KR101924623B1 - Liquid Crystal Display Device - Google Patents

Abstract

An embodiment of the present invention is a liquid crystal display device comprising: a liquid crystal panel; LED strings connected in parallel to an output terminal of the DC power supply unit and providing light to the liquid crystal panel; And LED drivers having channels for driving the LED strings and sharing the voltage information of the LED strings driven by the LED strings.

Description

[0001] The present invention relates to a liquid crystal display device,

An embodiment of the present invention relates to a liquid crystal display device.

As the information technology is developed, the market of display devices, which is a connection medium between users and information, is getting larger. Accordingly, a flat panel display (FPD) such as a liquid crystal display (LCD), an organic light emitting diode (OLED), and a plasma display panel (PDP) Usage is increasing. Among them, liquid crystal display devices capable of realizing high resolution and capable of not only miniaturization but also enlargement are widely used.

The liquid crystal display device includes a liquid crystal panel composed of a transistor substrate formed with a transistor, a storage capacitor, a pixel electrode, and the like, and a liquid crystal layer positioned between a color filter substrate and a color filter substrate on which a color filter and a black matrix are formed.

When a gate signal is supplied from a gate driver to a liquid crystal display device, a liquid crystal layer is driven by a difference between a data voltage supplied from the data driver and a common voltage supplied from the power supply, thereby controlling light incident from the backlight unit So that the image is displayed.

As a light source included in the backlight unit, a light emitting diode (hereinafter, LED) is mainly used. A plurality of LEDs form a unit light source in the form of a string (or string) connected in series, and the LED strings are used in a form in which a plurality of LED strings are connected in parallel to a DC power source.

On the other hand, the LED string is operated by an LED driver including a transistor for sinking a current supplied from a DC power source and a pulse width modulation circuit for supplying a signal for driving the transistor. The number of LED strings that the LED driver can drive is determined. Accordingly, when a plurality of LED driving units are used, they are driven by independent DC power sources.

Therefore, in the conventional backlight unit, when the number of the LED driving units increases, the number of the DC power supply units also increases in proportion to the increase in the number of the LED driving units.

An embodiment of the present invention for solving the problems of the background art described above is to provide a liquid crystal display device which can reduce the cost in constituting a device because only one direct current power source part is required even if a plurality of LED driving parts are used.

According to an embodiment of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal panel; LED strings connected in parallel to an output terminal of the DC power supply unit and providing light to the liquid crystal panel; And LED drivers having channels for driving the LED strings and sharing the voltage information of the LED strings driven by the LED strings.

The LED drivers include one master LED driver for driving LED strings connected to their channels and N (N is one or more) slave LED drivers for driving LED strings connected to their channels, The driving unit and the slave LED driving unit share the voltage information of the LED strings driven by the driving unit and the slave LED driving unit, and the master LED driving unit can control the output voltage of the DC power source unit using the shared voltage information.

The master LED driver can control the output voltage of the DC power supply unit based on the LED string having the highest voltage value among the shared voltage information.

The master LED driving unit and the slave LED driving unit can mutually share the voltage information of the LED strings driven by them in a manner of mutually connecting the terminals.

The slave LED driver can deliver the lowest voltage value to the master LED driver.

The master LED driving unit includes a transistor for sinking a current input through each channel, a comparator for monitoring a current flowing through the transistor and supplying a driving signal to a gate electrode of the transistor, a driving signal generating unit for generating a driving signal, And a power supply control unit for supplying a power supply control signal for controlling the output voltage of the DC power supply unit based on the shared voltage information.

The power control unit can control the output voltage of the DC power supply unit based on the LED string having the highest voltage value among the LED strings.

The slave LED driver includes a transistor for sinking a current input through each channel, a comparator for monitoring a current flowing through the transistor, supplying a driving signal to the gate electrode of the transistor, and a driving signal generator for generating a driving signal .

The master LED driving unit and the slave LED driving unit can share the voltage information of the LED strings driven by the communication method.

The slave LED driver can transmit all the voltage information of the LED strings driven by the slave LED driver to the master LED driver through the communication system.

The embodiment of the present invention has an effect of providing a liquid crystal display device which can reduce the cost in constituting the device since only one direct current power source part is required even if a plurality of LED driving parts are used. In addition, the embodiment of the present invention can independently drive the LED strings connected to the respective channels by one master LED driving unit and a plurality of slave LED driving units interlocked with one DC power supply unit, and can precisely control the output voltage of the DC power supply unit There is an effect of providing a liquid crystal display device capable of controlling the liquid crystal display device.

1 is a block diagram of a liquid crystal display device.
2 is a block diagram of a gate driver;
3 is a block diagram of a data driver;
4 is a configuration diagram of a backlight unit driving unit of a liquid crystal display device according to the first embodiment of the present invention.
5 is a circuit configuration diagram of the master LED driving unit shown in FIG.
6 is a circuit configuration diagram of the slave LED driver shown in FIG.
7 is an equivalent circuit configuration diagram for a part of the master and slave LED driver;
8 is a configuration diagram of a backlight unit driving unit of a liquid crystal display device according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a liquid crystal display, FIG. 2 is a block diagram of a gate driver, and FIG. 3 is a block diagram of a data driver.

1, a liquid crystal display includes a timing driver TCN, a liquid crystal panel PNL, a gate driver SDRV, a data driver DDRV, a backlight unit BLU, and a backlight unit driver BDRV. do.

The timing driver TCN receives a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, a clock signal CLK and a data signal DATA from the outside. The timing driver TCN supplies data signals to the data driver DDRV and the data driver DDRV using timing signals such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, and a clock signal CLK. And controls the operation timing of the driving unit SDRV.

The timing driver TCN can count the data enable signal DE in one horizontal period to determine the frame period so that the externally supplied vertical sync signal Vsync and horizontal sync signal Hsync can be omitted. The timing driver TCN generates control signals GDC and DDC for controlling the panel driver for driving the liquid crystal panel PNL such as the gate driver SDRV and the data driver DDRV. The control signals GDC and DDC are supplied with a gate timing control signal GDC for controlling the operation timing of the gate driver SDRV and a data timing control signal DDC for controlling the operation timing of the data driver DDRV. .

The liquid crystal panel (PNL) includes subpixels arranged in a matrix including a liquid crystal layer positioned between a transistor substrate (hereinafter abbreviated as TFT substrate) and a color filter substrate. A data line, a gate line, a TFT, a storage capacitor and the like are formed on the TFT substrate, and a black matrix, a color filter and the like are formed on the color filter substrate.

The subpixel SP is defined by a data line DL1 and a gate line SL1 which cross each other. The subpixel SP includes a TFT driven by a gate signal supplied through a gate line SL1, a storage capacitor Cst for storing a data signal supplied through the data line DL1 as a data voltage, a storage capacitor Cst And a liquid crystal cell Clc driven by the data voltage stored in the liquid crystal cell Clc.

The liquid crystal cell Clc is driven by the data voltage supplied to the pixel electrode 1 and the common voltage Vcom supplied to the common electrode 2. [ The common electrode is formed on a color filter substrate in a vertical field driving method such as a TN (Twisted Nematic) mode and a VA (Vertical Alignment) mode, and a horizontal electric field such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) Is formed on the TFT substrate together with the pixel electrode in the driving method. A polarizing plate is attached to the TFT substrate of the liquid crystal panel (PNL) and the color filter substrate, and an alignment film for setting a pre-tilt angle of the liquid crystal is formed. The liquid crystal mode of the liquid crystal panel PNL can be implemented in any liquid crystal mode as well as the TN mode, VA mode, IPS mode, and FFS mode described above.

The gate driving unit SDRV is responsive to the gate timing control signal GDC supplied from the timing driving unit TCN to turn on the gate driving voltage of the transistors of the subpixels SP included in the display panel PNL And sequentially generates the gate signal while shifting the level of the signal. The gate driver SDRV supplies the gate signal generated through the gate lines SL1 to SLm to the sub-pixels SP included in the display panel PNL.

As shown in FIG. 2, the gate driver SDRV is composed of gate drive ICs. The gate drive ICs each include a shift register 61, a level shifter 63, a plurality of AND gates 62 and a gate output enable signal GOE connected between the shift register 61 and the level shifter 63, And an inverter 64 for inverting the inverter 64 and the like. The shift register 61 shifts the gate start pulse GSP sequentially in accordance with the gate shift clock GSC using a plurality of D flip-flops depending thereon. The AND gates 62 logically multiply the output signal of the shift register 61 and the inverted signal of the gate output enable signal GOE to generate an output. The inverter 64 inverts the gate output enable signal GOE and supplies it to the AND gates 62. The level shifter 63 shifts the output voltage swing width of the end gate 62 to the swing width of the gate voltage at which the transistors included in the display panel PNL are operable. The gate signal output from the level shifter 63 is sequentially supplied to the gate lines SL1 to SLm.

The data driver DDRV samples and latches the data signal DATA supplied from the timing driver TCN in response to the data timing control signal DDC supplied from the timing driver TCN and converts the sampled data signal into data of a parallel data system . The data driver DDRV converts the data signal DATA into a gamma reference voltage when converting into data of a parallel data system. The data driver DDRV supplies the data signal DATA converted through the data lines DL1 to DLn to the subpixels SP included in the display panel PNL.

A shift register 51, a data register 52, a first latch 53, a second latch 54, a conversion section 55, an output circuit 56, and the like, as shown in Fig. The shift register 51 shifts the source sampling clock SSC supplied from the timing driver TCN. The shift register 51 transfers the carry signal CAR to the shift register of the next source drive IC in the neighboring stage. The data register 52 temporarily stores the data signal DATA supplied from the timing driver TCN and supplies it to the first latch 53. The first latch 53 samples and latches the data signal DATA serially input according to the clocks sequentially supplied from the shift register 51, and outputs the latched data at the same time. The second latch 54 latches the data supplied from the first latch 53 and then latches the latched data in synchronization with the second latch 54 of the other source drive ICs in response to the source output enable signal SOE Simultaneously output. The conversion unit 55 converts the data signal DATA input from the second latch 54 into gamma reference voltages GMA1 to GMAn. The data signal DATA output from the output circuit 56 is supplied to the data lines DL1 to DLn in response to the source output enable signal SOE.

The backlight unit (BLU) provides light to the liquid crystal panel (PNL). The backlight unit (BLU) may be variously configured as an edge type, a dual type, a direct type, and the like. Here, the edge type is one in which light emitting diodes (hereinafter referred to as LEDs or LEDs) are arranged in a string (or row) shape on one side of a liquid crystal panel PNL. In the dual type, LEDs are arranged on both sides of a liquid crystal panel (PNL) in the form of strings (or strings). In the direct type, LEDs are arranged in the form of a block or a matrix in the lower part of the liquid crystal panel (PNL).

The backlight unit driving unit BDRV drives the backlight unit BLU. The backlight unit driving unit (BDRV) includes a DC power supply unit for supplying DC power to the LED strings and LED driving units having channels for driving the LED strings. On the other hand, the backlight unit driving unit (BDRV) can detect a short when the LED strings are short-circuited to protect the devices from short-circuiting, which will be described in more detail below.

≪ Embodiment 1 >

4 is a circuit diagram of a driving unit of a backlight unit of a liquid crystal display according to a first embodiment of the present invention, FIG. 5 is a circuit diagram of a master LED driving unit shown in FIG. 4, Fig. 7 is an equivalent circuit diagram of a part of the master and slave LED driver. Fig.

4 to 7, the liquid crystal display according to the first embodiment of the present invention includes a backlight unit BLU for providing light and a backlight unit driving unit BDRV for driving the backlight unit BLU do.

The first LED strings RS11 through RS1n and the second LED strings RS11 through RS1n connected in parallel to the output terminal Vout of the DC power source unit 120 are connected to the LED strings RS11 through RS1n and RS21 through RS2n constituting the backlight unit BLU, The LED strings RS11 to RS1n and RS21 to RS2n are connected in series within the corresponding string of LEDs D1 to Dn included in the LED strings RS11 to RS1n and RS21 to RS2n, The anode electrodes of the first LEDs D1 included in the scan lines RS21 to RS2n are connected to the output terminal Vout of the DC power source unit 120 respectively and the cathode electrodes of the nLEDs Dn are connected to the channels of the LED drivers 130 and 140 (Ch1 to Chm).

One LED driver 130 and the second LED strings RS21 to RS2n for driving the first LED strings RS11 to RS1n are connected to the LED drivers 130 and 140 constituting the backlight unit driver BDRV, The master LED driver 130 and the slave LED driver 140 drive six LED strings using six channels, respectively, for example, and N (N is one or more) can do.

The DC power supply unit 120 constituting the backlight unit driving unit BDRV converts the first DC power inputted through the input terminal Vin into the second DC power and outputs the converted DC power through the output terminal Vout. The DC power supply unit 120 may be a conventional DC to DC converter, and may include an inductor, a transistor, a diode, a capacitor, and the like. The DC power supply unit 120 boosts the power of the transistor based on the power control signal GCS supplied from the master LED driving unit 130 so that the input power is boosted and output.

The master LED driver 130 independently drives the first LED strings RS11 to RS1n connected to the channels Ch1 to Chm and the slave LED driver 140 also drives its own channels Ch1 to Chm, And drives the second LED strings RS21 to RS2n connected to the second LED strings independently.

The master LED driver 130 and the slave LED driver 140 share the voltage information MVS of the LED strings RS11 to RS1n and RS21 to RS2n driven by the master LED driver 130 and the slave LED driver 140, respectively. The master LED driving unit 130 supplies the DC power supply unit 120 with a power supply control signal GCS that can control the output voltage of the DC power supply unit 120 using the shared voltage information MVS. At this time, the master LED driver 130 controls the output voltage of the DC power supply 120 based on the LED string having the highest voltage value among the shared voltage information MVS.

5, the master LED driving unit 130 includes transistors T1 through Tm, comparison units OP1 through OPm, monitor resistors R1 through Rm, a driving signal generating unit 131, and a power control unit 135, .

Transistors T1 to Tm sink the current input through each of the channels Ch1 to Chm and drive the LED string connected to the corresponding channel. The comparators OP1 to OPm monitor the current flowing through the transistors T1 to Tm and supply the driving signals to the gate electrodes of the transistors T1 to Tm. The driving signal generating unit 131 generates a driving signal to be supplied to the gate electrodes of the transistors T1 to Tm. The power control unit 135 serves to supply a power control signal GCS for controlling the output voltage of the DC power supply unit 120 based on the shared voltage information MVS.

The master LED driver 130 generates a driving signal based on the pulse width modulation signal generated from the driving signal generator 131. The transistor supplied with the driving signal drives the LED string connected to the corresponding channel by sinking the current do.

6, the slave LED driver 140 includes transistors T1 to Tm, comparators OP1 to OPm, monitor resistors R1 to Rm, and a driving signal generator 131. [

Transistors T1 to Tm sense the current input through each channel Ch1 to Chm and drive the LED string connected to the channel. The comparators OP1 to OPm monitor the current flowing through the transistors T1 to Tm and supply the driving signals to the gate electrodes of the transistors T1 to Tm. The driving signal generating unit 131 generates a driving signal to be supplied to the gate electrodes of the transistors T1 to Tm. The transistors T1 to Tm may be formed of a field effect transistor (FET), a bipolar junction transistor (BJT), or the like. When the transistors T1 to Tm are formed of FETs, each of the electrodes is referred to as a source electrode, a drain electrode, and a gate electrode. Alternatively, when the transistors T1 to Tm are formed of BJTs, each electrode is named as an emitter electrode, a collector electrode, and a base electrode.

The slave LED driver 140 generates a driving signal based on the pulse width modulation signal generated from the driving signal generator 141. The transistor supplied with the driving signal drives the LED string connected to the corresponding channel by synchronizing the current do.

As described above, the master LED driver 130 and the slave LED driver 140 may have the same configuration except for the power controller 135. Meanwhile, the master LED driver 130 and the slave LED driver 140 mutually share the voltage information MVS of the LED strings driven by the voltage information sharing terminals Chs. Since the master LED driving unit 130 is used as information for controlling the DC power supply unit 120, the master LED driving unit 130 receives the voltage information MVS and the slave LED driving unit 130 receives the voltage information MVS. The driving unit 140 supplies the voltage information MVS.

The master LED driving unit 130 and the slave LED driving unit 140 are devices for driving the respective channels Ch1 to Chm and include diodes D1 to Dm, switches T1 to Tm, (R1 to Rm).

Meanwhile, the master LED driving unit 130 and the slave LED driving unit 140 share the lowest voltage value in their own channel. For example, the slave LED driver 140 delivers voltage information MVS of the lowest channel (MinCh.) Having its lowest voltage value to the master LED driver 130. The power control unit 135 generates a power control signal GCS for adjusting the output voltage of the DC power supply unit 120 using the voltage information MVS and adjusts the output voltage of the DC power supply unit 120 based on the generated power control signal GCS .

The above description is described on the side of the LED drivers 130 and 140. However, on the side of the LED strings RS11 to RS1n, RS21 to RS2n, it is described that the voltage information MVS is configured based on the LED string having the highest voltage value among them. That is, the power supply control unit 135 controls the output voltage of the DC power supply unit 120 based on the LED string having the highest voltage value among the LED strings RS11 to RS1n and RS21 to RS2n.

As described above, the reason why the master LED driver 130 receives a specific voltage value and adjusts the output voltage of the DC power source 120 based on the specific voltage value is that the current supplied to each LED string is different. Therefore, if the specific voltage value (for example, the voltage information of the lowermost channel) is found, the voltage can be set as the reference (or representative value), and it is easy to adjust the output voltage of the DC power source 120 based on the voltage.

If one master LED driver 130 and the N slave LED drivers 140 share the voltage information MVS of the LED strings RS11 to RS1n and RS21 to RS2n, The master LED driving unit 130 and the N slave driving units 140 constitute a backlight unit driving unit (BDRV).

Accordingly, in the conventional liquid crystal display device, when the number of the LED driving units increases, the number of the DC power supply units also increases in proportion to the number of the LED driving units. However, in the liquid crystal display of the first embodiment, It is possible to increase the number of the light emitting diodes 140 only.

≪ Embodiment 2 >

8 is a configuration diagram of a backlight unit driving unit of a liquid crystal display device according to a second embodiment of the present invention.

As shown in FIG. 8, the liquid crystal display according to the second embodiment of the present invention includes a backlight unit BLU for providing light and a backlight unit driving unit (BDRV) for driving the backlight unit BLU.

The first LED strings RS11 through RS1n and the second LED strings RS11 through RS1n connected in parallel to the output terminal Vout of the DC power source unit 120 are connected to the LED strings RS11 through RS1n and RS21 through RS2n constituting the backlight unit BLU, The LED strings RS11 to RS1n and RS21 to RS2n are connected in series within the corresponding string of LEDs D1 to Dn included in the LED strings RS11 to RS1n and RS21 to RS2n, The anode electrodes of the first LEDs D1 included in the scan lines RS21 to RS2n are connected to the output terminal Vout of the DC power source unit 120 respectively and the cathode electrodes of the nLEDs Dn are connected to the channels of the LED drivers 130 and 140 (Ch1 to Chm).

One LED driver 130 and the second LED strings RS21 to RS2n for driving the first LED strings RS11 to RS1n are connected to the LED drivers 130 and 140 constituting the backlight unit driver BDRV, The master LED driver 130 and the slave LED driver 140 drive six LED strings using six channels, respectively, for example, and N (N is one or more) can do.

The DC power supply unit 120 constituting the backlight unit driving unit BDRV converts the first DC power inputted through the input terminal Vin into the second DC power and outputs the converted DC power through the output terminal Vout. The DC power supply unit 120 may be a conventional DC to DC converter, and may include an inductor, a transistor, a diode, a capacitor, and the like. The DC power supply unit 120 boosts the power of the transistor based on the power control signal GCS supplied from the master LED driving unit 130 so that the input power is boosted and output.

The master LED driver 130 independently drives the first LED strings RS11 to RS1n connected to the channels Ch1 to Chm and the slave LED driver 140 also drives its own channels Ch1 to Chm, And drives the second LED strings RS21 to RS2n connected to the second LED strings independently.

The master LED driving unit 130 and the slave LED driving unit 140 share the voltage information MVS of the LED strings RS11 to RS1n and RS21 to RS2n that are driven by the communication method. The master LED driving unit 130 supplies the DC power supply unit 120 with a power supply control signal GCS that can control the output voltage of the DC power supply unit 120 using the shared voltage information MVS. At this time, the master LED driving unit 130 controls the output voltage of the DC power supply unit 120 based on the LED string having the highest voltage value among the shared voltage information MVS.

To this end, the master LED driving unit 130 and the slave LED driving unit 140 include communication units Com1 and Com2 that can mutually share the voltage information MVS in a mutual communication manner. The slave LED driver 140 transmits all the voltage information MVS of the LED strings driven by the slave LED driver 140 to the master LED driver 130 in a communication manner.

Meanwhile, the first embodiment mutually shares the voltage information MVS of the LED strings RS11 to RS1n, RS21 to RS2n in such a manner that terminals related to the channel having the lowest voltage value are interconnected. Therefore, in the first embodiment, each LED driver 130 and 140 share the voltage information MVS for one channel, so that the master LED driver 130 drives all the LED strings RS11 to RS1n, It may be difficult to control the output voltage of the DC power supply unit 120 based on the voltage information MVS of the RS2n.

On the other hand, the second embodiment mutually shares voltage information MVS of the LED strings RS11 to RS1n and RS21 to RS2n in a communication manner. Therefore, in the second embodiment, the LED drivers 130 and 140 can share the voltage information MVS for all the channels, so that the master LED driver 130 drives the entire LED strings RS11- The output voltage of the DC power supply unit 120 can be easily controlled based on the voltage information MVS of the RSs RS1n and RS21 to RS2n.

If one master LED driver 130 and the N slave LED drivers 140 share the voltage information MVS of the LED strings RS11 to RS1n and RS21 to RS2n, The master LED driving unit 130 and the N slave driving units 140 constitute a backlight unit driving unit (BDRV).

In the conventional liquid crystal display device, the number of direct-current power sources increases in proportion to the number of LED driving units. However, in the liquid crystal display of the second embodiment of the present invention, the number of direct- It is possible to increase the number of the light emitting diodes 140 only. In addition, the second embodiment can easily control the output voltage of the DC power supply unit 120 based on the voltage information MVS for all channels, and can perform more precise power control.

The embodiment of the present invention has an effect of providing a liquid crystal display device which can reduce the cost in constituting the device because only one direct current power source part is required even if a plurality of LED driving parts are used. In addition, the embodiment of the present invention can independently drive the LED strings connected to the respective channels by one master LED driving unit and a plurality of slave LED driving units interlocked with one DC power supply unit, and can precisely control the output voltage of the DC power supply unit There is an effect of providing a liquid crystal display device capable of controlling the liquid crystal display device.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

TCN: timing driver PNL: liquid crystal panel
SDRV: Gate driver DDRV: Data driver
BLU: Backlight Unit BDRV: Backlight Unit Driver
120: DC power supply unit 130: Master LED driving unit
140: Slave LED driver Ch1 to Chm:
GCS: Power control signal Chs: Voltage information sharing terminal
Com1, Com2:

Claims (11)

A liquid crystal panel;
LED strings connected in parallel to an output terminal of the DC power supply unit and providing light to the liquid crystal panel; And
One master LED driver having channels for driving first LED strings and N LED drivers including N (N is one or more) slave LED drivers having channels for driving second LED strings,
The master LED driving unit and the slave LED driving unit are electrically connected to each other to mutually share voltage information of LED strings driven by the master LED driving unit and the slave LED driving unit,
The master LED driver and the slave LED driver
A transistor for sinking a current input through each channel,
A comparator for monitoring a current flowing through the transistor and supplying a driving signal to a gate electrode of the transistor,
And a drive signal generator for generating the drive signal,
The master LED driver
And a power supply control unit for supplying a power supply control signal for controlling an output voltage of the DC power supply unit,
Wherein the power control unit controls an output voltage of the direct current power unit based on an LED string having the highest voltage value among the shared voltage information. delete delete The method according to claim 1,
The master LED driver and the slave LED driver
And the voltage information of the LED strings driven by the LED strings is mutually shared. 5. The method of claim 4,
The slave LED driver
And transmits the lowest voltage value to the master LED driving unit. delete delete delete The method according to claim 1,
The master LED driver and the slave LED driver
And the voltage information of the LED string driven by itself is mutually shared by the communication method. 10. The method of claim 9,
The slave LED driver
And transmits all the voltage information of the LED strings driven by itself to the master LED driving unit in the communication mode. The method according to claim 1,
The master LED driver and the slave LED driver
And are electrically connected to each other through a voltage information sharing terminal.

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