KR100806851B1 - Back light unit for liquid crystal display - Google Patents

Abstract

A backlight unit for an LCD(Liquid Crystal Display) is provided to adopt a low-priced HCFL(Hot Cathode Fluorescent Lamp) as a light source of the backlight unit and control lighting of the HCFL by varying a driving frequency of a resonant tank and an inverter as continuously applying power to both ends of the HCFL, thereby preventing deterioration of life caused by frequent power shut-down as a weak point of the HCFL. A burst MCU(Micro Control Unit)(14) receives a synchronizing signal from a video board(10) or a power board of an LCD(Liquid Crystal Display), and outputs a driving pulse which is synchronized with the synchronizing signal and sequentially generated according to each channel. A scanning MCU(16) is installed according to each channel, and outputs an inverter driving frequency having a light frequency interval and a non-light frequency interval in correspondence with the driving pulse by channel outputted from the burst MCU. An inverter driver(18) generates the switching frequency as the frequency outputted from the scanning MCU, and converts the switching frequency into a square wave to be outputted. An LC(Liquid Crystal) resonant tank(20) causes resonances of the square wave outputted from the inverter driver, and converts the square wave into a sine wave to be outputted. An HCFL(Hot Cathode Fluorescent Lamp)(22) is lightened and driven by the output of the LC resonant tank.

Description

Back light unit for liquid crystal display

1 is a block diagram showing an example of a backlight unit according to the present invention;

2 is a circuit diagram illustrating a circuit configuration of a power supply unit;

3 is a circuit diagram illustrating a circuit configuration of a burst MCU

4 is a time chart showing the output pulse waveform of the burst MCU

5 is a circuit diagram illustrating a circuit configuration of a scanning MCU.

6 is a time chart showing the initial operating frequency waveform of the scanning MCU

7 is a time chart showing the output frequency waveform of the scanning MCU

8 is a circuit diagram showing an inverter configuration of the present invention

<Explanation of symbols for the main parts of the drawings>

10: video board 12: power supply

14: Burst MCU 16: Scanning MCU

18: Inverter driver 20: LC resonant tank

22: HCFL 24: protection circuit

26: converter MCU 28: isolated communication unit

The present invention relates to a backlight unit mounted on a liquid crystal display device, and more particularly, to reduce the size and weight of a device and to significantly reduce manufacturing costs, thereby improving product competitiveness, eliminating motion blur of an LCD, and greatly improving contrast ratio. A backlight unit for a liquid crystal display device.

In general, since a liquid crystal display (LCD) does not emit light by itself, light emitting means such as a back light unit (BLU) is mounted on a rear surface of the LCD to improve visibility of the LCD. Conventionally, as a backlight unit, a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) is used, and an attempt has been made to use some LEDs (Light Emitting Diode).

First, when the CCFL is adopted as the BLU, there is a problem in that an inverter used as a power supply device for driving the CCFL is enlarged. As a result, the BLU device becomes larger and the manufacturing cost increases, which hinders the compactness and weight of the LCD, which reduces the competitiveness of the product.

In addition, when the EEFL is adopted as a BLU, there is an advantage that the inverter device can be designed smaller than the CCFL, but the brightness is lower than the CCFL, the problem of the reliability of the external electrode is generated, and due to the use of square wave power As a product, there is a problem that inadequate EMI noise is generated.

On the other hand, when LED (Light Emitting Diode) is applied to BLU, it shows no burden on inverter device and shows excellent performance in color reproducibility and lifespan, but it is difficult to popularize LCD due to burden on relatively high manufacturing cost, It is difficult to cope with this when one of the LED's is broken, and there is a problem that the luminance decreases significantly when the heat is generated. Therefore, the LED is not suitable as a light source of the BLU.

LCDs, as is well known, are not self-luminous devices and thus cause some problems. As an example, as switched by the TFT, the LC panel simultaneously realizes a bright image and a dark image. In this case, when the luminance of the BLU is fixed, the LCD displays a low contrast ratio compared to other self-luminous devices. In addition, when the image implemented in the LC panel is rapidly changed, a motion blur occurs. These problems can be partially improved by improving the characteristics of the LCD panel itself (material, structure, and driving method), but ultimately, the response time is long and the dimming control is limited in the BLU represented by CCFL or EEFL. The limit is showing.

The present invention has been proposed in order to solve the above problems, but the HCFL (Hot Cathode Fluorescent Lamp), which shows high light output with a simple driving circuit and has long been the know-how of the technology, is applied as a light source of a BLU, Correspondingly, by varying the operating frequencies of the inverter and resonant tanks of each channel to control the lighting of the HCFL, HCFL with excellent light efficiency and low cost can be applied as the light source of the backlight unit, which aims to reduce the size and weight of LCD. It is an object of the present invention to provide a backlight unit for a liquid crystal display device that can reduce the manufacturing cost and improve the product competitiveness of the LCD.

In addition, the present invention by sequentially scanning the burst signal for each channel synchronized with the video signal of the LCD by driving the HCFL of each channel sequentially, thereby solving the motion blur phenomenon of the LCD through the lighting control of the backlight unit For the purpose of

In addition, the present invention provides a dimming control that is linked to the LCD image signal using the HCFL response time is quick and easy to control compared to the CCFL or EEFL, to solve the problem of contrast ratio degradation and motion blur phenomenon of the conventional LCD For the purpose of

A backlight unit for a liquid crystal display device of the present invention for achieving the above object is mounted on the back of the liquid crystal display device, the backlight unit for a liquid crystal display device having an inverter and a lamp for each of a plurality of channels; A burst MCU that receives a synchronization signal from an image board or a power board of a liquid crystal display device and synchronizes with the synchronization signal and outputs a driving pulse sequentially generated for each channel, and a driving pulse for each channel that is installed for each channel and output from the burst MCU A scanning MCU for outputting an inverter driving frequency having a lighting frequency section and a non-lighting frequency section corresponding to the inverter, an inverter driver generating a switching frequency equal to the frequency output from the scanning MCU and converting the square wave into a square wave; It characterized in that it comprises a LC resonant tank for resonating the output square wave to convert to a sinusoidal wave, and HCFL is turned on by the output of the LC resonant tank.

According to an embodiment of the present invention, the burst MCU further receives a dimming signal from the image board or power board, and changes the width of the driving pulse in response to the voltage level of the dimming signal to perform dimming control.

According to another embodiment of the present invention, the burst MCU further receives a dimming signal from the image board or the power board, the scanning MCU to increase or decrease the frequency of the lighting frequency section in response to the dimming signal to output dimming control Is carried out.

Preferably, an insulation communication unit is installed between the video board or power board and the burst MCU to insulate and communicate signals between the video board or the power board.

In addition, a converter MCU for converting an analog signal transmitted from an image board or a power board into a digital signal may be further connected to the front end of the insulation communication unit.

More preferably, the driving frequency output from the scanning MCU is linearly changed between the lighting frequency section and the non-lighting frequency section.

In addition, the scanning MCU generates a preheating frequency for a predetermined time so as to preheat the filament of the HCFL at the beginning of the driving pulse flow from the burst MCU, and then outputs an inverter driving frequency corresponding to the driving pulse of the burst MCU.

In addition, the inverter driver includes a buffer for removing noise components from the inverter driving frequency output from the scanning MCU.

Preferably, the protection circuit unit is connected between the LC resonant tank and the scanning MCU and detects whether the resonant terminal voltage of the LC resonant tank rises to an overvoltage higher than a predetermined voltage. Stop the corresponding inverter channel.

The apparatus may further include a protection circuit unit connected between the HCFL and the scanning MCU and detecting whether the HCFL is normally connected. When the protection circuit unit detects no load on the HCFL side, the scanning MCU stops the corresponding inverter channel.

In addition, when the scanning MCU detects an overvoltage on the LC resonant tank side or no load on the HCFL side in the protection circuit unit, the scanning MCU transmits a stop state of the corresponding inverter channel to the burst MCU, and the burst MCU displays the stopped inverter channel information. It transfers to the board, and the video board displays the A / S message to the user.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and embodiments. 1 is a block diagram illustrating an example of a backlight unit according to the present invention, FIG. 2 is a circuit diagram illustrating a circuit configuration of a power supply unit, FIG. 3 is a circuit diagram illustrating a circuit configuration of a burst MCU, and FIG. 4 is a diagram of a burst MCU. Figure 5 is a time chart showing the output pulse waveform, Figure 5 is a circuit diagram illustrating the circuit configuration of the scanning MCU, Figure 6 is a time chart showing the initial operating frequency waveform of the scanning MCU, Figure 7 shows the output frequency waveform of the scanning MCU 8 is a circuit diagram showing the inverter configuration of the present invention.

First, the backlight unit for the liquid crystal display device of the present invention uses HCFL as a core technical idea. HCFL is a lamp that uses a filament as an electrode to excite the phosphor inside the tube and emit light by hot electron emission of the filament. The lamp is excellent in light efficiency, easy to control, and has accumulated long-time technical know-how. However, due to the problem of shortening the lifespan during frequent interruptions of the power source, it has been difficult to be conventionally applied to the backlight unit of the LCD. The present invention overcomes the shortcomings of HCFL and utilizes the advantages of HCFL to the maximum and applies to backlight units.

To turn on the HCFL, an LC resonant tank is used. The LC resonant tank is configured to generate a resonant frequency for turning on the HCFL, and the HCFL cannot be turned on at the maximum luminance at frequencies other than the resonant frequency. For example, HCFL having a resonant frequency of 70 kHz is lit at maximum luminance when 70 kHz is supplied by the LC resonant tank. However, when a frequency of 170 kHz is supplied, the light is turned on with a very low luminance so that the lighting cannot be discerned by the naked eye. The present invention uses the characteristics of the HCFL, by continuously supplying power to the filament, which is the electrode of the HCFL to maintain the filament is heated state by varying the driving frequency of the HCFL, generating the lighting section and the non-illumination section of the HCFL To generate an effect of turning on / off the backlight unit. In addition, the present invention receives a synchronization signal from the image board of the TV in order to eliminate the motion blur phenomenon of the LCD and correspondingly drive the plurality of inverters in turn sequentially.

1 to 8 illustrate a backlight unit equipped with 14 channels of inverter and HCFL based on a 40-inch LCD.

First, FIG. 1 is a block diagram schematically showing a circuit configuration of the present invention. Referring to the present invention, the present invention provides a power supply unit 12, a burst MCU (Micro Control Unit) 14, a scanning MCU 16, and an inverter driver 18. Referring to FIG. ), LC resonant tank 20, HCFL 22, protection circuit 24, converter MCU 26, and isolated communication unit 28.

The power supply unit 12 is a configuration for supplying power to the entire circuit. In one embodiment of the present invention, the backlight unit uses an independent power source, but may be operated by receiving power from the LCD TV. Referring to the circuit example shown in Figure 2, using an active filter rectifier circuit is input to AC 90 ~ 260V to maintain a constant voltage circuit, DC 3.6V, the driving voltage of the burst MCU 14 and scanning MCU 16, DC 5V which is the driving voltage of the protection circuit section 24 and other logic circuits, and AC 380V which is the driving voltage of the inverter are output. The power supply unit 12 operates when AC power is applied to the TV set on which the LCD is mounted, for example, when AC 220V, which is a commercial AC power for home use, is supplied with the AC power from the TV SET. When the commercial AC power is input, the constant voltage is maintained in the active filter rectifier circuit including the bridge diode D4, and the output of the rectifier circuit is PWM (Pulse Width Modulation) at U1 to convert the reflux voltage of the coil T2 to the capacitor EC5. The DC constant voltage is boosted to AC 380V and output. AC 380V is output to the inverter of each channel. In addition, the output of the rectifier circuit is converted to DC 3.6V and DC 5V through the switching mode power supply (SMPS) T1, DC 3.6V is supplied to the drive power of the burst MCU 14 and scanning MCU 16, DC 5V is supplied to the driving power of each logic circuit.

3 is a circuit diagram illustrating a burst MCU 14. Referring to this, the burst MCU 14 applies a signal from an image board 10 or a power board (in the following embodiment, an image board) of a TV equipped with an LCD. Receiving a 60 Hz synchronization signal, and outputs a drive pulse synchronized with the synchronization signal and sequentially generated for each channel. In addition, a dimming signal of 0V to 3.3V is applied from the image board 10 to perform dimming control. In this case, in order to insulate the signal between the image board 10 and the burst MCU 14, an insulation communication unit 28 is installed between the image board 10 and the burst MCU 14. The isolated communication unit 28 is composed of an IC such as a photocoupler, and communicates signals with the TP10 and TP11 terminals of the burst MCU 14 in the circuit diagram shown in FIG. 3. In addition, the synchronizing signal and the dimming signal may be designed to be transmitted as a digital signal in the image board 10. Preferably, the signal from the image board 10 is transmitted as an analog signal, and the converter in front of the insulated communication unit 28. The MCU 26 is installed to convert the synchronization signal and the dimming signal into a digital signal and transmit the digital signal to the isolated communication unit 28.

In this embodiment, a single burst MCU 14 addresses each of the 14 channels of scanning MCU 16 via the BUR1 to BUR14 terminals. In addition, the driving pulse is output as shown in FIG. 4 through the RX and TX terminals according to the synchronization signal received through the TP10 and TP11 terminals. Referring to the time chart of FIG. 4, in this embodiment, the driving pulse of the CH1 inverter is the same 60 Hz pulse as the synchronization signal received from the image board 10, the on time is 3 ms, and the off time is 13.7 ms. The driving pulse of the CH2 inverter is a pulse with a time difference of approximately 1.1 ms compared to the CH1 inverter. The frequency of the pulse is 60 Hz, the on time is 3 ms, and the off time is 13.7 ms. The burst MCU 14 sequentially generates and outputs an inverter driving pulse from CH1 to CH14, and correspondingly, the scanning MCU 16 of each channel receives a driving pulse corresponding to its own address to drive the inverter driving frequency. Outputs On the other hand, the burst MCU 14 is a process of receiving and processing the dimming signal from the image board 10 will be described later.

FIG. 5 is a circuit diagram illustrating a scanning MCU 16. The scanning MCU 16 is installed one for each channel, and the embodiment of FIG. 5 illustrates only one scanning MCU 16 of one channel. Referring to this, the scanning MCU 16 receives a driving pulse output through the RX and TX terminals of the burst MCU 14, determines whether it is a signal corresponding to its own address, and if it corresponds to its own address. Outputs inverter drive frequency of the channel through CEX01 terminal. The scanning MCU 16 has a preheating mode for preheating the filament which is the electrode of the HCFL 22 when the initial driving pulse is introduced from the burst MCU 14 before outputting the driving frequency. 6 is a time chart showing the frequency waveform output from the scanning MCU 16 when the scanning MCU 16 is operated in the preheating mode. Referring to this, the scanning MCU 16 is operated in a stand-by state by receiving power from the power supply unit 12 when power is applied to the TV SET. When the driving pulse is output from the burst MCU 14 while maintaining the stand-by state, a frequency of 130 kHz is output in the preheating section for approximately 0.7 seconds. In this section, the HCFL 22 is not driven and only the filament is preheated. Thereafter, a frequency of 90 to 80 kHz is output in the lighting period of about 0.3 seconds. In this section, the current of the HCFL 22 gradually increases, and the HCFL 22 is turned on. This preheat mode operation is performed only at the initial stage when the scanning MCU 16 is enabled, and then the scanning MCU 16 is operated in a normal lighting mode.

7 is a time chart showing the frequency output waveform of the scanning MCU 16. Referring to this, when the scanning MCU 16 operates in the normal lighting mode after the preheating mode as described above, the scanning MCU 16 is powered on the HCFL 22 and the lighting frequency section in which the HCFL 22 is turned on. The inverter drive frequency in the non-lighting frequency range in which the HCFL 22 is not lit (actually lit with extremely low luminance) is output. That is, in response to the driving pulse sequentially output from the burst MCU 14, as shown in FIG. 7, the MIN frequency of 70 kHz corresponding to the resonance frequency of the HCFL 22 is output at the ON time of the driving pulse, and driving is performed. During the OFF time of the pulse, a voltage is applied to both ends of the HCFL 22, but the MAX frequency of 170 kHz is output in which the HCFL 22 is turned on with extremely low luminance. More preferably, the lighting frequency section of 70 kHz and the non-lighting frequency section of 170 kHz are changed linearly, as shown. Therefore, the noise of the inverter output transformer, the impact of the lamp, and the flicker phenomenon are prevented.

In the present invention, the process of processing the dimming signal from the image board 10 is as follows. First, the dimming signal of 0 to 3.3V output from the video board 10 is applied to the input side of the burst MCU 14 as a digital signal of a predetermined level through the converter MCU 26 and the insulation communication unit 28, and the burst MCU (14) adjusts and outputs the ON type width of a drive pulse. Correspondingly, the width of the lighting frequency section of the scanning MCU 16 is reduced to perform dimming control.

On the other hand, the dimming control may be performed by the lighting frequency variable method, not the pulse width modulation method as described above. In this case, the scanning MCU 16 adjusts the frequency of the lighting frequency section to 70 kHz or more according to the level of the dimming signal. For example, dimming control is performed by raising or decreasing the frequency of the lighting frequency section to 70 kHz to 170 kHz, changing the driving frequency of the HCFL 22 to adjust the luminance level of the HCFL 22.

FIG. 8 is a circuit diagram illustrating the configuration of an inverter, and illustrates an inverter of a single channel among a total of 14 channels of inverters. Referring to this, the inverter driver 18 alternately switches and controls two switching elements Q101 and Q102 according to the frequency received from the scanning MCU 16 through the CEX01 terminal, and outputs an AC square wave. At this time, the input terminal of the inverter driver 18 is provided with a buffer (U102) for removing noise from the output frequency waveform of the scanning MCU 16, to remove the noise component from the output of the scanning MCU (16). The AC square wave output from the inverter driver 18 is induced into the LC resonant tank 20, and is converted into a sine wave through the T101 and C103 series resonant circuits of the LC resonant tank 20. To be organic. At this time, the load side current is limited to C108 to prevent the load side abnormal voltage.

Referring to the circuit diagram of FIG. 8, the protection circuit unit 24 detects the resonant stage overvoltage from the LC resonant tank 20 and detects whether or not no load is applied from the HCFL 22 through a lamp fastening state.

First, in the circuit diagram of FIG. 8, the presence or absence of resonant stage overvoltage is monitored through D103. Usually, the resonant stage voltage of the LC resonant tank 20 rises together due to the increase of the lamp side voltage at the end of the lamp life or at an abnormal state. D103 of the LC resonant tank 20 decompresses the normal load state to 2.5 to 2.8V, which rises to 5V at the end of its life. The D103 output terminal of the LC resonant tank 20 is connected to the comparator U104 side of the protection circuit unit 24. The comparator U104 compares the reference voltage with the resonant end voltage of the LC resonant tank 20, so that the resonant end voltage is increased. If it rises above the reference voltage, it outputs H level through the PRTB1 terminal. Then, in the circuit diagram of FIG. 5, the H level is applied through the PRTB1 input terminal of the scanning MCU 14, and the scanning MCU 16 shuts down the inverter circuit through the MUTE terminal.

In addition, the presence or absence of normal connection of HCFL 22 is detected through D104 and D105 connected to both ends of LAMP101. If either side of the lamp is stuck due to lamp contact failure, breakage, incorrect wiring, etc., connect the PRTA1 terminal to the NAND gate (U103) of the protection circuit section 24 whose input pin is connected to the output terminals of D104 and D105. Through outputting the H level, the scanning MCU 16 stops the drive frequency output as above, and shuts down the inverter circuit through the MUTE terminal.

On the other hand, the scanning MCU 16 shuts down the inverter circuit, and then transfers this information to the burst MCU 14 side. The burst MCU 14 transmits load side overvoltage or no load state information to the image board 10 of the TV SET. send. Thereafter, the image board 10 outputs an A / S message to the user to inform the failure state.

The present invention described above is to solve the motion blur of the LCD by applying the HCFL to the backlight unit, and sequentially turn on and drive the HCFL of each channel, this embodiment has been described in this embodiment, the characteristics of the present invention In order to prevent dilution, a detailed circuit configuration, etc., which are obvious to those skilled in the art, will be omitted.

In addition, the present invention is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible in the technical field of the present invention without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

As described above, the backlight unit for a liquid crystal display device according to the present invention has a high light output of an individual light source, enables a compact design of an inverter, and a manufacturing cost, compared to a CCFL or an EEFL, which has been used as a light source of a conventional backlight unit. Inexpensive HCFL is adopted as a light source of the backlight unit, but by continuously applying power to both ends of the HCFL, the drive frequency of the inverter and the resonant tank is controlled to control the lighting of the HCFL, which reduces the lifespan due to frequent power interruptions, which is a disadvantage of the HCFL. It is possible to prevent the small size and light weight of the LCD, and significantly reduce the manufacturing cost has the effect of greatly improving the product competitiveness of the LCD.

In addition, according to the present invention, by using the HCFL response time is very fast and easy to control, the HCFL of each channel is sequentially turned on through the driving pulse for each channel sequentially generated in synchronization with the video signal of the TV SET video board It is possible to solve the motion blur phenomenon of LCD through the lighting control of backlight unit, and to control the brightness level of HCFL by controlling dimming level of HCFL in conjunction with the dimming signal of video board. Has

Further, according to the present invention, by linearly increasing or decreasing the frequency change between the lighting frequency section and the non-lighting frequency section in the frequency output from the scanning MCU, to prevent the output transformer noise of the inverter, minimize the HCFL side impact, It has an effect that can prevent the flicker phenomenon commonly occurring in the.

In addition, according to the present invention, the inverter circuit is shut down by detecting the resonance state of the resonant stage of the LC resonant tank and the HCFL binding state, thereby protecting the inverter circuit from the overvoltage, load side overvoltage, and no-load state at the end of the life of the HCFL. Have

Claims (11)

A backlight unit for a liquid crystal display device mounted on a rear surface of a liquid crystal display device, the backlight unit having an inverter and a lamp for each of a plurality of channels; A burst MCU that receives a synchronization signal from an image board or a power board of a liquid crystal display device and synchronizes with the synchronization signal and outputs driving pulses sequentially generated for each channel; A scanning MCU installed for each channel and outputting an inverter driving frequency having a lighting frequency section and a non-lighting frequency section corresponding to the driving pulse for each channel output from the burst MCU; An inverter driver generating a switching frequency equal to the frequency output from the scanning MCU and converting the square wave into output; An LC resonance tank for resonating a square wave output from the inverter driver and converting the square wave into a sine wave; Backlight unit for a liquid crystal display device characterized in that it comprises a HCFL is driven to be turned on by the output of the LC resonant tank. The method of claim 1, The burst MCU further receives a dimming signal from the image board or power board, and changes the width of the driving pulse in response to the voltage level of the dimming signal, the backlight unit for a liquid crystal display device. The method of claim 1, The burst MCU further receives a dimming signal from the image board or the power board, the scanning MCU is a backlight unit for a liquid crystal display device, characterized in that to increase or decrease the frequency of the lighting frequency section in response to the dimming signal. The method according to any one of claims 1 to 3, The backlight unit for the liquid crystal display device, characterized in that an insulating communication unit for insulated and communicate between the video board or the power board and the burst MCU is installed. The method of claim 4, wherein And a converter MCU further converting an analog signal transmitted from an image board or a power board into a digital signal in front of the insulation communication unit. The method of claim 1, The driving frequency output from the scanning MCU is a backlight unit for a liquid crystal display device, characterized in that the lighting frequency section and the non-illumination frequency section is changed linearly. The method of claim 1, The scanning MCU generates a preheating frequency for a predetermined time so as to preheat the filament of the HCFL at the beginning of the driving pulse flow from the burst MCU, and then outputs an inverter driving frequency corresponding to the driving pulse of the burst MCU. Backlight unit for a liquid crystal display device. The method of claim 1, The inverter driver includes a buffer for removing a noise component from the inverter drive frequency output from the scanning MCU, the backlight unit for a liquid crystal display device. The method of claim 1, And a protection circuit unit connected between the LC resonant tank and the scanning MCU and detecting whether the resonant terminal voltage of the LC resonant tank rises to an overvoltage higher than a predetermined voltage. When the overvoltage is detected by the protection circuit unit, the scanning MCU detects the corresponding inverter channel. A backlight unit for a liquid crystal display device, characterized in that for stopping. The method of claim 1, And a protection circuit unit connected between the HCFL and the scanning MCU and detecting whether the HCFL is normally connected, and when the protection circuit unit detects no load on the HCFL side, the scanning MCU stops the corresponding inverter channel. Backlight unit for display device. The method according to claim 9 or 10, When the protection MCU detects an overvoltage on the LC resonant tank side or no load on the HCFL side, the scanning MCU transmits a stop state of a corresponding inverter channel to the burst MCU, and the burst MCU transmits the stopped inverter channel information to an image board. The backlight unit for transmitting a liquid crystal display device, characterized in that for transmitting the A / S message screen to the user.

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