Data transmission method and related display driver circuit and host

Abstract

A data transmission method for a display driving circuit includes the following steps: receiving at least one first synchronization signal, the at least one first synchronization signal being used to determine a frame period for a plurality of image data on an image frame; receiving a first image data to be refreshed among the plurality of image data during a first transmission period corresponding to the first image data; and stopping receiving a second image data not to be refreshed among the plurality of image data during a second transmission period corresponding to the second image data.

Description

Technical Field

[0001] This invention relates to a data transmission method for a display driving circuit and a host device, and more particularly to a data transmission method that enables partial refresh of display data between the display driving circuit and the host device. Prior Technology

[0002] In recent years, most display data has been transmitted using the Mobile Industry Processor Interface (MIPI). Current MIPI specifications include video mode and command mode. In command mode, the display typically has a frame buffer. Display data transmitted through the MIPI is written to the frame buffer, and when the display needs to refresh the screen, it retrieves the corresponding display data from the frame buffer. In video mode, the display does not use a frame buffer; instead, the host computer directly refreshes the screen by transmitting display data through the MIPI. Summary of the Invention

[0003] Therefore, the main objective of this invention is to provide a data transmission method that enables partial refresh of display data between the display driver circuit and the host device.

[0004] One embodiment of the present invention discloses a data transmission method for a display driving circuit, comprising the following steps: receiving at least one first synchronization signal, the at least one first synchronization signal being used to determine a frame period for a plurality of image data on an image frame; receiving a first image data to be refreshed among the plurality of image data during a first transmission period corresponding to the first image data; and stopping receiving a second image data not to be refreshed among the plurality of image data during a second transmission period corresponding to the second image data.

[0005] Another embodiment of the present invention discloses a display driving circuit, which is used to receive at least one first synchronization signal, the at least one first synchronization signal being used to determine a frame period for a plurality of image data on an image frame; for a first image data to be refreshed among the plurality of image data, the first image data is received during a first transmission period corresponding to the first image data; and for a second image data not to be refreshed among the plurality of image data, the reception of the second image data is stopped during a second transmission period corresponding to the second image data.

[0006] Another embodiment of the present invention discloses a data transmission method for a host device, comprising the following steps: outputting at least one first synchronization signal, the at least one first synchronization signal being used to determine a frame period for a plurality of image data on a first image frame; transmitting a first image data to be refreshed within a first transmission period corresponding to the first image data; and stopping the transmission of a second image data not to be refreshed within a second transmission period corresponding to the second image data. Simple Explanation of the Diagram

[0007] Figure 1 is a schematic diagram of the display system according to Embodiment 1 of the present invention. Figure 2 is a schematic diagram of how the display panel in the display system refreshes the image using a conventional method. Figure 3 is a timing diagram of the transmission interface in normal video mode, in which the host device transmits image data to the display driver circuit so that the display panel can refresh the image. Figure 4 is a timing diagram of the transmission interface in an embodiment of the present invention, in which the host device transmits part of the image data to the display driving circuit for the display panel to refresh the image screen. Figure 5 is a schematic diagram of the display panel in the display system of the present invention performing a partial refresh of the image. Figure 6 illustrates the data transmission and refresh methods in the display system of this invention when the image remains unchanged. Figure 7 is a timing diagram of the signals and data transmitted between the host device and the display driver circuit under the data transmission method based on Figure 6. Figure 8 shows the data transmission and refresh methods in the display system according to another embodiment of the present invention. Figure 9 is a timing diagram of the signals and data transmitted between the host device and the display driver circuit under the data transmission method based on Figure 8. Figure 10 shows the data transmission method and refresh method in the display system according to another embodiment of the present invention. Figure 11 is a timing diagram of the signals and data transmitted between the host device and the display driver circuit under the data transmission method based on Figure 10. Figure 12 shows the data transmission method and refresh method in the display system according to another embodiment of the present invention. Figure 13 is a timing diagram of the signals and data transmitted between the host device and the display driver circuit under the data transmission method based on Figure 12. Figure 14 illustrates a data transmission method in which X-direction partitioning is added according to an embodiment of the present invention. Figure 15 illustrates another data transmission method in which X-direction partition refresh is added according to an embodiment of the present invention. Figure 16 is a schematic diagram of the data transmission process in Embodiment 1 of the present invention. Figure 17 is a schematic diagram of another data transmission process according to an embodiment of the present invention. Implementation

[0008] Figure 1 is a schematic diagram of a display system 10 according to an embodiment of the present invention. The display system 10 includes a host device 100, a display driving circuit 102, and a display panel 104. The host device 100 can serve as a video source or video providing unit, used to output image data to the display driving circuit 102 for display on the display panel 104. The display driving circuit 102 processes the image data and converts the image data into corresponding data voltages to be output to the pixels on the display panel 104. Correspondingly, the display driving circuit 102 can also output control signals to the display panel 104 to control each pixel to turn on sequentially to receive the data voltage. In one embodiment, the host device 100 can be, for example, an application processor (AP), a central processing unit (CPU), a microprocessor, a microcontroller unit (MCU), or any type of system processing device. In one embodiment, the display driving circuit 102 can be implemented in an integrated circuit (IC) to realize a display driver IC (DDIC). In one embodiment, the display panel 104 can be any type of display device, such as a light-emitting diode (LED) panel, an organic light-emitting diode (OLED) panel, a liquid crystal display (LCD) panel, etc., but is not limited thereto.

[0009] The display driver circuit 102 includes a memory 110, switches 112_1 and 112_2, and an image processing circuit 114. The memory 110 can be, for example, Static Random Access Memory (SRAM) or Graphics Random Access Memory (GRAM), which can serve as a frame buffer to store display data from the host device 100. The image processing circuit 114 can perform various image processing on the display data to improve visual effects. These image processing operations include subpixel rendering, demura, etc., but are not limited to these. Furthermore, the host device 100 can transmit display data to the display driver circuit 102 through a Mobile Industry Processor Interface (MIPI). As mentioned above, the specifications of the Mobile Industry Processor Interface include video mode and command mode. Therefore, the display driver circuit 102 can control the switches 112_1 and 112_2 according to the operation mode of the mobile processor interface, so that under different operation modes, the display data from the host device 100 can be directly output to the display panel 104 (such as video mode), or the display data can be written to the memory 110 for storage and then output from the memory 110 to the display panel 104 (such as command mode).

[0010] Figure 2 is a schematic diagram of the display panel 104 in the display system 10 refreshing the image using a normal method. Specifically, the display area (active area) of the display panel 104 can be divided into three regions Z1 to Z3, which display the letter "A" on the current image frame N. On the next image frame N+1, only the image content in region Z2 changes, while the images in other regions Z1 and Z3 remain unchanged.

[0011] Figure 3 is a timing diagram of the transmission interface in normal video mode, showing the host device 100 transmitting image data to the display driver circuit 102 for image refresh on the display panel 104. Specifically, Figure 3 illustrates the various data / signals transmitted on the transmission interface between the host device 100 and the display driver circuit 102, including a vertical synchronization signal (VSYNC), a horizontal synchronization signal (HSYNC), and display data. For clarity, Figure 3 also shows an external horizontal synchronization signal (EXT_HSYNC) received by the display driver circuit 102, as well as the status of the display panel 104 and the transmission channel status of the transmission interface (such as MIPI).

[0012] The display driver circuit 102 can use the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the external horizontal synchronization signal EXT_HSYNC to determine the timing of processing display data. The vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC can be provided to the display driver circuit 102 by the host device 100, while the external horizontal synchronization signal EXT_HSYNC can be received by the display driver circuit 102 from an external device. Specifically, the vertical synchronization signal VSYNC is used to determine the frame duration for a single image frame (e.g., image frames N, N+1, etc.). The horizontal synchronization signal HSYNC and the external horizontal synchronization signal EXT_HSYNC are used to determine the display time of a series of image data. The display driver circuit 102 can selectively receive at least one of the horizontal synchronization signal HSYNC and the external horizontal synchronization signal EXT_HSYNC to perform timing synchronization control for each series.

[0013] As shown in Figure 3, a frame period determined by the vertical synchronization signal VSYNC can include a data transmission period, a vertical front porch (VFP) VFP_0~VFP_M, and a vertical back porch (VBP) VBP_0~VBP_M. The vertical back porch VBP_0~VBP_M is the time interval from the pulse of the vertical synchronization signal VSYNC to the start of effective image data transmission, and the vertical front porch VFP_0~VFP_M is the time interval from the end of effective image data transmission to the pulse of the next vertical synchronization signal VSYNC. The data transmission period is the period used to transmit effective image data. Assuming that the display panel 104 contains 128 columns of pixels, and according to the horizontal synchronization signal HSYNC (or the external horizontal synchronization signal EXT_HSYNC), the data transmission period can include 128 columns of time, which are used to transmit the image data columns L0~L127 (hereinafter referred to as data columns) required for each column of pixels. Furthermore, in addition to the time interval used to transmit each data column L0~L127, each time column may also include a horizontal front porch (HFP) and a horizontal back porch (HBP) (omitted in Figure 3 for simplification).

[0014] Please refer to Figure 3 in conjunction with Figure 2. As described above, in normal video mode, the host device 100 needs to transmit the image data of the entire screen. Therefore, during data transmission, the host device 100 needs to transmit all data columns L0~L127 of an image frame (e.g., N+1) to the display driver circuit 102. Correspondingly, the display driver circuit 102 can control the display panel 104 to refresh the entire screen, that is, refresh areas Z1~Z3, regardless of whether their image content changes.

[0015] In this scenario, the mobile processor interface needs to transmit all image data throughout the entire data transmission period, resulting in significant power consumption. Furthermore, regardless of whether the image content changes, the display panel 104 is refreshed. This means that the display driver circuit 102 transmits image data and its corresponding control signals to all display areas on the display panel 104, causing numerous potential transitions on the data lines and scan lines of the display panel 104. This necessitates frequent charging and discharging, generating substantial power consumption.

[0016] To save power, the host device 100 can transmit only the image data that needs updating to the display driving circuit 102. The display driving circuit 102, based on the received image data and corresponding image position information, only refreshes the portion of the image on the display panel 104 that needs updating. In one embodiment, the host device 100 notifies the display driving circuit 102 of the range of image data that needs updating in the Nth frame. In the (N+1)th frame, the host device 100 only transmits the image data that needs updating, and the display driving circuit 102 only updates that portion of the image data.

[0017] Figure 4 is a timing diagram of the transmission interface in an embodiment of the present invention, showing how the host device 100 transmits partial image data to the display driving circuit 102 for image refresh on the display panel 104. Similar to the example in Figure 3, the host device 100 can transmit at least one synchronization signal to the display driving circuit 102, including a vertical synchronization signal VSYNC and a horizontal synchronization signal HSYNC. The display driving circuit 102 can also receive an external horizontal synchronization signal EXT_HSYNC from an external device. The functions and operation of each synchronization signal are the same as in Figure 3 and will not be repeated here.

[0018] Similarly, assuming that an image frame of the display panel 104 contains 128 columns of pixels (i.e., 128 data columns (L0~L127)), in this example, only columns 51 to 70 need to be refreshed. In this case, the host device 100 only transmits the corresponding data columns L50~L69 to the display driver circuit 102. Correspondingly, the display driver circuit 102 controls the display panel 104 to refresh only the pixel columns corresponding to data columns L50~L69, and not refresh the other pixel columns. Please further refer to Figure 5 in conjunction with Figure 4, where the display panel 104 only refreshes region Z2, and the images in regions Z1 and Z3 remain unchanged, therefore they are not refreshed.

[0019] For example, the host device 100 can write information or instructions regarding the image update range into a specific register of the display driver circuit 102 at frame N. This specific register stores information on starting and stopping the update of data columns. Then, at frame (N+1), the host device 100 will still transmit image data to the display driver circuit 102 according to the original timing, but only data will be transmitted in the timing corresponding to data columns L50~L69. For other data columns, the host device 100 will only transmit a horizontal synchronization signal HSYNC to the display driver circuit 102, or enter a low-power mode. Simultaneously, the display driver circuit 102 will only refresh the image data on the data lines (or source lines) in data columns L50~L69, while the remaining data columns will maintain the data from frame N. If the display panel 104 is an organic light-emitting diode (OLED) panel, the data lines that are not updating image data can be fixed at a specific voltage.

[0020] More specifically, as shown in Figure 4, based on the timing determined by the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC (or the external horizontal synchronization signal EXT_HSYNC), each data column L0 to L127 in an image frame contains its corresponding transmission period, where each data column L0 to L127 corresponds to the transmission period determined by one pulse of the horizontal synchronization signal HSYNC. In other words, based on the control of the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC (and / or the external horizontal synchronization signal EXT_HSYNC), the timing of the mobile industry processor interface can reserve transmission time for each data column L0 to L127. In data columns L0 to L127, for data columns L50 to L69 that are to be refreshed, the host device 100 can transmit data columns L50 to L69 to the display driver circuit 102 during their corresponding transmission period; for other data columns L0 to L49 and L70 to L127 that are not to be refreshed, the host device 100 can stop transmitting image data during their corresponding transmission period, and the display driver circuit 102 correspondingly stops receiving image data.

[0021] As shown in Figure 5, the display driver circuit 102 can operate in the video mode of the mobile processor interface. In this mode, switch 112_1 is turned on and switch 112_2 is turned off, so that data columns L50~L69 from the host device 100 can bypass memory 110 and be directly transmitted to the image processing circuit 114. After processing by the image processing circuit 114, corresponding data voltages are generated. The display driver circuit 102 then outputs these data voltages to the display panel 104 and outputs corresponding control signals to the display panel 104 to turn on the pixels on the display panel 104 located in the area to be refreshed, so that they can receive the corresponding data voltages. On the other hand, for other data columns L0~L49 and L70~L127 that have not been refreshed, the display driving circuit 102 can stop outputting any data voltage to the display panel 104 to reduce the power consumption generated by the charging and discharging behavior of the data lines on the display panel 104. At this time, the display driving circuit 102 can also stop outputting control signals to the display panel 104, or maintain the control signal at a specific level so that the corresponding pixels remain turned off.

[0022] In one embodiment, during the period when the host device 100 stops transmitting image data to the display driver circuit 102, the mobile industry processor interface can be set to a power-saving state. The power-saving state can be implemented in various ways. In one power-saving state, the mobile industry processor interface does not output image data during the data transmission period corresponding to the unrefreshed data column, thus stopping data transmission. At this time, the host device 100 only transmits packets of the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC to the display driver circuit 102 through the mobile industry processor interface. Correspondingly, the display driver circuit 102 can determine the timing of data transmission based on the horizontal synchronization signal HSYNC packets (such as the Horizontal Synchronization Start (HSS) signal in the packets).

[0023] In another power-saving mode, to further reduce power consumption, during the period when the host device 100 stops transmitting image data to the display driver circuit 102, the output of the horizontal synchronization signal HSYNC to the display driver circuit 102 can be simultaneously stopped. At this time, the transmission channel of the mobile industry processor interface does not switch levels to stop signal / data transmission. For example, as shown in Figure 4, during the transmission period originally reserved for data columns L0~L49 and L70~L127, since both image data and the horizontal synchronization signal HSYNC are stopped, the transmission channel in the mobile industry processor interface can be set to LP-11, which is a channel state in the low-power mode of the mobile industry processor interface. At this time, the differential channels in the transmission channel are all locked at the high level without switching, which reduces the power consumption of the mobile industry processor interface. It should be noted that since the host device 100 stops outputting the horizontal synchronization signal HSYNC, the display driver circuit 102 must receive the external horizontal synchronization signal EXT_HSYNC from the external device (through an interface other than the mobile industry processor interface) and use the external horizontal synchronization signal EXT_HSYNC to perform timing control of each column of image data, that is, to determine the transmission period of each column of image data.

[0024] In one embodiment, the host device 100 may output a command to the display driver circuit 102 before transmitting a portion of the display data of an image frame, indicating the range of image data to be refreshed and the range of image data not to be refreshed (e.g., the coordinates of the area or block to be refreshed). For example, as shown in Figure 4, for the display data of image frame N+1, the host device 100 may transmit the command at the vertical front corridor (e.g., VFP_0) before the pulse corresponding to image frame N+1 in the vertical synchronization signal VSYNC. Alternatively, the host device 100 may also transmit the command at the vertical back corridor before data transmission, or provide information about the range of image data to be refreshed to the display driver circuit 102 at some earlier time. Or, the host device 100 may transmit the relevant command of the range of image data to be refreshed to the display driver circuit 102 through other transmission interfaces.

[0025] For the display driver circuit 102, upon receiving an instruction from the host device 100, it can determine the range of image data to be refreshed and the range of image data not to be refreshed according to the instruction, and control the display panel 104 to refresh accordingly. Based on the timing information provided by the horizontal synchronization signal HSYNC (and / or the external horizontal synchronization signal EXT_HSYNC), the display driver circuit 102 can know the transmission period corresponding to each column of image data, and receive image data within the transmission period corresponding to the range to be refreshed.

[0026] It is worth noting that the instruction transmitted by the host device 100 regarding the range of image data to be refreshed is selective. In another embodiment, the host device 100 does not notify the display driver circuit 102 of the range of image data that needs to be updated / refreshed. In the data columns that do not need to be updated, the host device 100 only transmits the horizontal synchronization signal HSYNC or directly enters a low-power mode (such as LP-11). At this time, the display driver circuit 102 does not provide the range of image data to be refreshed through the host device 100, but instead determines the range of image data to be refreshed and the range of image data not to be refreshed based on the signal / data transmission status on the transmission interface. During the transmission period corresponding to each column of image data, the display driver circuit 102 can determine whether there is a high-speed switching signal on the data transmission channel of the mobile processor interface, or whether it is in a power-saving state, and determine the range of image data to be refreshed accordingly. For example, based on the horizontal synchronization signal HSYNC packet (and / or timing information provided by the external horizontal synchronization signal EXT_HSYNC), the display driver circuit 102 can count the received HSYNC / EXT_HSYNC pulses. Furthermore, the display driver circuit 102 knows how many HSYNC / EXT_HSYNC pulses are included in the length of the vertical rear corridor. This pulse counting can be used to determine the start time of data transmission and the corresponding transmission time for each subsequent column of image data. Therefore, if a high-speed signal is not received on the data transmission channel after the data transmission period has started, the display driver circuit 102 can determine that the corresponding image data has not been refreshed. If image data is subsequently received during a certain transmission period, it can be determined that the image data has started refreshing at that position.

[0027] In this way, the display driving circuit 102 refreshes the image data of the data lines (or source lines) only on the data columns that need updating, while the remaining data columns retain the data from the previous frame. If the display panel 104 is an organic light-emitting diode panel, the data lines that do not need to be updated can be fixed at a specific voltage.

[0028] It should also be noted that in the embodiment shown in Figure 5, switch 112_1 is turned on while switch 112_2 is turned off, allowing data columns L50~L69 to bypass memory 110 and be processed directly by image processing circuit 114 and output to display panel 104 in real time. In another embodiment, switch 112_2 can be turned on and switch 112_1 can be turned off, allowing image data from host device 100 to be transferred to memory 110 for storage. When a refresh is desired later, the image data is read from memory 110 and converted into corresponding data voltage for output to display panel 104. As long as display driving circuit 102 can receive synchronization signals to determine the transmission timing of display data and receive a partial frame of image data from host device 100 for partial refresh, all related implementation methods should fall within the scope of this invention.

[0029] Figure 6 illustrates the data transmission and refresh methods in the display system 10 under the condition that the image frame remains unchanged, according to an embodiment of the present invention. Figure 7 is a timing diagram of the signals and data transmitted between the host device 100 and the display driving circuit 102 under the data transmission method of Figure 6. In this example, the host device 100 can determine whether the image data of each image frame is completely identical to the previous image frame. When it determines that the image data of image frame N+1 is completely identical to the previous image frame N, it can stop all image data transmission during the frame period of image frame N+1. Correspondingly, the display panel 104 does not refresh any area on image frame N+1. That is, the image displayed on the display panel 104 on image frame N+1 is completely identical to the image displayed on image frame N. Therefore, the display driving circuit 102 does not output any data voltage to the display panel 104 during the frame period of image frame N+1.

[0030] Similarly, to further reduce power consumption, the host device 100 can selectively stop outputting the horizontal synchronization signal HSYNC to the display driver circuit 102, and the display driver circuit 102 receives the external horizontal synchronization signal EXT_HSYNC for timing control. As shown in Figure 7, in one embodiment (option 1), the host device 100 can still transmit the vertical synchronization signal VSYNC to the display driver circuit 102 to determine the frame duration of image frame N+1, and put the transmission channel into a power-saving state (such as LP-11) during the frame duration of image frame N+1. Specifically, the transmission channel is in a power-saving state during the vertical rear corridor VBP, data transmission, and vertical front corridor VFP. In another embodiment (option 2), to achieve extreme power saving, the host device 100 further stops outputting the vertical synchronization signal VSYNC to the display driver circuit 102. In this case, the original frame duration of image frame N+1 can be regarded as an extension of the vertical front corridor VFP of the previous frame N.

[0031] As shown in Figure 7, in this example, the host device 100 may also selectively transmit a command to the display driver circuit 102 to instruct all image data in image frame N+1 to stop transmission, or the display driver circuit 102 may determine whether to stop receiving image data based on the state of the transmission interface.

[0032] Figure 8 illustrates the data transmission and refresh methods in the display system 10 according to another embodiment of the present invention. Figure 9 is a timing diagram of the signals and data transmitted between the host device 100 and the display driving circuit 102 under the data transmission method of Figure 8. In this example, among the areas Z1 to Z3 of the display panel 104, only area Z2 needs to be refreshed, while areas Z1 and Z3 do not. Assuming that the image data range corresponding to the pixel column in area Z2 is data column L50 to L69, the host device 100 can transmit a data column (such as L20 to L99) slightly larger than the range of image data to be refreshed to the display driving circuit 102 so that the display driving circuit 102 can perform necessary image processing. As described above, before the display panel 104 is refreshed, the display driving circuit 102 needs to perform various image processing on the image data to improve the visual effect (such as through the image processing circuit 114). During the image processing, it may be necessary to refer to a large range of original image data. Even if the panel area corresponding to these additional image data is not refreshed, the host device 100 still needs to transmit these image data to the display driving circuit 102 to optimize the image processing effect.

[0033] As shown in Figure 8, although only the pixel column within region Z2 needs to be refreshed, the host device 100 still transmits some image data within regions Z1 and / or Z3 (such as image data near region Z2). In this case, the image processing circuit 114 in the display driving circuit 102 can refer to this additional received image data to perform image processing on the image data within region Z2.

[0034] In one embodiment, the display driving circuit 102 may transmit relevant information to the host device 100 in advance according to the range of image data that its internal image processing needs to reference. Therefore, the host device 100 can transmit corresponding additional image data columns during data transmission according to the needs of the display driving circuit 102, and the range of such data columns is not limited to the examples described in this specification.

[0035] Furthermore, regarding the unrefreshed image data in regions Z1 and Z3, its content is usually the same as the image data in a previous frame, and therefore it has been stored in memory 110 before the previous frame is displayed. Therefore, in one embodiment, if image processing is to be performed on the image data in refreshed region Z2, a portion of the image data in regions Z1 and / or Z3 (such as the image data near region Z2) can be retrieved from memory 110 as a reference.

[0036] It is worth noting that in the above embodiments, there is only one refresh area on the display panel 104. However, in other embodiments, based on the changes in the display data, the refresh area on the display panel can be arbitrarily set, and it can be located at any position on the panel, and there is no limitation to only one refresh area on a single frame. Figure 10 shows the data transmission method and refresh method in the display system 10 according to another embodiment of the present invention. Figure 11 is a timing diagram of the signals and data transmitted between the host device 100 and the display driving circuit 102 under the data transmission method of Figure 10. In this example, in areas Z1 to Z3 of the display panel 104, areas Z1 and Z3 are refreshed while area Z2 is not refreshed. Correspondingly, on the mobile industry processor interface between the host device 100 and the display driving circuit 102, the transmitted data columns are L0 to L49 (corresponding to area Z1) and L70 to L127 (corresponding to area Z3). During the transmission of data columns L50 to L69, image data transmission is stopped and a power-saving state is entered. The power-saving method is similar to that in the aforementioned embodiment, and will not be described in detail here.

[0037] Figure 12 illustrates the data transmission and refresh methods in the display system 10 according to another embodiment of the present invention. Figure 13 is a timing diagram of the signals and data transmitted between the host device 100 and the display driving circuit 102 under the data transmission method of Figure 12. In this example, region Z2 is refreshed while regions Z1 and Z3 are not refreshed. To save the transmission time of display data, the transmission period corresponding to the unrefreshed image data range can be omitted. Specifically, as shown in Figure 13, within the frame period of image frame N+1, the transmission period of unrefreshed data columns L0~L49 and L70~L127 is omitted, and the vertical rear corridor VBP and vertical front corridor VFP are also omitted. In this case, data columns L50~L69 can be transmitted in advance, thereby shortening the frame period and improving data transmission efficiency.

[0038] Similarly, to further reduce power consumption, the host device 100 can stop outputting the horizontal synchronization signal HSYNC to the display driver circuit 102, and the display driver circuit 102 can receive the external horizontal synchronization signal EXT_HSYNC for timing control. Furthermore, the host device 100 can selectively transmit relevant instructions to the display driver circuit 102 before the frame period of image frame N+1 to indicate a case where transmission time is omitted. It should be noted that in this example, since the display driver circuit 102 receives data columns L50~L69 in advance, it can write data columns L50~L69 into memory 110, so that the data can be read from memory 110 later when the panel is to be refreshed. In this case, switch 112_2 should be turned on and switch 112_1 should be turned off, as shown in Figure 12.

[0039] In the above embodiments, the display panel 104 is partitioned in the Y direction (vertical direction) to determine whether each area is refreshed or not, that is, refresh is determined on a per-pixel column basis. However, in other embodiments, partitioning can also be performed in the X direction (horizontal direction), that is, refresh is determined on a per-column basis, to achieve more flexible local refresh applications. The host device 100 can transmit the image data to be refreshed to the display driver circuit 102 at the corresponding transmission time according to the partitioning method of the X and Y directions.

[0040] Figure 14 illustrates a data transmission method incorporating X-direction partitioning refresh according to an embodiment of the present invention. As shown in Figure 14, the image data of the area to be refreshed is located in columns 51 to 70; therefore, the timing diagrams of these columns are enlarged for easier illustration. Specifically, a pulse of the horizontal synchronization signal HSYNC (or the external horizontal synchronization signal EXT_HSYNC) can be used to determine a column of time, and each column of time is used to transmit a column of data. Each column of time may include a horizontal rear corridor (HBP), a data transmission period, and a horizontal front corridor (HFP).

[0041] If a pure Y-direction partitioning method is used, the host device 100 can transmit all data columns L50~L69 of the area to be refreshed to the display driver circuit 102, and the display panel 104 can refresh the corresponding entire column of pixels. If an X-direction partitioning is added, the host device 100 only needs to transmit the image data of the area to be refreshed, that is, the portion of the image data to be refreshed in data columns L50~L69. The display driver circuit 102 can control the opening and closing of the data lines (source lines) and scan lines (gate lines) so that the display panel 104 only updates the image of a portion of the area. In this case, during the transmission period corresponding to other non-refreshed areas, the transmission interface can be controlled to enter a power-saving state. In one embodiment, if the host device 100 and the display driver circuit 102 use a mobile industry processor interface for data transmission, during the period when no image data is being transmitted, the transmission channel can be controlled to output data 0 or output a certain fixed data to reduce signal switching in the transmission channel. In this way, image data is transmitted only during the transmission period corresponding to the area to be refreshed (i.e., a portion of the transmission period in a column), minimizing the power consumption of the transmission interface.

[0042] It is worth noting that in the aforementioned embodiments, the power-saving state of LP-11 was used on the transmission interface during the transmission period when no image data was transmitted. However, the embodiment in Figure 14 uses output data 0 (or output a fixed data) to reduce power consumption. This is because, according to the protocol of the mobile industry processor interface, entering the power-saving state of LP-11 requires a mode switching process, which takes a considerable amount of time. In the embodiment of Figure 14, the image data of only a portion of the pixels in a column of pixels is stopped during a certain period of time, and the stop time may be extremely short, insufficient for the transmission interface to enter the power-saving state of LP-11. In this case, outputting a fixed data value can reduce switching. In another embodiment, if the image data stop transmission time is long enough, LP-11 or other suitable power-saving methods can also be used. As for the period of the horizontal / vertical rear corridor or the horizontal / vertical front corridor, the host device 100 can select fixed output data 0 or set it to enter LP-11, or use other suitable power-saving methods according to its length. All related implementation methods should fall within the scope of this invention.

[0043] Figure 15 illustrates another data transmission method incorporating X-direction partitioning refresh according to an embodiment of the present invention. The difference between the embodiment in Figure 15 and the embodiment in Figure 14 is that the embodiment in Figure 15 further incorporates data compression for panel refresh and corresponding data transmission. Due to the bandwidth limitations of mobile processor interfaces, to support the massive data volume of currently available high-resolution display panels, the host device 100 needs to compress the display data before transmission. The display driver circuit 102 then decompresses the received display data to restore it to its original form before subsequent image processing and / or writing to the display panel 104. Compression / decompression reduces the amount of data transmitted by the mobile processor interface, meeting its bandwidth requirements while simultaneously reducing power consumption during data transmission.

[0044] Currently, most compression of display data employs Display Stream Compression (DSC) technology. Its compression architecture involves two decoders (or decompressors) in the display driver circuit 102. One decoder processes the image data of the left half of the display panel 104, and the other processes the image data of the right half. For example, assuming the display panel 104 contains 128 rows of pixels, one decoder processes rows 1-64, and the other processes rows 65-128. In this case, the host device 100 should follow the same rules for compression, that is, compressing every 64 rows and N columns of pixels as a unit (N can be any positive integer within the total number of columns). In the display stream compression specification, the unit of compression is called a slice, and the size of the compression unit is determined by the slice width and slice height. In this example, the slice width is 64 and the slice height is N.

[0045] Under the aforementioned compression scheme, the smallest unit of display data transmitted by the host device 100 is a segment, the width of which is equal to half the total number of rows on the display panel 104. Even if the area to be refreshed due to changes in the image is smaller than the segment size, the host device 100 still needs to compress the entire segment of image data before transmitting it to the display driver circuit 102. Only then can the display driver circuit 102 decompress the data to restore the original data. In other words, a segment transmitted by the host device 100 may contain some image data to be refreshed and some image data not to be refreshed. The encoder (or compressor) built into the host device 100 can combine these image data for compression and then transmit the compressed data to the display driver circuit 102 through the mobile processor interface. Correspondingly, the decoder in the display driver circuit 102 can decompress the compressed data (i.e., the segment) from the host device 100 to restore the image data to be refreshed and the image data not to be refreshed.

[0046] As shown in Figure 15, when an X-direction partition is added, the image data transmitted through the transmission interface for the data columns L50~L69 containing the area to be refreshed is the portion covered by the segment width SL_W, which in this example is the left half of the panel. It should be noted that in the embodiment of Figure 15, the transmitted image data is only a portion of the image data in data columns L50~L69. However, in other embodiments, if the segment height exceeds the range of data columns L50~L69, the compressed image data transmitted through the transmission interface needs to extend to the upper and / or lower columns to match the segment height range.

[0047] It is worth noting that the main objective of this invention is to provide a data transmission method that can be used in the transmission interface between the display driver circuit and the host device to achieve partial refresh of display data. Those skilled in the art can make modifications or variations accordingly, but are not limited thereto. For example, in an embodiment of this invention, power saving can be achieved by stopping the transmission of image data during the transmission period corresponding to the image data in the unrefreshed area. Stopping transmission can be achieved in any way, such as using the channel state LP-11 of the mobile processor interface to stop data signal switching, outputting fixed data, or using various power-saving modes of the transmission interface to reduce power consumption. Such power-saving implementations should not be used to limit the scope of this invention. Furthermore, in the above embodiments, the display driver circuit 102 is provided with a memory 110 as a frame buffer. Therefore, in addition to supporting the video mode of the mobile processor interface according to the timing determined by the vertical / horizontal synchronization signal, it can also support command mode or hybrid mode applications, and can flexibly switch between various operating modes through the control of a switch. In another embodiment, the display driving circuit may also support only video mode. In this case, the display driving circuit can receive the image data of the part to be refreshed from the host device whenever the panel is to be refreshed, without the need to set a frame buffer, which can further save circuit area and reduce the power consumption required for memory read and write.

[0048] The data transmission method for the display driving circuit described above can be summarized as a data transmission process 160, as shown in Figure 16. Data transmission process 160 can be implemented in a display driving circuit within a display system, such as the display driving circuit 102 in Figure 1. It can transmit data with a host device through a transmission interface to partially refresh the display panel. As shown in Figure 16, data transmission process 160 includes the following steps:

[0049] Step 1602: Receive at least one first synchronization signal, which is used to determine a frame period for a plurality of image data on an image frame.

[0050] Step 1604: For a first image data to be refreshed among the plurality of image data, receive the first image data within a first transmission period corresponding to the first image data.

[0051] Step 1606: For a second image data that is not refreshed among the plurality of image data, stop receiving the second image data during a second transmission period corresponding to the second image data.

[0052] On the other hand, the data transmission method for the host device can be summarized as another data transmission process 170, as shown in Figure 17. Data transmission process 170 can be implemented in a host device within a display system, such as host device 100 in Figure 1, which can transmit data with a display driving circuit through a transmission interface to partially refresh the display panel. As shown in Figure 17, data transmission process 170 includes the following steps:

[0053] Step 1702: Output at least one first synchronization signal, which is used to determine a frame period for a plurality of image data on an image frame.

[0054] Step 1704: For a first image data that is to be refreshed among the plurality of image data, transmit the first image data within a first transmission period corresponding to the first image data.

[0055] Step 1706: For a second image data that is not refreshed among the plurality of image data, stop transmitting the second image data during a second transmission period corresponding to the second image data.

[0056] For detailed explanations of the operation and changes of data transmission processes 160 and 170, please refer to the above paragraphs; they will not be repeated here.

[0057] In summary, this invention proposes a data transmission method for the transmission interface between a display driving circuit and a host device in a display system, enabling partial refresh of display data. In embodiments of this invention, the display driving circuit can receive vertical / horizontal synchronization signals from the host device and / or receive external horizontal synchronization signals from an external device to control the timing of image data transmission based on the synchronization signals; that is, a transmission period is set for each image data column. For image data to be refreshed, the host device can transmit the image data to the display driving circuit during the corresponding transmission period, and the display driving circuit can receive the image data and drive the display panel to refresh accordingly. For image data not to be refreshed, the host device can stop transmitting image data to the display driving circuit during the corresponding transmission period, and the display driving circuit stops receiving image data; in this case, the display panel does not need to be refreshed. Through the above data transmission method, only a portion of the image data to be refreshed is transmitted between the host device and the display driving circuit, allowing the display panel to refresh only a portion of an image frame, thereby reducing the power consumption of the transmission interface between the host device and the display driving circuit, as well as the power consumption of the display panel. In one embodiment, the host device can determine the range of the area to be refreshed based on the content of the image data to be transmitted, and transmit the relevant information to the display driving circuit via a command. Alternatively, the display driving circuit can determine the range of image data to be refreshed and image data not to be refreshed based on the data transmission status of the transmission interface, and control the display panel to perform partial refresh accordingly, thereby achieving power saving. The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be covered by the present invention.

[0058] 10: Display System 100: Main unit 102: Display driver circuit 104: Display Panel 110: Memory 112_1, 112_2: Switches 114: Image processing circuit Z1~Z3: Area N, N+1, N+2: Image frames VSYNC: Vertical Synchronization Signal HSYNC: Horizontal synchronization signal EXT_HSYNC: External horizontal synchronization signal VFP, VFP_0~VFP_M: Vertical front porch VBP, VBP_0~VBP_M: Vertical rear corridor L0~L127: Data Series HBP: Horizontal Rear Corridor HFP: Horizontal Front Porch 160, 170: Data transmission process 1602~1606, 1702~1706: Steps

Claims

1. A data transmission method for a display driving circuit, the data transmission method comprising: receiving a vertical synchronization signal and a horizontal synchronization signal, the vertical synchronization signal being used to determine a frame period for a plurality of image data on an image frame, and the horizontal synchronization signal being used to determine a first transmission period and a second transmission period within the frame period; receiving a first image data to be refreshed among the plurality of image data during the first transmission period corresponding to the first image data; and ceasing to receive a second image data not to be refreshed among the plurality of image data during the second transmission period corresponding to the second image data.

2. The data transmission method as described in claim 1, wherein the frame period includes a data transmission period, a front porch, and a back porch, wherein, The first transmission period and the second transmission period are located within the data transmission period.

3. The data transmission method as described in claim 1, further comprising: stopping the reception of the horizontal synchronization signal from a host device during the second transmission period; and receiving an external horizontal synchronization signal from an external device to determine the first transmission period and the second transmission period using the external horizontal synchronization signal.

4. The data transmission method as described in claim 1, wherein the display driving circuit receives the first image data through a transmission interface, and during the second transmission period, the transmission interface is set to a power-saving state.

5. The data transmission method as described in claim 1 further includes: when the first image data is refreshed, outputting a data voltage corresponding to the first image data to a display panel; and when the second image data is not refreshed, stopping the output of any data voltage to the display panel.

6. The data transmission method as claimed in claim 1, wherein the plurality of image data includes a plurality of first image data and a plurality of second image data, and the data transmission method further includes: receiving an instruction from a host device before the frame period; and determining the range of the plurality of first image data and the plurality of second image data according to the instruction.

7. The data transmission method as described in claim 1, wherein the display driving circuit is configured to receive the plurality of image data through a transmission interface, the plurality of image data including a plurality of first image data and a plurality of second image data, and the data transmission method further includes: determining the range of the plurality of first image data and the plurality of second image data based on the state of the transmission interface.

8. The data transmission method as described in claim 1, further comprising: receiving, in addition to receiving the first image data during the first transmission period, a third image data that is not refreshed from the plurality of image data.

9. The data transmission method as described in claim 8 further includes: referring to the third image data to perform an image processing on the first image data.

10. The data transmission method as described in claim 8, further comprising: decompressing a segment containing the first image data and the third image data.

11. A display driving circuit, configured to: receive a vertical synchronization signal and a horizontal synchronization signal, the vertical synchronization signal being configured to determine a frame period for a plurality of image data on an image frame, and the horizontal synchronization signal being configured to determine a first transmission period and a second transmission period within the frame period; receive a first image data to be refreshed among the plurality of image data during the first transmission period corresponding to the first image data; and stop receiving a second image data not to be refreshed among the plurality of image data during the second transmission period corresponding to the second image data.

12. A data transmission method for a host device, the data transmission method comprising: outputting a vertical synchronization signal and a horizontal synchronization signal, the vertical synchronization signal being used to determine a frame period for a plurality of image data on a first image frame, and the horizontal synchronization signal being used to determine a first transmission period and a second transmission period within the frame period; transmitting a first image data to be refreshed among the plurality of image data during the first transmission period corresponding to the first image data; and stopping transmission of a second image data not to be refreshed among the plurality of image data during the second transmission period corresponding to the second image data.

13. The data transmission method as described in claim 12, wherein the frame period includes a data transmission period, a front porch, and a back porch, wherein, The first transmission period and the second transmission period are located within the data transmission period.

14. The data transmission method as described in claim 12, wherein the vertical synchronization signal, the horizontal synchronization signal, and the first image data are transmitted to a display driving circuit.

15. The data transmission method as described in claim 14, further comprising: stopping the transmission of the horizontal synchronization signal to the display driver circuit during the second transmission period.

16. The data transmission method as described in claim 12, wherein the host device transmits the first image data through a transmission interface, and during the second transmission period, the transmission interface is set to a power-saving state.

17. The data transmission method as described in claim 12 further comprises: when it is determined that a plurality of image data of a second image frame following the first image frame is the same as the plurality of image data of the first image frame, stopping the transmission of the plurality of image data of the second image frame during another frame period corresponding to the second image frame.

18. The data transmission method as described in claim 17 further includes: stopping the output of the horizontal synchronization signal and the vertical synchronization signal during the period of the other frame corresponding to the second image frame.

19. The data transmission method as claimed in claim 12, wherein the plurality of image data includes a plurality of first image data and a plurality of second image data, and the data transmission method further includes: before the frame period, outputting an instruction to a display driving circuit to indicate the range of the plurality of first image data and the plurality of second image data.

20. The data transmission method as described in claim 12, further comprising: in addition to transmitting the first image data during the first transmission period, transmitting a third image data that is not refreshed from the plurality of image data.

21. The data transmission method as described in claim 20 further includes: combining the first image data and the third image data for compression, and transmitting the compressed first image data and the third image data.

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