Patent Application
20070132711
This application claims the benefit of Korean Patent Application No. P05-0119970 filed in Korea on Dec. 8, 2005, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
This invention relates to a backlight of a display device, and more particularly to a driving apparatus of a backlight and a method of driving a backlight using the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for generating a burst dimming signal having a consistent On/Off duty cycle.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device displays images by controlling optical transmittance of liquid crystal cells. An active matrix type of liquid crystal display device having a switching device provided for each liquid crystal cell is advantageous in the implementation of moving pictures because of the speed at which the switching devices can be switched. The switching devices used for the active matrix liquid crystal display devices are typically thin film transistors (TFT).
When the scanning pulse is applied to the gate line GL, then the TFT is turned on to provide a channel between the source electrode and the drain electrode, so that a voltage on the data line DL is supplied to the pixel electrode of the liquid crystal cell Clc. The storage capacitor Cst receives the analog data voltage from the data line DL when the TFT is turned on and maintains the charged analog data voltage in the liquid crystal cell Clc. The alignment state of the liquid crystal molecules is changed by an electric field between the pixel electrode and the common electrode. As a result, the optical transmittance of the liquid crystal is changed according to the changed alignment of the liquid crystal.
The liquid crystal display panel 110 has a liquid crystal injected between upper and lower glass substrates (not shown). On the lower glass substrate of the liquid crystal display panel 110, the data lines DL1 to DLm and the gate lines GL1 to GLn perpendicularly cross each other. At each crossing of the data lines DL1 to DLm and the gate lines GL1 to GLn, TFTs are provided. The TFTs switch data from the data lines DL1 to DLm to the liquid crystal cells Clc in response to scanning pulses. The gate electrodes of the TFTs are connected to the gate lines GL1 to GLn while the source electrodes thereof are connected to the data lines DL1 to DLm. Further, the drain electrodes of the TFTs are connected to the pixel electrodes of the liquid crystal cells Clc and to the storage capacitors Cst.
The TFT is turned on in response to the scanning pulse applied, via the gate lines GL1 to GLn, to the gate terminal thereof. Upon turning-on of the TFT, a video data on the data lines DL1 to DLm is supplied to the pixel electrode of the liquid crystal cell Clc. The timing controller 150 supplies a digital video data RGB to the data driver 120. Also, the timing controller 150 generates a data driving control signal DDC and a gate driving control signal GDC using a horizontal/vertical synchronizing signal H and V, and a clock signal CLK. The data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polar control signal POL and a source output enable signal SOE. The data driving control signal DDC is supplied to the data driver 120. The gate driving control signal GDC includes a gate start pulse GSP, a gate shirt clock GSC and a gate output enable GOE. The gate driving control signal GDC is supplied to the gate driver 130.
The gate driver 130 sequentially generates a scanning pulse, such as a gate high pulse, in response to the gate driving control signal GDC supplied from the timing controller 150. The gate driver 130 includes a shift register (not shown) for sequentially generating the scanning pulse and a level shifter (not shown) for shifting the swing width of the scanning pulse voltage to voltages higher than the threshold voltage of the TFTs.
The data driver 120 supplies a data to the data lines DL1 to DLm in response to the data driving control signal DDC from the timing controller 150. Further, the data driver 120 samples and latches digital video data RGB fed from the timing controller 150. Then, the data driver converts the latched digital video data RGB into an analog voltage capable of expressing a gray scale level in the liquid crystal cell Clc.
The backlight assembly 160 provided at the rear side of the liquid crystal display panel 110 radiates light to each pixel of the liquid crystal display panel 110 in response to an alternating current (AC) voltage supplied from the inverter 170. The inverter 170 converts a square wave signal generated within the inverter into a triangular wave signal and then compares the triangular wave signal with a direct current (DC) voltage supplied from an exterior electronic device, such as a controller of the image display apparatus, thereby generating a burst dimming signal proportional to a result of the comparison. Herein, if the exterior electronic device is a controller for controlling a function of the image display apparatus, then the exterior electronic device supplies the DC voltage having a value approximately 0V to 3.3V to the inverter 170. If the burst dimming signal determined in accordance with the rectangular wave signal at the interior of the inverter 170, then a driving integrated circuit IC (not shown) for controlling a generation of the AC voltage within the inverter 160 controls a generation of the AC voltage supplied to the backlight assembly 160 in response to the burst dimming signal.
When the resistance of an interior resistance element changes due to an increase in temperature within the inverter 170 of the related art driving apparatus, then the On/Off duty cycle of the square signal oscillated within the interior of the inverter 170 is also changed. Accordingly, the On/Off duty cycle of a burst dimming signal used for controlling a magnitude of the AC voltage supplied to the backlight assembly 160 is also changed. The burst dimming signal is affected by the square signal being changed by an increase in temperature within the inverter. Such changes in the burst dimming signal can cause the problem of wavy noise to be generated on the liquid crystal display panel. Also, the inverter 170 having the related art driving apparatus is not controlled by the image display apparatus. Accordingly, if an irradiating system of the image display apparatus, for example, a PAL system or an NTSC system, is changed, the inverter 170 may not oscillate the correct square wave signal for the irradiating system.
Accordingly, the present invention is directed to a driving apparatus of a backlight and a method of driving a backlight using the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention to provide a driving apparatus of a backlight and a method of driving a backlight using the same that maintains burst dimming signal with a consistent On/Off Duty cycle.
Another object of the present invention is to provide a driving apparatus of a backlight and a method of driving a backlight using the same for supplying a constant alternating current voltage to a backlight assembly that is not affected by exterior environmental temperatures.
Another object of the present invention is to provide a driving apparatus of a backlight and a method of driving a backlight using the same for preventing generation of wavy noise on a liquid crystal display panel.
Another object of the present invention is to provide a driving apparatus of a backlight and a method of driving a backlight using the same that are adaptive to a change of scanning systems.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a driving apparatus of a backlight, includes a controller for controlling square wave oscillation, a square wave oscillator for oscillating a constant square wave signal in accordance with a control signal from the controller, and a signal generator for generating a burst dimming signal using the square wave signal.
In another aspect, a method of driving an backlight includes generating a square wave oscillation control signal for controlling a square wave oscillation, oscillating a constant square wave signal based upon with the square wave oscillation control signal, and generating a burst dimming signal having a consistent On/Off duty cycle in an inverter based upon the constant square wave signal.
In another aspect, an image display apparatus includes a controller for providing a control signal to control a square wave oscillation, a square wave oscillator for oscillating a constant square wave signal in accordance with the control signal of the controller, and an inverter for generating a burst dimming signal using the constant square wave signal from the square wave oscillator.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A square wave generation execution program for controlling generation of a constant square wave signal is provided in the controller 210. The execution program is carried out in accordance with a user's command inputted through a television remote control (not shown). If the square wave generation execution program is carried out, then the controller 210 outputs an oscillation control signal for generating a constant square wave signal to the square wave generator 220.
In an embodiment of the present invention, the square wave oscillation execution program is set in the controller 210 for controlling the image display function of the image display apparatus shown in
Referring to
The burst dimming signal outputted from the comparator 240 is input to a driving IC (not shown because this is the same element as in the related art) for controlling generation of the alternating current voltage within the inverter 300. Since an embodiment of the present invention oscillates a constant square wave signal irregardless of the temperature within the inverter 300, the comparator 240 outputs a consistent burst dimming signal to the driving IC. Accordingly, the driving IC outputs an alternating current voltage in which the magnitude is constantly adjusted to provide a consistent burst dimming signal to the backlight assembly 422 (in
A specific configuration of the circuit will be described with reference to
The comparator 240 compares the direct current voltage inputted to the non-inverting input terminal (+) on the basis of the triangular wave signal inputted to the inverting input terminal (−) and outputs the burst dimming signal from the output terminal. For example, a first signal is outputted at an interval when the triangular wave signal is greater than the direct current voltage. Since the triangular wave signal is inputted with the inverting input terminal (−), an inverted signal of the high signal, that is, a low signal is outputted. Otherwise, a second signal is outputted at an interval when the triangular wave signal is smaller than the direct current voltage. Since the triangular wave signal is inputted with the inverting input terminal (−), the inverted signal of the low signal, that is, the high signal is outputted. As a result, the comparator 240 outputs the burst dimming signal as shown in
The power board 410 transforms the alternating current voltage, such as 220VAC, inputted from the external power source into direct current power source voltage, such as 24V, and supplies the direct current power source voltage to the liquid crystal display device 420, the controller 210, the image processor 430, the panel driver 440 and the inverter 300. In the alternative, the power board 410 may be implemented in such a manner so as to supply a different direct current voltage, such as 12V to the inverter 300 in accordance with a capacitance value of the liquid crystal display device 420.
The liquid crystal display device 420 includes a liquid crystal display panel 421 for displaying the image and a backlight assembly 422 for generating a light for the image displayed on the liquid crystal display panel 421. The LCD panel 421 is driven by the direct current power source applied from the power board 410 to display the image signal transmitted from the panel driver 440. The brightness of the screen is varied in accordance with the intensity of the light irradiated from the backlight assembly 422, and the contrast of the outputted image is varied in accordance with the gain of the image signal outputted from the image processor 430. If the intensity of the light irradiated from the backlight assembly 422 is increased, then the brightness is increased, while if the intensity of the light irradiated from the backlight assembly 422 is decreased, then the brightness is decreased. If the gain of the image signal outputted from the image processor 430 is increased, then the contrast is increased, while if the gain of the image signal outputted from the image processor 430 is decreased, then the contrast is decreased.
The backlight assembly 422 includes a plurality of lamps (not shown) arranged in a row at a rear side of the LCD panel 421. The a plurality of lamps are turned-on by the alternating current voltage current supplied from the inverter 300. The intensity of the irradiated light varies in proportion to the current amount received from the inverter 300. In other words, if the inputted current amount is increased, then the intensity of the light irradiated from the backlight assembly 422 is increased, while if the inputted current amount is decreased, then the intensity of the light irradiated from the backlight assembly 422 is decreased. As a result, the brightness of the LCD panel 421 is made brighter or dimmer by respectively increasing or decreasing the intensity of the light irradiated into the LCD panel 421.
The controller 210 controls the brightness of the screen and the contrast of the image in accordance with the user's command. If the user inputs a brightness increase command using a remote control (not shown), then the controller 210 outputs a brightness control signal indicating a brightness increase, such as a brightness increase signal, to the inverter 300. The inverter 300 increases the current amount supplied to the backlight assembly 422 in accordance with the brightness up signal to increase the intensity of the light from the backlight assembly 422. Thus, the brightness of the screen on the LCD panel 421 increases.
If the user inputs a brightness decrease command using a remote control (not shown), then the controller 210 outputs a brightness control signal indicating a brightness decrease, such as a brightness decrease signal, to the inverter 300. The current supplied to the backlight assembly 422 from the inverter 300 decreases in accordance with the brightness decrease signal to decrease the intensity of the light from the backlight assembly 422. Thus, the brightness of the screen on the LCD panel 421 decreases.
The embodiment of the present invention uses a square wave oscillation execution program in the controller 210 so that the controller 210 outputs the square wave oscillation control signal for controlling a constant square wave signal from the square wave oscillator 220. The square wave oscillator 220 provides a constant square wave signal in accordance with the square wave oscillation control signal generated from the controller 210 and outputs the square wave signal to the inverter 300. The inverter 300 uses the direct current voltage supplied from the power board 410 to generate a driving current of the backlight assembly 422, and increases or decreases the current amount supplied to the backlight assembly 422 in accordance with the brightness control signal inputted from the controller 210. If the controller 210 outputs the brightness decrease signal, then the inverter 300 decreases the current amount supplied to the backlight assembly 422 to decrease the brightness of the display. On the other hand, if the controller 210 outputs the brightness increases signal, then the inverter 300 increases the current amount supplied to the backlight assembly 422 to increase the brightness.
The inverter 300 includes a integrator 230 for converting the square wave signal from the square wave oscillator 220 into a triangular wave signal and a comparator 240 for comparing the triangular wave signal outputted from the integrator 230 with the direct current voltage of 0V to 3.3V to output the burst dimming signal. Since the inverter 300 is implemented in such a manner as to generate the burst dimming signal in accordance with a control of the controller 210 controlling the image display function of the image display apparatus 400, then the inverter 300 can generate burst dimming signals for different scanning systems. The inverter 300 can be appropriately controlled to accommodate changes from the PAL system to the NTSC system or from the NTSC system to the PAL system.
The image processor 430 adjusts a screen size of the image displayed on the LCD panel 421 in accordance with the control of the controller 210 and also adjusts an offset and/or the gain of the image signal inputted from a video processor (not shown) to vary the contrast. The panel driver 440 provides the image signal outputted from the image processor 240 to the LCD panel 421 so as to display image data scaled by the image processor 430. The panel driver 440 also on/off switches or outputs a driving signal corresponding to a gray scale of an image data to the LCD panel 421 so as to adjust the offset and/or the gain of the LCD panel 421.
As described above, the present invention always provides a constant square wave from the outside of the inverter. Embodiments of the present invention are not affected by the temperature within the inverter because a constantly oscillating square wave is generated in accordance with the control of the controller. The constantly oscillating square wave is used to supply a burst dimming signal with a consistent On/Off duty cycle to the backlight assembly. Thus, the consistent On/Off duty cycle of the burst dimming signal prevents the generation of wavy noise on the screen. Because embodiments of the present invention generates the burst dimming signal using the constantly oscillating square wave, the burst dimming signal can be controlled to accommodate changes to different scanning systems, such as from the PAL system to the NTSC system or from the NTSC system to the PAL system.
It will be apparent to those skilled in the art that various modifications and variations can be made in the driving apparatus of a backlight and method of driving a backlight using the same of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2005-0119970 | Dec 2005 | KR | national |
