PATENT DOCUMENT

Publication Number: US-8907884-B2
Application Number: US-68341410-A
Country: US
Kind Code: B2

Title: LED backlight system

Abstract:
A method and system for modifying the pulse width modulation frequency for controlling the backlit illumination intensity of a liquid crystal display. The modified pulse width modulation frequency may be selected to reduce distortion in the display while allowing for a wide range of dimming settings for the display. A pulse width modulation signal may be also be phase shifted such that a string of light sources may be sequentially activated to generate a effective frequency greater than that of the frequency of the pulse width modulation signal.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display panel comprising a plurality of pixels; 
 a light source comprising a plurality of light emitting diode (LED) strings adapted to generate light to illuminate the plurality of pixels; 
 a sequencer configured to receive an PWM signal and to phase shift the PWM signal to create an effective frequency for controlling the LED strings, wherein an amount of phase shift applied to each LED string is based on a number of LED strings, and wherein a pulse of a first LED string of the plurality of LED strings overlaps at least one pulse of a different LED string of the plurality of LED strings; and 
 display control logic adapted to activate and deactivate each LED string of the plurality of LED strings in a sequence at the effective frequency of approximately at least 1 kHz. 
 
     
     
       2. The electronic device of  claim 1 , comprising a pulse width modulator configured to generate a pulsed signal and transmit the pulsed signal to the display control logic. 
     
     
       3. The electronic device of  claim 2 , wherein the display control logic is adapted to receive the pulsed signal and utilize the pulsed signal to sequentially activate and deactivate the plurality of LED strings. 
     
     
       4. The electronic device of  claim 2 , wherein each LED string of the plurality of LED strings comprises a plurality of LEDs. 
     
     
       5. The electronic device of  claim 4 , wherein each LED string includes six LEDs coupled in series. 
     
     
       6. The electronic device of  claim 1 , wherein the display control logic is adapted to sequentially activate and deactivate each LED string at a frequency of at least 8 kHz. 
     
     
       7. An electronic device, comprising:
 a pulse width modulator (PWM) adapted to generate an oscillating PWM signal at a frequency of at least approximately 1 kHz and at least at a 10-bit brightness resolution; and 
 a sequencer adapted to receive the oscillating PWM signal and to phase shift the oscillating PWM signal for controlling the activation and deactivation of light emitting diode (LED) string of a plurality of LED strings, wherein each of the light emitting diode strings are activated and deactivated sequentially, wherein an amount of phase shift applied to each LED string is based on a number of LED strings, and wherein a pulse of a first LED string of the plurality of LED strings overlaps at least one pulse of a different LED string of the plurality of LED strings. 
 
     
     
       8. The electronic device of  claim 7 , comprising a display, wherein the brightness of the display is controlled by adjusting a duty cycle of the oscillating PWM signal. 
     
     
       9. The electronic device of  claim 7 , wherein the sequencer phase shifts the oscillating PWM cycle to generate an effective frequency of at least approximately 6 kHz. 
     
     
       10. The electronic device of  claim 7 , wherein the sequencer phase shifts the oscillating PWM cycle to generate an effective frequency of at least approximately 48 kHz. 
     
     
       11. An electronic device, comprising:
 a display having a plurality of light emitting diode (LED) strings adapted to generate light to illuminate a plurality of pixels in the display; 
 a pulse width modulator (PWM) adapted to generate an oscillating PWM signal; and 
 display control logic adapted to activate and deactivate the plurality of LED strings sequentially at approximately at least 1 kHz, wherein the display control logic comprises delay circuitry adapted to phase shift the oscillating PWM signal for activation and deactivation of the light source at an effective frequency of at least approximately 10 kHz, wherein an amount of phase shift applied to each LED string is based on a number of LED strings, and wherein a pulse of a first LED sting of the plurality of LED stings overlaps at least one pulse of a different LED sting of the plurality of LED stings. 
 
     
     
       12. The electronic device of  claim 11 , wherein each of the LED strings comprises a plurality of LEDs. 
     
     
       13. The electronic device of  claim 11 , wherein display control logic is adapted to activate and deactivate the plurality of LED strings at approximately at least 8 kHz. 
     
     
       14. The electronic device of  claim 11 , wherein the PWM modifies a duty cycle of the oscillating PWM signal for control of the brightness of the display. 
     
     
       15. The electronic device of  claim 11 , wherein the display control logic is configured to lessen a brightness of the display by reducing a level of current through active LED strings if a duty cycle of the PWM signal is to be set below a threshold duty cycle level. 
     
     
       16. The electronic device of  claim 11 , wherein the display control logic comprises delay circuitry adapted to phase shift the oscillating PWM signal for activation and deactivation of the light source at an effective frequency of at least approximately 48 kHz. 
     
     
       17. A method of providing illumination to a display to reduce visual artifacts, comprising:
 generating an oscillating pulse width modulator (PWM) signal in a PWM; 
 receiving the PWM signal at a sequencer; and 
 phase shifting and sequentially routing the PWM signal from the sequencer to a plurality of light emitting diode (LED) strings in a display to activate and deactivate the LED stings sequentially at an effective frequency of at least approximately 6 kHz to reduce optical beating resulting from the frequency of the PWM signal and a refresh frequency of the display, wherein an amount of phase shift applied to each LED sting is based on a number of LED stings, and wherein a pulse of a first LED string of the plurality of LED stings overlaps at least one pulse of a different LED sting of the plurality of LED stings. 
 
     
     
       18. The method of  claim 17 , comprising adjusting the brightness of the display by adjusting the duty cycle of the PWM signal. 
     
     
       19. The method of  claim 18 , comprising adjusting the duty cycle of the PWM signal based on user input or based on a determination of the amount of internal power remaining in an internal power source. 
     
     
       20. The method of  claim 19 , comprising sequentially transmitting the PWM signal to the plurality of LED strings in the display at a frequency of at least approximately 8 kHz. 
     
     
       21. A method for illuminating a display, comprising:
 generating light from a light source; 
 directing the light towards a plurality of pixels in a display; and 
 toggling light emitting diode (LED) stings of the light source on and off sequentially at an effective frequency of approximately at least 48 kHz via a phase shifted pulse width modulator (PWM) signal, wherein an amount of phase shift applied to each LED sting is based on a number of LED stings, and wherein a pulse of a first LED string of the LED stings overlaps at least one pulse of a different LED sting of the LED strings. 
 
     
     
       22. The method of  claim 21 , comprising adjusting a duty cycle of the PWM signal in response to user initiated changes of brightness of the display. 
     
     
       23. The method of  claim 21 , wherein toggling the light source on and off comprises sequentially activating and deactivating at least one light emitting diode (LED) string in the light source. 
     
     
       24. The method of  claim 21 , wherein toggling the light source on and off comprises sequentially activating and deactivating each of six LED strings in sequence at approximately at least 8 kHz per string.

Description:
BACKGROUND 
     The present disclosure relates generally to controlling the backlight illumination source of a liquid crystal display. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic devices increasingly include display screens as part of the user interface of the device. As may be appreciated, display screens may be employed in a wide array of devices, including desktop computer systems, notebook computers, and handheld computing devices, as well as various consumer products, such as cellular phones and portable media players. Liquid crystal display (LCD) panels have become increasingly popular for use in display screens. This popularity can be attributed to their light weight and thin profile, as well as the relatively low power it takes to operate the LCD pixels. 
     The LCD typically makes use of backlight illumination because the LCD does not emit light on its own. Backlight illumination typically involves supplying the LCD with light from a cathode fluorescent lamp or from light emitting diodes (LEDs). To reduce power consumption, groupings of LEDs may be utilized such that the groupings are activated individually. However, this configuration may lead to reduced resolution, distortion or artifacts, and/or limited brightness adjustment ranges. Therefore, there exists a need for controlling LEDs of an LCD through techniques that minimize resolution loss, reduce distortion or artifacts, as well as allow for broad dimming ranges for the LCD. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     The present disclosure generally relates to a backlight unit for a display device, such as an LCD display. In one embodiment, an edge-lit backlight unit may include an architecture of stings of LEDs, each with a certain number of light sources per string. For example, a grouping of six strings of LEDs each with 3 LEDs thereon may be utilized. Control of the activation and deactivation of the strings may be generated via a pulse width modulator (a pulse width modulation device). The strings may be activated in such a manner that the first string is activated, followed by the second string, and so forth. The activation of these strings may cause LEDs thereon to emit light. Furthermore, the strings may be activated at a relatively high frequency, such as 8 kHz. The 8 kHz frequency of the strings combined with a total number of strings utilized, such as 6 strings, may yield an effective (or equivalent) frequency of 48 kHz on the display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view illustrating an electronic device, in accordance with one embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of an LCD, in accordance with one embodiment of the present invention; 
         FIG. 3  is a perspective view illustrating an LCD that may be used in the electronic device of  FIG. 1 , in accordance with one embodiment of the present invention; 
         FIG. 4  is a simplified block diagram illustrating components of the electronic device of  FIG. 1 , in accordance with one embodiment of the present invention; 
         FIG. 5  is a block diagram illustrating components for controlling the backlit illumination intensity the LCD of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 6  is a first timing sequence that may be applied to a light source of the LCD of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 7  is a second timing sequence that may be applied to a light source of the LCD of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 8  is flow diagram illustrating the operation of the components of  FIG. 5 , in accordance with one embodiment of the present invention; 
         FIG. 9  is an additional timing sequence that may be applied to a light source of the LCD of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 10  is another timing sequence that may be applied to a light source of the LCD of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 11  is a front view of the LCD display of  FIG. 3 , in accordance with one embodiment of the present invention; 
         FIG. 12  is a top view of a light source of  FIG. 3 , in accordance with one embodiment of the present invention; and 
         FIG. 13  is a top view of the light source of  FIG. 3 , in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The application is generally directed to a method and system for controlling backlighting of a display. A pulse width modulator (PWM) signal may be transmitted to a display. Through the control of the duty cycle of the PWM signal, the brightness of the display may be adjusted. Furthermore, the PWM signal may be provided to each of a group of LED strings, each with a series of LEDs thereon. The PWM signal may be provided to the LED strings, for example, in a sequential manner. The frequency at which the PWM signal may be transmitted to each of the LED strings may be a relatively high frequency, for example, 8 kHz. Rapidly transmitting the PWM signal to the LED strings in this manner may reduce visual artifacts on the display while maintaining a reduced overall power consumption of the display, since less than all of the strings may be activated at any given time. Moreover, the PWM signal may be phase shifted to allow for generation of an effective frequency on the display at a rate greater than the frequency of the PWM signal. 
     An electronic device  10  is illustrated in  FIG. 1  in accordance with one embodiment of the present invention. In some embodiments, including the presently illustrated embodiment, the device  10  may be a portable electronic device, such as a laptop computer. Other electronic devices may also include a viewable media player, a cellular phone, a personal data organizer, or the like. Indeed, in such embodiments, a portable electronic device may include a combination of the functionalities of such devices. In addition, the electronic device  10  may allow a user to connect to and communicate through the Internet or through other networks, such as local or wide area networks. For example, the portable electronic device  10  may allow a user to access the Internet and to communicate using e-mail, text messaging, or other forms of electronic communication. By way of example, the electronic device  10  may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. of Cupertino, Calif. In other embodiments, the electronic device may include other models and/or types of electronic devices employing LED backlights, available from any manufacturer. 
     In certain embodiments, the electronic device  10  may be powered by one or more rechargeable and/or replaceable batteries. Such embodiments may be highly portable, allowing a user to carry the electronic device  10  while traveling, working, and so forth. While certain embodiments of the present invention are described with respect to a portable electronic device, it should be noted that the presently disclosed techniques may be applicable to a wide array of other electronic devices and systems that are configured to render graphical data, such as a desktop computer. 
     In the presently illustrated embodiment, the electronic device  10  includes an enclosure or housing  12 , a display  14 , input structures  16 , and input/output (I/O) ports or connectors  18 . The enclosure  12  may be formed from plastic, metal, composite materials, or other suitable materials, or any combination thereof. The enclosure  12  may protect the interior components of the electronic device  10 , such as processors, circuitry, and controllers, among others, from physical damage, and may also shield the interior components from electromagnetic interference (EMI). 
     The display  14  may be a liquid crystal display (LCD). The LCD may be a light emitting diode (LED) based display or some other suitable display. As noted above, the electronic device  10  may also include input structures  16 . In one embodiment, one or more of the input structures  16  are configured to control the device  10 , such as by controlling a mode of operation, an output level, an output type, etc. For instance, the input structures  16  may include a button to turn the device  10  on or off. Further the input structures  16  may allow a user increase or decrease the brightness of the display  14 . Embodiments of the portable electronic device  10  may include any number of input structures  16 , including buttons, switches, a control pad, a keypad, or any other suitable input structures that may be used to interact with electronic device  10 . These input structures  16  may operate to control functions of the electronic device  10  and/or any interfaces or devices connected to or used by the electronic device  10 . For example, the input structures  16  may allow a user to navigate a displayed user interface, such as a graphical user interface (GUI), and/or other applications running on the electronic device  10 . 
     The device  10  may also include various I/O ports  18  to allow connection of additional devices. For example, the device  10  may include any number of input and/or output ports  18 , such as headphone and headset jacks, universal serial bus (USB) ports, IEEE-1394 ports, Ethernet and modem ports, and AC and/or DC power connectors. Further, the electronic device  10  may use the I/O ports  18  to connect to and send or receive data with any other device, such as a modem, networked computers, printers, or the like. For example, in one embodiment, the electronic device  10  may connect to an iPod via a USB connection to send and receive data files, such as media files. 
     Additional details of the display  14  may be better understood through reference to  FIG. 2 , which is an exploded perspective view of one example of the LCD type display  14 . The display  14  includes a top cover  20 . The top cover  20  may be formed from plastic, metal, composite materials, or other suitable materials, or any combination thereof. In one embodiment, the top cover  20  is a bezel. The top cover  20  may also be formed in such a way as combine with a bottom cover  38  to provide a support structure for the remaining elements illustrated in  FIG. 2 . A liquid crystal display (LCD) panel  22  is also illustrated. The LCD panel  22  may be disposed below the top cover  20 . The LCD panel  22  may be used to display an image through the use of a liquid crystal substance typically disposed between two substrates. For example, a voltage may be applied to electrodes, residing either on or in the substrates, creating an electric field across the liquid crystals. The liquid crystals change in alignment in response to the electric field, thus modifying the amount of light which may be transmitted through the liquid crystal substance and viewed at a specified pixel. In such a manner, and through the use of various color filters to create colored sub-pixels, color images may be represented across individual pixels of the display  14  in a pixelated manner. 
     The LCD panel  22  may include a group of individually addressable pixels. In one embodiment, LCD panel  22  may include a million pixels, divided into pixel lines each including one thousand pixels. The LCD panel  22  may also include a passive or an active display matrix or grid used to control the electric field associated with each individual pixel. In one embodiment, the LCD panel  22  may include an active matrix utilizing thin film transistors disposed along pixel intersections of a grid. Through gating actions of the thin film transistors, luminance of the pixels of the LCD panel  22  may be controlled. The LCD panel  22  may further include various additional components, such as polarizing films and anti-glare films. 
     The display  14  also may include optical sheets  24 . The optical sheets  24  may be disposed below the LCD panel  22  and may condense the light passing to the LCD panel  22 . In one embodiment, the optical sheets  24  may be prism sheets which may act to angularly shape light passing through to the LCD panel  22 . The optical sheets  24  may include either one or more sheets. The display  14  may further include a diffuser plate or sheet  26 . The diffuser plate  26  may be disposed below the LCD panel  22  and may also be disposed either above or below the optical sheets  24 . The diffuser plate  26  may diffuse the light being passed to the LCD panel  22 . The diffuser plate  26  may also reduce glaring and non-uniform illumination on the LCD panel  22 . A guide plate  28  may also assist in reducing non-uniform illumination on the LCD panel  22 . In one embodiment, the guide plate  28  is part of an edge type backlight assembly. In an edge type backlight assembly, a light source  30  may be disposed along one side of the guide plate  28 , such as the bottom edge  32  of the guide plate  28 . The guide plate  28  may act to channel the light emanating from the light source  30  upwards towards the LCD panel  22 . 
     The light source  30  may include light emitting diodes (LEDs)  34 . The LEDs  34  may be a combination of red, blue, and green LEDs, or the LEDs  34  may be white LEDs. In one embodiment, the LEDs  34  may be arranged on a printed circuit board (PCB)  36  adjacent to an edge of the guide plate  28 , such as bottom edge  32 , as part of an edge type backlight assembly. In another embodiment, the LEDs  34  may be arranged on one or more PCBs  36  along the inside surface of bottom cover  38 . For example, the one or more PCBs  36  may be aligned along an inner side  40  of the bottom cover  38 . The LEDs  34  may be arranged in one or more strings, whereby a number of the LEDs  34  are coupled in series with one another in each string. For example, the LEDs  34  may be grouped into six strings, whereby each string includes three LEDs  34  connected in series. However, it should be noted, that as few as one or two LED  34  may be connected on each string or more than three LEDs  34 , such as six LEDs, may be connected on each string. Furthermore, the strings may be positioned in an end to end configuration, a side by side configuration, and/or in any other suitable configuration. 
     The display  14  also may include a reflective plate or sheet  42 . The reflective plate  42  is generally disposed below the guide plate  28 . The reflective plate  42  acts to reflect light that has passed downwards through the guide plate  28  back towards the LCD panel  22 . Additionally, the display includes a bottom cover  38 , as previously discussed. The bottom cover  38  may be formed in such a way as to combine with the top cover  20  to provide a support structure for the remaining elements illustrated in  FIG. 2 . The bottom cover  38  may also be used in a direct-light type backlight assembly, whereby one or more light sources  30  are located on a bottom edge  43  of the bottom cover  38 . In this configuration, instead of using a light source  30  positioned adjacent the diffuser plate  26  and/or guide plate  28 , the reflective plate  42  may be omitted and one or more light sources (not shown) on the bottom edge  43  of the bottom cover  38  may emit light directly towards the LCD panel  22 . 
       FIG. 3  depicts an embodiment of display  14  employing an edge-lit backlight. Display  14  includes the LCD panel  22  held in place, as illustrated, by the top cover  20 . As described above, the display  14  may utilize a backlight assembly such that a light source  30  may include LEDs  34  mounted on, for example, a Metal Core Printed Circuit Board (MCPCB), or other suitable type of support situated upon an array tray  44  in the display  14 . This array tray  44  may be secured to the top cover  20  such that the light source  30  is positioned in the display  14  for light generation, which may be utilized to generate images on the LCD panel  22 . 
     The light source  30  may also include circuitry required to translate an input voltage into an LED voltage usable to power the LEDs  34  of the light source  30 . Since the light source  30  may be used in a portable device, it is desirable to use as little power as possible to increase the battery life of the electronic device  10 . To conserve power, the light source  30 , i.e., the LEDs  34  thereon, may be toggled on and off. In this manner, power in the system may be conserved because the light source  30  need not be powered continuously. Furthermore, this toggling will appear to create constant images to a viewer if the frequency of toggling is kept above at least the flicker-fusion frequency of the human eye, about 30 Hz. 
     In addition to conserving power, by adjusting the duty cycle (the ratio of the time that the light source  30  is on relative to the amount of time that the light source  30  is on and off) of the toggled light source  30 , the overall brightness of the LCD panel  22  may be controlled. For example, a duty cycle of 50% would result in an image being displayed at roughly half the brightness of constant backlight illumination. In another example, a duty cycle of 20% results in an image being displayed at roughly 20% of the brightness that constant backlight illumination would provide. Thus, by adjusting the duty cycle of a toggled signal, the brightness of a displayed image may be adjusted with the added benefit of reducing the power consumed in the electronic device  10 . 
     Internal components of electronic device  10  may be used to accomplish the toggling of the light source  30  in the LCD panel  22 .  FIG. 4  is a block diagram illustrating the components that may be used to perform the toggling procedure described above. Those of ordinary skill in the art will appreciate that the various functional blocks shown in  FIG. 4  may include hardware elements (including circuitry), software elements (including computer code stored on a machine-readable medium) or a combination of both hardware and software elements. It should further be noted that  FIG. 4  is merely one example of a particular implementation, other examples could include components used in Apple products such as an iPod®, MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro®, iPhone®, or another electronic device utilizing an LCD. 
     In the presently illustrated embodiment of the electronic device  10 , the components may include the display  14 , input structures  16 , I/O ports  18 , one or more processors  46 , a memory device  48 , non-volatile storage  50 , expansion card(s)  52 , a networking device  54 , a power source  56 , and a display control logic  58 . With regard to each of these components, it is first noted that the display  14  may be used to display various images generated by the device  10  and may be provided in conjunction with a touch-sensitive element, such as a touchscreen, that may be used as part of the control interface for the device  10 . 
     The input structures  16  may include the various devices, circuitry, and pathways by which user input or feedback is provided to the processor(s)  46 . Such input structures  16  may be configured to control a function of the electronic device  10 , applications running on the device  10 , and/or any interfaces or devices connected to or used by the device  10 . For example, the input structures  16  may allow a user to navigate a displayed user interface or application interface. Non-limiting examples of the input structures  16  include buttons, sliders, switches, control pads, keys, knobs, scroll wheels, keyboards, mice, touchpads, and so forth. User interaction with the input structures  16 , such as to interact with a user or application interface displayed on the display  12 , may generate electrical signals indicative of user input. These input signals may be routed via suitable pathways, such as an input hub or bus, to the processor(s)  46  for further processing. 
     Additionally, in certain embodiments, one or more input structures  16  may be provided together with the display  14 , such an in the case of a touchscreen, in which a touch sensitive mechanism is provided in conjunction with the display  14 . In such embodiments, the user may select or interact with displayed interface elements via the touch sensitive mechanism. In this way, the displayed interface may provide interactive functionality, allowing a user to navigate the displayed interface by touching the display  14 . 
     As noted above, the I/O ports  18  may include ports configured to connect to a variety of external devices, such as a power source, headset or headphones, or other electronic devices (such as handheld devices and/or computers, printers, projectors, external displays, modems, docking stations, and so forth). The I/O ports  18  may support any interface type, such as a universal serial bus (USB) port, a video port, a serial connection port, an IEEE-1394 port, an Ethernet or modem port, and/or an AC/DC power connection port. 
     The processor(s)  46  may provide the processing capability to execute the operating system, programs, user and application interfaces, and any other functions of the electronic device  10 . The processor(s)  46  may include one or more microprocessors, such as one or more “general-purpose” microprocessors, one or more special-purpose microprocessors and/or ASICS, or some combination of such processing components. For example, the processor(s)  46  may include one or more reduced instruction set (RISC) processors, as well as graphics processors, video processors, audio processors, and the like. As will be appreciated, the processor(s)  46  may be communicatively coupled to one or more data buses or chipsets for transferring data and instructions between various components of the electronic device  10 . 
     Programs or instructions executed by the processor(s)  46  may be stored in any suitable manufacture that includes one or more tangible, computer-readable media at least collectively storing the executed instructions or routines, such as, but not limited to, the memory devices and storage devices described below. Also, these programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor(s)  46  to enable the device  10  to provide various functionalities, including those described herein. 
     The instructions or data to be processed by the processor(s)  46  may be stored in a computer-readable medium, such as memory  48 . The memory  48  may include a volatile memory, such as random access memory (RAM), and/or a non-volatile memory, such as read-only memory (ROM). The memory  48  may store a variety of information and may be used for various purposes. For example, the memory  48  may store firmware for the electronic device  10  (such as basic input/output system (BIOS)), an operating system, and various other programs, applications, or routines that may be executed on the electronic device  10 . In addition, the memory  48  may be used for buffering or caching during operation of the electronic device  10 . 
     The components of device  10  may further include other forms of computer-readable media, such as non-volatile storage  50  for persistent storage of data and/or instructions. The non-volatile storage  50  may include, for example, flash memory, a hard drive, or any other optical, magnetic, and/or solid-state storage media. The non-volatile storage  50  may also be used to store firmware, data files, software programs, wireless connection information, and any other suitable data. 
     The embodiment illustrated in  FIG. 4  may also include one or more card or expansion slots. The card slots may be configured to receive one or more expansion cards  52  that may be used to add functionality, such as additional memory, I/O functionality, or networking capability, to electronic device  10 . Such expansion cards  52  may connect to device  10  through any type of suitable connector, and may be accessed internally or external to the housing of electronic device  10 . For example, in one embodiment, the expansion cards  52  may include a flash memory card, such as a SecureDigital (SD) card, mini- or microSD, CompactFlash card, Multimedia card (MMC), or the like. Additionally, the expansion cards  52  may include one or more processor(s)  46  of the device  10 , such as a video graphics card having a GPU for facilitating graphical rendering by device  10 . 
     The components depicted in  FIG. 4  also include a network device  54 , such as a network controller or a network interface card (NIC), internal to the device  10 . In one embodiment, the network device  54  may be a wireless NIC providing wireless connectivity over any 802.11 standard or any other suitable wireless networking standard. The network device  54  may allow electronic device  10  to communicate over a network, such as a personal area network (PAN), a local area network (LAN), a wide area network (WAN), or the Internet. Further, electronic device  10  may connect to and send or receive data with any device on the network, such as portable electronic devices, personal computers, printers, and so forth via the network device  54 . Alternatively, in some embodiments, electronic device  10  may not include an internal network device  54 . In such an embodiment, an NIC may be added as an expansion card  52  to provide similar networking capability as described above. 
     Further, the device  10  may also include a power source  56 . In one embodiment, the power source  56  may be one or more batteries, such as a lithium-ion polymer battery or other type of suitable battery. The battery may be user-removable or may be secured within the housing of the electronic device  10 , and may be rechargeable. Additionally, the power source  56  may include AC power, such as provided by an electrical outlet, and the electronic device  10  may be connected to the power source  56  via a power adapter. This power adapter may also be used to recharge one or more batteries of the device  10 . Additionally, as illustrated in  FIG. 4 , the power source  56  may transmit power to the display  14  across path  57 . The use of this power by the display  14  may be regulated by display control logic  58 , as discussed below. 
     The display control logic  58  may be coupled to the display  14  and may be used to control light source  30  of the display  14 . Alternatively, the display control logic may be internal to the display  14 . In one embodiment, the display control logic  58  may act to toggle the light source  30  on and off. This toggling, for example, may be used to decrease the overall brightness of the display  14  when the power source  56 , such as a battery, is being used. Additionally and/or alternatively, when the power source  56  is an AC power source, the overall brightness of the display  14  may be modified simply by raising and/or lowering the constant voltage level supplied to the light source  30 . 
     In one embodiment, control of the brightness level of the display  14  may be adjusted through changing the duty cycle of an activation signal transmitted to the light source  30 . For instance, if the duty cycle of the activation signal was 0%, then the light source  30  would remain off and the display  14  would be dark. Conversely, if the duty cycle of the activation signal was 100%, then the display  14  would be at full brightness because the light source  30  would always be active (however, as much power would be consumed as was used in the AC power source example above). In another example, if the duty cycle of the activation signal was at 50%, the display  14  would be at half the brightness of the display  14  being always on, however, the power consumption of the display  14  could be reduced by as much as 50% versus the light source  30  being continuously and fully powered. 
     Additionally, in an embodiment, control of the brightness level of the display  14  may be adjusted through changing the duty cycle of an activation signal transmitted to the light source  30  in conjunction with adjustment of the amount of current transmitted to the light source  30 . This adjustment of the current transmitted to, for example, LED strings of the light source, may occur when the duty cycle of an activation signal (such as a PWM signal) is to be set below a threshold level. For instance, if desired brightness of the display  14  would call for the duty cycle of the activation signal to be less than, for example, 20%, then the duty cycle may be set to 20% and the current to be transmitted to active LED strings of the light source  30  may be reduced. In this manner, the brightness of the display may be adjusted through control of both the duty cycle of an activation signal and through the control of the current transmitted to the light source  30 . 
     In one embodiment, a pulse width modulator (PWM)  60  may provide the activation signal to the light source  30  as a PWM signal. Furthermore, the duty cycle of the PWM signal may be adjusted in response to user initiated changes to the display  14  brightness via, for example, inputs  16 . In another embodiment, as described above, the display control logic  58  may be used to automatically adjust the brightness of the display  14  by varying the duty cycle of the PWM signal when the power source  56  is a battery. For example, the duty cycle of the PWM signal may be adjusted based on the amount of internal power remaining in the battery. 
     In one embodiment, the display control logic  58  may be coupled to the pulse-width modulator (PWM)  60 , which may generate a PWM signal. Alternatively, in one embodiment, the PWM  60  may be internal to the display control logic  58 . The PWM signal generated by the PWM  60  may be an oscillating signal used to toggle the light source  30  on and off. Moreover, the duty cycle of the PWM signal may be selectable and may vary anywhere from 0-100%. As described previously, the duty cycle of the PWM signal may determine the overall brightness of the display  14 . In this manner, the PWM signal may also reduce the overall power consumption of the display  14  by controlling the amount of time that the LEDs  34  of the light source  30  are “on” during any period of time. The PWM signal may also provide high brightness resolution (i.e., at least 10-bit resolution) in the device  10 . That is, the PWM signal may allow for 1024 different brightness levels to be achieved by the light source  30 . 
       FIG. 5  is a block diagram illustrating the components controlling the backlit illumination intensity of the display  14 . As noted above, the display control logic  58  may operate to control the ratio of time that the LEDs  34  of the light source  30  are on and off. In one embodiment, the LEDs  34  may be activated in a sequential manner to control the overall output of the light source  30 . To accomplish this control of the light source  30 , the display control logic  58  may include a sequencer  62 . The sequencer  62  may, for example, be a microprocessor, one or more special-purpose microprocessors and/or ASICS, a controller, or some combination of such components. The sequencer may operate to receive a PWM signal generated by the PWM  60  and received along path  64 . In one embodiment, the PWM signal received from path  64  may be filtered by, for example, a low pass filter  66  including a resistor  68  and a capacitor  70 . The resistor  68  and capacitor  70  may be selected in such a manner as to control the amount of smoothing of the PWM signal by the low pass filter  66 . 
     Once the PWM signal is received by the sequencer  62 , a determination may be made as to which gate control line  72 - 77  the PWM signal will be transmitted. It should be noted that while six gate control lines  72 - 77  are illustrated, more or less than six gate control lines may be utilized. As will be described below in greater detail, each gate control line  72 - 77  may control a dedicated gate coupled to an individual LED string utilized in the light source  30 . That is, there may be one gate control line and a dedicated gate for each LED string in the light source  30 . 
     Each of the gate control lines  72 - 77  may be coupled to an individual gate  78 - 83 . The gates  78 - 83  may each be, for example, a field effect transistor (FET) such as a metal-oxide semiconductor field effect transistor (MOSFET). Alternatively, the gates may include other types of switches, transistors, or other components that may connect and break an electrical circuit. In the present embodiment, each gate  78 - 83  may be activated by the signal transmitted along its corresponding gate control line  72 - 77 . For example, if voltage is transmitted across gate control line  72 , gate  78  may be activated. That is, the voltage applied to gate  78  may cause gate  78  to operate as a closed switch, allowing current to flow through the gate  78  along the current path  84  to ground  86 . Conversely, if no voltage is transmitted across gate control line  72 , gate  78  may be deactivated, causing gate  78  to operate as an open switch, thus preventing current from flowing along the current path  84  through the gate  78  to ground  86 . 
     Additionally, the sequencer  62  may include delay circuitry  88 . In one embodiment, the delay circuitry  88  may operate to hold the PWM signal received along path  64  until the sequencer  63  selects a gate control line  72 - 77  for transmission of the PWM signal. In this manner, the sequencer may allow for a phase shift of the PWM signal received along path  64 . In one embodiment, the amount of phase shift performed by the sequencer  62  may be equivalent to the period of the PWM signal divided by the total number of gate control lines  77 - 83  (i.e. the total amount of LED strings in the light source  30 ). For example, where six gate control lines  77 - 83  exist, the sequencer  62  may transmit the PWM signal unaltered to gate control line  72 . Subsequently, the sequencer may receive a phase shifted (delayed) PWM signal from the delay circuitry  88  equivalent to the period of the PWM signal delayed by  1 / 6  of the total period of the PWM signal and may transmit this phase shifted PWM signal to gate control line  73 . This process may continue for each of the subsequent gate control lines  74 - 77 , whereby each of the gate control lines  74 - 77  receives a phase shifted PWM signal delayed by an additional ⅙ of the total period of the PWM signal, relative to the signal transmitted to the preceding gate control line  73 - 76 . This process may be illustrated in  FIG. 6 . 
       FIG. 6  illustrates a timing sequence  90  that the sequencer  62  may output when utilized with the delay circuitry  88  to phase shift a received PWM signal, as described above. Pulse waveform  92  may represent the PWM signal received by the sequencer  62  from path  64 . In one embodiment, the pulse waveform  92  may have a frequency of 8 kHz and a duty cycle of 50%. To phase shift the pulse waveform  92 , the sequencer  62  may first transmit the PWM waveform  92  along gate control line  72  as pulse waveform  93 . Next, the sequencer  62  may transmit pulse waveform  94  along gate control line  73 . As may be seen, pulse waveform  94  may be phase shifted by ⅙ (i.e. 60 degrees) relative to the pulse waveform  92  (i.e. the PWM signal). As noted above, this phase shift may be accomplished by delay circuitry  88 . Subsequently, the sequencer  62  may transmit pulse waveform  95  along gate control line  74 . As may be seen, pulse waveform  95  may be phase shifted by ⅙ (i.e. 60 degrees) relative to the pulse waveform  94  and by ⅓ (i.e. 120 degrees) relative to pulse waveform  92  (i.e. the PWM signal). This process may continue for pulse waveforms  96 - 98 , transmitted along gate control lines  75 - 77 , respectively. That is, each of the pulse waveforms  96 - 98  may be phase shifted by 60 degrees relative to the preceding waveform  95 - 97  and the phase shifting may be accomplished via the delay circuitry  88 . The total effect of phase shifting with respect to the pulse waveforms  93 - 98  may be such that the 8 kHz PWM waveform  92  may lead to an effective rate frequency (i.e. the product of the frequency of the pulse waveforms  93 - 98  by the total number of gate control lines  72 - 77 ) of 48 kHz on the display  14 . 
       FIG. 7  illustrates a timing sequence  100  that the sequencer  62  may output when utilized with the delay circuitry  88  to phase shift a received PWM signal. Pulse waveform  102  may represent the PWM signal received by the sequencer  62  from path  64 . In one embodiment, the pulse waveform  102  may have a frequency of  8  kHz and a duty cycle of 25%. To phase shift the pulse waveform  102 , the sequencer  62  may first transmit the PWM waveform  102  along gate control line  72  as pulse waveform  103 . Next, the sequencer  62  may transmit pulse waveform  104  along gate control line  73 . As may be seen, pulse waveform  104  may be phase shifted by ⅙ (i.e. 60 degrees) relative to the pulse waveform  102  (i.e. the PWM signal). As noted above, this phase shift may be accomplished by delay circuitry  88 . Subsequently, the sequencer  62  may transmit pulse waveform  105  along gate control line  74 . As may be seen, pulse waveform  105  may be phase shifted by ⅙ (i.e. 60 degrees) relative to the pulse waveform  104  and by ⅓ (i.e. 120 degrees) relative to pulse waveform  102  (i.e. the PWM signal). This process may continue for pulse waveforms  106 - 108 , transmitted along gate control lines  75 - 77 , respectively. That is, each of the pulse waveforms  106 - 108  may be phase shifted by 60 degrees relative to the preceding waveform  105 - 107  and the phase shifting may be accomplished via the delay circuitry  88 . The total effect of phase shifting with respect to the pulse waveforms  103 - 108  may be such that an 8 kHz PWM waveform  102  may lead to an effective rate frequency (i.e. the product of the frequency of the pulse waveforms  103 - 108  by the total number of gate control lines  72 - 77 , also the total number of LED strings in the light source  30 ) of 48 kHz on the display  14 . 
     Returning to  FIG. 5 , if the sequencer  62  selects gate control line  72 , the PWM signal received from path  64  (which may be phase shifted via delay circuitry  88 ) may be transmitted along gate control line  72  to gate  78 . As the PWM signal is an oscillating signal that fluctuates between no voltage and a high voltage (Vcc), the gate  78  will be activated and deactivated in conjunction with the pulses of the PWM signal. As will be discussed in greater detail below, the alternating activation and deactivation of the gate  78  will cause an LED string (e.g., LED string  110 ) to be activated and deactivated in a synchronized manner with the gate  78 . That is, as gate  78  is activated, current may flow along current path  84 . 
     This current may be supplied by the power source  56  and may pass through, for example, the LED string  110 . Moreover, to insure that the current flows only in a direction from the power source  56 , through any given LED string  110 - 115  and through the selected gate  78 - 83 , and to ground  86 , a diode  116  may be placed between the power source  56  and the LED strings  110 - 115 . This diode may generally prevent current from flowing from the LED strings  110 - 115  back towards the power source  56 . Furthermore, at least one inductor  118  may be placed in series with the diode  116  so as to resist abrupt changes in current from the power source  56 , thus operating to smooth the current transmitted to the LED strings  110 - 115 , as well as to provide boost functionality for a backlight controller of the display  14 . That is, the input voltage may be boosted in relation to the number of LEDs present on each LED string  110 - 115  to properly bias the LEDs. Additionally, resistances may be present in  FIG. 5 . These resistances may be illustrated as resistors  120 A- 120 F. The resistors  120 A- 120 F may, for example, represent the internal resistance of the various lines on which the resistors  120 A- 120 F are illustrated. In another embodiment, specific resistance values may be selected for resistors  120 A- 120 F as required to alter performance characteristics of, for example, the display  14  (e.g., for debugging). 
     As current passes from the power source  56  through the diode  116  and, for example, to LED string  110  (when gate  78  has been activated), the current will cause the LEDs  122 A- 122 C located on LED string  110  to generate light. It should be noted that LEDs  122 A- 122 C may all be identical to LEDs  34  discussed above. In the present embodiment, three LEDs (e.g., LEDs  122 A- 122 C) may be placed in series as part of a respective LED string (e.g., LED string  110 ); however, it should be noted that greater or less than three LEDs, such as six LEDs, may be utilized in conjunction with a given LED string (e.g., LED string  110 ). 
     In operation, the activation and deactivation of the various gates  78 - 83  via a PWM signal transmitted along the control lines  72 - 77  may, thus, control the activation and deactivation of the LED strings  110 - 115 . The activation and deactivation of the LED strings  110 - 115  may, in turn, control the activation of the LEDs  122 A- 127 C thereon. As such, the sequencer  62  may, by providing the PWM signal to the various gate control lines  72 - 77 , control the operation of the various LED strings  110 - 115  in the light source  30 . 
     Moreover, the sequencer  62  may actively select which of the LED strings  110 - 115  will generate light at a given time. As illustrated in flow chart  128  of  FIG. 8 , the sequencer  62  may receive a PWM signal generated by the PWM  60  in step  130 . In step  132 , the sequencer  62  may determine the sequence to be initiated. Step  132  may include determining the order of transmitting the PWM signal to the gate control lines  72 - 77 , the use of the delay circuitry  88  to initiate a phase shift of the received PWM signal prior to transmission to gate control lines  72 - 77 , and/or other steps as required for control of the light source  30 . 
     In step  134 , the sequencer may determine if the current level to be transmitted to the LED strings  110 - 115  should be reduced. As previously noted, control of the brightness level of the display  14  may be adjusted through changing the duty cycle of the PWM signal in conjunction with an adjustment to the amount of current transmitted to the light source  30 . This adjustment of the current transmitted to the LED strings  110 - 115 , selected in the sequencing step of  132 , may occur when the brightness level of the display  14  is to be set below a threshold level. For instance, if desired brightness of the display  14  would otherwise call for the duty cycle of the PWM signal to be less than, for example, 20%, then the duty cycle of the PWM signal may be set to 20% and the current to be transmitted to active LED strings  110 - 115  of the light source  30  may be reduced. This reduction may, for example, be set by the display controller  58 . If, however, the duty cycle of the PWM signal is to be set above a threshold level, for example, 20%, then the brightness level of the display  14  could be controlled by the duty cycle of the PWM signal without modification of the current passing through the activated LED strings  110 - 115 . 
     Subsequent to step  134 , the sequencer  62 , in step  136 , may route the PWM signal (which may be phase shifted) to the LED strings  110 - 115 . This routing may be accomplished in a sequential manner. That is, the PWM signal may be sequentially transmitted to gate control line  72  for a given cycle of the PWM signal. The sequencer  62  may then transmit the PWM signal for a subsequent cycle to gate control line  73 . This procedure may continue in sequence for each gate control line until the sequencer  62  transmits a PWM signal to gate control line  77 . Once the PWM signal has been transmitted to gate control line  77 , the sequencer may restart the process of transmitting the PWM signal to gate control line  72 . In this manner, each of the LED strings  110 - 115  may be enabled sequentially. This sequential activation may be performed as previously discussed with respect to  FIGS. 6 and 7 , that is, with a phase shift. Additionally or alternatively, the sequential activation may be accomplished without the use of the delay circuitry  88 , and without phase shift, as illustrated in  FIGS. 9 and 10 . 
       FIG. 9  illustrates a timing sequence  138  that the sequencer  62  may employ in an embodiment. Pulse waveform  140  may represent the PWM signal received by the sequencer  62  from path  64 . The pulse waveform  140  may have a frequency of at least approximately 1 kHz and a duty cycle of 100%. To activate the various LED strings  110 - 115 , the sequencer  62  may first transmit the PWM waveform  140  along gate control line  72  as pulse waveform  141 . Subsequently pulse waveform  140  may be transmitted to gate control line  73  and so forth until pulse waveform  140  is transmitted to gate control line  77  as pulse waveform  146 . Accordingly, the pulse waveforms  141 - 146  may correspond to the pulses transmitted to each of the gate control lines  72 - 77 . As each pulse is received at each of the gates  78 - 83  associated with the gate control lines  72 - 77 , the pulse may allow for current to flow through the respective LED string (e.g., LED string  110 ) thus generating light for use in the display  14 . It should be noted that in the illustrated embodiment the PWM pulse waveform  140  transmitted to each of the gate control lines  72 - 77  may have a duty cycle of 100%. That is, at least one of the LED strings  110 - 115  is always activated. 
       FIG. 10  illustrates a timing sequence  148  that the sequencer  62  may employ in an embodiment whereby the PWM signal is at a 50% duty cycle. Pulse waveform  149  may represent the PWM signal received by the sequencer  62  from path  64 . The pulse waveform  149  may have a frequency of at least approximately 1 kHz and a duty cycle of 50%. To activate the various LED strings  110 - 115 , the sequencer  62  may first transmit the PWM waveform  149  along gate control line  72  as pulse waveform  150 . Subsequently pulse waveform  149  may be transmitted to gate control line  73  and so forth until pulse waveform  149  is transmitted to gate control line  77  as pulse waveform  155 . Accordingly, the pulse waveforms  150 - 155  may correspond to the pulses transmitted to each of the gate control lines  72 - 77 . As each pulse is received at each of the gates  78 - 83  associated with the gate control lines  72 - 77 , the pulse may allow for current to flow through the respective LED string (e.g., LED string  110 ) thus generating light for use in the display  14 . It should be noted that in the illustrated embodiment the PWM pulse waveform  149  transmitted to each of the gate control lines  72 - 77  may have a duty cycle of 50%. Thus, each of pulse waveforms  150 - 155  have a gap of time  156  in which none of the LED strings  110 - 115  are active. Moreover, each the gaps of time  156  may be equivalent to the time that voltage is driven to the gates  78 - 83 , activating each of the LED strings  110 - 115 . Thus, taken in the aggregate, the light source  30  may be transmitting light at a 50% duty cycle. This, for example, may cause the display  14  to be at 50% the brightness as generated via the timing sequence  138  (which, in turn, is dimmer than that provided by timing sequences  90  and  100  above). 
     Accordingly, the pulse waveforms  93 - 98 ,  103 - 108 ,  141 - 146 , and  150 - 155  may correspond to the pulses transmitted to each of the gate control lines  72 - 77 , depending on the desired frequency and duty cycle of the display  14 . Furthermore, in one embodiment, the amount that the duty cycle of the PWM signal is varied may directly correspond to the amount that the display  14  is dimmed. Thus, it is envisioned that the duty cycle of the PWM signals transmitted along path  64  may be varied from 0-100%. Additionally, as discussed above, the sequencer  62  may sequentially rotate the pulses received from the PWM signal amongst the gate control lines  72 - 77  at a high frequency, for example, at an effective rate of 48 kHz so as to minimize distortion and artifacts on the display  14 . 
     In one embodiment, the sequencer  62  may activate each of the LED strings  110 - 115  at a high frequency. Activating the LED strings  110 - 115  at a high frequency may be beneficial as artifacts that might typically be seen from the use of only one LED string (e.g., LED string  110 ) may be reduced if the LED strings  110 - 115  are activated and deactivated at a high rate. In one embodiment, each of the LED strings  110 - 115  may be selected by the sequencer  62  at a rate of approximately 8 kHz. Thus, in the embodiment where six LED strings  110 - 115  are utilized, with a phase shift as illustrated in each of  FIGS. 6 and 7 , the effective frequency for the display  14  would be 48 kHz (i.e. the product of the frequency of selection of each of the LED strings  110 - 115  by the sequencer  62  and the total number of LED strings  110 - 115 ). In another embodiment, the each of the LED strings  110 - 115  may be selected by the sequencer  62  at a greater or lesser rate, such as at a rate of approximately at least 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz, 6 kHz, 7 kHz, 8 kHz, 9 kHz, or 10 kHz. This may lead to an effective rate of approximately at least 6 kHz, 12 kHz, 18 kHz, 24 kHz, 30 kHz, 36 kHz, 42 kHz, 48 kHz, 54 kHz, or 60 kHz. Regardless of the frequency selected by the sequencer  62 , through the use of high frequency activation and deactivation, as well as through the use of a PWM signal and/or through phase shifting of the PWM signal to activate the LED strings  110 - 115 , a large dimming range for the display  14  as well as removal of visual artifacts on the display  14  may be concurrently accomplished. 
       FIG. 11  illustrates a front view of the display  14  in which the duty cycle of a phase shifted PWM signal is applied to gate control lines  74  and  75 , causing the activation of LED strings  112  and  113 . As illustrated, the display  14  includes the LCD panel  22  and the light source  30 . The light source  30  includes LEDs  122 A- 127 C, which may be organized into LED strings  110 - 115 . The display  14  is shown, for example, as the phase shifted PWM signal is being transmitted to gate control lines  74  and  75 , thus activating gates  80  and  81 . As gates  80  and  81  are activated, current is free to pass through LED strings  112  and  113 , which, in turn, activate LEDs  124 A- 124 C and  125 A- 125 C. Accordingly, light may be generated by LEDs  124 A- 125 C, resulting in light transmitted to the LCD panel  22 . This transmitted light is represented by light cones  158 . As illustrated, these light cones  158  may overlap in such a manner as to reduce optical beating or other artifacts. That is, the overlap of the light cones  158  generated by LEDs  122 A- 127 C allow for a more complete coverage of the display  14 . This overlap, in conjunction with the high effective PWM dimming frequency (i.e., equal to the product of the base PWM frequency times the number of phase-shifted LED strings), may reduce optical beating (or other artifacts) that may otherwise occur as a result of interference between the dimming frequency and the display refresh frequency, for example. 
     In a phase shift embodiment, as pulse waveform  95  is being transmitted to gate control line  74 , gate  80  is activated As gate  80  is activated, current is free to pass through LED string  112 , which, in turn, activates LEDs  124 A- 124 C. Accordingly, light may be generated by LEDs  124 A- 124 C, resulting in light transmitted to the LCD panel  22 . This may be illustrated in  FIG. 12 , which shows a top view of the light source  30 . As illustrated in  FIG. 12 , LEDs  124 A- 124 C are activated as pulse waveform  95  goes high. However, as may be seen in  FIG. 6 , as pulse waveform  95  goes high, pulse waveforms  93  and  94  are also high. Accordingly, each of LEDs  122 A- 122 C and  123 A- 123 C may be active as pulse waveform  95  goes high. 
     Additionally,  FIG. 13  shows a top view of the light source  30  as pulse waveform  95  is about to transition from high to low. As illustrated in  FIG. 13 , LEDs  124 A- 124 C are active as pulse waveform  95  is about to transition from high to low. However, as may be seen in  FIG. 6 , as pulse waveform  95  nears its transition to low, pulse waveforms  96  and  97  remain high. Accordingly, each of LEDs  125 A- 125 C and  126 A- 126 C may be active as pulse waveform  95  nears the transition from high to low. Thus,  FIGS. 12 and 13 , taken in conjunction, illustrate the phase shift activation of LED strings  110 ,  111 ,  113 , and  114  as LED string  112  is sequentially activated and deactivated. 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Metadata:
Filing Date: 20100106
Publication Date: 20141209
Grant Date: 20141209
Priority Date: 20100106
Inventors: THOMPSON PAUL M.
KIM FLORIANO
YOSHIMOTO MARK A.
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/342", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2320/0633", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/064", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B33/0818", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0233", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B20/346", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0247", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05B45/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05B45/38", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02B20/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B20/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y02B20/30", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 43034366