 120 includes a local dimming structure in which brightness is controlled for each region.

The display driver 112 drives the screen display unit 114 according to the output of the signal processor 110. The display driver 112 includes a gate driver connected to a pixel of the screen display 114 through a gate line, a data driver connected to a pixel through a data line, a timing controller that controls operation timings of the gate driver and the data driver. can do.

The screen display unit 114 includes a plurality of pixels arranged in a matrix so as to output a predetermined image according to an image signal. The plurality of pixels may include a liquid crystal capable of adjusting the amount of light transmitted by illumination of the backlight unit 120, an electrode for controlling the liquid crystal, a color filter for expressing color, and the like.

The backlight module 140 includes a backlight unit 120 that provides illumination to the screen display unit 114, and a backlight unit driver 130 that drives the backlight unit 120. The backlight unit driver 130 receives the rectified power and the power factor correction power, and controls the operation of the backlight unit 120 according to a preset control signal or a dimming signal from the signal processor 110.

In the backlight module 140 according to the present exemplary embodiment, a method of using the power factor correction power source so that a non-light emitting period does not occur while driving the backlight unit has been described with reference to FIGS. 1 to 6. Detailed description is omitted.

In the display device according to the present exemplary embodiment, the power rectifier 102 and the power factor corrector 104 may be implemented as a single AC-DC converter that compensates for the power factor of the AC power and outputs the power factor correction power. In addition, the power rectifier 102, the power factor correction unit 104, and the backlight unit driver 130 may be implemented as a single integrated circuit 130A for driving a backlight having a power factor correction function. In this case, the backlight module 140A corresponds to the one provided with the backlight unit driver having the power factor correction function. Of course, the backlight unit driver having the power factor correction function includes the power factor corrector 104 but does not include the power rectifier 102 or the power rectifier 102 but does not include the power factor corrector 104. It may be implemented in the form of a single integrated circuit.

FIG. 8 is a circuit diagram of an AC-DC converter employable in the display device of FIG. 7.

Referring to FIG. 8, the AC-DC converter 101b of the display apparatus according to the present exemplary embodiment has an interleaved boost converter type in which two boost converters are connected in parallel.

The AC-DC converter 101b of the present embodiment is a parallel connection of two AC-DC converters 101a described above with reference to FIG. 3. The inductor L2, the switch S2, and the resistor ( Since R2) and diode D2 and their coupling relationship are substantially the same as the corresponding components of AC-DC converter 101a and their coupling relationship, detailed description thereof will be omitted to avoid duplication of explanation.

When using the AC-DC converter 101b in the form of a polyphase boost converter, the input voltage corresponding to the voltage across the input capacitor Cin and the output voltage corresponding to the voltage across the output capacitor Cout are approximately half. By dividing each other, the volume and capacity of the capacitors C1 and C2 and the inductors L1 and L2 can be made smaller than in the case of the AC-DC converter 101a in the form of a single boost converter to meet the thinning of the flat panel display device. In addition, the current flowing through the AC-DC converter 101b may be reduced to increase power efficiency by lowering power loss.

9 is a block diagram illustrating a power supply apparatus of a display apparatus according to another embodiment of the present invention.

Referring to FIG. 9, the power supply device 130B of the display device according to the present embodiment may include a filter 102a, a power rectifier 102, a power factor corrector 104, a first DC-DC converter 106a, A second DC-DC converter 106b, a Temporary OverVoltage (TOV) generator 107, and a backlight unit driver 130A are provided. The power supply device 130B has a switch mode power supply having a power factor correction function and a backlight unit driving function.

The first DC-DC converter 106a corresponds to the standby power DC-DC converter, and the second DC-DC converter 106b corresponds to the module power DC-DC converter of the display module. In this case, the second DC-DC converter 106b corresponds to a converter for supplying the module driving power supply Vout2 to the PMIC (Power Management Integrated Circuit) of the display module, and the first DC-DC converter 106a corresponds to the display device. When the power is turned on for the first time, the display device may correspond to a converter supplying standby power Vout1 separated from the second DC-DC converter 106b to operate only the minimum standby power. Depending on the implementation, the first and second DC-

DC converters

106a and 106b may have a form integrated into one DC-DC converter.

In the power supply device 130B of the present embodiment, the backlight unit driver 130A, which belongs to the backlight module, rectifies AC power input through the wiring 105c connected to the input terminal of the power rectifier 102 to generate rectified power. Another power rectifier may be provided to supply the generated rectified power to the backlight unit.

In addition, the backlight unit driver 130A disposed in the power supply device 130B of the present embodiment not only controls the non-light emitting period in the backlight unit by using the power factor correction voltage V _PFC but also controls the backlight unit. Increasing the driving voltage by a predetermined basic voltage TOV allows the plurality of LED groups of the backlight unit to drive a high voltage, thereby increasing efficiency due to high voltage and low current driving. Here, the high voltage means a voltage higher than the maximum value of the AC voltage V _AC or the rectified voltage V _REC of the input AC power source 10.

FIG. 10 is a block diagram of a backlight module employable in the display apparatus of FIG. 9.

Referring to FIG. 10, the backlight module 140A according to the present exemplary embodiment includes a backlight unit 120 and a backlight unit driver 130A disposed in an SMPS type power supply device 130B.

In the present embodiment, since the backlight unit 120 is the same as the backlight unit in the other embodiments described above, detailed description thereof will be omitted in order to avoid duplication of description. The backlight unit driver 130A is substantially the same as the backlight unit driver 130 described with reference to FIG. 3 except for the bridge diode 136, the first input terminal 137a, and the second input terminal 137b. In order to avoid duplication, detailed descriptions of the remaining components of the backlight unit driver 130A (a plurality of current controllers, control signal generators, and voltage compensators and their connection relationships) and their operation principles will be omitted.

In the backlight unit driver 130A, the bridge diode 136 generates and generates rectified power by rectifying AC power input through a wire 105c connected to an input terminal of a power rectifying unit (see 102 in FIG. 9) of the display device. One rectified power is supplied to the backlight unit 120. The bridge diode 136 corresponds to another power rectifier different from the power rectifier 102 of the display device. When the bridge diode 136 is used, the backlight module 140A may be driven by using an input AC power source separately from the power supply of the display device.

The first input terminal 137a corresponds to the input terminal of the basic voltage TOV, and the second input terminal 137b corresponds to the input terminal of the dimming signal V _DIMM . Here, the basic voltage (TOV) is to increase the driving voltage of the backlight unit by a predetermined voltage TOV so that a plurality of LED groups of the backlight unit are driven at high voltage. The dimming signal V _DIMM is to adjust the brightness of the backlight unit to correspond to the brightness of the image displayed on the screen display unit.

That is, the backlight unit driver 130A operates so that the overall luminance of the backlight unit follows the level of the dimming signal according to the level (average level, etc.) of the dimming signal for a predetermined period. In order to ensure that the overall luminance of the backlight unit follows the level of the dimming signal, the backlight unit driver 130A may set the average level of the dimming signal in each multi-stage driving section as the following target level in the multi-stage driving.

FIG. 11 is a waveform diagram illustrating an operating principle of the display device of FIG. 9.

Referring to FIG. 11, the display apparatus according to the present exemplary embodiment includes multiple stages of a plurality of LED groups of the backlight unit by the driving voltage V _LED and the driving current I _LED increased by a predetermined magnitude by the basic voltage TOV. Drive it.

In the display device according to the present embodiment, the first to fourth voltages Vf5, Vf6, Vf7, and Vf8, which are the reference for the multi-stage driving for the plurality of LED groups, are described with reference to FIG. 4. Since Vf2, Vf3, and Vf4 are higher than the basic voltage TOV, they have substantially the same operating principle as those of the display device of FIG. 4, and thus detailed descriptions thereof will be omitted to avoid duplication.

Here, the forward voltages of the first to

fourth LED groups

122, 124, 126, and 128 of the plurality of LED groups may also be input AC voltages or rectified voltages according to the first to fourth voltages Vf5, Vf6, Vf7, and Vf8. Higher voltage is achieved, and for this purpose, each LED group may use an LED device having a higher forward voltage than the LED group of FIG. 4 or may have a larger number of LED devices.

In the present embodiment, the method of driving the backlight module will be described with reference to a process of driving the backlight module by a backlight unit driver that provides illumination to the display apparatus by driving the backlight unit. Here, the backlight unit includes a plurality of LED (Light Emitting Diode) groups each having at least one light emitting diode.

Referring to FIG. 12, in the driving method of the backlight module of the present embodiment, the rectified voltage is first generated by rectifying the input AC power through the power rectifying unit (S121). The rectified voltage has a form of pulsation in which the magnitude of the voltage varies periodically with time.

Next, a power factor correction voltage is generated by compensating the power factor of the AC power through the power factor compensator arranged at the output terminal of the power rectifier (S122). The power factor correction voltage has a DC component of a predetermined magnitude or more. Here, the predetermined size corresponds to a DC voltage that all the light emitting diodes of the backlight unit can drive.

Next, the rectified voltage is received to generate the main driving voltage or the main driving current, and the generated main driving voltage or the main driving current is supplied to the backlight unit (S123).

In the step S123, the backlight unit driver is configured to increase the number of LED groups emitting light among the plurality of LED groups as the magnitude of the rectified voltage increases based on the rectified voltage whose voltage varies periodically over time. The unit may be controlled, and the backlight unit may be controlled to reduce the number of LED groups emitting light among the plurality of LED groups as the magnitude of the rectified voltage decreases.

Next, when the dimming signal is not received and the magnitude of the rectified voltage is smaller than the preset threshold, the backlight unit driver supplies the supplementary driving voltage or the supplementary driving current by the power factor correction voltage to the backlight unit (S124, S125 and S127).

In the above-described series of steps S124, S125, and S127, the backlight unit driver includes a rectified voltage V _REC that is higher than the minimum voltage V _R1 for driving at least one LED group of the plurality of LED groups. When small, the supplementary driving voltage or the supplementary driving current by the power factor correction voltage V _PFC may be supplied to the backlight unit BLU.

Meanwhile, the method of driving the backlight module according to an embodiment of the present invention may further include receiving a dimming signal for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current from the display module. If a dimming signal is received and the set dimming voltage (V _DI ) is greater than the LED drive voltage (V _LED ) or the set dimming current is greater than the LED drive current, the supplementary drive voltage by the power factor correction voltage (V _PFC ) or The supplementary driving current is supplied to the backlight unit (S124, S126, and S127).

Here, the dimming signal may correspond to a control signal for maintaining the brightness of the backlight unit at a preset level. The backlight unit driver may generate a set dimming voltage or a set dimming current corresponding to a preset luminance according to the level of the dimming signal. In addition, the set dimming voltage or the set dimming current corresponds to the LED driving voltage or the LED driving current corresponding to the level of the dimming signal. The LED driving voltage corresponds to a voltage obtained by adding the aforementioned main driving voltage and the supplementary driving voltage, and the LED driving current corresponds to a current obtained by adding the aforementioned main driving current and the supplementary driving current.

In the above-described case, the backlight unit driver may control the backlight unit such that the overall brightness of the backlight unit follows the level of the dimming signal (eg, an average level in a predetermined period) according to the level of the dimming signal.

The present invention has been shown and described with reference to the preferred embodiments as described above, but is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes, substitutions, and modifications will be possible by the present invention. Such changes, substitutions, and modifications should be regarded as falling within the claims of the present invention.

Claims

A power rectifier for rectifying AC power and outputting a rectified voltage;

A power factor correction unit configured to receive the rectified voltage from the power rectifier and compensate the power factor of the AC power and output a power factor correction voltage including a DC voltage component having at least a predetermined magnitude;

A display module driven by the power factor correction voltage;

A backlight unit having a plurality of light emitting diodes for providing backlight illumination to the display module; And

Receiving the rectified voltage to generate a main driving voltage or a main driving current and supplying the main driving voltage or the main driving current to the backlight unit, and when the magnitude of the rectifying voltage is smaller than a preset threshold, the power factor correction voltage And a backlight unit driver configured to receive the supplementary driving voltage or the supplementary driving current, and supply the supplementary driving voltage or the supplementary driving current to the backlight unit.
The method of claim 1,

The backlight unit driver may supply the supplementary driving voltage or the supplementary driving current to the backlight unit when the main driving voltage is smaller than a minimum voltage for driving at least one light emitting diode. .
The method of claim 1,

The display module generates a dimming signal for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current,

When the dimming signal is received, the backlight unit driver supplies the supplementary driving voltage to the backlight unit when the main driving voltage is less than the set dimming voltage, or when the main driving current is less than the set dimming current. And a supplementary driving current to the backlight unit.
The method of claim 1,

A first wiring connecting the output terminal of the power rectifying unit and the first input terminal of the backlight unit driving unit and transferring the rectified voltage from the power rectifying unit to the backlight unit driving unit; And

And a second wiring connecting the output terminal of the power factor compensator to the second input terminal of the backlight unit driver and transferring the power factor compensation voltage from the power factor compensator to the backlight unit driver.
The method of claim 1,

The backlight unit driver may increase the number of light emitting diodes emitting light among the plurality of light emitting diodes as the size of the rectified voltage increases based on the rectified voltage whose voltage varies periodically with time. And the backlight unit is controlled to reduce the number of light emitting diodes emitting light among the plurality of light emitting diodes as the size decreases.
The method of claim 5,

The backlight unit driver,

A connection between an output terminal and a reference potential of a plurality of light emitting diode (LED) groups each having at least one light emitting diode among the plurality of light emitting diodes, and between the output terminal of each LED group and the reference potential according to a control signal A plurality of current controllers forming a current path; And

And a control signal generator configured to apply the control signal to the plurality of current controllers to control the operations of the plurality of current controllers according to the magnitude of the main driving voltage.
The method of claim 6,

And the backlight unit driver further includes a voltage compensator disposed between an output terminal of the power factor compensator and an input terminal of the backlight unit, and configured to control supply of the power factor compensation voltage to the backlight unit.
The method of claim 7, wherein

The voltage compensator,

A switching element having a first terminal connected to an output terminal of the power factor correction unit; And

A diode having an anode connected to a second terminal of the switching element and a cathode connected to an input terminal of the backlight unit;

And the switching element is turned on or off by a control signal of the control signal generator.
The method of claim 8,

The backlight unit driver may be configured to apply the control signal to the voltage compensating unit by applying the control signal to the voltage compensator when the magnitude of the rectified voltage is smaller than a minimum voltage for driving at least one LED group among the plurality of LED groups. The supplementary driving voltage or the supplementary driving current is supplied to the plurality of LED groups.
The method of claim 6,

When a dimming signal for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current is received from the display module,

The backlight unit driver may supply the supplementary driving voltage to the backlight unit when the main driving voltage is less than the set dimming voltage, or the supplementary driving current when the main driving current is less than the set dimming current. Display device characterized in that the supply.
The method of claim 1,

The power rectifier,

A first power rectifier disposed at an input of the power factor corrector and configured to supply a rectified voltage obtained by rectifying the AC power to the power factor corrector; And

And a second power rectifying unit provided in the backlight unit driving unit and supplying a rectified voltage obtained by rectifying the AC power to the backlight unit.
The method of claim 1,

The power factor correction unit,

An inductor having a first terminal connected to a high potential first terminal of an input capacitor connected in series to an output terminal of the power rectifier;

A switch having a first terminal connected to the second terminal of the inductor, and a second terminal connected to the second terminal of the low potential side of the input capacitor;

A diode having an anode commonly connected to a second terminal of the inductor and a first terminal of the switch, and a cathode connected to the high potential side first terminal of the output capacitor; And

And an output capacitor having a first terminal connected to the cathode of the diode, and a second terminal connected in common with the low potential second terminal of the input capacitor and the second terminal side of the switch. Device.
The method of claim 12,

And the power factor compensator has an interleaved boost converter in which two power factor compensators each having the inductor, the switch, the diode, and the output capacitor are connected in parallel to each other.
The method of claim 12,

At least one of the power rectifier and the power factor correction unit is disposed in the form of a single integrated circuit with the backlight unit driver.
A power factor correction unit configured to compensate for the power factor of the AC power source and output a power factor correction power source;

A backlight unit including a plurality of light emitting diodes; And

And a backlight unit driver configured to drive the plurality of light emitting diodes according to a dimming signal.

And the backlight unit driver is configured to selectively supply the AC power and the power factor correction power to the plurality of light emitting diodes according to the dimming signal and the magnitude of the AC power.
The method of claim 15,

The backlight unit includes the plurality of light emitting diodes connected in series.

The backlight unit driver,

A power rectifier for rectifying the AC power and supplying a rectified voltage to the backlight unit;

A plurality of current controllers connected between one terminal of the light emitting diode and a reference potential and forming a current path between the light emitting diode and the reference potential according to a control signal; And

And a control signal generator configured to generate the control signals for controlling operations of the plurality of current controllers according to the dimming signal and the magnitude of the rectified voltage.
The method of claim 16,

And the control signal generator adjusts a current value flowing through the backlight unit by controlling an operation state of the current controller according to the level of the dimming signal.
The method of claim 15,

And a voltage compensator configured to supply a voltage output from the power factor compensator to the backlight unit according to the magnitude of the rectified voltage and the level of the dimming signal.
The method of claim 18,

And the voltage compensator supplies a voltage output from the power factor compensator to the backlight unit during a period where the rectified voltage is equal to or less than a threshold value.
The method of claim 18,

The voltage compensator includes a switching device configured to perform a switching operation according to a compensation control signal generated based on the dimming signal during a period when the rectified voltage is less than or equal to a threshold value

And the switching device connects an output terminal of the power factor correction unit to the backlight unit according to the compensation control signal.
The method of claim 20,

The voltage compensator further includes a diode in which one terminal of the switching element and an anode are connected in series,

And the other terminal of the switching element is connected to an output terminal of the power factor correction unit, and the cathode of the diode is connected to a node to which the input terminal of the backlight unit and the power rectifier are connected.
A method of driving a backlight module by a backlight unit driver for driving a backlight unit including a plurality of light emitting diode (LED) groups each having at least one light emitting diode to provide lighting to a display module.

Rectifying the AC power to generate a rectified voltage;

A second step of compensating the power factor of the AC power source to generate a power factor correction voltage including a DC voltage component having at least a predetermined magnitude;

Receiving the rectified voltage to generate a main driving voltage or a main driving current, and supplying the main driving voltage or the main driving current to the backlight unit; And

And supplying the supplementary driving voltage or the supplementary driving current by the power factor correction voltage to the backlight unit when the magnitude of the rectified voltage is smaller than a preset threshold value.
The method of claim 22,

In the third step, the number of LED groups emitting light among the plurality of LED groups increases as the size of the rectified voltage increases based on the rectified voltage whose voltage varies periodically with time, and the rectified voltage is increased. And controlling the operation of the backlight unit to reduce the number of LED groups emitting light among the plurality of LED groups as the size of the LED decreases.
The method of claim 23,

The fourth step may include the supplementary driving voltage or the supplementary driving current caused by the power factor correction voltage when the magnitude of the rectified voltage is smaller than a minimum voltage for driving at least one LED group among the plurality of LED groups. A method of driving a backlight module, characterized in that the supply to a plurality of LED groups.
The method of claim 22,

Before the fourth step, further comprising receiving a dimming signal from a display module for controlling the backlight unit driver to generate a set dimming voltage or a set dimming current,

Here, in the fourth step, the supplementary driving voltage is supplied to the backlight unit when the main driving voltage is lower than the set dimming voltage, or when the main driving current is smaller than the set dimming current, the supplementary driving current is measured. A driving method of a backlight module, characterized in that the supply to the backlight unit.