Abstract:
A display apparatus, an integrated circuit and method thereof are disclosed. The display apparatus includes a frame buffer, a controller circuit, and a display driver circuit. The frame buffer is configured to retain a plurality of image frames to be displayed. The controller circuit, coupled to the frame buffer, is configured to determine whether a change in the image frames has occurred and whether a refresh time is expired. The display driver circuit, operatively coupled to the frame buffer and adapted to couple to an active display device, is configured to receive the image frames to be displayed from the frame buffer and dynamically refreshing the active display device when the change is determined or when a refresh time is expired.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of U.S. Provisional Application No. 61/551,763, filed on 26 Oct. 2011, and the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to display devices, and in particular relates to an integrated circuit for a display apparatus and a method thereof. 
     2. Description of the Related Art 
     Power saving is one primary objective of electronics design. Particularly for a mobile application, power saving is important due to the limited power storage. The display and graphics card may consume a considerable portion of the total power consumption of any electronic device. 
     In general, a display apparatus employs a display controller to generate data at a predetermined refresh rate supported by the display apparatus. As technology advances, new display types are now capable of supporting a refresh rate slower than an update rate of the image data. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect of the invention, a display apparatus is disclosed, comprising a frame buffer, a controller circuit, and a display driver circuit. The frame buffer is configured to retain a plurality of image frames to be displayed. The controller circuit, coupled to the frame buffer, is configured to determine whether a change in the image frames has occurred and whether a refresh time is expired. The display driver circuit, operatively coupled to the frame buffer and adapted to couple to an active display device, is configured to receive the image frames to be displayed from the frame buffer and dynamically refreshing the active display device when the change is determined or when a refresh time is expired. 
     In yet another aspect of the invention, an integrated circuit is described, comprising a frame buffer and a controller. The frame buffer is configured to retain a first image data and a second image data. The controller, coupled to the frame buffer and the transceiver, is configured to determine whether a second image data is received and whether a refresh time is expired. The transceiver is further configured to transmit the second image data to the display device when the second image data is received and transmit the first image data to the display device when the refresh time is expired. 
     In yet another aspect of the invention, a method performed by an integrated circuit is revealed, comprising: retaining a plurality of image frames to be displayed in a frame buffer; determining whether a change in a pair of image frames to be display consequently has occurred; counting a refresh time; and dynamically refreshing the active display device when the change is determined or when the refresh time is expired. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a block diagram of a conventional display apparatus  1 ; 
         FIG. 2  is a block diagram of an exemplary display apparatus  2  according to an embodiment of the invention; 
         FIG. 3  is a block diagram of an exemplary display apparatus  3  according to another embodiment of the invention; 
         FIG. 4  is a flowchart of an exemplary display refresh method  4  according to an embodiment of the invention; and 
         FIG. 5  is a flowchart of an exemplary display refresh method  5  according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a block diagram of a conventional display apparatus  1  comprising a controller circuit  10 , a display driver circuit  12 , and an LCD display  14 . The controller circuit  10  downloads and stores image frame data D i  from external data sources to a frame buffer  100 . The frame buffer  100  is a memory space that is allocated to maintain the image frame and to be accessed by a display driver IC  12  to display the image frame on an LCD display  14 . The image frames may be written onto the frame buffer  100  at a frame rate, which is determined by a number of image frames that are written into the frame buffer  100  per second. In the conventional approach, the LCD display  14  is refreshed at a refresh rate exceeding a minimum limit in order to prevent flicker occurrence on the display  14  due to TFT (Thin-Film-Transistor) current leakage. Typically, the display refresh rate is 60 Hz. The controller circuit  10  moves image data D i  from the frame buffer  100  to the display driver  12  at a fixed refresh rate, irrespective of the image frame rate. The refresh rate may be different from the frame rate. For example, the image frame is sent to the frame buffer  100  at a frame rate of 30 Hz and the image is refreshed on the LCD display  14  at a refresh rate of 60 Hz. In some implementations, the display driver circuit  12  also comprises a frame buffer (not shown) to keep the received image frame before refreshing image data on the LCD display  14 . In all cases the display driver IC  12  updates an image frame to the LCD display  14  by the refresh rate, regardless of the frame rate. 
       FIG. 2  is a block diagram of an exemplary display apparatus  2  according to an embodiment of the invention, comprising a controller circuit  20 , a display driver circuit  22 , and a display device  24 . The controller circuit  20  and the display driver circuit  22  can be integrated as a part of an integrated circuit for a communication or personal computing system, or can be made up by discrete components in a discrete circuit. The configuration of the controller circuit  20  and the display driver circuit  22  can be established through programmable options for display type, resolution, pixel depth, display refresh rate, and output data formats. The controller circuit  20  transfers frame data D i  to the display driver circuit  22  at a dynamic refresh rate determined by a frame rate or a display refresh rate. The frame rate is defined by a number of times per second in which an image frame is being transferred to the controller circuit  20 . The display refresh rate is defined by a number of times per second in which a display image is being refreshed on the display device  24 . The display driver circuit  22  is further coupled to a display device  24 , and refreshes images on a screen (not shown) of the display device  24  at the refresh rate. 
     It has been difficult to decrease the image refresh rate because of image flicker due to TFT leakage current. As multimedia display technology advances, the refresh rate of a display device  24  may be reduced to 1 Hz or lower, i.e., the display driver IC  12  can drive the display device at the refresh rate as low as 1 image frame per second. 
     The controller circuit  20  comprises a frame buffer  200 , an image comparator  202 , a time checker  204 , and a controller  206 . The controller  206  controls the operations of the frame buffer  200 , the image comparator  202 , and the time checker  204 . The frame buffer  200  may comprise single or multiple buffers. In the single-buffer system, the frame buffer  200  contains a partially downloaded frame, wherein a remaining portion of a previous frame is overwritten. In the double-buffer systems, the frame buffer  200  employs two buffers to reduce overwriting of the frame data. Newly downloaded frames are rendered in a second buffer while the previous frame is in a first buffer. The two buffers are swapped when the new frame transmission is completed so that the new frame can be refreshed and displayed on the display device. The image comparator  202  receives and compares the new frame D i     —     new  and the previous frame data D i     —     pre  from the frame buffer  200  to determine any differences therebetween. In some implementations, the image comparator  202  receives partial new frame data D i     —     new  ′ as soon as the partial new frame data D i     —     new  ′ is written into the frame buffer  200  and makes a partial comparison for the partial new data D i     —     new  ′ and the previous frame data D i     —     pre  accordingly. In other implementations, the image comparator  202  receives a predetermined size of partial new frame data D i     —     new  ′ at a predetermined? time to make a partial comparison with the previous frame data D —pre . In yet other implementations, the image comparator  202  receives the complete new frame data D i     —     new  and makes a complete comparison between the complete new frame data D i     —     new  and the previous frame data D i     —     pre . The image comparator  202  may temporarily keep the complete new frame data D i     —     new  in a local data buffer as the previous frame after the image comparison is finished. The image comparator  202  may signify the detection as soon as a difference is detected, or after the comparison has been performed for all data in the new frame data and the previous frame data. The controller circuit  20  may receive information on the minimum display refresh rate of the display device  24 , when it is set by a manufacturer or during a startup setup procedure. The time checker  204  may be realized by a timer or a counter, timing or counting a predetermined display refresh time. The predetermined display refresh time is selected such that it is less than an inverse value of the minimum display refresh rate. The controller  206  loads the new frame data D i     —     new  from sources such as the operating system, application programs, internet, local area network or an external data storage such as a flash memory or disk drive to the frame buffer  200 . The controller circuit  20  can provide image data to the display driver circuit  22  in response to an instruction from the comparator  202 . The comparator  202  can determine whether a change in the image frame has occurred and send out the instruction indicating that the change has occurred. That is, the controller circuit  20  can determine whether the received frame data is new according to the image difference detection result from the image comparator  202 , determine whether the predetermined display refresh time has been reached, and send the new frame data D i     —     new  to the display driver circuit  22  when a new frame data has been received or when the predetermined refresh time has been reached. 
     The display device  24  can be any type of video display, particularly, all types of active displays with a TFT structure like TFT-LCDs and AMOLEDs. The active displays include a liquid crystal display (LCD), Light emitting diode display (LED), Thin film transistor liquid crystal display (TFT-LCD), Electroluminescent display (ELD), Plasma display panel (PDP), Liquid crystal on silicon (LCoS) display, Organic light-emitting diode (OLED) display, Organic light-emitting transistor (OLET) display, Surface-conduction electron-emitter display (SED) display, Field emission display (FED) display, Laser TV display, MEMS display, Quantum dot display (QD-LED), Ferro liquid display (FLD), Thick-film dielectric electroluminescent (TDEL), Telescopic pixel display (TPD), or Laser phosphor display (LPD). 
     In some implementations, the controller circuit  20  is implemented by an integrated circuit, and may be, for example, a microcontroller for a mobile phone or a processor for a laptop computer. The frame buffer  200  is configured to receive and retain a first image data and a second image data from the internal data storage and external network, where the first image data is from the previous image frame and the second image data is from the current image frame. In some implementations, the controller  206  may send a request message to the external network to request for the first or the second image data. The controller circuit  20  may comprises a transceiver (not shown) that is coupled to the display driver circuit  22  and configured to transmit the first and the second image data to the display device via the display driver circuit  22 . The controller  206  is coupled to the frame buffer  200  and the transceiver and configured to determine whether a second image data has been received and whether a refresh time is expired. The transceiver is configured to transmit the second image data to the display device  24  when the second image data has been received and transmit the first image data to the display device  24  when the refresh time is expired, thereby supplying the display device  24  with a timely and stable image signal. 
     The controller circuit  20  comprises the image comparator  202  acquiring image data from the frame buffer  200  to compare the second image data with the first one. The comparison result may be outputted to the controller  206  for determining whether a new image data has been received. For example, the first and the second image may be image frames with the same pixel dimension m×n, where m and n are the number of pixels of the image frame along the x-axis and y-axis dimension. The image comparator  202  compares corresponding pixels in the first and second image data and prompts a difference signal to the controller  26  upon detecting a difference therebetween. In other examples, the comparator  202  outputs a comparison result indicating one or more differences between the first and second image data. The realization of data comparison for the first and second image data is up to the actual implementation, so long as the controller  206  can distinguish the second image data as an updated image, allowing the transceiver to update the updated second image data to the display device  24  whenever the new image is available. 
     The controller circuit  20  comprises the time checker  204  (a timer or a counter) configured to count the refresh time. In some implementations, the refresh time is configurable by the controller  206  according to the supported refresh rates of the display device  24 . The time checker  204  counts the refresh time, either by incrementing or decrementing at a fixed frequency clock (not shown) to establish a measure of the refresh time. Upon the refresh time being expired, the controller circuit  20  refreshes image data displayed on the display device  24  by retransmitting the first image data to the display device  24  via the display driver circuit  22 . The controller  206  may reset the time checker  204  after the refresh time is expired. 
     The display apparatus  2  refreshes the display device according to a display refresh rate or new frame data determination, thereby providing a dynamic frame refresh mechanism for the display device  24 . 
       FIG. 3  is a block diagram of an exemplary display apparatus  3  according to another embodiment of the invention. The circuit configuration and circuit operation of the display apparatus  2  are identical to those in the display apparatus  2 , except that the frame buffer  200 , image comparator  202 , and the time checker  204  are moved to the display driver circuit  32 . The controller circuit  30  still comprises a frame buffer  200  therein to provide a data storage space to buffer the loaded image frame. The display controller  306  receives the new frame data D i      —     new  from the frame buffer  200  for storage in the frame buffer  300 . The display buffer  300  may further comprise a base plane and a set of overlays that represent display content as a superposition on the base plane. The display controller  306  then moves the new frame data from the frame buffer  300  to the image comparator  302  for an image comparison, determines whether the received frame data is new according to the image difference detection result from the image comparator  302 , determines whether the predetermined display refresh time has been reached, and refreshes the new frame data D i     —     new  to the display device  24  when a new frame data has been received or when the predetermined refresh time has been reached. 
     In some implementations, the controller circuit  30  is implemented by an integrated circuit, and may be, for example, a display driver in a mobile phone, a display device, or a computer. The circuitry connection and configuration is identical to that of the controller  20  in  FIG. 2 , thus, reference may be made to the preceding paragraphs and will not repeated here for brevity. 
     The display apparatus  3  refreshes the display device  24  according to a display refresh rate or new frame data determination, thereby providing a dynamic frame refresh mechanism for the display device  24 . 
       FIG. 4  is a flowchart of an exemplary display refresh method  4  according to an embodiment of the invention, incorporating the display apparatus  1  in  FIG. 1 . 
     Any time when the display device  24  is active and the controller  206  requests to update a display image frame from the internal or external image sources (S 402 ), the controller  206  receives and saves the new image frame data D i     —     new  from the internal or external image sources to the frame buffer  200 (S 404 ). Upon reception of the new image frame data D i     —     new , the image comparator  202  compares the partial or full new image frame data D i     —     new  with the previous image frame data D i     —     pre  to determine any differences therebetween (S 406 ). If a difference is detected, the controller  206  determines that an updated image has been received and sends the new image frame data D i     —     new  to the display driver circuit  22  (S 408 ). If no difference is detected, the controller  206  takes no action to update the image frame data and refresh the display device  24  (S 410 ). Concurrently, the time checker  204  counts the time to determine whether the predetermined display refresh time has been reached (S 412 ). If so, the controller  206  renews the image frame data by sending the image data D i     —     new  from the frame buffer  200  to the display driver circuit  22  (S 408 ). If not so, the time checker  204  continues counting the time (S 412 ). Upon receiving a complete new frame data D i     —     new , the display driver circuit  22  drives the display device  24  using the new image data D i     —     new  (S 414 ), thereby completing the display refresh procedure  4  (S 416 ). After the display refresh procedure (S 414 ) is done, the time checker  204  resets its timer and restarts to count the next refresh time immediately. 
     In some implementations, the display refresh method  4  is carried out in an integrated circuit in a mobile device that comprises the controller circuit  20  in  FIG. 2 . The display refresh method  4  comprises transmitting a first image data to a display device, determining whether a second image data has been received (S 406 ), determining whether a refresh time is expired (S 412 ), transmitting the second image data to the display device when the second image data has been received, and transmitting the first image data to the display device when the refresh time is expired (S 408 ). In some implementations, the controller  206  sends request messages requesting for the first and second image data to a service network, and, in response, receives the first and second image data to be retained in the frame buffer  200 . 
     In some implementations, the determining whether the second image data has been received step (S 406 ) comprises comparing the second image data with the first image data, and determining that the second image data has been received when the second image data is different from the first image data. 
     In some implementations, the determining whether a refresh time is expired step (S 412 ) comprises counting, by a timer, the refresh time. In some embodiments, the display refresh method  4  may further comprise resetting the timer after the refresh time is expired. The display refresh method  4  may comprise setting up the refresh time according to a supported refresh rate of the display device. 
     The display refresh method  4  offers a means to refresh the display device  24  not by a fixed refresh rate, but a dynamic refresh rate determined by the event of a new data frame being transferred into the frame buffer or when the display refresh time has been received. 
       FIG. 5  is a flowchart of an exemplary display refresh method  5  according to another embodiment of the invention, incorporating the display apparatus  3  in  FIG. 3 . Steps S 500 -S 502 , S 506 -S 514  are identical to Steps S 400 -S 402 , S 406 -S 416 , except that Steps S 404 -S 416  are performed in the controller circuit, while the Step S 504 -S 514  are carried out in the display driver circuit. Accordingly, reference to the preceding explanation for  FIG. 4  can be made for corresponding detailed descriptions. Step S 504  is different from the Step S 404 , where the controller circuit  30  sends the image frame data from the frame buffer  200  to the frame buffer  300  in the display driver circuit  32 . Then the display driver circuit  32  carries out Steps S 506 -S 514  to refresh the display device  34  when a new image frame is received by the frame buffer  300 , or when the predetermined refresh time has been reached. After the display refresh procedure (S 508 ) is done, the time checker  304  resets its timer and restarts to count the next refresh time immediately. 
     Similar to the method  4 , the display refresh method  5  provides a means to refresh the display device  24  by a dynamic refresh rate determined by the event of a new data frame coming into the frame buffer or when the display refresh time has arrived, and can be carried out by the display driver circuit  32 . 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.