Patent Application
20230072161
The present invention relates to a method of display control for a display driver circuit and an application processor, and more particularly, to a method of display control based on communications between a display driver circuit and an application processor.
Modern organic light-emitting diode (OLED) panels in the market mostly apply the low-temperature polycrystalline silicon (LTPS) technology, where the substrate of the OLED panels is composed of polycrystalline silicon synthesized at relatively low temperatures as compared to traditional manufacturing methods. The low-temperature polycrystalline oxide (LTPO) technology is an evolution of the LTPS. In an LTPO panel, an additional oxide layer is inserted on the substrate, allowing the electrons to pass through the thin-film transistors (TFTs) implemented on the substrate more rapidly and efficiently, reducing the power required to activate the display pixels, so as to reduce the overall power consumption.
The display of the LTPO panel supports an extremely low frame rate such as 1 Hz. In the LTPO panel, the low frame rate may be realized by refreshing several image frames and not refreshing several image frames to be displayed on the panel. For example, in a display architecture having 60 Hz frame rate, the LTPO panel may be refreshed in one of every 60 frames, and may omit the refreshing in other 59 frames, so as to achieve the 1 Hz frame rate equivalently.
In a display system, the display panel may be controlled by a display driver circuit, and the image data are provided from an application processor (AP) and forwarded through the display driver circuit. The LTPO panel may enter an operation mode having a low frame rate through a display sequence when the AP does not need to update the images. In this low frame rate mode, the LTPO panel should be accurately controlled to be refreshed in one or several frames and not refreshed in other frames periodically, in order to realize the low frame rate. In such a situation, the display driver circuit and the AP should provide the image data appropriately based on the refreshing scheme of the panel.
In general, the display driver circuit and the AP may perform display control in a video mode or a command mode. In the command mode, the display control circuit is equipped with a frame buffer which may be implemented with a random-access memory (RAM). The AP sends instructions in addition to the image data to the display driver circuit, and the image data are written into the frame buffer through the control of the instructions. As for an LTPO panel operated in a low frame rate mode, the AP may output the image data at any time before the image data is requested to be sent to the panel, and the image data may be stored in the frame buffer. When the LTPO panel needs to be refreshed, the display driver circuit may read out the image data from the frame buffer.
In the video mode, the AP provides the image data in the form of a real-time data stream. The display driver circuit correspondingly processes the data stream and directly forwards it to the panel. Thus, in order to reduce the cost and complexity, there may be no frame buffer implemented in the display driver circuit. When the panel needs to be refreshed, the AP should output the image data immediately. As for an LTPO panel operated in a low frame rate mode, the image may not be refreshed in most image frames; hence, the AP does not need to output image data for these image frames.
However, the display sequence of the LTPO panel is configured in the display driver circuit, but the AP does not know any information associated with the display sequence. Therefore, when the LTPO panel is operated in the low frame rate mode and meanwhile the display system applies the video mode and the display driver circuit has no frame memory, the AP may not know when to output image data. Thus, there is a need for improvement over the prior art.
It is therefore an objective of the present invention to provide a novel display control method applicable to the display driver circuit and the application processor, allowing the display driver circuit and the application processor to communicate with each other to satisfy the low frame rate application of the low-temperature polycrystalline oxide (LTPO) panel.
An embodiment of the present invention discloses a method of display control for a display driver circuit. The display driver circuit is operated in a video mode. The method comprises steps of: driving a display panel to display a plurality of image frames having a plurality of active frames and a plurality of blanking frames; and determining whether to transmit a notification to an application processor to indicate whether the application processor needs to output image data according to whether an incoming image frame among the plurality of image frames is one of the plurality of active frames or one of the plurality of blanking frames. Wherein, the display panel is refreshed in each of the plurality of active frames, and not refreshed in each of the plurality of blanking frames.
Another embodiment of the present invention discloses a display driver circuit, which is configured to be coupled to an application processor and a display panel. The display driver circuit is operated in a video mode, and configured to drive the display panel to display a plurality of image frames having a plurality of active frames and a plurality of blanking frames; and determine whether to transmit a notification to the application processor to indicate whether the application processor needs to output image data according to whether an incoming image frame is one of the plurality of active frames or one of the plurality of blanking frames. Wherein, the display panel is refreshed in each of the plurality of active frames, and not refreshed in each of the plurality of blanking frames.
Another embodiment of the present invention discloses a method of display control for an application processor. The application processor is configured to control a display driver circuit operated in a video mode. The method comprises steps of: providing a plurality of image frames for the display driver circuit to be displayed on a display panel; outputting first image data for a first image frame among the plurality of image frames to the display driver circuit; and after outputting the first image data, determining whether to transmit a command to the display driver circuit for a second image frame among the plurality of image frames, to indicate whether the application processor is configured to proactively output second image data for the second image frame.
Another embodiment of the present invention discloses an application processor, which is configured to be coupled to a display driver circuit and a display panel. The display driver circuit is operated in a video mode. The application processor is configured to provide a plurality of image frames for the display driver circuit to be displayed on the display panel; output first image data for a first image frame among the plurality of image frames to the display driver circuit; and after the first image data are output, determine whether to transmit a command to the display driver circuit for a second image frame among the plurality of image frames, to indicate whether the application processor is configured to proactively output second image data for the second image frame.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Please refer to
In detail, each skip sequence SEQ1-SEQ5 may have one or more active frames (ACT) and one or more blanking frames (BLK). The panel is refreshed in the active frame(s) and is not refreshed in the blanking frame(s). If the frame rate equals 60 Hz in the normal display mode, in order to realize the extremely low frame rate such as 1 Hz, there may be 1 active frame and 59 blanking frames in the repeated skip sequence SEQ5. In other words, the panel may be refreshed in only one of every 60 image frames as the skip sequence SEQ5 is performed repeatedly.
Please refer to
In an embodiment, the display driver circuit 202 may be implemented in an integrated circuit (IC) to be realized as a display driver IC. In addition, the display driver IC may be integrated with touch sensing functions to realize a touch and display driver IC (TDDI), or further integrated with fingerprint sensing functions to realize a fingerprint, touch and display driver IC (FTDI). The AP 200 may be, but not limited to, a central processing unit (CPU), microprocessor, microcontroller unit (MCU), or any other type of processing circuit of an electronic device. In the embodiments of the present invention, the display system may be operated in the video mode, where there is no frame buffer included in the display driver circuit 202, and the AP 204 should output the image data when the display panel 200 needs to be refreshed.
Please note that the display sequence of the LTPO panel is configured in the display driver circuit 202; that is, the display driver circuit 202 may control the flow of the skip sequences with configurations of the active frames and the blanking frames. In the prior art, the AP 204 may not know when to output image data in the video mode because it is not aware of the information of the skip sequences. In order to solve this problem, the display driver circuit 202 may transmit a notification to the AP 204, to indicate whether the AP 204 needs to output image data according to whether an incoming image frame is the active frame or the blanking frame. In other words, the notification may carry the information associated with the active frame and the blanking frame, and thus the AP 204 will output the image data only when the notification indicates that the incoming image frame is the active frame.
Sometimes the AP 204 may need to proactively output image data. For example, the AP 204 may need to update the image content when the user activates a specific event to modify the displayed image. In such a situation, the AP 204 may transmit a command to the display driver circuit 202, to indicate whether the AP 204 needs to proactively output the image data, i.e., update the image content.
As can be seen, the display panel 200 is driven by the display driver circuit 202 while the image data are output from the AP 204. The present invention provides a communication scheme that allows the display driver circuit 202 and the AP 204 to negotiate with each other to appropriately output image data, so as to successfully control the panel refresh in the extremely low frame rate when the display system and the display driver circuit 202 are operated in the video mode.
In general, the AP 204 may deliver the image data to the display driver circuit 202 through a transmission interface. Examples of the transmission interface may include, but not limited to, the Mobile Industry Processor Interface (MIPI), Serial Peripheral Interface (SPI), and Inter-Integrated Circuit (I2C) interface. This transmission interface may usually be a bidirectional interface. In an embodiment, the display driver circuit 202 and the AP 204 may communicate with each other through this interface used for delivering the image data, as shown in
In another embodiment, the notification NTF and the command CMD may be transmitted in another manner. For example, as shown in
When the notification NTF and/or the command CMD are sent through the interface for delivering image data, the notification NTF and/or the command CMD may be carried in the blanking interval in which no valid image data are transmitted. For example, the command CMD may be carried in a front porch or a back porch in the image data format, and/or may be indicated in a horizontal synchronization start (HSS) packet, a vertical synchronization start (VSS) packet, or a vertical synchronization end (VSE) packet.
In another embodiment, the display driver circuit 202 may transmit a notification NTF to the AP 204 through the GPO pin of the display driver circuit 202, while the AP 204 may transmit a command CMD to the display driver circuit 202 through the interface for delivering image data, as shown in
Please refer to
Each skip sequence SEQ1-SEQ5 includes one or more active frames and one or more blanking frames. The arrangements of the active frames and the blanking frames are also shown in
As mentioned above, the display driver circuit 202 may transmit the notification NTF to the AP 204, to indicate whether the incoming image frame is the active frame or the blanking frame. In this embodiment as shown in
Please refer to
Step 400: Start.
Step 402: Drive the display panel to display a plurality of image frames having a plurality of active frames and a plurality of blanking frames.
Step 404: Determine whether to transmit a notification to an AP to indicate whether the AP needs to output image data according to whether an incoming image frame among the plurality of image frames is one of the plurality of active frames or one of the plurality of blanking frames.
Step 406: End.
According to the display control process 40, the display driver circuit may drive the display panel to display image frames, which consist of the active frames and the blanking frames in the skip mode, where the display panel is refreshed in the active frame and is not refreshed in the blanking frame. In this embodiment, the display driver circuit is operated in the video mode and deployed with no frame memory; hence, the AP may output image data only when the display panel needs to refresh the image frames (i.e., the active frames). The display driver circuit thereby determines whether to transmit the notification to the AP, to indicate whether the AP needs to output the image data according to whether the incoming image frame is the active frame or the blanking frame.
A detailed implementation of the display control process 40 is illustrated in
Subsequently, when the display system determines to enter the skip mode, the AP may send a command to the display driver circuit. Upon receiving this command, the display driver circuit may start the display sequence in the skip mode consisting of the skip sequences SEQ1-SEQ5, to go through the skip sequences SEQ1-SEQ4 by one time and then repeatedly perform the skip sequence SEQ5. The table in
The display driver circuit may determine whether to transmit the notification to the AP to indicate whether the incoming image frame is the active frame or the blanking frame through the GPO pin. Note that the display panel is refreshed in the active frame and is not refreshed in the blanking frame; hence, the notification may indicate whether the display panel needs to be refreshed in the incoming image frame. In an embodiment, the display driver circuit may transmit a notification when the incoming image frame is the active frame, and stop transmitting the notification when the incoming image frame is the blanking frame. The notification may be realized as a toggle or a pulse on the GPO pin. As shown in
In this embodiment, the AP outputs the image data A for each active frame, which means that the AP does not proactively update the image data and thus the same image data A are continuously output. Correspondingly, the AP may transmit the command CMDA for each image frame, to indicate that the image data need not to be updated. In detail, the AP may transmit the command CMDA in the vertical front porch (VFP) of the previous frame, to indicate that the image data output in the current frame are identical to those image data previously output (i.e., the image data A), or indicate that there are no image data output in the current frame.
Please refer to
Step 600: Start.
Step 602: Provide a plurality of image frames for the display driver circuit to be displayed on a display panel.
Step 604: Output first image data for a first image frame among the plurality of image frames to the display driver circuit.
Step 606: Determine whether to transmit a command to the display driver circuit for a second image frame among the plurality of image frames, to indicate whether the AP is configured to proactively output second image data for the second image frame.
Step 608: End.
According to the display control process 60, the AP may determine whether to transmit a command to the display driver circuit, to indicate whether the AP needs to proactively output the image data. More specifically, when the AP needs to update the image data, the AP may transmit the command correspondingly. In the above embodiment shown in
Please refer to
As shown in
Please note that the present invention aims at providing a novel display control method applicable to the display driver circuit and the AP. Those skilled in the art may make modifications and alterations accordingly. For example, the numbers of active frames and blanking frames in each skip sequence may be configured flexibly. In an embodiment, the numbers of active frames and blanking frames may be configured based on the display characteristics of the panel, and/or based on the frame rate value to be achieved in the skip mode. The frame counts ACT_NUM and BLK_NUM recorded in the tables in the above embodiments are merely served to illustrate an example, and this should not be a limitation of the scope of the present invention. In addition, the number of transitional skip sequences may also be configured flexibly. Also, the embodiments of the present invention are applicable to any types of display panels capable of realizing the extremely low frame rate by refreshing partial image frames. These types of display panels may include, but not limited to, the LTPO panel.
Further, in the above embodiments, the command sent by the AP for the current image frame is carried in the VFP of the previous image frame, but the implementation of the command transmission is not limited thereto. As shown in the zoom-in diagrams of
In another embodiment, the notification sent by the display driver circuit may be transmitted through the interface for delivering image data, to be carried in the VBP, VFP, or any other blanking interval. In addition, the display driver circuit may provide different types of notifications for the active frame and the blanking frame. For example, the display driver circuit may transmit a first notification to the AP if the incoming image frame is the active frame, and transmit a second notification different from the first notification to the AP if the incoming image frame is the blanking frame. The AP thereby determines whether to output image data by recognizing the received notification.
Similarly, although the commands sent by the AP are transmitted through the interface for delivering image data in the embodiments shown in
As shown in
In an embodiment, the display panel such as an LTPO panel may be configured with multiple low frame rates, which may be applicable to different scenarios. Therefore, different applications may use different skip modes so as to achieve different frame rates. For example, the frame rate may be decreased to 10 Hz in the first skip mode and 5 Hz in the second skip mode. The display panel will enter the first skip mode when an application requesting 10 Hz frame rate is open, and enter the second skip mode when another application requesting 5 Hz frame rate is open. Therefore, in the display system of the present invention, the display panel may be configured with any number of skip modes, and switched between the skip modes flexibly based on the control of the AP. The AP may transmit the mode change signal to notify the display driver circuit to change the skip mode. In an embodiment, the mode change signal may carry information indicating which skip mode the display panel will enter, and the display driver circuit may control the display sequence correspondingly.
As shown in
Another difference between
Please note that the embodiments shown in
To sum up, the present invention provides a novel display control method applicable to the display driver circuit and the AP, where the display driver circuit and the AP may negotiate with each other to appropriately control the panel refresh when the display system is operated in the video mode. As for a display panel capable of realizing a low frame rate in the skip mode by refreshing in partial image frames such as the LTPO panel, the AP is requested to output the image data only when the image frame needs to be refreshed. Therefore, the display driver circuit may determine whether to transmit a notification to the AP, to indicate whether the image frame needs to be refreshed based on the display sequence of the skip mode. Sometimes the AP may need to proactively update the image data, and the AP may determine whether to transmit a command to the display driver circuit, to indicate whether the AP needs to proactively output the image data. In an embodiment, the command and/or the notification may be sent through the interface used for delivering image data, and/or may be sent through a GPO pin. As a result, the operations of the AP and the display driver circuit will be well synchronized, so as to refresh the display panel appropriately in the skip mode.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
