1. Field of the Invention
The present invention relates to a display driving system, and more particularly, to a display driving system using single level signaling with embedded clock signals, which includes a timing control section configured to embed a clock signal of the same level between data signals and transmit the signals to a panel driving section, and the panel driving section configured to recover the embedded clock signal from the transmitted data signals, sample data using the clock signal stabilized during a clock training interval and output image data, so that a data transmission speed is maximized, the level of signals to be transmitted and the frequency of the embedded clock signal are minimized, and impedance mismatch and EMI (electromagnetic interference) are suppressed to the minimum.
2. Description of the Related Art
These days, as the digital home appliance market is grown and the distribution of personal computers and portable communication terminals is increased, display devices as final output devices of home appliances and communication terminals are required to be light in weight and consume a small amount of power. Techniques for meeting these requirements are continuously proposed in the art. Accordingly, flat display devices, such as an LCD (liquid crystal display), a PDP (plasma display panel) and an OELD (organic electro-luminescence display), which replace the conventional CRT (cathode ray tube), have been developed and are being distributed.
Each of the flat display devices includes a timing controller which processes image data and generates a timing control signal so as to drive a panel used for displaying received image data, and column driving sections and row driving sections which drive the panel using the image data and the timing control signal transmitted from the timing controller.
In particular, recently, as display devices having a large screen size and a high resolution are demanded, a technique for transmitting data at a high speed from the timing controller to the column driving sections is required. In this regard, since electromagnetic interference (EMI) is caused by electromagnetic waves while transmitting data at a high speed, the level of a signal to be transmitted has been considerably decreased.
Under these situations, differential signal transmission schemes capable of reducing electromagnetic interference (EMI) and transmitting data at a high speed, such as mini-LVDS (low voltage differential signaling) and RSDS (reduced swing differential signaling), have been increasingly used.
Referring to
While the multi-drop scheme has advantages in that the timing controller 10 can be used irrespective of the number of outputs depending upon a resolution, that is, the number of the column driving sections 20, it encounters a problem in that signal distortion by reflection waves is caused and electromagnetic interference (EMI) increases due to impedance mismatch occurring at points where the data differential signal and the clock differential signal are supplied to the respective column driving sections 20, and in that an operation speed is limited due to a large load applied to the clock differential signal.
In order to overcome the problem caused in the multi-drop scheme, PPDS (point-to-point differential signaling), in which data differential signals are separately supplied to respective column driving sections and a clock differential signal is shared by the column driving sections, has been proposed in the art.
Referring to
In the PPDS, the clock differential signal should be transmitted at a high speed. In this regard, because the PPDS shown in
Further, as display devices trend toward a large screen size and a high resolution and the number of column driving sections increases accordingly, the PPDS scheme encounters a problem in that the numbers of data and clock signal lines increase at the same rate, connection of entire signal lines is complicated, and a high manufacturing cost results.
Referring to
As a consequence, as described above, in the multi-drop scheme such as the conventional mini-LVDS and RSDS for transmitting data at a high speed from the timing controller to the column driving sections, a problem is caused in that impedance mismatch and overloading of the signal line for transmitting the clock differential signal occur. In the conventional PPDS, while data differential signals and clock differential signals are separately supplied to respective column driving sections so as to overcome the problem caused in the multi-drop scheme, as display devices trend toward a large screen size and a high resolution, the number of signal lines increases compared to the multi-drop scheme, whereby the complexity of signal lines for connecting the timing controller and the column driving sections is increased and a lot of costs is incurred.
Moreover, in the recently proposed AiPi transmission scheme, while signals are transmitted by embedding clock signals between data to decrease the number of signal lines and prevent the occurrence of skew between the data and clock signals, since the embedded clock signals are transmitted to constitute multi-level signals by having a level greater or less than data signals, problems are caused in that it is impossible to minimize the level of signals to be transmitted and reduction of electromagnetic interference (EMI) is poor.
As a consequence, an interface for transmitting data at a high speed between a timing controller and column driving sections, which can decrease the number of signal lines for transmitting data differential signals and clock differential signals, minimize electromagnetic interference (EMI), and prevent the occurrence of skew and jitter between signal lines, is keenly demanded in the art.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a display driving system using single level signaling with embedded clock signals, in which a clock signal of the same level is embedded between data signals in a timing control section and is transmitted through an independent data signal line to each panel driving section in the type of a single level signal, and the clock signal is recovered in the panel driving section, data is sampled and image data is outputted to a panel, so that a data transmission speed can be maximized and the level of signals to be transmitted and the frequency of the embedded clock signal can be minimized.
Another object of the present invention is to provide a display driving system using single level signaling with embedded clock signals, which can minimize impedance mismatch and EMI (electromagnetic interference) caused due to multi-drop type signaling of data and clock signals in the conventional art, decrease the number of signal lines, and prevent the occurrence of skew and jitter between signals.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a display driving system including a timing control section having an LVDS receiving unit for receiving data signals, a data processing unit for temporarily storing the data signals, processing the data signals and outputting processed data signals, a timing generation unit for generating clock signals and timing control signals, and a transmission unit for transmitting the data signals; and a panel driving section having row driving units for sequentially emitting gate signals toward a display panel and column driving units for receiving the signals transmitted through signal lines from the transmission unit and supplying the received signals to the display panel, wherein, in the timing control section, the transmission unit has driving parts which embed the clock signals between the data signals at the same level and generate and output single level transmission data.
According to another aspect of the present invention, the column driving unit includes a clock recovery circuit which recovers the clock signal embedded between the data signals and having a transmission speed lower than that of the data signals and generates the received clock signal to be used for sampling data, and a receiving part which samples and outputs control data and image data signals included in the transmission data at a transition time (a rising edge or a falling edge) of the received clock signal.
The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description taken in conjunction with the drawings, in which:
Reference will now be made in greater detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.
Referring to
The panel driving section 200 is composed of row driving units 210 which sequentially emit gate signals G1 through GM to the display panel 300 and column driving units 220 which supply source signals S1 through SN to be displayed.
The timing control section 100 transmits only a CED (clock embedded data) signal as a differential pair, in which a clock signal is embedded at the same level between the data signals, to each column driving unit 220 of the panel driving section 200 via one signal line.
Before transmitting data, the timing control section 100 transmits transmission data (a CED signal) comprising only a clock signal to start clock training, and thereafter, transmits to the panel driving section 200 a signal LOCK0 informing that the clock signal is stabilized. The column driving units 220 of the panel driving section 200 recover received clock signals to be used for sampling data in response to CED signals transmitted during the clock training interval, after LOCK signals inputted from the timing control section 100 or other column driving units 220 are in an “H” state (a logic high state). If the received clock signals are stabilized, LOCK signals LOCK1 through LOCKN are outputted in the “H” state. That is to say, after a LOCK signal LOCK0 informing that clock signals are stabilized is inputted in the “H” state from the timing control section 100, if received clock signals are stabilized, the column driving units 220 sequentially output the LOCK signals LOCK1 through LOCKN-1 in the “H” state to next column driving units 220.
The timing control section 200, which is finally inputted with the signal LOCKN of the “H” state from the panel driving section 200, ends the clock training and starts to transmit the data signals with the embedded clock signals. If the signal LOCKN changes to an “L” state (a logic low state) while transmitting the data, the timing control section 100 immediately starts the clock training and continues the clock training until the signal LOCKN becomes the “H” state. Also, after the signal LOCKN becomes the state, the timing control section 100 can interrupt data transmission and start the clock training as the occasion demands.
Referring to
Since the frequency of the clock signal embedded between the data signals is remarkably lower than the frequency of the data signals, the panel driving section 200 generates a clock signal used for sampling data, by employing a clock recovery circuit 233 which uses a delay locked loop (DLL) or a phase locked loop (PLL).
The column driving unit 220 cannot distinguish the clock signal and the dummy signal from the data signals in the signaling scheme in which the dummy signal is inserted to represent the rising edges of the clock signal. Therefore, a transmission unit 140 provided in the timing control section 100 transmits a clock training signal during the clock training interval in an initial transmission stage, as shown in
Accordingly, each column driving unit 220 provided in the panel driving section 200 generates a received clock signal through the clock recovery circuit 233 using the clock training signal. The received clock signal can be constructed as a multi-phase clock signal having a transmission rate lower than the data or a multi-phase clock signal having the same frequency as the data.
A receiving part 230 of the column driving unit 220 samples data transmitted after the clock training interval, using the received clock signal that is stabilized during the clock training interval. In other words, in first data transmitted after the clock training interval, if the value of a first bit transmitted after the clock signal is “0,” the first data is recognized as control data, and it is recognized that image data are inputted from second data. Because the value of a corresponding position is always “1” during the clock training interval, the receiving part 230 can recognize that the clock training interval does not end.
The panel driving section 200 is supplied with a source output enable signal SOE, a gate start pulse signal GSP, a gate output enable signal GOE and a gate start clock signal GSC that are generated by the timing control section 100, and the column driving unit 220 recovers a data signal DATA and a clock signal CLK for representing image data and displays the data signal on a line of the display panel 300 which is selected by the gate start pulse signal GSP in response to the source output enable signal SOE.
The column driving units 220 recover received clock signals from transmission data transmitted as single level signals from the timing control section 100, through clock training signals, and outputs respective data signals. Due to this fact, not only the number of signal lines for transmitting data from the timing control section 100 to the column driving units 220 can be decreased, but also electromagnetic interference (EMI) can be reduced.
Referring to
The transmission unit 140 includes a demultiplexer (DEMUX) 141 which receives the LVDS data signals processed at the data processing unit 120 and divides and outputs data to be transmitted to the respective column driving units 220, parallel-to-serial conversion parts 142 which convert the transmission data outputted from the demultiplexer 141, and driving parts 143 which receive the clock signals generated in the timing generation unit 130 and transmit to the respective column driving units 220 the transmission data CEDs with the clock signals embedded between the data signals at the same level. The timing control section 100 transmits the transmission data including the data signals made serial in the parallel-to-serial conversion parts 142 to any one of a plurality of panel driving sections 200.
Each transmission data CED is a signal in which a clock signal is embedded between data signals. The level of the data signals is selected depending upon the value of 1-bit data, and the level of the embedded clock signal is selected depending upon the value of 1-bit data in the same manner as the level of the data signals.
Hence, each transmission data transmitted from the timing control section 100 includes the clock signal embedded between the data signals, and the level of the embedded clock signal is the same as the level of the data signals.
As shown in
Further, as shown in
Thus, the data transmitted from the timing control section 100 to the column driving unit 220 can include only the clock signal CLK and the image data DATA to be displayed on the display panel 300, or can include the clock signal CLK, the image data DATA and the source output enable signal SOE as a separate control signal for controlling the column driving unit 220.
Referring to
The receiving part 230 includes a sampler 231 which samples the data signal DATA from the CED signal transmitted through the signal line from the timing control section 100 and outputs a resultant signal, a data masking circuit 232 which masks a data portion of the CED signal and transmits the CED signal to a clock recovery circuit 233, the clock recovery circuit 233 which extracts the embedded clock signal from the masked data and generates the received clock signal to be used for sampling the data signal, and a serial-to-parallel conversion portion 234 which converts the data sampled by the sampler 231 into parallel data.
The shift registers 240 sequentially shift and output start pulses inputted thereto. The data latches 250 sequentially store and then output in parallel the data signal converted by the serial-to-parallel conversion portion 234, in response to the output signals of the shift registers 240. The DACs 260 convert the signals outputted from the data latches 250 into analog signals Y1, Y2 through YN and supply the converted signals to the display panel 300.
Referring to
Referring to
Accordingly, a received clock signal CK0 having the same phase and frequency as the CED signal inputted during the clock training interval is recovered in synchronism with the rising edge of the CED signal, and a plurality of received clock signals CK1 through CKN that are the same in frequency as and only different in phase from the received clock signal CK0 are generated.
If the value of a first bit next to the clock signal of a first data of the CED signal transmitted after the clock training interval is “0,” the data is recognized as control data for controlling the column driving unit 220, and it is recognized that image data are inputted from second data. Therefore, the values of respective control data or image data are sampled at the rising edges of the received clock signals CK0 through CKN recovered during the clock training interval, and are outputted to the display panel 300.
Accordingly, the sequence of the respective data can be distinguished based on the fact that the data are sampled by the received clock signals having which phases.
Referring to
Hence, the received clock signal CK0 that is synchronized with the rising edge of the data signal inputted during the clock training interval and has higher frequency than and the same phase as the data signal is recovered, and a plurality of received clock signals CK90, CK180 and CK270 that are the same in frequency as and different in phase from the received clock signal CK0 are generated.
The values of the respective control data or image data are sampled at the rising edges or the falling edges as the transition times of the received clock signals CK0 through CK270 recovered during the clock training interval, and are outputted to the display panel 300. In this case, in order to learn the sequence of the respective data, a separate counter circuit for counting the received clock signals used for sampling the data is required.
As described above, in the present invention, unlike the conventional multi-level signaling scheme in which the levels of data signals and a clock signal embedded therebetween are different from each other, data signals and a clock signal embedded therebetween are generated to have the same level so that single level signals are used. As a consequence, the level of signals to be transmitted can be minimized, the received clock signals can be generated in advance using the clock training signal, and the frequency of the received clock signal can be made significantly less than the frequency of the data to be actually transmitted.
As a result, compared to the conventional multi-level signaling scheme, the level of signals can be considerably lowered, and correspondingly, electromagnetic interference (EMI) of the entire display driving system can be reduced. Also, compared to the case in which the data signals and the clock signal are separated from each other, the number of signal lines can be significantly decreased, and the occurrence of skew or jitter can be prevented, whereby stable operation of the display driving system at a high speed can be ensured.
As is apparent from the above description, the present invention provides advantages in that, since data signals and a clock signal embedded therebetween are produced to have the same level so as to use single level signals, the level of signals to be transmitted and recovered can be minimized, and a recovered received clock signal can be stabilized using a clock training signal, whereby the level of signals to be transmitted and the frequency of the embedded clock signal can be significantly decreased and the electromagnetic interference (EMI) of an entire display driving system can be reduced.
Also, the present invention provides advantages in that skew or jitter that can be induced when a data signal and a clock signal are separated can be prevented, whereby stable operation can be ensured even at a high speed.
Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.
Number | Date | Country | Kind |
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10-2008-0102492 | Oct 2008 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR2009/005732 | 10/7/2009 | WO | 00 | 9/7/2010 |