Patent Publication Number: US-9842551-B2

Title: Display driver circuitry with balanced stress

Description:
This application is a continuation-in-part of patent application Ser. No. 14/301,121, filed Jun. 10, 2014, which is hereby incorporated by reference herein in its entirety. This application claims the benefit of and claims priority to patent application Ser. No. 14/301,121, filed Jun. 10, 2014. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and more particularly, to electronic devices with touch screen displays. 
     Touch screen displays are prevalent in many applications, including consumer electronics devices such as smartphones, tablet devices, and laptop and desktop computers. The display function in such devices is typically performed by a liquid crystal display (LCD), plasma, or organic light emitting diode (OLED) display element array that is connected to a grid of source (data) and gate (select) metal traces. The display element array is often formed on a transparent panel such as a glass panel, which serves as a protective shield. The data and select lines of the display element array may be driven by a display driver integrated circuit (IC). The driver IC receives an image or video signal, which it then decodes into raster scan pixel values (color or gray scale) and writes them to the display element array during each frame, by driving the data and select lines. This process is repeated at a high enough frame rate so as to render video. 
     The touch gesture detection function in such devices is typically performed using a capacitance sensing subsystem in which a touch transducer grid structure overlays the display element array. The touch transducer structure is stimulated and sensed by touch controller circuitry. A touch stimulus signal is applied to the row segments of the grid, while simultaneously sensing the column segments (to detect a single-touch or a multi-touch gesture). Touch detection is typically performed during a blanking interval portion of the frame, while the display function is performed during a display interval portion of the frame. 
     The touch transducer grid structure can be implemented as a light transparent electrode plate that covers the display element array and may be formed on a rear surface of the protective panel. In some cases, the transparent electrode plate is also connected to the display elements, serving to deliver a “common voltage” to the display elements from a voltage source circuit often referred to as a Vcom conditioning circuit. The Vcom conditioning circuit helps improve the display function by adjusting a voltage on the transparent conductor plate that changes the light modulation characteristics of the connected display elements (during the display interval). As such, the transparent electrode plate is dual purposed in that it is used for both the display function and as the touch transducer grid structure. 
     As such, the touch screen display alternates between the display interval during which the display element array is activated and the blanking (or touch) interval during which the touch gesture detection function is activated. During each display interval, an entire frame is loaded into the display element array. The touch interval is typically positioned between successive display intervals (i.e., each touch interval occurs only after an entire frame has been scanned in). Performing inter-frame touch detection in this way may not be frequent enough for certain applications. 
     SUMMARY 
     An electronic device having a liquid crystal display (LCD) is provided. The liquid crystal display may include display pixel circuitry formed on a glass substrate. Thin-film transistor structures may be formed on the glass substrate. 
     The display pixel circuitry may include a display pixel array and gate driver circuitry coupled to the array. The gate driver circuitry may include at least one gate driver circuit that is formed on one side of the array. The gate driver circuit may include multiple gate driver units, each of which is configured to output a gate line output signal to display pixels arranged along a corresponding row in the array. 
     The display pixel circuitry may be used to output a given image/video frame. The gate driver circuitry may be configured to load a first sub-frame in the given frame during a first display interval and to load a second sub-frame in the given frame during a second display interval. Touch sensing operations may be performed during an intra-frame blanking interval (sometimes referred to as an intra-frame pause or “IFP”) inserted immediately after the first display interval and immediately before the second display interval. Each gate driver unit may include a respective drive transistor that passes a clock signal to the output terminal of that gate driver unit. In general, it may be desirable for the drive transistor at the IFP row to experience the same amount of stress as drive transistors in other rows. Methods for applying stress to or removing stress from one or more gate driver units for balancing the amount of stress presented to each gate driver unit are provided herein. 
     In accordance with one suitable arrangement, at least some gate driver units may include an analog control circuit for selectively applying a predetermined voltage to the gate terminal of the drive transistor during the IFP period. As an example, the analog control circuit may be configured to discharge the gate terminal of the drive transistor (e.g., to remove stress from an internal stress node). In this example, the analog control circuit may include a capacitor, a first control transistor that is coupled in series with the capacitor, and a second control transistor that is coupled in series with the first control transistor. The second control transistor may receive control signals that are only asserted during the IFP period. The first control transistor may have a gate terminal that is either coupled to the gate terminal of the drive transistor or coupled to a separate capacitor that stores a constant high voltage during the entirety of the IFP period. As another example, the analog control circuit may be configured to charge the internal stress node. In such example, the control circuit may include a pull-up transistor that pulls up the voltage of the internal stress node at the beginning of the IFP period and a pull-down transistor that pulls down the voltage at the internal stress node at the end of the IFP period. 
     In accordance with another suitable arrangement, at least some gate driver units may be implemented using digital control circuits that selectively apply a predetermined voltage onto the gate terminal of the drive transistor. The drive transistor may be part of a digital transmission gate and may be referred to herein as a pass transistor. The digital control circuit may be a digital logic gate that is coupled between the pass transistor and a digital circuit latch (e.g., a typical flip-flop or a set-reset latch). The digital logic gate may be a logic NOR gate for forcing the gate terminal of the pass transistor low (e.g., to remove stress from the transmission gate in the gate driver unit at the IFP position) or a logic NAND gate for forcing the gate terminal of the pass transistor high during the IFP interval (e.g., to introduce stress to the transmission gate in gate driver units at non-IFP positions). 
     In accordance with another suitable arrangement, the gate driver circuitry may include a plurality of gate driver segments, where each gate driver segment in the plurality of gate driver segments includes a series of active gate driver units, a first dummy gate driver unit coupled to a leading (first) active gate driver unit in the series of active gate driver units, and a second dummy gate driver unit coupled to a trailing (last) active gate driver unit in the series of active gate driver units. The gate driver circuitry may also include multiplexing circuitry (e.g., demultiplexing circuitry) for routing a gate start signal to a selected one of the plurality of gate driver segments. For example, the demultiplexing circuitry may include an array of pass transistors and logic gates and may have outputs each of which is coupled to the first dummy gate driver unit in a respective gate driver segment in the plurality of gate driver segments. 
     This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the subject matter described herein. Accordingly, it will be appreciated that the above-described features are merely examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following Detailed Description, Figures, and Claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device having a display such as a liquid crystal display in accordance with an embodiment of the present invention. 
         FIG. 2  is cross-sectional side view of an illustrative display in accordance with an embodiment of the present invention. 
         FIG. 3  is an illustrative diagram showing how a display may be provided with image pixel structures and touch sensor elements in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram illustrating a single intra-frame pause (IFP) in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram illustrating multiple intra-frame pauses (IFPs) in accordance with an embodiment of the present invention. 
         FIG. 6A  is a diagram showing gate driver circuitry formed on only one side of a display pixel array in accordance with an embodiment of the present invention. 
         FIG. 6B  is a timing diagram showing how the gate driver circuitry of  FIG. 6A  may be used to provide IFP capabilities in accordance with an embodiment of the present invention. 
         FIG. 7A  is a diagram showing gate driver circuitry formed on two opposing sides of a display pixel array in accordance with an embodiment of the present invention. 
         FIG. 7B  is a timing diagram showing how the gate driver circuitry of  FIG. 7A  may be used to provide IFP capabilities in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of a conventional display element array having a single gate driver chain formed on each of two opposing sides of the array. 
         FIG. 9  is a top view of an illustrative display element array having multiplexing circuitry for selectively routing start pulse signals in accordance with an embodiment of the present invention. 
         FIG. 10  is a circuit diagram of illustrative multiplexing circuitry of the type shown in  FIG. 9  in accordance with an embodiment of the present invention. 
         FIG. 11  is a circuit diagram of a conventional gate driver unit. 
         FIG. 12  is a timing diagram illustrating the operation of the conventional gate driver unit of  FIG. 11 . 
         FIG. 13  is a diagram of an illustrative analog gate driver unit that includes internal node discharging circuitry in accordance with an embodiment of the present invention. 
         FIG. 14  is a circuit diagram of one implementation of the gate driver unit of  FIG. 13  in accordance with an embodiment of the present invention. 
         FIG. 15  is a timing diagram that illustrates the operation of the gate driver unit of  FIG. 14  in accordance with an embodiment of the present invention. 
         FIG. 16  is a circuit diagram of another implementation of the gate driver unit of  FIG. 13  in accordance with an embodiment of the present invention. 
         FIG. 17  is a timing diagram that illustrates the operation of the gate driver unit of  FIG. 16  in accordance with an embodiment of the present invention. 
         FIG. 18  is a diagram of an illustrative analog gate driver unit that includes internal node charging circuitry in accordance with an embodiment of the present invention. 
         FIG. 19  is a circuit diagram of one implementation of the gate driver unit of  FIG. 18  in accordance with an embodiment of the present invention. 
         FIG. 20  is a top view showing how gate driver units with internal node charging circuitry may be formed at non-IFP rows in a display element array in accordance with an embodiment of the present invention. 
         FIG. 21  is a timing diagram that illustrates the operation of the display element array of  FIG. 20  in accordance with an embodiment of the present invention. 
         FIG. 22  is a diagram of a conventional digital gate driver unit. 
         FIG. 23  is a diagram of illustrative digital gate driver units having flip-flop circuits and IFP gating logic in accordance with an embodiment of the present invention. 
         FIG. 24  is a circuit diagram of an illustrative digital gate driver unit of the type shown in  FIG. 23  and that exhibits reduced stress in accordance with an embodiment of the present invention. 
         FIG. 25  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 24  in accordance with an embodiment of the present invention. 
         FIG. 26  is a circuit diagram of an illustrative digital gate driver unit having flip-flop circuits and that exhibits balanced stress in accordance with an embodiment of the present invention. 
         FIG. 27  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 26  in accordance with an embodiment of the present invention. 
         FIG. 28  is a diagram of illustrative digital gate driver units having set-reset latch circuits and IFP gating logic in accordance with an embodiment of the present invention. 
         FIG. 29  is a circuit diagram of an illustrative digital gate driver unit of the type shown in  FIG. 28  and that exhibits reduced stress in accordance with an embodiment of the present invention. 
         FIG. 30  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 29  in accordance with an embodiment of the present invention. 
         FIG. 31  is a circuit diagram of an illustrative digital gate driver unit having a set-reset latch and that exhibits balanced stress in accordance with an embodiment of the present invention. 
         FIG. 32  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 31  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Displays are widely used in electronic devices. For example, displays may be used in computer monitors, laptop computers, media players, cellular telephones and other handheld devices, tablet computers, televisions, and other equipment. Displays may be based on plasma technology, organic-light-emitting-diode technology, liquid crystal structures, etc. Liquid crystal displays are popular because they can exhibit low power consumption and good image quality. Liquid crystal display (LCD) structures are sometimes described herein as an example. 
     A perspective view of an illustrative electronic device with a display is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  6  may have a housing such as housing  8 . Housing  8  may be formed from materials such as plastic, glass, ceramic, metal, fiber composites, and combinations of these materials. Housing  8  may have one or more sections. For example, device  6  may be provided with a display housing portion and a base housing portion that are coupled by hinges. In the arrangement of  FIG. 1 , device  6  has a front face and a rear face. Display  10  of  FIG. 1  is mounted on the front face of housing  8 . Other configurations may be used if desired. 
     The illustrative configuration of device  6  in  FIG. 1  is merely illustrative. In general, electronic device  6  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     Display  10  may be a liquid crystal display. A touch sensor array may be incorporated into display  10  (e.g., to form a touch screen display). The touch sensor may be based on acoustic touch technology, force sensor technology, resistive sensor technology, or other suitable types of touch sensor. With one suitable arrangement, the touch sensor portion of display  10  may be formed using a capacitive touch sensor arrangement. With this type of configuration, display  10  may include a touch sensor array that is formed from rows and columns of capacitive touch sensor electrodes. 
     A cross-sectional side view of a portion of a display of the type that may be used in forming display  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , display  10  may include color filter (CF) layer  12  and thin-film-transistor (TFT) layer  14 . Color filter layer  12  may include an array of colored filter elements. In a typical arrangement, the pixels of layer  12  each include three types of colored pixels (e.g., red, green, and blue subpixels). Liquid crystal (LC) layer  16  includes liquid crystal material and is interposed between color filter layer  12  and thin-film-transistor layer  14 . Thin-film-transistor layer  14  may include electrical components such as thin film transistors, capacitors, and electrodes for controlling the electric fields that are applied to liquid crystal layer  16 . Optical film layers  18  and  20  may be formed above and below color filter layer  12 , liquid crystal layer  16 , and thin-film-transistor layer  14 . Optical films  18  and  20  may include structures such as quarter-wave plates, half-wave plates, diffusing films, optical adhesives, and birefringent compensating layers. In other suitable arrangements, thin-film transistor layer  14  may be formed on top of the liquid crystal material while the color filter layer  12  may be formed below the liquid crystal material. 
     Display  10  may have upper and lower polarizer layers  22  and  24 . Backlight  26  may provide backside illumination for display  10 . Backlight  26  may include a light source such as a strip of light-emitting diodes. Backlight  26  may also include a light-guide plate and a back reflector. The back reflector may be located on the lower surface of the light-guide panel to prevent light leakage. Light from the light source may be injected into an edge of the light-guide panel and may scatter upwards in direction  28  through display  10 . An optional cover layer such as a layer of coverglass may be used to cover and protect the layers of display  10  that are shown in  FIG. 2 . 
     Touch sensor structures may be incorporated into one or more of the layers of display  10 . In a typical touch sensor configuration, an array of capacitive touch sensor electrodes may be implemented using pads and/or strips of a transparent conductive material such as indium tin oxide. Other touch technologies may be used if desired (e.g., resistive touch, acoustic touch, optical touch, etc.). Indium tin oxide or other transparent conductive materials or non-transparent conductors may also be used in forming signal lines in display  10  (e.g., structures for conveying data, power, control signals, etc.). 
     In black and white displays, color filter layer  12  can be omitted. In color displays, color filter layer  12  can be used to impart colors to an array of image pixels. Each image pixel may, for example, have three corresponding liquid crystal diode subpixels. Each subpixel may be associated with a separate color filter element in the color filter array. The color filter elements may, for example, include red (R) color filter elements, blue (B) color filter elements, and green (G) color filter elements. These elements may be arranged in rows and columns. For example, color filter elements can be arranged in stripes across the width of display  10  (e.g., in a repeating patterns such as a RBG pattern or BRG pattern) so that the color filter elements in each column are the same (i.e., so that each column contains all red elements, all blue elements, or all green elements). By controlling the amount of light transmission through each subpixel, a desired colored image can be displayed. 
     The amount of light transmitted through each subpixel can be controlled using display control circuitry and electrodes. Each subpixel may, for example, be provided with a transparent indium tin oxide electrode. The signal on the subpixel electrode, which controls the electric field through an associated portion of the liquid crystal layer and thereby controls the light transmission for the subpixel, may be applied using a thin film transistor. The thin film transistor may receive data signals from data lines and, when turned on by an associated gate line, may apply the data line signals to the electrode that is associated with that thin-film transistor. 
     A top view of an illustrative display is shown in  FIG. 3 . As shown in  FIG. 3 , display  10  may include an array of image pixels  52 . Pixels  52  (which are sometimes referred to as subpixels) may each be formed from electrodes that give rise to an electric field and a portion of liquid crystal layer  16  ( FIG. 2 ) that is controlled by that electric field. Each image pixel may have an electrode that receives a data line signal from an associated transistor and a common electrode. The common electrodes of display  10  may be formed from a layer of patterned indium tin oxide or other conductive planar structures. The patterned indium tin oxide structure or other conductive structures that are used in forming the common plane for image pixels  52  may also be used in forming capacitive touch sensor elements  62 . 
     As illustrated by touch sensor elements  62  of  FIG. 3 , touch sensor elements (electrodes) may be coupled to touch sensor circuitry  68 . Touch sensor elements  62  may include rectangular pads of conductive material, vertical and/or horizontal strips of conductive material, and other conductive structures. Signals from elements  62  may be routed to touch sensor processing circuitry  68  via traces  64  on flex circuit cable  66  or other suitable communications path lines. 
     In a typical arrangement, there are fewer capacitor electrodes  62  in display  10  than there are image pixels  52 , due to the general desire to provide more image resolution than touch sensor resolution. For example, there may be hundreds or thousands of rows and/or columns of pixels  52  in display  10  and only tens or hundreds of rows and/or columns of capacitor electrodes  62 . 
     Display  10  may include display driver circuitry  38 . Display driver circuitry  38  may receive image data from processing circuitry in device  6  using conductive lines  70  in path  72 . Path  72  may be, for example, a flex circuit cable or other communications path that couples display driver circuitry  38  to integrated circuits on a printed circuit board elsewhere in device  6  (as an example). 
     Display driver circuitry  38  may include control circuit  38 - 0 , gate line driver circuit  38 - 1 , and gate line driver circuit  38 - 2 . Display driver control circuit  38 - 0  may be implemented using one or more integrated circuits (e.g., one or more display driver integrated circuits). Circuits  38 - 1  and  38 - 2  (sometimes referred to as gate line and Vcom driver circuitry) may be incorporated into control circuit  38 - 0  or may be implemented using thin-film transistors on layer  14  ( FIG. 2 ). Gate line driver circuits  38 - 1  and  38 - 2  implemented using thin-film transistor structures on layer  14  may sometimes be referred to as gate driver on array or “GOA.” Paths such as paths  60  may be used to interconnect display driver circuitry  38 . Display driver circuitry  38  may also be implemented using external circuits or other combinations of circuitry, if desired. 
     Display driver circuitry  38  may control the operation of display  10  using a grid of signal lines such as data lines  48 , gate lines  46 , and Vcom lines (not shown). In the example of  FIG. 3 , gate driver circuit  38 - 1  may serve to provide gate line signals to display pixels  52  arranged along even rows in the array (e.g., by supplying gate line signals on even gate lines  46 - 1 ), whereas gate driver circuit  38 - 2  may serve to provide gate line signals to display pixels  52  arranged along odd rows in the array (e.g., by supplying gate line signals on odd gate lines  46 - 2 ). This type of interlaced driving scheme in which gate line driver circuits drive signals from two different sides of the array in this way is merely illustrative. In other suitable arrangements, gate drivers may be formed on only one side, or on more than two sides of the image pixel array. 
     Note that the touch function may be performed during a touch interval portion of the video frame, and in particular during a “blanking” interval (rather than during a display interval) of the video frame. In conventional displays, the touch interval is typically inserted only between successive display intervals that each display an entire image/video frame (i.e., conventional touch screen displays are only configured to implement inter-frame pause for touch sensing). 
     In some arrangements, it may be desirable to perform touch sensing at more frequent intervals. In accordance with an embodiment of the present invention, display  10  may be configured to implement an intra-frame pausing (IFP) scheme to allow touch sensing operations to be performed at relatively higher frequencies compared to the inter-frame pausing scheme.  FIG. 4  is a diagram showing a single intra-frame pause. As shown in  FIG. 4 , a display pixel array  100  that includes image pixels  52  arranged in rows and columns may be organized into a first sub-frame  102 - 1  and a second sub-frame  102 - 2 . First sub-frame  102 - 1  may be loaded with new display data during time period T 1 , whereas second sub-frame  102 - 2  may be loaded with new display data during time period T 2 . To implement a single IFP, an initial blanking interval may occur prior to loading first sub-frame  102 - 1  (i.e., immediately prior to period T 1 ), and a single IFP blanking interval may be inserted after loading of first sub-frame  102 - 1  and prior to loading of second sub-frame  102 - 2  (i.e., between periods T 1  and T 2 ). After the second sub-frame  102 - 2  has been loaded with new display data, the steps described above may be repeated for the next frame. 
     Each blanking interval may have a duration T IFP  during which touch sensing operations or other display/non-display related operations may be performed. The example of  FIG. 4  in which the IFP is inserted at the middle of the frame is merely illustrative. If desired, the position of the IFP may be adjusted (e.g., the intra-frame pause may be inserted more towards the top of the frame or more towards the bottom of the frame). If desired, the duration of each blanking interval can also be adjusted (e.g., period T IFP  may be adjusted). 
     In other suitable arrangements, multiple IFPs may be inserted within a single frame (see,  FIG. 5 ). As shown in  FIG. 5 , display pixel array  100  may be organized into a first sub-frame  102 - 1 , a second sub-frame  102 - 2 , a third sub-frame  102 - 3 , and a fourth sub-frame  102 - 4 , each of which displays data for a quarter of the entire frame. First sub-frame  102 - 1  may be loaded with new display data during display interval T 1 ; second sub-frame  102 - 2  may be loaded with new display data during display interval T 2 ; third sub-frame  102 - 3  may be loaded with new display data during display interval T 3 ; and fourth sub-frame  102 - 4  may be loaded with new display data during display interval T 4 . To implement multiple IFPs in this scenario, an initial blanking interval may occur prior to loading first sub-frame  102 - 1  (i.e., immediately prior to period T 1 ), a first IFP blanking interval may be inserted after accessing sub-frame  102 - 1  and prior to accessing sub-frame  102 - 2  (i.e., between periods T 1  and T 2 ), a second IFP blanking interval may be inserted after accessing sub-frame  102 - 2  and prior to accessing sub-frame  102 - 3  (i.e., between periods T 2  and T 3 ), a third IFP blanking interval may be inserted after accessing sub-frame  102 - 3  and prior to accessing sub-frame  102 - 4  (i.e., between periods T 3  and T 4 ). After the fourth sub-frame  102 - 4  has been loaded with new display data, the steps described above may be repeated for the next frame. 
     The example of  FIG. 5  in which the IFP is inserted at regular intervals within the frame is merely illustrative. In general, any number of IFPs may be inserted at any suitable location within the frame. If desired, the duration of each blanking interval may be adjusted, and the duration of each IFP blanking interval need not be the same. 
       FIG. 6A  is a diagram of a display having gate line driver circuitry  38  formed on only one side of display pixel array  100 . As shown in  FIG. 6A , gate line driver circuitry  38  may include a series of gate line driver units connected in a chain. A given gate line driver unit in the chain may be referred to as gate line driver unit “n” that is configured to output a corresponding gate line output signal G(n). The gate line driver unit preceding the given driver unit in the chain may be referred to as gate line driver unit “(n−1)” that is configured to output a corresponding gate line output signal G(n−1). The gate line driver unit following the given driver unit in the chain may be referred to as gate line driver unit “(n+1)” that is configured to output a corresponding gate line output signal G(n+1). Driver units preceding unit (n−1) may be referred to as units (n−2), (n−3), (n−4) . . . , whereas driver units succeeding unit (n+1) may be referred to as units (n+2), (n+3), (n+4), etc. 
     In the example of  FIG. 6A , each gate driver unit has an output that is coupled to an input of a subsequent gate driver unit via a feed-forward path. For example, gate line output G(n−1) may be routed to unit n; gate line output G(n) may be routed to unit (n+1), gate line output G(n+1) may be routed to unit (n+2), etc. Connected in this way, an asserted gate line pulse signal can be propagated down the chain of gate driver units to provide desired raster scanning (e.g., so that new display pixel values can be sequentially written into the display pixel array on a row-by-row basis). 
     The output of each gate driver unit may also be fed back to a corresponding gate driver unit that is three rows above that gate driver unit. For example, gate line output G(n) may be fed back to unit (n−3), as indicated by feed-back path  190 . As another example, gate line output signal G(n−2) may be fed back to unit (n−5), as indicated by path  192 . Connected in this way, the output signal of a second gate driver unit subsequent to (but not necessarily immediately following) a first gate driver unit in the chain may be used to “reset” the gate line output signal of the first gate driver unit (e.g., assertion of the output signal generated by the second gate driver unit may drive the output signal of the first gate driver unit low). This is merely exemplary. The output of each gate driver unit may be fed back to any suitable preceding gate driver unit (i.e., the output of a given gate driver unit may be fed back to a corresponding gate driver unit that is less than three rows above the given gate driver unit or more than three rows above the given gate driver unit). 
     Gate driver circuitry  38  may receive gate clock signals CLKx and an intra-frame pause control signal EN_IFP. Control signal EN_IFP may serve as an enable signal that activates the blanking interval when asserted and that permits the display interval when deasserted.  FIG. 6B  is a timing diagram that illustrates the behavior of relevant signals during the operation of gate driver circuitry  38  of the type shown in  FIG. 6A . As shown in  FIG. 6B , active data signals provided on data lines  48  ( FIG. 3 ) may be loaded into corresponding rows in the display pixel array during the display intervals. During the display or “non-blanking” intervals (e.g., when enable signal EN_IFP is deasserted), clock signals CLK 1 - 8  direct the gate driver units to sequentially assert the gate line output signals. The number of clock signals in this example is merely illustrative. In general, any number of clock signals CLKx may be used to control the various gate line driver units. 
     In the example of  FIG. 6B , an intra-frame pause is inserted right after G(n) is asserted. During the IFP blanking interval, enable signal EN_IFP is asserted for a duration T IFP . While EN_IFP is asserted, the clock signals CLKx are temporarily suspended, which prevents any gate line signals from being generated (e.g., no display pixels are being accessed during the blanking intervals). At the end of the IFP blanking interval, signal EN_IFP is deasserted, which allows the clock signals to toggle and to continue generating gate line output signals G(n+1), G(n+2), G(n+3), and so no until the next blanking interval. 
       FIG. 7A  is a diagram of a display having gate line driver circuits  38  formed on at least two opposing sides of display pixel array  100 . As shown in  FIG. 7A , a first gate line driver circuit  38 - 1  may be formed on a first edge of array  100 , whereas a second gate line driver circuit  38 - 2  may be formed on a second opposing edge of array  100 . Each gate line driver circuits  38 - 1  and  38 - 2  may include multiple gate line driver units coupled in a chain. Gate line driver circuit  38 - 1  may include gate line driver units that are used to generate gate line output signals G(n−4), G(n−2), G(n), G(n+2), G(n+4), etc. for “even” pixel rows in the array, whereas  38 - 2  may include gate line driver units that are used to generate gate line output signals G(n−3), G(n−1), G(n+1), G(n+3), G(n+5), etc. for “odd” pixel rows in the array. 
     Even row gate driver circuit  38 - 1  may receive gate clock signals CLKx and an IFP control signal EN_IFP, whereas odd row gate driver circuit  38 - 2  may receive gate clock signals CLKx′ and control signal EN_IFP. The clock signals controlling the gate driver units in circuit  38 - 1  may be different or may be the same as those controlling the gate driver units in circuit  38 - 2 . Similarly, signal EN_IFP controlling the gate driver units in circuit  38 - 1  may be the same or may be different than that controlling the gate driver units in circuit  38 - 2 . 
       FIG. 7B  is a timing diagram that illustrates the behavior of relevant signals during the operation of gate driver circuitry  38  of the type shown in  FIG. 7A . As shown in  FIG. 7B , active data signals provided on data lines  48  ( FIG. 3 ) may be loaded into corresponding rows in the display pixel array during the display intervals. During the display or “non-blanking” intervals (e.g., when enable signal EN_IFP is deasserted), clock signals CLK 1 - 4  may direct the even gate driver units to sequentially assert the gate line output signals while clock signals CLK 1   a - 4   a  may direct the odd driver units to sequentially assert the gate line output signals. The number of clock signals in this example is merely illustrative. In general, any number of clock signals CLKx may be used to control the various gate line driver units. 
     In the example of  FIG. 7B , the intra-frame pause is inserted after G(n) is asserted by circuit  38 - 1  and after G(n−1) is asserted by circuit  38 - 2 . During the IFP blanking interval, enable signal EN_IFP is asserted for time period T IFP . While EN_IFP is asserted, the clock signals CLK 1 - 4  and CLK 1   a - 4   a  are temporarily suspended, which prevents any gate line signals from being generated (e.g., no display pixels are being accessed during the blanking intervals). At the end of the IFP blanking interval, signal EN_IFP is deasserted, which allows the clock signals to toggle and to continue generating gate line output signals G(n+1), G(n+2), G(n+3), and so no until the next blanking interval. 
       FIG. 8  is a diagram of an LCD display pixel array  256  that is coupled to gate driver circuits implemented using conventional gate driver units  200 . As shown in  FIG. 8 , gate driver circuits  252 - 1  and  252 - 2  are coupled to array  256  via associated routing circuitry  254 . Each gate driver circuit  252  (i.e., circuits  252 - 1  and  252 - 2 ) includes  1024  gate driver units  200  connected in a chain. The  1024  conventional gate driver units  200  in gate driver circuit  252 - 1  are used to provide gate line output signals to the  1024  odd-numbered rows in array  256 , whereas the  1024  conventional gate driver units  200  in gate driver circuit  252 - 2  are used to provide gate line output signals to the  1024  even-numbered rows in array  256 . 
     In each gate driver circuit  252 , a first group of dummy gate driver units  260  are coupled to the top of the chain, and a second group of dummy gate driver units  262  are coupled to the bottom of the chain. These “dummy” gate driver units are not actively coupled to the display pixels in array  256  (i.e., they do not have outputs that are directly connected to the image pixels). Gate driver units  260  may serve as dummy units to properly initialize the active gate driver units  200  (i.e., to send appropriate initialization signals to the leading gate driver units  200  in the chain via the feed forward paths described in connection with  FIGS. 6 and 7 ). Gate driver units  262  may serve as dummy units to properly reset the trailing gate driver units  200  in the chain by sending signals via the feedback paths described in connection with  FIGS. 6 and 7 . Without units  260 , the first few gate driver units  200  won&#39;t be properly initialized at the beginning of a given frame. Without units  262 , the last few gate driver units  200  won&#39;t be properly reset at the end of the given frame. 
     Each of circuits  252 - 1  and  252 - 2  are controlled by respective clock signals CLKx. Gate driver circuit  252 - 1  is activated by gate start pulse signal GSP 1 , which triggers the clock signals that are controlling circuit  252 - 1  to start toggling. Similarly, gate driver circuit  252 - 2  is activated by gate start pulse signal GSP 2 , which triggers the clock signals that are controlling circuit  252 - 2  to start toggling. Gate driver circuitry implemented using this conventional approach may suffer from reliability issues when operated to support one or more intra-frame pauses. For example, at least one driver transistor in gate driver units  200  surrounding the IFP location may be subject to elevated stress levels for a substantially longer period of time relative to gate driver units  200  further away from the IFP position. Subjecting driver transistors to elevated stress levels can result in degraded drive strength of gate driver unit  200  (i.e., stress to thin-film transistors can cause hot carrier degradation, gate bias degradation, and self heating effects), which can cause visible line noise and other undesirable image artifacts near the IFP row position in the display. 
     In one suitable arrangement, the gate driver circuits may be divided into multiple individual segments, each of which is responsible for driving respective rows in the display pixel array  100 .  FIG. 9  shows an example where the gate driver circuitry is split on opposing sides of array  100 . As shown in  FIG. 9 , first gate driver circuit  38 - 1  may be formed on one side of array  100  to drive the odd-numbered rows (e.g., rows  1 ,  3 ,  5 , . . . ,  2047 ), whereas second gate driver  38 - 2  may be formed on an opposing side of array  100  to drive the even-number rows (e.g., rows  2 ,  4 ,  6 , . . . ,  2048 ). 
     In particular, each of gate driver circuits  38 - 1  and  38 - 2  may include multiple gate driver segments  120 . Each gate driver segment  120  may include a series of gate driver units  122  (e.g., gate driver units  122  connected in a chain) and associated dummy gate driver units  124  and  126 . One or more gate driver units  124  may be formed at the front of each segment  120  and may serve as dummy units for initializing the first few active gate driver units  122  in the chain. One or more gate driver units  126  may be formed at the end of each segment  120  and may serve as dummy units for resetting the last few active gate driver units  122  in the chain. The active gate driver units  122  in each segment  120  may be coupled to corresponding rows in array  100  via routing circuitry  100  (sometimes referred to as “fanout” circuitry), whereas the dummy gate driver units  124  and  126  have outputs that are not actively coupled to array  100 . The number of dummy gate driver units  124  and  126  that are required in each gate driver segment  120  may depend on the particular feed-forward and feed-back routing configuration among the active gate driver units (see,  FIGS. 7A and 7B ). 
     Each gate driver segment  120  may be separately controlled by a respective gate start pulse signal. In the example of  FIG. 9 , each gate driver segment  120  in the left gate driver circuit  38 - 1  may receive a gate start pulse from a first multiplexing circuit  121 - 1 , whereas each gate driver segment  120  in the right gate driver circuit  38 - 2  may receive a gate start pulse from a second multiplexing circuit  121 - 2 . Multiplexing circuit  121 - 1  may have an input that receives a gate start pulse signal GSP L , a first output that is coupled to the first segment  120  in circuit  38 - 1  (e.g., to the dummy gate driver unit  124  in that segment), a second output that is coupled to the second segment  120  in circuit  38 - 1 , a third output that is coupled to the third segment  120  in circuit  38 - 1 , a fourth output that is coupled to the fourth segment  120  in circuit  38 - 1 , and a control input for receiving control signals CTR L  that configure multiplexing circuit  121 - 1  to route GSP L  to a selected one of its outputs. Similarly, multiplexing circuit  121 - 2  may have an input that receives a gate start pulse signal GSP R , a first output that is coupled to the first segment  120  in circuit  38 - 2  (e.g., to the dummy gate driver unit  124  in that segment), a second output that is coupled to the second segment  120  in circuit  38 - 2 , a third output that is coupled to the third segment  120  in circuit  38 - 2 , a fourth output that is coupled to the fourth segment  120  in circuit  38 - 2 , and a control input for receiving control signals CTR R  that configure multiplexing circuit  121 - 2  to route GSP R  to a selected one of its outputs. Multiplexing circuits  121 - 1  and  121 - 2  configured in this way are sometimes referred to as “demultiplexing” circuits. 
       FIG. 10  shows one suitable arrangement of a demultiplexing circuit  121 . The example of  FIG. 10  illustrates a demultiplexing circuit that can be used to control ten gate driver segments  120 . As shown in  FIG. 10 , circuit  121  may include an input for receiving a global gate start pulse signal GSP L,R  and pass transistors  123  for selectively passing through the global gate start pulse to one of the output paths. Each pass transistor  123  may receive one of the control signals CTR[ 5 : 1 ]. For example, output signal SP 1  that controls the first gate driver segment  120  will only be asserted if control signals CTR[ 2 ] and CTR[ 1 ] are both high. As another example, output signal SP 2  that controls the second gate driver segment  120  will only be asserted if control signals CTR[ 3 ] and CTR[ 1 ] are both high. As yet another example, output signal SP 10  that controls the tenth gate driver segment  120  will only be asserted if control signals CTR] 5 ] and CTR[ 4 ] are both high. This particular implementation of demultiplexing circuit  121  is merely illustrative. If desired, demultiplexing circuit  121  may be implemented using logic gates such as logic AND gates, using n-channel or p-channel TFTs, and/or any suitable type of switching circuits. In yet other suitable arrangements, shift register circuitry can be used to provide the gate start pulses to the different gate driver segments. 
     Connected in this way, the IFP location is fixed. In other words, the IFP may only be inserted at the junction of two adjacent gate driver segments  120 . In general, each circuit  38 - 1  and  38 - 2  may include any number of gate driver segments  120  for implementing any desired number of IFPs at predetermined row locations in array  100 . The duration of each IFP may also be individually adjusted by controlling when the gate start pulses are launched. For example, the first IFP duration between rows  512  and  513  merely can be adjusted by delaying when GSP L  and GSP R  are launched by the desired amount. If desired, a similar multi-segment approach can be implemented for gate driver circuitry that is formed on only one side of array  100  (see,  FIGS. 6A and 6B ). 
     Configured in this way, none of the transistors in the active gate driver units  122  will suffer from elevated stress levels since the gate output signals are allowed to freely propagate down the entire chain in each segment  120  without interruption. In other words, no transistor in gate driver units  122  will be subject to a prolonged level of applied stress during IFP intervals since during blanking intervals, any active gate driver unit  122  should have already been reset by dummy units  126 , and the IFP interval can be arbitrarily extended by delaying the next gate start pulse. 
       FIG. 11  is a circuit diagram of a conventional gate line driver unit  200 . Gate driver unit  200  includes a capacitor  204  and n-channel thin-film transistors  202 ,  206 ,  208 , and  210 . Transistor  202  has a drain terminal that receives a clock signal CLK, a gate terminal that is connected to an intermediate node X, and a source terminal that is connected to the output of unit  200  (i.e., an output terminal on which Gout is provided). Capacitor  204  has a first terminal that is connected to node X and a second terminal that is connected to the source terminal of transistor  202 . Transistor  206  has a drain terminal that is connected to the source terminal of transistor  202 , a gate terminal, and a source terminal that is connected to a ground line. 
     Transistor  208  has a source terminal that is connected to node X, a drain terminal, and a gate terminal that is connected to its drain terminal. Transistor  210  has a drain terminal that is connected to node X, a source terminal that is connected to the ground line, and a gate terminal. The gate and drain terminals of transistor  208  are connected to the gate line output of a preceding gate driver unit via feed-forward path  212 , whereas the gate terminals of transistors  206  and  210  are connected to the gate line output of a succeeding gate driver unit via feedback path  214 . 
       FIG. 12  is a timing diagram showing the waveform at node X in a series of conventional gate driver units  200 . In particular, consider the voltage X G(n-3)  at node X in gate driver unit (n−3). Voltage X G(n−3)  may rise from 0 V to 20 V when the gate output from a preceding unit is asserted (i.e., the asserted gate output routed from the preceding unit via path  212  will turn on transistor  208  to pull up X G(n−3) ). Voltage X G(n−3)  may then rise from 20 V to 40 V when the clock signal is asserted (i.e., the incoming clock pulse will enable transistor  202  to pull up X G(n−3) ). When signal CLK is deasserted, X G(n−3)  will fall accordingly back to 20 V. Voltage X G(n−3)  is then reset back down to zero volts when the gate output from a succeeding unit is asserted (i.e., the asserted gate output routed from the succeeding unit via path  214  will turn on transistor  210  to pull down X G(n−3) ). 
     In this particular scenario, each gate driver unit  200  is reset by a succeeding gate driver unit  200  that is three rows below that gate driver unit. For example, voltage X G(n−2)  is only reset to ground when G(n+1) is asserted. When implementing an intra-frame pause in this scenario, it is possible for at least some voltages X G  to be partially asserted during the IFP blanking interval. As indicated by portions  250  in  FIG. 12 , voltages X G(n−2) , X G(n−1) , X G(n) , X G(n+1) , and X G(n+2)  may be biased at 20 V for the entirety of the IFP interval assuming the IFP is inserted after G(n) is asserted. As described above, voltage X G(n−2)  is only driven back down to zero voltages when G(n+1) is asserted, which can only occur after T IFP  since all gate clocking signals are suspending during the blanking interval. Similarly, voltage X G(n−1)  is only driven back down to zero voltages when G(n+2) is asserted, which can only occur after T IFP . In other words, voltage X G  for gate driver units  200  near the IFP location will be at least partially asserted during the IFP interval. 
     As illustrated by  FIG. 12 , node X in gate driver units  200  surrounding the IFP location may be subject to elevated stress levels for a substantially longer period of time relative to gate driver units  200  further away from the IFP position. Node X may therefore sometimes be referred to as the “internal IFP stress node.” Subjecting transistor  202  to elevated stress levels can result in degraded drive strength of gate driver unit  200 , which can cause image artifacts near the IFP row position and other undesirable reliability issues for the display. 
     In at least one suitable embodiment, a gate driver unit  300  that eliminates the elevated stress levels experienced during an IFP interval is provided. As shown in  FIG. 13 , gate driver unit  300  may include n-channel thin-film transistors (TFTs) Td,  310 ,  320 , and  304 , a capacitor C 1 , and an associated gate driver control circuit  302 . Transistor Td may have a drain terminal that receives a clock signal CLK, a gate terminal that is coupled to an internal node X, and a source terminal that drives the gate driver output signal G(n). Transistor Td is therefore sometimes referred to as the “drive TFT.” Capacitor C 1  may be coupled between the gate and source terminals of the drive transistor Td. 
     Transistor  310  may have a drain terminal that is coupled to the source terminal of transistor Td, a gate terminal, and a source terminal that is coupled to ground (i.e., a ground power supply line  304 ). Transistor  320  may have a drain terminal, a gate terminal that is coupled to its drain terminal, and a source terminal that is coupled to internal node X. Transistor  322  may have a drain terminal that is coupled to internal node X, a gate terminal, and a source terminal that is coupled to ground  304 . The drain terminal of transistor  320  may receive signal G(n−1) from a preceding gate driver unit in the chain via a feed-forward path, whereas the gate terminals of transistors  310  and  322  may receive signal G(n+1) from a subsequent gate driver unit in the chain via a feedback path. The example of  FIG. 13  in which the gate driver unit  300  receives a feed-forward signal G(n−1) from an immediately preceding gate driver unit and a feedback signal G(n+1) from an immediately succeeding gate driver unit is merely illustrative. 
     Still referring to  FIG. 13 , gate driver control circuit  302  may be coupled to the internal node X and may receive control signals IFP EN  and IFP PULSE . As described in connection with  FIG. 12 , it is generally not desirable to having node X be partially asserted during IFP intervals. In order to reduce the amount of stress that is experienced by gate driver unit  300 , gate driver control circuit  302  may be configured to discharge internal node X during the intra-frame pausing period. By discharging node X during intra-frame pauses, transistor Td in gate driver units  300  at or surrounding the IFP row will no longer experience elevated stress levels. Gate driver control circuit  302  may therefore sometimes be referred to as internal node discharge circuitry. 
       FIG. 14  is a circuit diagram of one implementation of gate driver unit  300  of the type shown in  FIG. 13 . As shown in  FIG. 14 , gate driver control circuit  302  may include n-channel thin-film transistors  350 ,  352 , and  354  and capacitors C 2  and C 3 . Capacitor C 2  may have a first terminal that is coupled to node X and a second terminal that is coupled to another internal node Y. Transistor  350  may have a drain terminal that is coupled to node Y, a gate terminal that is coupled to the gate terminal of transistor  310 , and a source terminal that is coupled to ground. Transistor  352  may have a drain terminal that is coupled to node Y, a gate terminal that is coupled to node X, and a source terminal. Capacitor C 3  may have a first terminal that is coupled to node X and a second terminal that is coupled to the source terminal of transistor  352 . Transistor  354  may have a drain terminal that is coupled to the source terminal of transistor  352 , a gate terminal that receives control signal IFP EN , and a source terminal that receives control signal IFP PULSE . 
       FIG. 15  is a timing diagram that illustrates the operation of gate driver unit  300  of  FIG. 14 . At time t 1 , clock signal CLK 2  may be pulsed high during the display interval, which causes output signal G(n−1) at the output of gate driver unit (n−1) to be driven high for the duration of the CLK 2  pulse. Assuming the chain of gate driver units  300  uses the feed-forward routing as shown in  FIG. 14 , the assertion of G(n−1) may turn on transistor  320  in the succeeding gate driver unit (n), which may result in the partial assertion of internal node voltage X(n) in the succeeding gate driver unit (n). While G(n−1) is asserted, capacitor C 1  in gate driver unit (n) may be charged up to store the voltage as seen on node X in that gate driver unit. Voltage X(n) may remain asserted until it is actively driven back down to ground using one of transistors  322 ,  350 , and/or  354  in gate driver unit (n). 
     At time t 2 , clock signal CLK 1  may be pulsed high during the display interval, which causes output signal G(n) at the output of gate driver unit (n) to be driven high for the duration of the CLK 1  clock pulse. At the rising edge of CLK 1 , transistor Td in gate driver unit (n) may charge up its source terminal accordingly. Since the voltage on capacitor C 1  has nowhere to discharge at this time, voltage X(n) may be temporarily boosted by the amount of voltage change seen at the source terminal of transistor Td. Capacitor C 1  operated in this way is sometimes referred to as a “bootstrapping” capacitor. Assuming the chain of gate driver units  300  uses the feed-forward routing as shown in  FIG. 14 , the assertion of G(n) may turn on transistor  320  in the succeeding gate driver unit (n+1), which may result in the partial assertion of internal node voltage X(n+1) in the succeeding gate driver unit (n+1). While G(n) is asserted, capacitor C 1  in gate driver unit (n+1) may be charged up to store the voltage as seen on node X in that gate driver unit. 
     In preparation of the upcoming intra-frame pause, controls signal IFP EN  may be asserted around time t 2 . As shown in  FIG. 15 , control signal IFP PULSE  may be nominally asserted (e.g., signal IFP PULSE  may be driven high during display intervals and may only be driven low during IFP intervals). At time t 2 , IFP PULSE  may still be driven high. Asserting signal IFP EN  while IFP PULSE  is driven high may turn on transistor  354  and charge up the source terminal of transistor  352  towards a logic one. This may result in node Y being charged towards logic one in gate driver units having node X at least partially driven high (i.e., in gate driver units (n) and (n+1) in this example), since transistor  352  will be turned on for these gate driver units. Prior to time t 3 , there may be minimal voltage drop across capacitor C 2 . 
     At time t 3 , control signal IFP PULSE  is driven low. Doing so turns transistor  354  into a pull-down transistor, which drives the source terminal of transistor  354  towards logic zero. Meanwhile, transistor  352  may gradually discharge node Y. Since the voltage on capacitor C 2  has nowhere to discharge, node X will be pulled down accordingly (see,  FIG. 15 , voltages X(n) and X(n+1) drop to ground at time t 3 ). When the internal node voltage X falls below a predetermined threshold, transistor  352  may be turned off. Capacitor C 3  may serve as an auxiliary coupling capacitor for helping node X fall by the desired amount. Operated in this way, the internal node voltages X(n) and X(n+1) for both gate driver units have successfully been driven down to ground during the entirety of the IFP period, thereby eliminating or at least reducing the stress experienced by one or more transistors Td in the chain of gate driver units. 
     At time t 4 , control signal IFP PULSE  is driven back high. Doing so may result in transistor  354  charging up the source terminal of transistor  352  towards logic one. The coupling capacitor C 3  may then push node X above the ground level so as to at least activate transistor  352 . When transistor  352  is turned back on, transistor  352  will charge node Y back up high, which will restore the internal storage node voltages X(n) and X(n+1) to their pre-IFP levels via the use of capacitor C 2 . Capacitor C 2  operated in this way may therefore serve effectively as a storage capacitor for temporarily memorizing the voltage at the internal node X. In general, the capacitance of C 2  should be greater than the capacitance of C 1  to ensure that the voltage of node X can be accurately restored. The capacitance of coupling capacitor C 3  may be less than the capacitance of C 1  to save area. 
     At time t 5 , control signal IFP EN  may be deasserted to turn off transistor  354 , indicating the end of the IFP period. At time t 6 , signal CLK 2  may resume clocking to assert output signal G(n+1). In particular, the assertion of G(n+1) may serve to reset the internal nodes of the preceding gate driver unit (e.g., by turning on transistor  322  to discharge node X, by turning on transistor  350  to discharge node Y, and by turning on transistor  310  to discharge capacitor C 1 ) via the use of the feedback path described in connection with  FIG. 14 . At time t 7 , signal CLK 1  may resume clocking to assert output signal G(n+2) to reset the internal nodes of the preceding gate driver unit (see, voltage X(n+1) is driven back down to ground). Processing may continue in this way to display the remaining portion of the image/video frame. 
     The example of  FIGS. 14 and 15  in which the feed-forward paths are routed from one gate driver unit to an immediately succeeding gate driver unit and in which the feedback paths are routed from one gate driver unit to an immediately preceding gate driver unit is merely illustrative and does not serve to limit the scope of the present invention. If desired, the internal node discharge scheme described in connection with  FIGS. 14 and 15  may be extended to reduce the stress of the drive transistor Td during intra-frame pauses for gate driver chains having any suitable feed-forward and feedback routing configuration. 
     In the arrangement of  FIG. 14 , transistor  352  turns off when node X falls below a predetermined threshold. When transistor  352  is turned off, node Y may not be pulled completely down to ground, which can result in node X not being pulled all the way down.  FIG. 16  shows another suitable arrangement of gate driver unit  300  that ensures node Y is completely pulled down during an IFP period. 
     As shown in  FIG. 16 , gate driver control circuit  302  may include n-channel thin-film transistors  370 ,  372 ,  374 ,  376 , and  378  and capacitors Ca and Cb. Capacitor Cb may have a first terminal that is coupled to internal node X and a second terminal that is coupled to another internal node Y. Transistor  370  may have a drain terminal that is coupled to node Y, a gate terminal that is coupled to the gate terminal of transistor  310 , and a source terminal that is coupled to ground. Transistor  372  may have a drain terminal that is coupled to node Y, a gate terminal that is coupled to yet another internal node Z, and a source terminal. Capacitor C 3  may have a first terminal that is coupled to node Z and a second terminal that is coupled to ground. Transistor  374  may have a drain terminal that is coupled to the source terminal of transistor  372 , a gate terminal that receives control signal IFP EN , and a source terminal that receives control signal IFP PULSE . Transistor  376  may have a source terminal that is coupled to node Z and drain and gate terminals that are coupled to the gate terminal of transistor  320  (e.g., drain and gate terminals that are coupled to the feed-forward path). Transistor  378  may have a drain terminal that is coupled to node Z, a gate terminal that is coupled to the gate terminal of transistor  310  (e.g., a gate terminal that is coupled to the feedback path), and a source terminal that is coupled to ground. 
     Configured in this way, capacitor Cb may serve to store an asserted voltage signal during the IFP duration so that transistor  372  remains on during the intra-frame pause.  FIG. 17  is a timing diagram illustrating the operation of such type of gate driver unit, where voltage Z(n+1) remains asserted during the IFP interval. Capacitor Cb may be charged up when the gate output signal from a preceding gate driver unit is asserted (e.g., via the feed-forward path routed to transistor  376 ) and may be discharged when the gate output signal from a succeeding gate driver unit is asserted (e.g., via the feedback path routed to transistor  378 ). Controlled as such, the assertion and deassertion of internal node Z may be synchronized with the assertion and deassertion of node X. Having node Z kept high ensures that the pull-down path exhibits low resistance during the entirety of the IFP period, which helps to drive node X completely down to ground. 
     Gate control circuit  302  of the type described in connection with  FIG. 13-17  are configured to discharge the internal nodes X so that the gate driver units around the IFP row do not experience elevated stress levels. In another suitable embodiment, it is possible to charge the internal nodes X of gate driver units that do not experience elevated stress levels during an IFP interval so as to balance the stress among all the gate driver units in the gate driver chain.  FIG. 18  is a diagram of gate driver unit  300  that includes a gate driver control circuit  402  that charges the internal node X for that gate driver unit. As shown in  FIG. 18 , gate driver control circuit  402  may be coupled to the internal node X and may receive control signals IFP 1  and IFP 2 . 
       FIG. 19  is a circuit diagram of one implementation of gate driver unit  300  of the type shown in  FIG. 18 . As shown in  FIG. 19 , gate driver control circuit  402  may include n-channel thin-film transistors  404  and  404 . Transistor  404  may have a source terminal that is coupled to node X and gate and drain terminals that receive signal IFP 1 . Transistor  404  may have a drain terminal that is coupled to node X, a source terminal that is coupled to ground, and a gate terminal that receives control signal IFP 2 . Only one of control signals IFP 1  and IFP 2  may be asserted at any given point in time. When signal IFP 1  is asserted, transistor  404  may be turned on to pull node X high. When signal IFP 2  is asserted, transistor  406  may be turned on to pull node X low. This is merely illustrative. In general, other ways of driving internal node X high/low may be implemented. 
       FIG. 20  is a diagram showing how internal node charging circuitry  402  may only be included in gate driver units  300  in non-IFP rows. As shown in  FIG. 20 , a first group of display elements  450 - 1  may be separated from a second group of display elements  450 - 2  by a row of display elements  103  at the IFP row. Display elements  450 - 1  and  450 - 2  may be considered to be in non-IFP rows. The gate driver unit  300  corresponding to the IFP row need not include gate driver control circuit  402 , since the internal node X in that gate driver unit will already be driven high by a preceding gate output signal. The gate driver units  300  in the non-IFP rows should, however, include a gate driver control circuit  402  for asserting node X for balancing the stress that is experienced by all the gate driver units  300  in gate driver circuit  38 . 
       FIG. 21  is a timing diagram that shows how gate driver control unit  402  may be operated. As shown in  FIG. 21 , the internal node X in the gate driver unit(s) at or near the IFP row may be high during the IFP period, whereas the internal node X in the remaining gate driver units (i.e., the “non-IFP-disturbed” rows) may be asserted during a separate vertical blanking period (VBP) that is inserted between each successive frame. The assertion of node X in the non-IFP rows may be provided using the internal node charging circuit  402  of the type described in connection with  FIG. 19  (as an example). Control signal IFP 1  may be pulsed high at the beginning of the vertical blanking interval to charge up the internal nodes X, whereas signal IFP 2  may be pulsed high at the end of the vertical blanking interval to discharge the internal nodes X. In general, the time period between the IFP 1  pulse and the IFP 2  pulse in each vertical blanking period should be substantially similar to the IFP interval to ensure that each gate driver unit is subject to the same amount of stress during each display frame. 
     The gate driver units  300  of the type described in connection with  FIGS. 13-21  having bootstrapping capacitors are sometimes referred to as “analog” gate driver units. In yet other suitable embodiments, “digital” gate driver units that include digital logic gates and circuits may be used. 
       FIG. 22  is a diagram of a conventional digital gate driver unit  500 . Gate driver unit  500  includes a flip-flop  502 , a transmission gate  508 , and an inverter  510 . Flip-flop  502  has a data input D that is coupled to a feed-forward path  504 , a clock input that receives clock signal CLK, and a data output Q that is coupled to another feed-forward path  506 . The transmission gate  508  has an n-channel transistor input that receives an output signal from the data output Q of the flip-flop  502 , a p-channel transistor input that receives an inverted version of the output signal via inverter  510 , a data input that receives gate clock signal GCK, and a data output on which gate driver output signal G(n) is provided. In this conventional arrangement, the signal at output Q of flip-flop  502  may be asserted during the IFP interval, which can undesirably degrade the re-channel and p-channel transistor in transmission gate  508  and cause visible line noise at the IFP row(s). 
       FIG. 23  is a diagram of illustrative gate driver units  600  having flip-flop circuits and IFP gating logic in accordance with an embodiment. As shown in  FIG. 23 , each gate driver unit  600  may include a digital flip-flop circuit  602  (sometimes referred to as a “D latch”), a logic NOR gate  606 , a transmission gate  608 , and an inverting circuit  610 . Transmission gate  608  may include an n-channel transistor and a p-channel transistor coupled in parallel to pass signals from one source-drain terminal to another. Flip-flop circuit  602  in a given gate driver unit may have a data input D that receives signals from a preceding gate driver unit via path  604 , clock inputs that receive clock signal CLK and clock signal CLK′ (e.g., an inverted version of CLK), and a data output Q that is coupled to a succeeding gate driver unit via path  605 . 
     Logic NOR gate  606  may have a first input that is coupled to the data bar output QB of flip-flop  602 , a second input that receives an IFP control signal IFP EN , and an output. Transmission gate  608  may have an n-channel transistor gate input terminal that receives an output signal from the output of gate  606 , a p-channel transistor gate input terminal that receives an inverted version of the output signal from the output of gate  606  via inverter  610 , a data input that receives a gate clock signal GCK, and a data output on which gate driver output signal G(n) is generated. 
       FIG. 24  shows a more detail implementation of gate driver unit  600 . The particular circuit implementation of flip-flop  602  as shown in  FIG. 24  is merely illustrative and does not serve to limit the scope of the present invention. In general, a logic NOR gate behaves like an inverter when one of its inputs is at logic zero but is configured to drive its output low when one of its inputs is at logic one. Therefore, gate driver unit  600  may be allowed to operate normally when IFP EN  is low, but when IFP EN  is asserted, logic NOR gate  606  may drive signal Q and QB low and high, respectively to completely deactivate transmission gate  608 . Still referring to  FIG. 24 , an n-channel transistor  622  having its drain terminal coupled to the output of transmission gate  608 , its gate terminal coupled to the output of inverter  610 , and its source terminal coupled to ground may be turned on whenever transmission gate  608  is deactivated to pull gate driver unit output signal G(n) low. 
       FIG. 25  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 24 . At time t 1 , signal CLK 2  may be pulsed high to assert gate driver output signal G(n−1) and a high voltage signal may be latched by the succeeding gate driver unit to assert signal Q(n) (i.e., which deasserts QB(n)). At time t 2 , CLK 2  may be pulsed low to deassert gate driver output signal G(n−1). At time t 3 , signal CLK 1  may be pulsed high to assert gate driver output signal G(n). Signal G(n) may be pulsed high since transmission gate  608  is activated by the asserted signals Q(n) and QB(n). At the beginning of the IFP period (time t 4 ), control signal IFP EN  may be asserted to force Q(n) and QB(n) low and high, respectively. Doing so turns off transmission gate  608  and helps to prevent transmission gate  608  from being exposed to a prolonged period of elevated stress levels during intra-frame pauses. At the end of the IFP interval (time t 5 ), control signal IFP EN  may be deasserted and signals Q(n) and QB(n) may be restored to their pre-IFP levels. At time t 6 , the clock signals may resume toggling to display the remainder of the frame. 
     The example of  FIGS. 23-25  in which the stress level is reduced via use of a logic NOR gate is merely illustrative.  FIG. 26  shows another suitable arrangement of a gate driver unit  600  that is configured to balance/equalize the stress level that is applied to each gate driver unit (e.g., by applying an equal amount of elevated stress to each and every gate driver unit in the chain). As shown in  FIG. 26 , gate driver unit  600  may include a logic NAND gate  607  instead of a logic NOR gate. In particular, logic NAND gate  607  may have a first input that is coupled to the data output Q of flip-flop  602 , a second input that receives an IFP control signal IFP EN , and an output that is coupled to the control inputs of transmission gate  608 . 
     In general, a logic NAND gate behaves like an inverter when one of its inputs is at logic one but is configured to drive its output high when one of its inputs is at logic zero. Therefore, gate driver unit  600  of  FIG. 26  may be allowed to operate normally when IFP EN  is high, but when IFP EN  is asserted (e.g., when IFP EN  is driven low), logic NAND gate  607  may drive signal Q and QB high and low, respectively to completely activate transmission gate  608 . 
       FIG. 27  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 26 . As shown in  FIG. 27 , the gate clock signals GCK 1  and GCK 2  may take turns pulsing during each display interval to sequential assert the gate driver output signals in each row. During the display intervals, signal IFP EN  may be deasserted (i.e., driven high). During an IFP period, however, IFP EN  may be asserted (i.e., driven low) such that logic NAND gate  607  will charge up node Q in all the non-IFP rows so that the stress experienced by transmission gate  608  in the non-IFP rows is substantially equal to that experienced by transmission gate(s)  608  at or near the IFP row. The example of  FIG. 27  in which signal IFP EN  is asserted during the IFP interval is merely illustrative. If desired, signal IFP EN  may instead be asserted during the vertical blanking interval VBP or other suitable time periods to balance the amount of stress applied across all of the gate driver units  600 . If signal IFP EN  is asserted during the vertical blanking period, the gate driver unit at the IFP row should not include the logic NAND gate  607  to prevent node Q from being asserted twice during each frame. 
       FIG. 28  is a diagram of illustrative gate driver units  700  having set-reset flip-flop (RS-FF) circuits and associated IFP gating logic in accordance with another embodiment. As shown in  FIG. 28 , each gate driver unit  700  may include a digital RS-FF circuit  702  (sometimes referred to as an “RS latch”), a logic NOR gate  706 , a transmission gate  708 , and an inverting circuit  710 . Transmission gate  708  may include an n-channel transistor and a p-channel transistor coupled in parallel to pass signals from one source-drain terminal to another. Flip-flop circuit  702  in a given gate driver unit may have a set input S that receives an output signal from a preceding gate driver unit via path  704 , a reset input R that receives an output signal from a succeeding gate driver unit via path  705 , and a data bar output QB. 
     Logic NOR gate  706  may have a first input that is coupled to the data output QB of flip-flop  702 , a second input that receives an IFP control signal IFP EN , and an output. Transmission gate  608  may have an n-channel transistor gate input terminal that receives an output signal from the output of gate  706 , a p-channel transistor gate input terminal that receives an inverted version of the output signal from the output of gate  706  via inverter  710 , a data input that receives a gate clock signal GCK, and a data output on which gate driver output signal G(n) is generated. 
       FIG. 29  shows a more detail implementation of gate driver unit  700 . The particular circuit implementation of RS flip-flop  702  as shown in  FIG. 29  is merely illustrative and does not serve to limit the scope of the present invention. As described above, a logic NOR gate behaves like an inverter when one of its inputs is at logic zero but is configured to drive its output low when one of its inputs is at logic one. Therefore, gate driver unit  700  may be allowed to operate normally when IFP EN  is low, but when IFP EN  is asserted, logic NOR gate  706  may drive signal Q and QB low and high, respectively to completely deactivate transmission gate  708 . Still referring to  FIG. 29 , an n-channel transistor  722  having its drain terminal coupled to the output of transmission gate  708 , its gate terminal coupled to the output of inverter  710 , and its source terminal coupled to ground may be turned on whenever transmission gate  708  is deactivated to pull gate driver unit output signal G(n) low. 
       FIG. 30  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 29 . At time t 1 , signal GCK 2  may be pulsed high to assert gate driver output signal G(n−1). At this time, a high voltage signal may also be latched by the succeeding gate driver unit to assert signal Q(n). At time t 2 , signal GCK 1  may be pulsed high to assert gate driver output signal G(n). Signal G(n) may be pulsed high since transmission gate  708  has already been activated by the asserted signals Q(n) and QB(n). At the beginning of the IFP period (time t 3 ), control signal IFP EN  may be asserted to force Q(n) and QB(n) low and high, respectively. Doing so turns off transmission gate  708  and helps to prevent transmission gate  708  from being exposed to a prolonged period of elevated stress levels during intra-frame pauses. At the end of the IFP interval (time t 4 ), control signal IFP EN  may be deasserted and signals Q(n) and QB(n) may be restored to their pre-IFP levels. At time t 6 , the clock signals may resume toggling to display the remainder of the frame. At this time, Q(n) and QB(n) may be reset to their deasserted states by feeding back an asserted G(n+1) via path  705  (see, e.g.,  FIG. 28 ). 
     The example of  FIGS. 28-30  in which the stress level is reduced via use of a logic NOR gate is merely illustrative.  FIG. 31  shows another suitable arrangement of a gate driver unit  700  that is configured to balance/equalize the stress level that is applied to each gate driver unit (e.g., by applying an equal amount of elevated stress to each and every gate driver unit in the chain). As shown in  FIG. 31 , gate driver unit  700  may include a logic NAND gate  707  instead of a logic NOR gate. In particular, logic NAND gate  707  may have a first input that is coupled to the data output Q of set-reset (RS) flip-flop  702 , a second input that receives an IFP control signal IFP EN , and an output that is coupled to the control inputs of transmission gate  708 . 
     As described above, a logic NAND gate behaves like an inverter when one of its inputs is at logic one but is configured to drive its output high when one of its inputs is at logic zero. Therefore, gate driver unit  700  of  FIG. 31  may be allowed to operate normally when IFP EN  is high, but when IFP EN  is asserted (e.g., when IFP EN  is driven low), logic NAND gate  707  may drive signal Q and QB high and low, respectively to completely activate transmission gate  708 . 
       FIG. 32  is a timing diagram that illustrates the operation of the digital gate driver unit of  FIG. 31 . As shown in  FIG. 32 , the gate clock signals GCK 1  and GCK 2  may take turns pulsing during each display interval to sequential assert the gate driver output signals in each row. During the display intervals, signal IFP EN  may be deasserted (i.e., driven high). During an IFP period, however, IFP EN  may be asserted (i.e., driven low) such that logic NAND gate  707  will charge up node Q in all the non-IFP rows so that the stress experienced by transmission gate  708  in the non-IFP rows is substantially equal to that experienced by transmission gate(s)  708  at or near the IFP row. The example of  FIG. 32  in which signal IFP EN  is asserted during the IFP interval is merely illustrative. If desired, signal IFP EN  may instead be asserted during the vertical blanking interval VBP or other suitable time periods to balance the amount of stress applied across all of the gate driver units  700 . If signal IFP EN  is asserted during the vertical blanking period, the gate driver unit at the IFP row should not include the logic NAND gate  707  to prevent node Q from being asserted twice during each frame. 
     In general, the use of logic NOR gates and logic NAND gates to provide the desired voltage levels at the gate terminals of the transmission gates is merely illustrative. If desired, other types of logic gates such as logic OR gates, logic AND gates, logic XOR gates, logic XNOR gates, and other any other suitable type of digital logic circuitry can be used to selectively charge/discharge node Q and QB. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.