Patent Application
20160093237
This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2014-0130188 filed on Sep. 29, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein.
1. Technical Field
Embodiments of the inventive concepts described herein relate to a display device, and more particularly, relate to a source driver to control image data to be output to a display panel.
2. Discussion of Related Art
A display device includes a plurality of pixels that are arranged at intersections of gate lines and source lines. The display device includes a gate driver to drive the gate lines and a source driver to provide image information to a display panel of the display device. The source driver may include a shift register that generates a control signal for controlling the timing of when image information is output to the display panel.
The source driver generates a signal for controlling the timing of when image information is output to the display panel, based on a carry signal. That is, each shift register (e.g., a stage) of a group of shift registers generates a timing control signal using a carry signal from a previous stage.
Various problems occur when the timing control signal is generated using a carry signal. For example, when an operating frequency or a scanning rate of the display device is high and the number of pixels is high, it can be difficult to control the output timing of data precisely due to an excessive delay that arises upon transferring a carry signal between shift registers. In addition, the time taken to charge pixels is reduced and causes a problem where image information is not normally output to the display panel.
An exemplary embodiment of the inventive concept is directed to provide a source driver circuit which includes a plurality of digital multi-spread (hereinafter referred to as “DMS”) blocks (e.g., main circuits) configured to generate DMS signals for controlling an output timing of a data signal to be transmitted to a display panel from a plurality of clocks which are delayed by a reference period one another, each DMS block including a plurality of sub blocks (e.g., sub circuits). Each of the sub blocks includes an enable signal generator and a delay unit. The enable signal generator generates an enable signal for outputting target DMS signals (e.g., a subset) of the DMS signals using clocks selected from the plurality of clocks. The delay unit delays the target DMS signals such that the target DMS signals are sequentially delayed by the reference period. Each sub block outputs the target DMS signal in response to the enable signal.
The source driver circuit may further include control logic configured to generate the clocks to be transmitted to the DMS blocks, to convert external image information into parallel image information, and to generate a gamma reference voltage used to output the data signal to the display panel.
The source driver circuit may further include a first latch configured to receive the parallel image information from the control logic.
The source driver circuit may further include a second latch configured to receive the parallel image information from the first latch and the DMS signals from the DMS blocks.
The source driver circuit may further include a decoder configured to convert the parallel image information, stored at the second latch, into the data signal depending on the gamma reference voltage, during a period where the DMS signals are activated.
The source driver circuit may further include display panel.
The control logic may enable the DMS blocks to generate the DMS signals according to one of a left-shift manner, a right-shift manner, or a dual-shift manner.
The enable signal may be generated based on one, having the greatest delay, from among the selected clocks.
The reference period may correspond to a value obtained by dividing a period of the clocks by the number of the clocks.
The enable signal that each sub block generates may be delayed by an integer multiple of the reference period and an enable signal generated from an adjacent sub block.
An exemplary embodiment of the inventive concept is directed to provide a method of operating a display device. The method includes generating a plurality of clocks which are delayed by a reference period one another from a clock received from an external device; generating an enable signal for outputting target DMS signals (e.g., a subset) of DMS signals, which control an output timing of a data signal to be transmitted to a display panel, using clocks selected from the plurality of clocks; and generating the target DMS signals from the selected clocks using the enable signal; and outputting the data signal to the display panel during a period where the target DMS signals are activated.
The DMS signals may be delayed by the reference period.
The enable signal may be generated using a first one among the selected clocks having the greatest delay.
The enable signal may be delayed by an integer multiple of the reference period and an enable signal generated from a second other one of the selected clocks.
The DMS signals may be generated according to one of a left-shift manner, a right-shift manner, or a dual-shift manner.
An exemplary embodiment of the inventive concept is directed to provide a display device which includes a timing controller, a display panel, a source driver, and a gate driver. The timing controller receives a plurality of clocks which are delayed by a reference period from one another, image information, source control signals, and gate control signals. The display panel includes pixels arranged at intersections of source lines and gate lines. The source driver receives the source control signals and the image information and outputs a data signal corresponding to the image information to the source lines. The gate driver receives the gate control signals and drives the gate lines connected to the pixels. The source drivers includes a plurality of DMS blocks (e.g, main circuits) that generate DMS signals for controlling an output timing of a data signal to be transmitted to a display panel from the clocks, each DMS block including a plurality of sub blocks (e.g., sub circuits). Each of the sub blocks includes an enable signal generator and a delay unit. The enable signal generator generates an enable signal for outputting target DMS signals (e.g., a subset) of the DMS signals using clocks selected from the plurality of clocks. The delay unit delays the corresponding target DMS signals such that the target DMS signals are sequentially delayed by the reference period. Each sub block outputs the target DMS signals in response to the enable signal.
The display device may further include control logic configured to generate the clocks to be transmitted to the DMS blocks, to convert the image information into parallel image information, and to generate a gamma reference voltage used to output the data signal to the display panel.
The display device may further include a first latch configured to receive the parallel image information from the control logic.
The display device may further include a second latch configured to receive the parallel image information from the first latch and the DMS signals from the DMS blocks.
The display device may further include a decoder configured to convert the parallel image information, stored at the second latch, into the data signal depending on the gamma reference voltage, during a period where the DMS signals are activated.
According to an exemplary embodiment of the inventive concept, a source driver circuit is provided including a plurality of main circuits configured to generate signals for controlling an output timing of a data signal to be transmitted to a display panel, wherein the signals are generated from a plurality of clocks which are delayed by a reference period from one another. Each main circuit includes a plurality of sub circuits. Each sub circuit generates an enable signal from a distinct two of the clocks, generates a first one of the signals from performing an AND operation on one of the two clocks and the enable signal, and generates a second one of the signals from performing an AND operation on the other of the two clocks and the enable signal.
Exemplary embodiment of the inventive concept will become apparent from the following description with reference to the following figures, wherein like reference numerals refer to like parts throughout the various figures unless otherwise specified, and wherein
Embodiments will be described in detail with reference to the accompanying drawings. The inventive concept, however, may be embodied in various different forms, and should not be construed as being limited only to the illustrated embodiments. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the concept of the inventive concept to those skilled in the art. Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and written description, and thus descriptions will not be repeated. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that when an element or layer is referred to as being “on”, “connected to”, “coupled to”, or “adjacent to” another element or layer, it can be directly on, connected, coupled, or adjacent to the other element or layer, or intervening elements or layers may be present.
The timing controller 100 receives image information RGB and a control signal CTRL. The image information RGB may include red, green, and blue data for one or more pixels of the display panel 400. The control signal CTRL may include the following: a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and a clock CLK. The timing controller 100 converts a format of the image information RGB to a format compatible with the specification of the source driver 300 to generate serialized data DATA. The timing controller 100 transmits the data DATA to the source driver 300. In an exemplary embodiment, the timing controller 100 simultaneously transmits the data DATA and the clock CLK through one channel in the form of an embedded clock. For example, time division multiplexing may be used to transmit both the data DATA and the clock CLK using a single channel. However, the inventive concept is not limited thereto. For example, the data and the clock CLK may be transmitted through separate channels, respectively.
The timing controller 100 generates a gate control signal GCS in response to the control signal CTRL and provides the gate control signal GCS to the gate driver 200. The gate control signal GCS may include the following: a signal indicating a start of a scan, a signal for controlling an output period of a gate on voltage, and a signal for adjusting the duration of the gate on voltage. The gate lines may be sequentially driven in various orders. For example, in a forward scan, the gate lines are sequentially scanned (e.g., a gate on voltage is applied to each gate line) in order from the first gate line through the last gate line and the start of the scan refers to the time when this scan begins.
The gate driver 200 drives gate lines in response to the gate control signal GCS such that data is sequentially output to the display panel.
The source driver 300 provides the display panel 400 with a gray scale voltage corresponding to data through source lines in response to a source control signal. In an exemplary embodiment, the clock CLK is the source control signal. The source driver 300 may generate a signal for controlling timing when the data is output to the display panel 400.
A carry signal is generally used to generate a signal for controlling the timing. However, when an operating frequency or a scanning rate of a display device is high and the number of pixels is high, it can be difficult to generate the timing control signal using the carry signal. In an exemplary embodiment of the inventive concept, the carry signal is not used to generate a timing signal that enables data to be output to the display panel 400. Instead, a timing control signal is generated using a clock CLK that is provided to the source driver 300. Accordingly, a display device may operate stably under a high frequency and a low voltage.
The display panel 400 includes pixels PX that are arranged at intersections of gate lines and source lines. The display panel 400 may be implemented with a liquid crystal display panel (LCD), an electrophoretic display panel, an electrowetting display panel, a plasma display panel (PDP), an organic light-emitting diode (OLED), and so on.
Each of the pixels PX of the display panel 400 includes a thin film transistor T and a liquid crystal capacitor Clc. Each pixel may display red, green, or blue image data.
In each pixel, the thin film transistor T is connected to a source line SL, operates in response to a gate voltage transferred through a gate line GL, and provides a data signal transferred through a source line SL to the liquid crystal capacitor Clc.
The liquid crystal capacitor Clc is connected to the thin film transistor T and includes a liquid crystal layer for adjusting a penetration ratio of light based on a voltage level.
The control logic 310 is supplied with clocks CLK1 through CLK10 from a receiver (not shown) of the source driver 300. The receiver may generate the clocks CLK1 through CLK10, based on a clock CLK from a timing controller 100 (refer to
The control logic 310 converts input data DATA into parallel data. The control logic 310 outputs the parallel data to the first latch 330. The control logic 310 generates gamma reference voltages VG1 through VGk that are used to convert the parallel data into a data voltage, that is, a gray scale voltage. The control logic 310 outputs the gamma reference voltages VG1 through VGk to the decoder 350.
The control logic 310 contains DMS logic 312. The DMS logic 312 processes the input clocks CLK1 through CLK10 in various manners. For example, the DMS logic 312 enables 1UI-delayed clocks CLK1 through CLK10 to be delayed by 2UI and 3UI. Alternatively, the DMS logic 312 changes an output order of the delayed clocks CLK1 through CLK10 from CLK1 to CLK10 or from CLK10 to CLK1. The DMS logic 312 outputs the changed clocks DCLK1 through DCLK10 to the DMS shifter 320. The DMS logic 312 may be embodied by various combinations of different logic circuits (e.g., an AND gate, an inverter, an
OR gate, etc.). An embodiment of the inventive concept is exemplified as the clocks DCLK1 through DCLK10 being delayed by 1UI from each other.
The DMS logic 312 changes a direction in which scanning of parallel data is performed on a display panel 400 through the source driver 300. For example, data may be scanned in one of the following manners: a right-shift manner in which data scanning is performed from a left end to a right end in a row of the display panel 400, a left-shift manner in which data scanning is performed from a right end to a left end in a row of the display panel 400, and a dual-shift manner in which data scanning is performed from a center to left and right ends in a row of the display panel 400. For example, in the right-shift manner, data is applied sequentially to the source lines in an order beginning from the left most source line and ending at the right most source line. For example, in the left-shift manner, data is applied sequentially to the source lines in an order beginning from the right most source line and ending at the left most source line. For example, in the dual-shift manner, data is applied sequentially to the source lines in an order beginning from a center most source line and continues to the left most source line, and begins again at a source line to the right of the center most source line and continues to the right most source line. The DMS logic 312 selects one of the data scanning manners as an operating mode of a display device randomly or as needed.
The DMS shifter 320 generates DMS signals for adjusting timing when data stored at the second latch 340 is output to the display panel 400 through the first latch 330. The DMS shifter 320 operates on a group of delayed clocks to generate right shifted signals, left shifted signals, or a combination of right and left shifted signals. For example, during a given period of time, the delayed clocks have multiple pulses, and during the same given period, the shifted signals only include a single one of those pulses. In an exemplary embodiment of the inventive concept, a carry signal is not used to generate the DMS signals, and the DMS signals are instead generated from one clock CLK. A device and method for generating DMS signals will be more fully described with reference to
The first latch 330 temporarily stores parallel data received from the control logic 310. The parallel data may be sequentially stored at the first latch 330 to correspond to a position where it is output to the display panel 400.
The second latch 340 receives the parallel data from the first latch 330. The second latch 340 outputs the parallel data to the decoder 350 at a required time in response to the DMS signal from the DMS shifter 320.
The decoder 350 converts the parallel data stored in the second latch 340 into a data voltage, that is, a gray scale voltage, based on the gamma reference voltages VG1 through VGk from the control logic 310.
The output buffer 360 may include a plurality of buffers (not shown). The output buffers receive the data voltage from the decoder 350 and output image data to the display panel 400. Red, green, and blue data may be sequentially output through channels Y1 through Yn connected to the output buffer 360. However, this order may be changed.
Each of the DMS blocks 320-1 through 320-m receives DCLK1 through DCLK10 to generate DMS signals. For example, one DMS block may generate ten DMS signals. A plurality of DMS signals DMS1 through DMS10m may be delayed by as much as a reference period (e.g., 1UI) from one another. The DMS signals DMS1 through DMS10m are used to adjust output timing of data signals output through channels Y1 through Yn of an output buffer 360 (refer to
In an exemplary embodiment of the inventive concept, a carry signal is not used to generate a DMS signal for adjusting output timing of image data. A plurality of DMS clocks are generated using a plurality of DCLKs that are generated using one clock CLK.
Since output timing of image data is adjusted using DMS clocks without use of a carry signal, the time taken to charge pixels may be reduced and the output timing of image data may be changed more easily.
The first DMS block 320-1 includes a plurality of sub blocks 321-1 through 325-1 (e.g., sub circuits). Each of the sub blocks 321-1 through 325-1 contains an enable signal generator and a delay unit.
Each of the sub blocks 321-1 through 325-1 receives two of the DCLK signals. For example, if there are 10 DCLK signals, five sub blocks are present where each sub block receives a next two DCLK signals among the 10 DCLK signals. The sub blocks 321-1 through 325-1 internally generate enable signals 1st EN_A through 1st EN_E using the corresponding two DCLK signals, respectively. The sub blocks 321-1 through 325-1 delay and output corresponding DCLK signals in response to corresponding enable signals 1st EN_A through 1st EN_E. In an exemplary embodiment, the DCLK signals DCLK1 through DCLK10 and the DMS signals DMS1 through DMS10 are sequentially delayed for as long as a reference period (e.g., 1UI).
In an exemplary embodiment of the inventive concept, the sub blocks 321-1 through 325-1 generate DMS signals for changing output timing of an image signal using the DCLK signals, thereby preventing a signal delay between DMS blocks for using a carry signal.
In an exemplary embodiment, the enable signal generator (e.g., EN Gen) generates the first enable signal 1st EN_A using two flip-flops, an inverter, and an AND gate. In an exemplary embodiment, the flip-flops are implemented with a positive edge trigger type of flip-flop. That is, the flip-flops may output logic “1” during a rising period of a DCLK2 bar signal. In an exemplary embodiment, an additional inverter is present to invert the DCLK2 signal so it can be applied to a clock terminal of the positive edge trigger type flip flop. However, the inventive concept is not limited thereto. For example, the flip-flops may be implemented with a negative edge trigger type of flip-flop. The DCLK2 signal may be applied to the clock terminal of the negative edge trigger type of flip flop. A waveform of the enable signal 1st EN_A is illustrated in
As described above, an enable signal is generated using DCLK2. An AND operation is performed on DCLK1 as well as DCLK2 to generate more accurate DMS1 and DMS2 signals. Upon performing an AND operation on DCLK1 and an enable signal generated using DCLK1, a tail portion of the DMS1 signal being output is removed by as much as 1UI. This means a reduction in timing when data is output. In other words, a time taken to charge pixels is insufficient. In contrast, it is possible to generate an enable signal using DCLK1, but a component is required for delaying the generated enable signal by 1UI or more.
Since the delay unit is implemented as illustrated in
Referring to
A first sub block 321-1 (refer to
A second sub block 322-1 (refer to
DMS5 through DMS10 for the remaining sub blocks of the first DMS block may be produced in a similar manner.
A first sub block of a second DMS block 320-2 generates 2nd EN_A using DCLK1 and DCLK2. DMS11 is produced through an AND operation performed on DCLK1 and 2nd EN_A, and DMS12 is generated through an AND operation performed on DCLK2 and 2nd EN_A.
A second sub block of the second DMS block 320-2 generates 2nd EN_B using DCLK3 and DCLK4. DMS13 is produced through an AND operation performed on DCLK3 and 2nd EN_B, and DMS14 is generated through an AND operation performed on DCLK4 and 2nd EN_B.
DMS15 through DMS20 for the remaining sub blocks of the second DMS block generate may be produced in a similar manner. In addition, DMS31 through DMS10m for sub blocks of third through M-th DMS blocks may be produced in a similar manner.
Each sub block of the DMS blocks 320-1 through 320-m includes an enable signal generator (e.g., EN Gen) to generate an enable signal and a delay unit, and a DMS shifter 320 (refer to
The fundamental configuration and function of a first DMS block 320-1 is similar to that shown in
Referring to
Reverse enable signals that sub blocks generate may be sequentially delayed in order from a reverse enable signal M-th REV_EN_E, which a fifth sub block of an M-th DMS block generates, to a reverse enable signal 1st REV_EN_A which a first sub block of a first DMS block generates. Because one reverse enable signal is generated using two DCLK signals, delay among reverse enable signals may correspond to “2UI”.
A left-shift manner shown in
Referring to
The DMS shifter 320-1, first latch 330-1, second latch 340-1, decoder 350-1, and output buffer 360-1 may be used to enable scanning of image data to be performed from a left end of a display panel to a center thereof (R-shift). The image data may be supplied to the display panel through channels Y1 through Yn/2 connected to the output buffer 360-1 under a control of an LDMS signal that the DMS shifter 320-1 generates.
The DMS shifter 320-2, first latch 330-2, second latch 340-2, decoder 350-2, and output buffer 360-2 may be used to enable scanning of image data to be performed from a right end of the display panel to a center thereof (L-shift). The image data may be supplied to the display panel through channels Y(n/2)+1 through Yn connected to the output buffer 360-2 under a control of an RDMS signal that the DMS shifter 320-2 generates.
DMS signals DMS1 through DMSn/2 are sequentially output through channels Y1 through Yn/2 connected to an output buffer 360-1 (refer to
In an exemplary embodiment of the inventive concept, no carry signal is used to generate DMS signals for controlling output timing of image data. DCLK signals are generated using a clock provided to a receiver (not shown) of a source driver, and LDMS signals and RDMS signals are produced using the DCLK signals. Thus, since a carry signal is not used, the time taken to charge pixels may be reduced and the output timing of image data may be changed more easily.
When scanning of image data is performed in the dual-shift manner (V-shift) as illustrated in
The method includes generating clocks using a clock received from an external device (S110). A delay between the clocks may correspond to a reference period. For example, a receiver of a source driver may include a phase locked loop (PLL) that generates a plurality of clocks based on the external clock.
The method includes generating enable signals based on the generated clocks (S120). The enable signals are used to generate DMS signals for controlling output timing of a data signal to be transmitted to a display panel. The enable signals may be selectively generated based on an operating mode of the display device, such as left-shift, right-shift, or dual-shift. The enable signals are constantly generated based on the clocks generated in step S110 without a carry signal.
The method includes generating DMS signals that are based on the clocks generated in step S110 using the enable signals (S130). Likewise, the DMS signals may be selectively generated based on an operating mode of the display device, such as left-shift, right-shift, or dual-shift.
The method includes outputting image data to the display panel during a period where the DMS signals are activated (S140).
In embodiments of a device and method capable of generating DMS signals as described above, the time taken to charge pixels may be reduced, thereby making it possible to more precisely control timing when image data is output. Accordingly, the performance of the display device may be improved.
While the inventive concept has been described with reference to exemplary embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the inventive concept. Therefore, it should be understood that the above embodiments are not limiting, but illustrative.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2014-0130188 | Sep 2014 | KR | national |
