Patent Grant
8411019
This application claims priority from Korean Patent Application No. 10-2007-0119417, filed on Nov. 21, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a display apparatus and a control method thereof, and more particularly, to a display apparatus which is capable of controlling an inverter to cause an overcurrent emission while scanning a light source unit.
2. Description of the Related Art
Display apparatuses such as liquid crystal display (LCD) televisions (TVs) have a problem of a blurring effect that an image edge appears blurred, unclear and hazy due to a slow response speed of liquid crystals in displaying a moving picture. Thereupon, conventional display apparatuses have suppressed such a blurring effect occurring in an image using a scanning method of sequentially driving a plurality of lamps in correspondence to a response speed of liquid crystals.
In the conventional display apparatuses driven by the scanning method, a backlight unit includes a plurality of blocks, each of which includes a plurality of lamps. A scanning signal having a certain frequency (for example, 60 Hz to 120 Hz) is generated to drive the backlight unit so that the plurality of blocks can be sequentially turned on/off.
However, although the conventional display apparatuses driven by the scanning method have suppressed the blurring effect, they have a problem of low average image luminance. Thereupon, the conventional display apparatuses could increase the average image luminance by causing the backlight unit to emit light with more than a reference luminance for scanning for a predetermined period of time.
An inverter supplies current to the backlight unit, and a control signal to control the inverter may be generated by a digital circuit such as a field programmable gate array (FPGA), a microcomputer integrated circuit (IC) or the like. However, the conventional display apparatuses require the digital circuit such as the FPGA, the microcomputer IC or the like to generate the control signal, and the digital circuit has a very complicated structure as well as a high unit price of its parts, which may result in increase of product costs.
Accordingly, it is an aspect of the present invention to provide a display apparatus which may reduce production costs by implementing an inverter control signal generating circuit with simpler and less expensive parts, and a control method thereof.
Additional aspects of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present invention.
The foregoing and/or other aspects of the present invention can be achieved by providing a display apparatus comprising: a display panel that displays an image; a light source unit including a plurality of light sources that irradiate the display panel with light; a first control signal generating unit that inverts and forward rectifies a scan signal for scanning of the light source unit; a second control signal generating unit that inverts and backward rectifies an overdrive signal for overcurrent emission of the light source unit and has its output port coupled to an output port of the first control signal generating unit; and an inverter that supplies current to the light source unit based on a control signal output from the output port of the first control signal generating unit and the output port of the second control signal generating unit.
The inverter may include an inverter controller that controls the inverter to supply current to the plurality of light sources based on a preset reference signal, a feedback signal for current flowing through the plurality of light sources, and the control signal.
The inverter controller may include a first operational amplifier having a positive terminal which receives the reference signal and a negative terminal which receives the feedback signal and the control signal.
The first operational amplifier may output control signals having a first voltage level for overcurrent emission of the light source unit, a second voltage level for reference current emission, which is lower than the first voltage level, and a third voltage level for stop of current supply, which is lower than the second voltage level according to the feedback signal and the control signal.
The inverter controller may include a second operational amplifier having a positive terminal which receives an output of the first operational amplifier.
The above and/or other aspects of the present invention will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings, in which:
Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The exemplary embodiments are described below so as to explain the present invention by referring to the figures.
As shown in
The display panel 110 displays an image. The display panel 110 may be implemented by an LCD panel.
The light source unit 120 includes a plurality of light sources 121 and 122 that irradiate the display panel with light. Unlike a plasma display panel (PDP) or a field emission display (FED), a display apparatus using a liquid crystal panel is not self-luminous and serves only to control the transmission amount of light through liquid crystals, and thus requires a light source that supplies uniform light throughout a screen.
The light source unit 120, i.e., the backlight unit, may include a plurality of blocks, each of which is defined by a plurality of lamps which are located in parallel at a rear side of the liquid crystal panel. The lamps used for the light sources may be implemented by cathode fluorescent lamps that emit white light, such as cold cathode fluorescent lamps (CCFLs), hot cathode fluorescent lamps (HCFLs) or the like.
The first control signal generating unit 130 inverts and forward rectifies the scan signal for scanning of the light source unit 120. As shown in
For example, the first control signal generating unit 130 outputs a LOW level signal of 0 V with an input of a HIGH level signal of 3.3 V and outputs a HIGH level signal of 3.3 V with an input of a LOW level signal of 0 V.
The second control signal generating unit 140 inverts and backward rectifies the overdrive signal for overcurrent emission of the light source unit 120 and has its output port coupled to an output port of the first control signal generating unit 130. As shown in
The overdrive signal is used for overcurrent emission of the light source unit 120 and its waveform is as shown in
In addition, since the output port of the second control signal generating unit 140 is coupled in parallel to the output port of the first control signal generating unit 130, a signal having a higher voltage of a first control signal and a second control signal is output, as a final control signal IS, to an inverter controller 151. A level of voltage of the control signal IS according to the input of the scan signal SS and the overdrive signal ODS may be obtained from the following equation (1).
3.3[(SS OR ODS)′]+(0.5˜2)[(SS AND ODS′)]=IS (1)
The inverter 150 supplies current to the light source unit 120 based on the control signals output from the output port of the first control signal generating unit 130 and the output port of the second control signal generating unit 140. The inverter 150 may also include the inverter controller 151 that controls the inverter to supply current to the plurality of light sources based on a preset reference signal, a feedback signal for current flowing through the plurality of light sources, and a control signal. Here, the feedback signal has a level of voltage corresponding to the current supplied to the light source unit 120.
As shown in
The first operational amplifier 152 may output control signals having a first voltage level for overcurrent emission of the light source unit 120, a second voltage level for reference current emission, which is lower than the first voltage level, and a third voltage level for stopping current supply, which is lower than the second voltage level according to the feedback signal and the control signal IS. As shown in
The output signal FB of the first operational amplifier 152 is input to the positive terminal of the second operational amplifier 153 and a second reference signal having a frequency of 48.5 kHz is input to a negative terminal of the second operational amplifier 153. The second operational amplifier 153 adjusts a duty cycle of an inverter 154 according to the output signal FB of the first operational amplifier 152 and a driving signal so as to supply current to the light source unit 120.
From the timing diagram of the above signals, which is shown in
The following Table 1 shows a voltage level of the control signal IS and a voltage level of the output signal FB of the first operational amplifier 152 according to the scan signal SS and the overdrive signal ODS.
As can be seen from the above Table 1, when the scan signal SS has a HIGH voltage level and the overdrive signal ODS has a LOW voltage level, the voltage levels of the control signal IS and the output signal FB of the first operational amplifier 152 are determined to have a voltage value of 0.5 V to 2 V according to the feedback signal.
First, the first control signal generating unit 130 inverts and forward rectifies the scan signal for scanning of the light source unit 120, to generate the first control signal (S10).
The second control signal generating unit 130 inverts and backward rectifies the overdrive signal for overcurrent emission of the light source unit 120 to generate the second control signal (S20). The first control signal and the second control signal are input to the first operational amplifier 152 as the control signal IS.
The first operational amplifier 152 outputs the output signals FB having one of the first voltage level for overcurrent emission of the light source unit 120, the second voltage level for reference current emission, which is lower than the first voltage level, and the third voltage level for stopping current supply, which is lower than the second voltage level according to the feedback signal and the control signal IS (S30).
The second operational amplifier 153 adjusts a duty cycle of an inverter 154 according to the output signal FB so as to supply current to the light source unit 120. After then, current is supplied to the light source unit 120 (S40) and the generated light is irradiated to the display panel 110 (S50).
As described above, exemplary embodiments of the present invention provide a display apparatus which is capable of reducing production costs by implementing an inverter control signal generating circuit with more simple and more inexpensive parts, and a control method thereof.
Although a few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0119417 | Nov 2007 | KR | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20030169247 | Kawabe et al. | Sep 2003 | A1 |
| 20060279516 | Yun | Dec 2006 | A1 |
| 20090021468 | Pankaj et al. | Jan 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 213 699 | Jun 2002 | EP |
| 1 617 712 | Jan 2006 | EP |
| Entry |
|---|
| European Search Report dated Feb. 6, 2009 issued in counterpart EP application No. 08167174.5. |
| Number | Date | Country | |
|---|---|---|---|
| 20090128544 A1 | May 2009 | US |
