KR20170020097A - Apparatus for driving of light emitting diode array and liquid crystal display device comprising the same - Google Patents

Abstract

The present invention provides a driving apparatus for a light emitting diode array capable of high-speed dimming and a liquid crystal display including the driving apparatus. The driving apparatus for a light emitting diode array according to the present invention includes a light emitting diode array Can be turned on / off at a second frequency higher than the first frequency.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a light emitting diode array, and a liquid crystal display device including the driving apparatus. 2. Description of the Related Art [0002]

The present invention relates to a driving apparatus for a light emitting diode array and a liquid crystal display including the same.

Light Emitting Diode is eco-friendly compared to cold cathode tube lamps, has a response speed of several nanoseconds and is capable of high-speed response, and color reproducibility is more than 80% to 100%. Further, the light emitting diode has an advantage that the luminance and the color temperature of the backlight can be arbitrarily adjusted by adjusting the light amount. The driving apparatus for lighting the light emitting diodes includes a light emitting diode array in which a plurality of light emitting diodes are electrically connected in series.

1 is a circuit diagram for schematically explaining a driving apparatus of a conventional light emitting diode array.

1, a driving apparatus of a conventional LED array includes a plurality of light emitting diode arrays 101 to 10m, a driving power supply unit 20, a plurality of transistors T1 to Tn, and a plurality of light emitting diode driving units 301 To 30n.

Each of the plurality of light emitting diode arrays 101 to 10m includes a plurality of light emitting diodes electrically connected in series. Each of the plurality of light emitting diode arrays 101 to 10m is electrically connected in parallel to an output terminal of the driving power supply unit 20. [

The driving power supply unit 20 generates driving power Vd necessary for driving the plurality of light emitting diode arrays 101 to 10m by using the input power supply Vin and supplies the driving power supply Vd to the plurality of light emitting diode arrays 101 to 10m . The driving power supply unit 20 varies the driving power Vd according to the plurality of feedback signals FB1 to FBm supplied from the plurality of light emitting diode driving units 301 to 30n, 10m) is controlled to be constant.

Each of the plurality of transistors T1 to Tn is connected between an output terminal and a ground terminal of each of the plurality of light emitting diode arrays 101 to 10m. The transistors T1 to Tn are switched according to the pulse width modulation signals PWM1 to PWMn supplied from the corresponding LED drivers 301 to 30n to control current flow in the corresponding LED arrays 101 to 10m .

Each of the plurality of light-emitting diode drivers 301 to 30n generates a duty-on (Ddim) signal according to the array-dependent dimming data Bdim1 to Ddimn supplied from the outside, based on an internal clock signal having a driving frequency set in an internal clock generator width modulation signals PWM1 to PWMn having duty-on intervals are separately generated and the switching of the corresponding transistors T1 to Tn is controlled using each of the generated pulse width modulation signals PWM1 to PWMn And emits the corresponding light emitting diode arrays 101 to 10m. For example, as shown in FIG. 2, when the first pulse width modulation signal PWM1 has a driving frequency of 120 Hz, the first transistor T1 generates 120 Hz of the first pulse width modulation signal PWM1 So that the first light emitting diode array 101 has an ON / OFF frequency of 120 Hz. Similarly, the driving voltage supplied to the second light emitting diode array 102 also has the same frequency as the driving frequency generated by the internal clock generator.

Each of the plurality of light emitting diode driving units 301 to 30n generates feedback signals FB1 to FBm corresponding to the voltages applied to the sensing resistors Rs connected between the corresponding transistors T1 to Tn and the ground terminal And supplies it to the driving power supply unit 22.

In such a conventional LED array driving apparatus, since it is necessary to secure a timing for individual current control for each of the plurality of light emitting diode arrays 101 to 10m, the frequency of the pulse width modulation signals PWM1 to PWMn is increased There is a limit. In particular, in the driving apparatus of the conventional light emitting diode array, due to the limitation of the frequency of the internal clock generated in the internal clock generator, there is a limit to increase the frequency of the pulse width modulation signals PWM1 to PWMn only by the frequency of the internal clock. Accordingly, in a liquid crystal display device using a driving device of a conventional light emitting diode array, a picture quality defect such as a stripe or a black pattern occurs due to a dimming interference phenomenon due to a difference between a frame frequency of a liquid crystal display panel and an image pickup frequency .

The conventional KSF red phosphor uses a KSF (K ₂ SiF ₆ ) red phosphor for dimming reproduction of a high color. In the dimming-off of a light emitting diode, a current decay time Red dots (dotted circle) are induced. For example, when a moving picture having an imaging frequency of 240 FPS (frame per second) is displayed on a liquid crystal display panel while driving the light emitting diode array at 120 Hz, which is the same as the frame frequency of the liquid crystal display panel, As in the circle, a red afterglow phenomenon occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a driving apparatus for a light emitting diode array capable of high-speed dimming and a liquid crystal display including the same.

According to an aspect of the present invention, there is provided a driving apparatus for a light emitting diode array, including: a light emitting diode array having a first frequency and a second frequency higher than a first frequency; At this time, the second frequency may be multiplied by N (N is a natural number of 2 or more) times from the first frequency.

According to another aspect of the present invention, there is provided a liquid crystal display device including a backlight unit having a light emitting diode array for emitting light to a liquid crystal display panel and a backlight driver for driving the backlight unit, The light emitting diode array can be turned on / off at a second frequency higher than the first frequency based on the internal clock signal.

According to the solution of the above-mentioned problems, the present invention has the following effects.

First, the switching unit connected to the light emitting diode array can be switched at a high speed by using a plurality of pulse width modulated signals having a phase difference from each other. Therefore, the light emitting diode array can be rapidly turned on and off with only the internal clock signal without increasing the frequency of the pulse width modulation signal. Off.

Second, the light emitting diode array can be dimmed at a higher speed than the frequency driving capability of the light emitting diode driver.

Third, even when a light emitting diode including a KSF red phosphor is used for high color reproduction, the red afterglow phenomenon can be improved by high-speed dimming of the light emitting diode.

In addition to the effects of the present invention mentioned above, other features and advantages of the present invention will be described below, or may be apparent to those skilled in the art from the description and the description.

1 is a circuit diagram for schematically explaining a driving apparatus of a conventional light emitting diode array.
FIG. 2 is a waveform diagram showing the frequency of the pulse width modulation signal shown in FIG. 1 and the on / off frequency of the light emitting diode array.
3 is a view showing red afterglow phenomenon generated in a liquid crystal display device including a driving device of a conventional light emitting diode array.
4 is a view for explaining a driving apparatus of a light emitting diode array according to an example of the present invention.
FIG. 5 is a view for explaining a first switching unit and a first LED driving unit according to an embodiment of the present invention shown in FIG.
FIG. 6 is a waveform diagram showing the frequency of each of the first and second pulse width modulation signals shown in FIG. 5 and the on / off frequency of the first light emitting diode array.
FIG. 7 is a view for explaining a first switching unit and a first LED driving unit according to another example of the present invention shown in FIG.
8 is a view for explaining a liquid crystal display device according to an example of the present invention.
9 is a diagram showing an improvement of red afterglow phenomenon in the liquid crystal display according to the present invention.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms. It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one. The term "on" means not only when a configuration is formed directly on top of another configuration, but also when a third configuration is interposed between these configurations.

Hereinafter, preferred embodiments of a driving apparatus for a light emitting diode array and a liquid crystal display including the same according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals are used to denote like elements throughout the drawings, even if they are shown on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

4 is a view for explaining a driving apparatus of a light emitting diode array according to an example of the present invention.

Referring to FIG. 4, a driving apparatus 100 of a light emitting diode array according to an exemplary embodiment of the present invention includes first to mth light emitting diode arrays 1101 to 110m, a driving power supply unit 120, (1301 to 130m), and first to mth light emitting diode drivers 1401 to 140m.

Each of the first through m-th light emitting diode arrays 1101 through 110m is electrically connected in parallel to the output terminal of the driving power supply unit 120. Each of the first to mth light emitting diode arrays 1101 to 110m includes a plurality of light emitting diodes (LEDs) electrically connected in series between the output terminal of the driving power supply unit 120 and each of the switching units 1301 to 130m. Each of the first to mth light emitting diode arrays 1101 to 110m emits light by a current flowing from the output terminal of the driving power supply unit 120 to the ground terminal in accordance with the ON / OFF of each of the switching units 1301 to 130m, Release.

The light emitting diode (LED) may include a KSF (K2SiF6) red phosphor for high color reproduction, but is not limited thereto and may be a known light emitting diode for irradiating light to a liquid crystal display.

The driving power supply unit 120 generates driving power Vd necessary for driving the first to mth light emitting diode arrays 1101 to 110m based on the input power Vin supplied from the outside, And supplies them to the light emitting diode arrays 1101 to 110m.

The driving power supply unit 120 according to an exemplary embodiment may be a DC-DC converter including an inductor (not shown), a power switching device (not shown), a diode (not shown), and a capacitor (not shown). The inductor, the power switching device, and the diode operate as a power conversion circuit, thereby converting the input power supply Vin into the driving power supply Vd in accordance with the switching of the power switching device. The capacitor serves to smoothen the driving power supply Vd output through the diode to a DC voltage.

Each of the first to mth switching units 1301 to 130m is connected to the output terminal of the first to mth light emitting diode arrays 1101 to 110m in a one-to-one manner between the output terminal and the ground terminal, and the corresponding light emitting diode arrays 1101 to 110m On / off.

Each of the plurality of LED driving units 1401 to 140m is connected to each of the first to mth switching units 1301 to 130m in a one-to-one manner to control switching of the corresponding switching units 1301 to 130m. At this time, each of the plurality of light emitting diode drivers 1401 to 140m switches the corresponding switching units 1301 to 130m based on an internal clock signal having a first frequency to output the corresponding light emitting diode arrays 1101 to 110m And turns on / off the second frequency higher than the first frequency.

Each of the first to mth switching units 1301 to 130m is switched according to each of a plurality of pulse width modulation signals PWM11 to PWM1n to PWMm1 to PWMmn supplied from the corresponding LED driving units 1401 to 140m, And turns on / off the light emitting diode arrays 1101 to 110m at a high speed. Here, the plurality of pulse width modulation signals PWM11 to PWM1n to PWMm1 to PWMmn supplied to one of the switching units 1301 to 130m are sequentially shifted so as to have the same phase difference with the same duty- do. Accordingly, one of the switching units 1301 to 130m is switched according to a plurality of pulse width modulation signals PWM11 to PWM1n to PWMm1 to PWMmn having a first frequency and a phase difference from each other, And turns on / off the corresponding light emitting diode arrays 1101 to 110m at a second frequency corresponding to the combined frequency of each of the width modulation signals PWM11 to PWM1n to PWMm1 to PWMmn.

Each of the plurality of LED driving units 1401 to 140m generates feedback signals FB1 to FBm corresponding to the sensing voltage corresponding to the current flowing to the ground terminal through corresponding switching units 1301 to 130m, And supplies it to the power supply unit 120. Accordingly, the driving power supply unit 120 adjusts the switching of the power switching devices based on the feedback signals FB1 to FBm supplied from the first to mth light emitting diode drivers 1401 to 140m, respectively, The currents flowing through the light emitting diode arrays 1101 to 110m are controlled to be constant.

FIG. 5 is a view for explaining a first switching unit and a first LED driving unit according to an embodiment of the present invention shown in FIG. 2. Referring to FIG.

4 and 5, a first switching unit 1301 according to an exemplary embodiment of the present invention includes N (where N is a natural number of 2 or more) transistors T11 to T1n and N resistors Rs do.

Each of the N transistors T11 to T1n is electrically connected in parallel between the output terminal of the first light emitting diode array 1101 and the ground terminal and is supplied with N pulse width modulation signals separately supplied from the first light emitting diode driver 1401. [ (PWM11 to PWM1n), respectively. Accordingly, the first light emitting diode array 1101 can be turned on / off at a second frequency corresponding to the composite frequency of the N pulse width modulation signals PWM11 to PWM1n having the first frequency and the phase difference from each other. Each of the N transistors T11 to T1n according to an example includes a gate terminal (or base terminal), a drain terminal (or collector terminal), and a source terminal (or emitter terminal).

In each of the N transistors T11 to T1n, the gate terminal is connected to the first light emitting diode driver 1401, the drain terminal is commonly connected to the output terminal of the first light emitting diode driver 1401, Lt; RTI ID = 0.0 > Rs < / RTI >

Each of the N resistors Rs is connected between each of the N transistors T11 to T1n and a ground terminal. Each of the N resistors Rs serves to detect a sensing voltage corresponding to a current flowing to the ground terminal through each of the N transistors T11 to T1n.

The first light emitting diode driver 1401 according to an exemplary embodiment of the present invention is a driving integrated circuit that generates N pulse width modulation signals PWM11 through PWM1n based on first dimming data Bdim1 input from the outside, The first LED array 1101 is turned on / off at a high speed according to the switching of each of the N transistors T11 to T1n by sequentially switching each of the transistors T11 to T1n. At this time, the first LED driving unit 1401 generates a reference pulse width modulation signal having a second duty-on period by dividing the first duty-on period corresponding to the first dimming data Bdim1 by N, The N pulse width modulation signals PWM11 to PWM1n can be generated by sequentially shifting the phase of the reference pulse width modulation signal by N times the period of one cycle. The first LED driving unit 1401 includes a duty setting unit 141, a signal generating unit 143, a phase shifting unit 145, N comparators OP1 through OPn, and a controller 147 ).

The duty setting unit 141 divides the first duty-on period corresponding to the first dimming data Bdim1 input from the outside into N, and generates the duty data DD having the second duty-on period. For example, when the first duty-on period is 60% in one period of the first frequency and the first duty-on period is divided into two equal halves, the second duty-on period may have 30% in one period of the first frequency have. As another example, when the first duty-on period is 60% in one period of the first frequency and the first duty-on period is divided into three equal intervals, the second duty-on period may have 20% in one cycle of the first frequency have.

The signal generator 143 generates a reference pulse width modulation signal having a second duty-on period according to the duty data DD set by the duty setting unit 141 based on the internal clock signal of the first frequency generated in the internal clock generator, And generates a signal Rpwm. That is, the signal generator 143 sets the duty-on interval of the internal clock signal having the first frequency to the second duty-on interval corresponding to the duty data DD, thereby generating the reference pulse width modulated signal having the second duty- (Rpwm).

The phase shifting unit 145 sequentially shifts the phase of the reference pulse width modulation signal Rpwm having the second duty-on interval supplied from the signal generating unit 143 by a phase difference time obtained by dividing the period of the first frequency by N And generates N pulse width modulation signals PWM11 to PWM1n. That is, the phase shifting unit 145 sequentially shifts the second duty-on period of the reference pulse width modulation signal Rpwm by the phase difference time to generate N pulse width modulation signals PWM11 to PWM1n, It is possible to generate N pulse width modulation signals PWM11 to PWM1n for fast dimming the first light emitting diode array 1101. [

Each of the N comparators OP1 to OPn is connected to the N transistors T11 to T1n on a one-to-one basis, and the voltage of the corresponding pulse width modulation signals PWM11 to PWM1n and the corresponding resistor Rs is used Thereby switching the transistors T11 to T1n.

Each of the N comparators OP1 through OPn according to an example may include a non-inverting terminal (+), an inverting terminal (-), and an output terminal Vo. In each of the N comparators OP1 to OPn, the corresponding pulse width modulation signals PWM11 to PWM1n are supplied to the non-inverting terminal (+) and the sensing voltage applied to the corresponding resistor Rs is supplied to the inverting terminal (- And the output terminal Vo is connected to the gate terminal of the corresponding transistor T11 to T1n.

Each of the N comparators OP1 to OPn according to an example operates as a voltage follower using the pulse width modulation signals PWM11 to PWM1n as a reference voltage so that a current flowing in the first light emitting diode array 1101 is And switches the corresponding transistors T11 to T1n to be constant. Thus, each of the N transistors T11 to T1n is individually switched by the pulse width modulated signals PWM11 to PWM1n having the first frequency supplied through the corresponding comparators OP1 to OPn, The light emitting diode array 1101 is turned on / off at a second frequency multiplied N times from the first frequency by the composite frequency according to the switching frequency of each of the N transistors T11 to T1n. For example, as shown in FIG. 6, when the first and second transistors T11 and T12 are individually switched by the first and second pulse width modulation signals PWM11 and PWM12 having a frequency of 120 Hz , The first light emitting diode array 1101 is turned on / off at a second frequency of 240 Hz according to the combination of the switching frequencies of the first and second transistors T11 and T12 having the first frequency of 120 Hz and alternately switched, Off. As a result, according to the present invention, the first LED array 1101 is turned on at a second frequency of 120 Hz by using the synthesized frequency of the two pulse width modulated signals PWM11 and PWM12 having a first frequency of 120 Hz and a phase difference from each other / Off.

The controller 147 generates the first feedback signal FB1 based on the output signals of the N comparators OP1 to OPn and provides the first feedback signal FB1 to the driving power supply unit 120. [ The controller 147 generates the first feedback signal FB1 based on the output signal having the largest value among the output signals of the N comparators OP1 to OPn and supplies the first feedback signal FB1 to the driving power supply unit 120 can do.

The driving apparatus of the light emitting diode array including the first switching unit 1301 and the first light emitting diode driving unit 1401 according to the exemplary embodiment of the present invention may be configured such that the combined frequency of a plurality of pulse width modulated signals The first switching unit 1301 can be switched at a high speed. Therefore, the first light emitting diode array 1101 can be turned on / off at high speed using only the internal clock signal without increasing the frequency of the pulse width modulation signal.

In addition, each of the second to m-th switching units 1302 to 130m shown in FIG. 4 is connected to the first to the m-th light emitting diode arrays 1102 to 110m, 1301, and thus a duplicate description thereof will be omitted.

Likewise, each of the second to m-th LED driving units 1402 to 140m shown in FIG. 4 is connected to the second to m-th switching units 1302 to 130m in a one-to- The driving unit 1401 has the same configuration as that of the driving unit 1401, and a duplicate description thereof will be omitted.

FIG. 7 is a view for explaining a first switching unit and a first LED driving unit according to another example of the present invention shown in FIG.

Referring to FIG. 7 with reference to FIG. 4, the first switching unit 1301 according to another example of the present invention includes a transistor T1 and a resistor Rs.

The transistor T1 is connected between the output terminal of the first LED array 1101 and the ground terminal and is connected to the first N LED driver 1401 through N pulse width modulation signals PWM11 through PWM1n Lt; / RTI > Accordingly, the first light emitting diode array 1101 can be turned on / off at a second frequency corresponding to the composite frequency of the N pulse width modulation signals PWM11 to PWM1n having the first frequency and the phase difference from each other. The transistor T1 according to one example includes a gate terminal (or base terminal), a drain terminal (or collector terminal), and a source terminal (or emitter terminal).

In the transistor T1, the gate terminal is connected to the first light emitting diode driving part 1401, the drain terminal is commonly connected to the output terminal of the first light emitting diode driving part 1401, and the source terminal is connected to each of the resistors Rs .

The resistor Rs is connected between the transistor T1 and the ground terminal. The resistor Rs serves to detect a sensing voltage corresponding to the current flowing through the transistor T1 to the ground terminal.

The first switching unit 1301 according to another exemplary embodiment of the present invention may include one transistor T1 so that the configuration of the first switching unit 1301 according to an exemplary embodiment of the present invention shown in FIG. The first light emitting diode array 1101 can be turned on / off at a high speed.

The first light emitting diode driver 1401 according to another exemplary embodiment of the present invention is a driving integrated circuit that generates N pulse width modulation signals PWM11 through PWM1n based on first dimming data Bdim1 input from the outside, The first light emitting diode array 1101 is turned on / off at a high speed according to fast switching of the transistor T11 by switching the first transistor T1. At this time, the first LED driving unit 1401 generates a reference pulse width modulation signal having a second duty-on period by dividing the first duty-on period corresponding to the first dimming data Bdim1 by N, The N pulse width modulation signals PWM11 to PWM1n can be generated by sequentially shifting the phase of the reference pulse width modulation signal by N times the period of one cycle. The first LED driver 1401 includes a duty setting unit 141, a signal generator 143, a phase shifter 145, N comparators OP1 through OPn, and a controller 147 ).

The duty setting unit 141, the signal generating unit 143 and the phase shifting unit 145 of the duty setting unit 141 are the same as those in FIG. 5, and therefore, the same reference numerals are given to the duty setting unit 141, Is omitted.

Each of the N comparators OP1 to OPn is commonly connected to the transistor T1 to switch the transistor T1 using the pulse width modulation signals PWM11 to PWM1n and the voltage applied to the corresponding resistor Rs .

Each of the N comparators OP1 through OPn according to an example may include a non-inverting terminal (+), an inverting terminal (-), and an output terminal Vo. In each of the N comparators OP1 to OPn, the corresponding pulse width modulation signals PWM11 to PWM1n are supplied to the non-inverting terminal (+) and the sensing voltage applied to the resistor Rs is commonly connected to the inverting terminal (- And the output terminal Vo is commonly connected to the gate terminals of the transistors T11 to T1n.

Each of the N comparators OP1 to OPn according to an example operates as a voltage follower using the pulse width modulation signals PWM11 to PWM1n as a reference voltage so that a current flowing in the first light emitting diode array 1101 is Thereby switching the transistor T1 to be constant. Accordingly, the transistor T1 is switched at a high speed by the pulse width modulated signals PWM11 to PWM1n having the first frequency supplied through each of the N comparators OP1 to OPn, whereby the first light emitting diode array 1101 are turned on / off to a second frequency multiplied N times from the first frequency by the switching frequency of the transistor T1. 6, when the transistor T1 is switched by the first and second pulse width modulation signals PWM11 and PWM12 having a frequency of 120 Hz, the first light emitting diode array 1101 is turned on, Is turned on / off at a second frequency of 240 Hz according to the switching frequency of the transistor T1, which is switched by the first and second pulse width modulation signals PWM11 and PWM12 having a first frequency of 120 Hz and a phase difference . As a result, the present invention turns on / off the first light emitting diode array 1101 at a second frequency of 120 Hz by using two pulse width modulation signals PWM11 and PWM12 having a first frequency of 120 Hz and a phase difference from each other .

The controller 147 generates the first feedback signal FB1 based on the voltage corresponding to the current flowing through the node between the output terminal of the first LED array 1101 and the transistor T1 and outputs the first feedback signal FB1 to the driving power supply unit 120. [ .

The driving apparatus of the light emitting diode array including the first switching unit 1301 and the first light emitting diode driving unit 1401 according to another example of the present invention uses a plurality of pulse width modulation signals having a phase difference from each other, Since one transistor T1 provided in the switching unit 1301 can be switched at a high speed, the first light emitting diode array 1101 can be turned on / off at high speed by only the internal clock signal without increasing the frequency of the pulse width modulation signal .

In addition, each of the second to m-th switching units 1302 to 130m shown in FIG. 4 is connected to the second to m-th light emitting diode arrays 1102 to 110m in a one-to- The first switching unit 1301 has the same configuration as that of the first switching unit 1301, so a duplicate description thereof will be omitted.

Similarly, each of the second to m-th LED driving units 1402 to 140m shown in FIG. 4 is connected to the second to m-th switching units 1302 to 130m in a one-to- Since the first LED driving unit 1401 has the same configuration as the first LED driving unit 1401, a detailed description thereof will be omitted.

In addition, in the driving apparatus for a light emitting diode array according to an example of the present invention, one light emitting diode driver may include i channels, and each of i channels provided in one light emitting diode driver may include i light emitting diode arrays One-to-one. One light emitting diode driver may include i channel drivers (not shown) and an integrated controller. Each of the i channel driving units may include the duty setting unit 141, the signal generating unit 143, the phase shifting unit 145, and the N comparators OP1 to OPn shown in FIG. 5 or 7 . The integrated controller may generate a feedback signal based on the output signal of the comparators OP1 to OPn supplied from each of the i channel driving units or the voltage corresponding to the current flowing through the LED array and supply the feedback signal to the driving power supply unit .

As described above, the driving apparatus of the LED array according to the present invention can turn on and off the LED array at a high speed by using a plurality of pulse width modulation signals having a frequency of an internal clock signal and a phase difference from each other. Accordingly, the present invention can rapidly turn on / off the light emitting diode array with only the internal clock signal without raising the frequency of the pulse width modulation signal, and furthermore, dimming the light emitting diode array at high speed more than the frequency driving ability of the light emitting diode driving part can do.

8 is a view for explaining a liquid crystal display device according to an example of the present invention.

Referring to FIG. 8, a liquid crystal display device according to an exemplary embodiment of the present invention includes a liquid crystal display panel 500, a panel driver 600, a backlight unit 700, and a backlight driver 800.

The liquid crystal display panel 500 includes a pixel P formed in each pixel region defined by intersection of a plurality of gate lines GL and a plurality of data lines DL. The plurality of pixels P may include a thin film transistor (not shown) connected to the gate line GL and the data line DL, and a liquid crystal cell connected to the thin film transistor. The thin film transistor supplies a data voltage supplied from the data line DL to the liquid crystal cell in response to a scan pulse supplied from the gate line GL. Since the liquid crystal cell is composed of the common electrode facing the liquid crystal layer and the pixel electrode connected to the thin film transistor, the liquid crystal cell can be equivalently expressed by a liquid crystal capacitor (not shown). In addition, the liquid crystal cell includes a storage capacitor (not shown) for holding the data voltage charged in the liquid crystal capacitor (not shown) until the next data voltage is supplied. The liquid crystal display panel 500 displays a predetermined image using light passing through the liquid crystal layer in accordance with the driving of the liquid crystal layer superimposed on each pixel P according to the data voltage supplied from the panel driver 600. [

The panel driver 600 receives the image data Idata and the timing synchronization signal TSS supplied from an external host system and outputs the image data Idata in accordance with the received timing synchronization signal TSS. And supplies a corresponding data voltage to each pixel P to display an image corresponding to the image data Idata on the liquid crystal display panel 500. [ At the same time, the panel driver 600 divides the liquid crystal display panel 500 into a plurality of blocks, analyzes the image data Idata to be displayed in each block, and generates dimming data Bdim1 to Bdimm for each block The brightness of each block of the liquid crystal display panel 500 is individually controlled by driving the backlight driver 800. [ For this, the panel driver 600 may include a timing controller 610, a data driver circuit 620, and a gate driver circuit 630.

The timing controller 610 receives the image data Idata and the timing synchronization signal TSS supplied from the host system and outputs the image data Idata to the liquid crystal display panel 500 according to the received timing synchronization signal TSS. And supplies the generated pixel data RGB to the data driving circuit unit 620. The data driving circuit unit 620 supplies the pixel data RGB to the data driving circuit unit 620. [ The timing control unit 610 controls the timing of driving the data driving circuit unit 620 to control the driving timing of the gate driving circuit unit 630 and the data control signal DCS for controlling the driving timing of the data driving circuit unit 620 based on the timing synchronization signal TSS. And generates a gate control signal GCS. The timing controller 610 divides the liquid crystal display panel 500 into a plurality of blocks and analyzes the pixel data RGB to be supplied to each block on a block by block basis to generate dimming data Bdim1 to Bdimm for each block, And supplies it to the driving unit 800. Here, the timing controller 610 can generate the average gray-scale values of the pixel data (RGB) for each block by the dimming data (Bdim1 to Bdimm) for each block.

The data driving circuit 620 receives the pixel data RGB and the data control signal DCS supplied from the timing controller 610 and outputs the pixel data RGB in analog Type data voltage and supplies it to the data line DL.

The gate driving circuit 630 generates a scan pulse in response to a gate control signal GCS supplied from the timing controller 610 and sequentially supplies the scan pulse to the gate line GL. Here, the gate driving circuit unit 630 may be integrated with the liquid crystal display panel 500 together with the thin film transistor manufacturing process of each pixel P so as to be connected to each gate line GL.

The backlight unit 700 includes m light emitting diode arrays 710 that are divided into n blocks and disposed on the back surface of the liquid crystal display panel 500.

Each of the m light emitting diode arrays 710 includes a plurality of light emitting diodes (LEDs) connected in series. Each of the m light emitting diode arrays 710 emits a plurality of light emitting diodes (LEDs) according to the dimming voltages Vbd1 to Vbdm for each block supplied from the backlight driving unit 800, Light is irradiated. At this time, each of the m light emitting diode arrays 710 is disposed so as to overlap one another on a plurality of blocks defined in the liquid crystal display panel 500, and individually irradiates light to each block.

The backlight driver 800 drives each light emitting diode array 710 of the backlight unit 700 individually based on the block-by-block dimming data Bdim1 to Bdimm supplied from the timing controller 610, The luminance to be applied to each block of the liquid crystal display panel 500 is controlled individually. To this end, the backlight driver 800 includes the driving device 100 of the LED array according to the present invention shown in FIGS. 4 to 7, and thus a duplicate description thereof will be omitted.

In the liquid crystal display device according to an embodiment of the present invention, the m light emitting diode arrays 710 are turned on / off at a high speed by the driving device of the light emitting diode array, so that the frame frequency of the liquid crystal display panel 500, Due to the dimming interference due to the difference in frequency, image quality defects such as stripe or black pattern can be minimized.

Also, in the liquid crystal display device according to an exemplary embodiment of the present invention, even if a light emitting diode including KSF (K ₂ SiF ₆ ) red phosphor is used for high color reproduction, red afterglow phenomenon can be improved through high- have. For example, as shown in FIG. 9, when a moving image having an imaging frequency of 240 frames per second (FPS) is displayed on a liquid crystal display panel while the light emitting diode array is turned on / off at high speed through a driving device of a light emitting diode array , The red afterglow phenomenon occurring in the dotted circle compared to the conventional technique shown in FIG. 3 is improved.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of. Therefore, the scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

1101 to 110m: light emitting diode array 120: driving power supply part
1301 to 130m: switching units 1401 to 140m: light emitting diode driver
141: duty setting unit 143: signal generating unit
145: phase shifting unit 147: control unit
500: liquid crystal display panel 600: panel driver
610: timing control unit 620: data driving circuit unit
630: Gate driving circuit part 700: Backlight unit
800: backlight driving part

Claims (14)

A light emitting diode array having a plurality of light emitting diodes connected in series;
A driving power supply for supplying driving power to the light emitting diode array;
A switching unit connected to the light emitting diode array; And
And a light emitting diode driver for switching the switching unit,
Wherein the light emitting diode driver controls the switching unit based on an internal clock signal having a first frequency to turn on / off the light emitting diode array at a second frequency higher than the first frequency. The method according to claim 1,
And the second frequency is multiplied by N from the first frequency (where N is a natural number of 2 or more). The method according to claim 1,
The switching unit includes:
N (N is a natural number of 2 or more) transistors connected in parallel to the light emitting diode array; And
And N resistors connected between each of the N transistors and the ground terminal. The method of claim 3,
Wherein the light emitting diode driver generates N pulse width modulation signals based on dimming data input from the outside to sequentially switch each of the N transistors. 5. The method of claim 4,
Wherein the light emitting diode array is turned on / off at a second frequency higher than the first frequency in accordance with switching of each of the N transistors according to each of the N pulse width modulation signals. 5. The method of claim 4,
Wherein the light emitting diode driver generates a reference pulse width modulation signal having a second duty-on interval by dividing a first duty-on interval corresponding to the dimming data by N, And sequentially shifts the phase of the reference pulse width modulation signal to generate the N pulse width modulation signals. The method of claim 3,
The light emitting diode driver includes:
A duty setting unit for generating duty data having a second duty-on interval by dividing a first duty-on interval corresponding to dimming data input from the outside into N equals;
A signal generator for generating a reference pulse width modulation signal having the second duty-on interval in accordance with the duty data based on the internal clock signal of the first frequency;
A phase shifter for sequentially shifting the phase of the reference pulse width modulation signal by N times the period of the first frequency to generate N pulse width modulated signals;
N comparators connected to each of the N transistors; And
And a control unit for generating a feedback signal based on output signals of the N comparators and providing the feedback signal to the driving power supply unit,
Wherein each of the N comparators switches a corresponding transistor using a corresponding pulse width modulation signal and a voltage across the corresponding resistor. The method according to claim 1,
The switching unit includes:
A transistor coupled to the light emitting diode array; And
And a resistor connected between the transistor and the ground terminal. 9. The method of claim 8,
Wherein the light emitting diode driver generates N pulse width modulation signals based on dimming data input from the outside to switch the transistors. 10. The method of claim 9,
Wherein the light emitting diode array is turned on / off at a second frequency higher than the first frequency in accordance with switching of the transistors according to each of the N pulse width modulation signals. 10. The method of claim 9,
Wherein the light emitting diode driver generates a reference pulse width modulation signal having a second duty-on interval by dividing a first duty-on interval corresponding to the dimming data by N, And sequentially shifts the phase of the pulse width modulation signal to generate the N pulse width modulation signals. 9. The method of claim 8,
The light emitting diode driver includes:
A duty setting unit for generating duty data having a second duty-on interval by dividing a first duty-on interval corresponding to dimming data input from the outside into N equals;
A signal generator for generating a reference pulse width modulation signal having the second duty-on interval in accordance with the duty data based on the internal clock signal of the first frequency;
A phase shifter for sequentially shifting the phase of the reference pulse width modulation signal by N times the period of the first frequency to generate N pulse width modulated signals;
N comparators commonly connected to the transistors; And
And a control unit for generating a feedback signal based on a voltage corresponding to a current flowing in a node between the light emitting diode array and the transistor and providing the feedback signal to the driving power supply unit,
Wherein each of the N comparators switches the transistor using a corresponding pulse width modulation signal and a voltage across the resistor. A liquid crystal display panel having pixels formed in regions defined by intersections of a plurality of gate lines and a plurality of data lines;
A panel driver for converting input data from the outside into data signals and supplying the data signals to pixels;
A backlight unit having a light emitting diode array for emitting light to the liquid crystal display panel;
And a backlight driver for driving the light emitting diode array,
Wherein the backlight driving unit includes the driving device of the light emitting diode array according to any one of claims 1 to 12. 14. The method of claim 13,
Wherein the panel driver analyzes input data to be displayed on the liquid crystal display panel to calculate dimming data and provides the dimming data to the backlight driver.

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