KR101705366B1 - Back Light Unit and Liquid Crystal Display Device Using the same - Google Patents

Abstract

According to an embodiment of the present invention, there is provided an electronic apparatus comprising: a DC power supply unit for generating a DC power supply voltage; Light emitting units including light emitting diodes connected in series to a power supply wiring connected to an output terminal of the direct current power supply unit; A common wiring connected to the ground wiring to form a node connecting the cathode electrodes of the light emitting portions in common; A current inducing unit for inducing a current flowing in the common wiring; And a power source control unit for controlling an output of the DC power source unit using a current derived from the current induction unit.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THE Same,

Embodiments of the present invention relate to a backlight unit and a liquid crystal display using the same.

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 transistor substrate on which a thin film transistor, a storage capacitor, a pixel electrode, and the like are formed, and a liquid crystal layer disposed between the color filter substrate and the color filter substrate on which the color filter and the black matrix are formed. The liquid crystal display displays images in such a manner that light incident from the backlight unit is emitted by adjusting the arrangement direction of the liquid crystal layer on the electric field applied to the pixel electrode, the transistor substrate, or the common electrode formed on the color filter substrate.

The backlight unit has a structure in which a plurality of light emitting diodes (LEDs) having the same temperature characteristics are arranged. In the case of a light emitting diode included in a backlight unit, power consumption during driving is minimized by using a switching device having low power consumption for dimming. However, since the light emitting diode is a device in which the power supply voltage deviation Vf changes according to the temperature, the current varies depending on the temperature. Accordingly, a method of controlling a power supply voltage deviation (Vf) of a light emitting diode by using a field effect transistor (FET) and a sensing resistor has been proposed in the related art. However, this method is required to improve the power consumption.

An embodiment of the present invention for solving the problems of the background art described above is to provide a backlight unit capable of minimizing power consumption and reducing a manufacturing cost and a liquid crystal display device using the same.

According to an embodiment of the present invention, there is provided a power supply circuit comprising: a DC power supply for generating a DC power supply voltage; Light emitting units including light emitting diodes connected in series to a power supply wiring connected to an output terminal of the direct current power supply unit; A common wiring connected to the ground wiring to form a node connecting the cathode electrodes of the light emitting portions in common; A current inducing unit for inducing a current flowing in the common wiring; And a power source control unit for controlling an output of the DC power source unit using a current derived from the current induction unit.

The current guiding portion may be an inductor or a transformer.

If the current induced from the current induction unit is higher than the previously induced current, the power control unit lowers the DC power supply voltage output from the DC power supply unit. If the current induced from the current induction unit is lower than the previously induced current, A control signal for increasing the DC power supply voltage to be supplied to the DC power supply unit.

The power supply control unit may include a rectification unit for converting the current derived from the current induction unit and a control unit for comparing the current converted by the rectification unit with the reference set in the rectification unit and controlling the DC power supply unit according to the comparison result.

The light emitting diodes may further include switches between one of the cathode electrodes of the light emitting diodes and one of the common electrodes of the light emitting diodes, and the other ends of the light emitting diodes are commonly connected to the common electrode.

The on / off times of the switches can be controlled in accordance with the pulse width signal supplied from the outside.

According to another aspect of the present invention, there is provided a liquid crystal display device comprising: a liquid crystal panel; And a backlight unit for supplying light to the liquid crystal panel, wherein the backlight unit includes: a direct current power source for generating a direct current power source voltage; light emitting units including light emitting diodes connected in series to a power source wiring connected to an output terminal of the direct current power source; A common induction portion connected to the ground wiring, a current induction portion for inducing a current flowing through the common wiring, and a power source for controlling the output of the direct current power source portion by using a current induced from the current induction portion, A liquid crystal display device including a controller is provided.

The current guiding portion may be an inductor or a transformer.

If the current induced from the current induction unit is higher than the previously induced current, the power control unit lowers the DC power supply voltage output from the DC power supply unit. If the current induced from the current induction unit is lower than the previously induced current, A control signal for increasing the DC power supply voltage to be supplied to the DC power supply unit.

The power supply control unit may include a rectification unit for converting the current derived from the current induction unit and a control unit for comparing the current converted by the rectification unit with a reference set in the rectification unit and controlling the DC power supply unit according to the comparison result.

The embodiment of the present invention provides a backlight unit capable of minimizing the power consumption due to the constant current control and requiring only one DC power source unit so that the manufacturing cost can be reduced when there are many light emitting diodes and a liquid crystal display using the backlight unit .

1 is a block diagram of a liquid crystal display according to an embodiment of the present invention;
2 is a block diagram of a gate driver;
3 is a block diagram of a data driver;
4 is a partial configuration view of a backlight unit according to an embodiment of the present invention.
5 is a detailed view of a part of a backlight unit according to an 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 according to an embodiment of the present invention, 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 according to an exemplary embodiment of the present invention 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 driving unit (BDRV).

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 control signals generated in the timing driver TCN include 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. ) May be included. The gate timing control signal GDC includes a gate start pulse GSP, a gate shift clock GSC and a gate output enable signal GOE. The gate start pulse GSP is supplied to a gate drive IC (Integrated Circuit) generating the first gate signal. The gate shift clock GSC is a clock signal commonly input to the gate drive ICs, and is a clock signal for shifting the gate start pulse GSP. The gate output enable signal GOE controls the output of the gate drive ICs. The data timing control signal DDC includes source start pulses (Source, Start Pulse, SSP), Source Sampling Clock (SSC), Source Output Enable (SOE), and the like. The source start pulse SSP controls the data sampling start timing of the data driver DDRV. The source sampling clock SSC is a clock signal for controlling the sampling operation of data in the data driver DDRV based on the rising or falling edge. The source output enable signal SOE controls the output of the data driver DDRV. On the other hand, the source start pulse SSP supplied to the data driver DDRV may be omitted depending on the data transfer method.

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. One subpixel SP is defined by the intersecting data line DL1 and the gate line SL1. 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. Each of the gate drive ICs includes a shift register 61, a level shifter 63, a plurality of AND gates 62 connected between the shift register 61 and the level shifter 63, And an inverter 64 for inverting the gate output enable signal GOE. 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 AND 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 includes a light source circuit portion including a direct current power source, a light emitting portion, a current induction portion, and a power source control portion, and an optical mechanism including a cover bottom, a light guide plate, and an optical sheet. The backlight unit (BLU) may be variously configured as an edge type, a dual type, a direct type, and the like. In the edge type, the light emitting diodes are arranged in a line (or string) shape on one side of the liquid crystal panel PNL. In the dual type, light emitting diodes are arranged in a line (or string) form on both sides of a liquid crystal panel (PNL). In the direct type, light emitting diodes are arranged in a block or matrix form in the lower part of the liquid crystal panel (PNL).

The backlight unit driving unit BDRV receives a data signal DATA and a dimming signal Dim from a timing controller TCN or an external system board and generates a pulse width signal PWM Thereby driving the unit BLU. The backlight unit driver BDRV global dims or local dims the backlight unit BLU using the pulse width signal PWM.

Hereinafter, the backlight unit according to one embodiment of the present invention will be described in more detail.

FIG. 4 is a partial configuration view of a backlight unit according to an embodiment of the present invention, and FIG. 5 is a detailed view of a backlight unit according to an embodiment of the present invention.

4, a backlight unit according to an exemplary embodiment of the present invention includes a DC power source DCDC, light emitting units DP1 to DPn, switches SW1 to SWn, a current induction unit 170, 150).

The DC power supply unit DCDC may be configured as a DC to DC converter that converts a first DC power supply voltage to a second DC power supply voltage (hereinafter referred to as a DC power supply voltage) and controls the constant voltage and the constant current . The DC power supply unit DCDC outputs the DC power supply voltage generated through the power supply wiring VCC connected to the output terminal.

The light emitting units DP1 to DPn include light emitting diodes D1 to Dn connected in series to the power supply line VCC connected to the output terminal of the DC power supply unit DCDC. The anode electrodes of the light emitting units DP1 to DPn are connected in parallel to the power supply line VCC. Here, one light emitting portion DP1 is referred to as an "LED String ".

The switches SW1 to SWn are connected at one ends to the cathode electrodes of the nth light emitting diodes Dn included in the light emitting units DP1 to DPn and the other ends thereof are commonly connected to the common line COM. The ON / OFF times of the switches SW1 to SWn are controlled in accordance with the pulse width signal PWM supplied from the backlight unit driving unit BDRV of FIG. 1, for example, the first to the n-th pulse width signals PWM1 to PWMn. The light emitting units DP1 to DPn emit light in global dimming or local dimming according to on / off time control of the switches SW1 to SWn. The widths of the first to n-th pulse width signals PWM1 to PWMn supplied to the global dimming switches SW1 to SWn are the same, but the first to n-th pulse width signals PWM1 to PWMn, which are supplied to the local dimming switches SW1 to SWn, The widths of the n-th pulse width signals (PWM1 to PWMn) are between 0% and 100%, so they may be the same or different.

The common line COM forms a node connecting all the cathode electrodes of the nth light emitting diodes Dn located at the ends of the light emitting diodes D1 to Dn included in the light emitting units DP1 to DPn And is connected to the ground wiring (GND).

The current induction unit 170 induces a current flowing in the common line COM and delivers the induced current to the power source control unit 150. [ The current inducing unit 170 may be formed of an element such as an inductor or a transformer capable of inducing a current flowing in the common line COM, but is not limited thereto.

The power control unit 150 controls the output of the DC power supply unit DCDC using the current derived from the current induction unit 170. The power supply control unit 150 measures the current flowing through the common line COM using the current induction unit 170 and controls the DC power supply unit DCDC based on the measured current. The power control unit 150 supplies a control signal FB for lowering the DC power supply voltage output from the DC power supply unit DCDC to the DC power supply unit DCDC if the current induced from the current induction unit 170 is higher than the previously induced current do. Alternatively, if the current induced from the current induction unit 170 is lower than the previously induced current, the power control unit 150 may supply the control signal FB, which increases the DC power supply voltage output from the DC power supply unit DCDC, DCDC).

As shown in FIG. 5, the power supply controller 150 includes a rectifier 151 and a controller 155. The rectifying part 151 converts the current induced from the current guiding part 170. The rectifying part 151 may be formed of a passive element such as a diode or a capacitor, but is not limited thereto.

The control unit 155 compares the current converted by the rectifying unit 151 with a reference VREF set therein and generates a control signal FB for controlling the DC power supply unit DCDC according to the comparison result. The control unit 155 may generate the control signal FB by the comparator 156 comparing the current converted by the rectifying unit 151 and the reference VREF set therein but is not limited thereto.

5, the current induction unit 170 and the power source control unit 150 may be configured such that each of the light emitting diodes D1 to Dn included in the light emitting units DP1 to DPn generates heat, The current change can be detected through the common line COM connected to the cathode electrodes of the light emitting diodes D1 to Dn even when the power supply voltage deviation Vf is generated. Since the output of the DC power supply unit DCDC can be controlled by the amount of the changed current, the DC power supply unit DCDC can always output a constant constant current.

The backlight unit BLU according to the embodiment detects the current flowing through the light emitting units DP1 to DPn by the current induction unit 170 and controls the output of the DC power source unit DCDC to the power source control unit 150 do. The backlight unit BLU according to the embodiment can minimize the power consumption due to the constant current control during driving and requires only one DC power supply unit DCDC, so that the manufacturing cost can be reduced when the number of the light emitting diodes is large.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, 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.

PNL: liquid crystal panel BLU: backlight unit
DCDC: DC power source parts DP1, DPn: Light emitting parts
SW1, SWn switches 170:
150:

Claims (10)

A DC power supply unit for generating a DC power supply voltage;
Light emitting units including light emitting diodes connected in series to a power supply wiring connected to an output terminal of the direct current power supply unit;
A common wiring connected to the ground wiring and forming a node for commonly connecting the cathode electrodes of the light emitting units;
A current inducing unit for inducing a current flowing in the common wiring; And
And a power control unit for controlling the output of the direct current power unit using the current derived from the current induction unit,
The power control unit includes:
A rectification unit for converting a current induced from the current induction unit;
And a control unit for comparing the current converted by the rectifying unit with a reference set therein and controlling the DC power supply unit according to a comparison result,
The power control unit includes:
The DC power supply voltage output from the DC power supply unit is lowered when the current induced from the current induction unit is higher than the previously induced current,
And supplies a control signal for increasing the DC power supply voltage outputted from the DC power supply section to the DC power supply section when the current induced from the current induction section is lower than the previously induced current,
Wherein the current induction unit is an inductor or a transformer. delete delete delete The method according to claim 1,
Between the cathode electrodes of the light emitting diodes and the common wiring,
Further comprising switches connected at one end to the cathode electrodes of the light emitting diodes and connected at the other end to the common wiring. 6. The method of claim 5,
The switches,
And the ON / OFF time is controlled in accordance with a pulse width signal supplied from the outside. A liquid crystal panel; And
And a backlight unit for providing light to the liquid crystal panel,
The backlight unit includes:
A DC power supply unit for generating a DC power supply voltage,
Light emitting units including light emitting diodes connected in series to a power supply wiring connected to an output terminal of the direct current power supply unit,
A common wiring connected to the ground wiring and forming a node for commonly connecting the cathode electrodes of the light emitting units,
A current induction unit for inducing a current flowing in the common wiring;
And a power control unit for controlling the output of the direct current power unit using the current derived from the current induction unit,
The power control unit includes:
A rectification unit for converting a current induced from the current induction unit;
And a control unit for comparing the current converted by the rectifying unit with a reference set therein and controlling the DC power supply unit according to a comparison result,
The power control unit includes:
The DC power supply voltage output from the DC power supply unit is lowered when the current induced from the current induction unit is higher than the previously induced current,
And supplies a control signal for increasing the DC power supply voltage outputted from the DC power supply section to the DC power supply section when the current induced from the current induction section is lower than the previously induced current,
Wherein the current induction unit is an inductor or a transformer. delete delete delete

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