EMI Mitigation with Shifted Source Line Precharge

Abstract

A method of driving pixels of a display device includes, for a set of N pixels of the display device connected to a switch, each of the N pixels to be driven for a period T, applying a first precharge signal to a first pixel of the set, and sequentially applying corresponding precharge signals to each remaining pixel of the set, such that the initiation of the precharge signal for the Kth pixel is delayed by a time Δtk from the initiation of the precharge signal for the (K-1)th pixel.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to display devices, such as those in automobiles, and more particularly to mitigating electromagnetic interference (EMI) by shifting the source line precharge of the display device in time. [Background technology]

[0002] In automotive applications, EMI noise suppression is necessary to avoid interference with other electrical components that may be operating within the vehicle. Generally, the EMI noise suppression requirements for automotive applications are significantly more stringent than those for portable device applications such as smartphones, tablets, and notebook computers.

[0003] Display devices using multiplexer (MUX) switching systems have been used to connect one input to multiple outputs through a set of switches equal in number to the number of outputs. These systems reduce the number of output pads required to connect the display driver integrated circuit (IC) to the display panel, thereby allowing for a smaller border width on the driver side of the display panel and also allowing for a smaller chip size for the display driver IC. In a conventional display panel driving method, each of the MUX switches is sequentially turned on once per horizontal period of the display, as shown in Figure 3A, for example.

[0004] This sequential turning on of the MUX switches several times per horizontal period generates noise each time a switch is turned on or closed. The noise frequency can directly interfere with the long wave (LW) band, and its higher harmonics can interfere with the amplitude modulation (AM) band. As a result, conventional switching methods, especially in automotive implementations, result in significant noise signals that can be detected in EMI tests. Summary of the Invention

[0005] This Summary is provided to introduce a selection of concepts in a concise form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0006] The disclosed embodiments describe a display device and associated display panel switching system that mitigates EMI noise from the display panel without degrading the quality of the displayed image.

[0007] In one embodiment, a method for driving pixels of a display device is disclosed, the method referring to a set of N pixels of the display device connected to a switch, the N pixels being to be driven for a time period T. The method includes applying a first precharge signal to a first pixel of the set and sequentially applying corresponding precharge signals to each remaining pixel of the set such that the initiation of the precharge signal for the Kth pixel is delayed by a time Δt k from the initiation of the precharge signal for the (K−1)th pixel.

[0008] In some embodiments, the time Δt k for the Kth pixel is the same for each of the N pixels and is shorter than the duration of the precharge signal for the immediately preceding (K−1)th pixel.

[0009] In another embodiment, a display device is disclosed that includes a display panel including a plurality of pixels, a gate driver configured to enable the plurality of pixels, and a display driver coupled to each of the plurality of pixels via a multiplexing switch. The display device further includes a processor coupled to the gate driver and the display driver and configured to control the gate driver to enable the plurality of pixels and to control the display driver to apply a first precharge signal to a first pixel of the plurality of pixels. The processor is further configured to sequentially apply a corresponding precharge signal to each remaining pixel of the set such that an initiation of the precharge signal for a Kth pixel of the plurality of pixels is delayed by a time Δt from an initiation of the precharge signal for a (K-1)th pixel of the plurality of pixels.

[0010] In another embodiment, a method for driving pixels of a display device is disclosed. The method includes setting a precharge signal to be followed by a pixel drive signal for each pixel in a set of pixels for a predefined period of time on the display device. The method further includes setting a precharge signal for a first pixel of the set of pixels at the beginning of the predefined period, and for each remaining pixel in the set of pixels, staggering the start of each corresponding precharge signal so that there is a minimum delay between any two precharge signals. The method further includes driving the set of pixels for one or more predefined periods, measuring a level of electromagnetic interference (EMI) generated when driving the set of pixels, and outputting the EMI value to a user. [Brief explanation of the drawings]

[0011] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure, briefly summarized above, may be had with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only some embodiments of the present disclosure and should not be considered to limit the scope of the present disclosure, since the present disclosure admits of other equally effective embodiments.

[0012] [Figure 1] FIG. 1 shows an exemplary display device configured to arrange for precharging of pixels in accordance with one or more embodiments.

[0013] [Figure 2] FIG. 2 illustrates an exemplary pixel array of the exemplary display device of FIG. 1 according to one or more embodiments.

[0014] [Figure 3A] FIG. 3A illustrates an exemplary set of conventional drive signals for each of the red, green, and blue sub-pixels over four exemplary horizontal periods of a conventional display device.

[0015] [Figure 3B] FIG. 3B illustrates an exemplary set of conventional drive signals with precharge signals for each subpixel over four exemplary horizontal periods of a conventional display device.

[0016] [Figure 4A] FIG. 4A illustrates another exemplary set of drive signals, including precharge signals for each subpixel, over four exemplary horizontal periods of a display device in accordance with one or more embodiments.

[0017] [Figure 4B] FIG. 4B is an expanded view of a portion of the signal shown in FIG. 4A.

[0018] [Figure 4C]FIG. 4C illustrates an alternative example of a drive signal according to one or more embodiments.

[0019] [Figure 4D] FIG. 4D illustrates another example of a drive signal according to one or more embodiments.

[0020] [Figure 4E] FIG. 4E illustrates yet another alternative set of drive signals according to one or more embodiments.

[0021] [Figure 5A] FIG. 5A is an exemplary plot of the conventional drive signal of FIG. 3A and the corresponding surface noise.

[0022] [Figure 5B] FIG. 5B is an exemplary plot of the conventional drive signal of FIG. 3B and the corresponding surface noise.

[0023] [Figure 6] FIG. 6 is an example plot of a drive signal with a shifted precharge signal and corresponding surface noise in accordance with one or more embodiments.

[0024] [Figure 7] FIG. 7 is an example plot of noise level versus frequency for an example display panel implementing the example sub-pixel drive signals shown in FIGS. 4A and 4B according to one or more embodiments.

[0025] [Figure 8] FIG. 8 is a process flowchart for an exemplary method for driving sub-pixels in a display device according to one or more embodiments.

[0026] For ease of understanding, the same reference numerals have been used, where possible, to designate identical elements common to the figures. It is anticipated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific description. The drawings should not be understood to be drawn to scale unless specifically noted. Also, for clarity of presentation and explanation, the drawings may be simplified by omitting details or components. The drawings and discussion serve to explain the principles discussed below, with like numerals indicating like elements. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following detailed description is merely exemplary in nature and is not intended to limit the disclosure or its application and uses.Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding background, summary or the following detailed description.

[0028] In the following description, bird's-eye views such as top / bottom, inside / outside, top / bottom, etc. Such views are used merely to facilitate discussion and are not intended to limit the application of the embodiments described in this application to any particular direction.

[0029] In the following description, the phrases "in one embodiment," "in one or more embodiments," or "in some embodiments" may be used, which may refer to one or more of the same or different embodiments, respectively. Additionally, when used with respect to embodiments of the present disclosure, terms such as "comprising," "including," and "having" are synonymous. The terms "coupled with," "coupled to," and "connected to" are used throughout this application, including the claims. The terms "coupled" or "connected" may mean one or more of the following: "coupled" or "connected" may mean that two or more elements are in direct physical or electrical contact. However, the terms "coupled" or "connected" may also mean that two or more elements are in indirect contact with each other but still cooperate or interact with each other, or that one or more other elements are coupled or connected between the elements that are referred to as coupled or connected to each other. The terms "directly coupled" or "directly connected" may mean that two or more elements are in direct contact with each other.

[0030] In this application, including the claims, the term "circuitry" may refer to, be part of, or include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or collection of) processors executing one or more software or firmware programs and / or memory (shared, dedicated, or collection of) memory, combinatorial logic, and / or other suitable components that provide the described functionality.

[0031] In this application, including the claims, a "display device" may refer to a user device that has both display and touchscreen capabilities. A display device may have a display driver along with a display panel. In this application, including the claims, the terms "display panel" or "display / touch panel" refer to the actual top surface of the display device on which images are displayed and which a user may touch and / or hover over to interact with the touch-sensing capabilities of the display device. When the focus of discussion is on the touch-sensing aspects of the display / touch panel, it may also sometimes be referred to as a touchscreen.

[0032] In one or more embodiments, EMI emitted from a display panel of a display device may be reduced by shifting or staggering the precharge timing for a set of pixels. In one or more embodiments, the pixels are driven by an amplifier connected to a common switch, such as a multiplexer (MUX) switch that connects a single input to multiple outputs. In one or more embodiments, each pixel may include a MOSFET transistor, and the pixel may be driven by first enabling the gate of the MOSFET and then applying a voltage to its source. In one or more embodiments, for each pixel, a precharge voltage is applied first at the beginning of a horizontal display refresh period, followed by a pixel drive voltage. In one or more embodiments, the precharge voltages are staggered. Thus, each precharge voltage is applied sequentially to each source line such that the precharge voltage for each pixel is applied after a predetermined time delay from the start of the precharge voltage for the previous pixel. In some embodiments, the noise frequency is one-third that of a conventional MUX switching system, which improves EMI noise levels in both the LW and AM bands.

[0033] Liquid crystal displays (LCDs), organic light-emitting diode (OLED) displays, and other display devices use multiplexer (MUX) switching systems. Typically, MUX switching systems connect one input to multiple outputs through a set of switches equal in number to the number of outputs. These systems reduce the number of output pads that need to run from the display driver integrated circuit (IC) to the display panel. This allows for smaller border widths on the driver side of the display panel and smaller chip sizes for the display driver ICs. For example, in a 3-MUX switch system, each MUX on the display panel connects to a set of three pixels (or subpixels). In a conventional method of driving a display panel, each of the MUX switches is sequentially turned on once during each horizontal period of the display device to provide drive voltages to the pixels or subpixels.

[0034] EMI noise is generated every time a switch is turned on or closed. For a display's horizontal period of 33 kHz to 66 kHz, the noise frequency for a 3MUX switch system, for example, would be 100 to 200 kHz. These noise frequencies directly interfere with the LW band (150 kHz to 300 kHz). Furthermore, their higher harmonics interfere with the AM band (530 kHz to 1.8 MHz). As a result, conventional switching methods result in significant noise signals that can be detected in EMI tests. In automotive applications, there are strict limits on EMI noise; therefore, it is beneficial to reduce it as much as possible.

[0035] A precharge signal may be provided to a set of pixels or subpixels of a display device that are driven by a single amplifier. In one or more embodiments, a precharge signal is provided to each of the pixels of the set at the beginning of a horizontal period of the display panel, but the precharge signals are not transmitted simultaneously. Rather, they are shifted or staggered in time. In one or more embodiments, a first precharge signal is provided to a first pixel (or subpixel) of the set of pixels, then, after a first time delay, a second precharge signal is provided to a second pixel (or subpixel) of the set of pixels, then, after a second time delay, a third precharge signal is provided to a third pixel (or subpixel) of the set of pixels, and so on, each after a time delay following the start time of the previous precharge signal, until all precharge signals have been transmitted. In this application, the feature of transmitting each subsequent precharge signal after a delay from the previous precharge signal may be referred to as "shifting" the precharge signal, "staggering" the precharge signal, or "shifting / staggering" the precharge signal.

[0036] 1 illustrates a schematic diagram of an exemplary display device 100 according to one or more embodiments. Display device 100 includes a display driver 150 and a display panel 160. Display panel 160 includes multiple groups of subpixels, each connected to an amplifier that may be provided in display driver 150 via a MUX switch. Display device 100 may be implemented in, for example, a smartphone, a laptop computer, a desktop computer, a public booth, or an in-vehicle infotainment system. As mentioned above, display device 100 may also include touchscreen functionality.

[0037] Continuing with reference to FIG. 1 , display driver 150 provides drive signals, e.g., as voltages, to display panel 160, thereby providing drive signals to each of six subpixels 171-176 of display panel 160. As noted, display driver 150 may include multiple amplifiers, each providing a voltage signal to multiple pixels or subpixels of display panel 160. For ease of presentation, only two amplifiers, amplifier 1 151 and amplifier 2 153, are shown in FIG. 1 , each of which drives three subpixels in display panel 160. It is understood that display driver 150 may include any number of amplifiers, each driving one or more pixels of display panel 160, and that display panel 160 may include a variable number of pixels connected to, and thus driven by, each amplifier. In one or more embodiments, each amplifier 151, 153 is connected to an input of a MUX switch. In one or more embodiments, each MUX switch includes at least two switches. In the exemplary embodiment of FIG. 1 , each MUX switch includes three switches. However, in other embodiments, each MUX switch may have more than two or three switches. For example, as shown in Figure 1, amplifier 1 151 is connected to MUX A 151A, which comprises three switches MUX A1, MUX A2, and MUX A3, and amplifier 2 153 is connected to MUX B 153B, which comprises three switches MUX B1, MUX B2, and MUX B3.

[0038] Continuing with reference to Figure 1, display driver 150 also includes a timing controller 154. Timing controller 154 controls, via a set of control links 152 (shown by dashed lines), when each switch in each MUX—e.g., switches MUX A1, MUX A2, and MUX A3 in MUX A 151A and switches MUX B1, MUX B2, and MUX B3 in MUX B 153B—opens or closes. Thus, timing controller 154, control links 152, and the two MUX switches, MUX A 151A and MUX B 153B, may be collectively referred to as the "switching system" of display panel 160.

[0039] Conventionally, only one switch in each MUX is closed at a time, once per horizontal period of a display device, to provide the appropriate luminance signal (known herein as a "pixel signal") for that horizontal period to one of the subpixels connected to the MUX. As shown in FIG. 1 , only the middle switch (MUX A2 and MUX B2, respectively) in each of MUX A 151A and MUX B 153B is closed. Thus, in the example of FIG. 1 , only the green subpixel is actively driven in each of the two sets of subpixels. As discussed above, sequentially closing each of the MUX switches during a horizontal period generates excessive EMI noise. In another conventional approach, each switch in each MUX is closed for a short period at the beginning of each horizontal period to "precharge" the subpixel. Closing the switches during this short initial period distributes a signal, referred to herein as a "precharge signal," to each switch. Thus, referring to the example of Figure 1, in this alternative conventional approach, all three switches in each of MUX A 151A and MUX B 153B would be closed for a short period of time at the beginning of a horizontal period (this is not shown in Figure 1). However, while this precharge approach eliminates some of the noise generated when the MUX switches are closed later in the same horizontal period to distribute the pixel signals, it also generates significant noise when all three switches are closed at the beginning of the horizontal period due to the precharge signals. In one or more embodiments, this noise generated by the precharge signals may be reduced by staggering or shifting the various precharge signals in time.

[0040] 1, in some embodiments, amplifiers 151, 153 and timing controller 154 may be integrated onto a single chip. In other examples, amplifiers 151, 153 may be separate from timing controller 154, e.g., provided on a different chip.

[0041] As shown in FIG. 1 , the signal from each amplifier is fed to a MUX switch, which feeds the signal to each of the three pixels connected to it. In some embodiments, the pixels may be subpixels, and thus may include red (R), green (G), and blue (B) subpixels, as shown in FIG. 1 . Alternatively, the pixels may be subpixels used in alternative subpixeled displays, such as displays ordered as blue, green, red (BGR), or in displays using color systems with more than three primary colors, such as the red, green, blue, yellow (RGBY) or red, green, blue, white (RGBW) color systems, or the red, green, blue, yellow, cyan (RGBYC) color system. Thus, it is understood that the techniques and methods of this disclosure may be applied to any set of pixels connected to a single switch or switching device, whether the pixels are subpixels or individual pixels, and whether used in connection with any type of black-and-white, grayscale, or color system.

[0042] Thus, for example, and continuing with reference to FIG. 1 , in an exemplary subpixeled display using the RGB color system, amplifier 1 151 is connected to MUX A 151A, which is connected to three subpixels R 171, G 172, and B 173. Similarly, amplifier 2 153 is connected to MUX B 153B, which is connected to three subpixels R 174, G 175, and B 176. In one or more embodiments, each subpixel may include a transistor, such as a MOSFET transistor. A MOSFET transistor may be turned on, or selected, by a voltage applied to its gate 155. Once it is selected, a voltage applied to its source 146 via one of source lines 145 is passed to the subpixel's pixel electrode or LED, shown in the example of FIG. 1 as LEDs 171C-176C. These LEDs are shown diagrammatically as containing capacitances, and it is this capacitance that is first precharged (by a precharge signal) and then charged (by a pixel signal) during the horizontal display period by the voltage supplied to it by its respective amplifier when its respective MUX switch is turned on, as explained below. As mentioned above, the value of the voltage applied by the pixel signal to the source 146 of the MOSFET determines the brightness of the subpixel. In other examples using an LCD display panel 160 (without LEDs), this voltage is passed to the pixel electrode.

[0043] Continuing with reference to FIG. 1 , in one or more embodiments, subpixels R171, G172, B173, R174, G175, and B176 may all be disposed in a row, e.g., as part of an array of pixels in a display panel 160. To simultaneously select a row of the exemplary pixel array, all of the gates 155 of the subpixels in the row may be connected, as shown. Thus, in one or more embodiments, the display driver 150 may send an enable signal via gate driver 159 to each subpixel in a row of the pixel array in the display panel 160. In one or more embodiments, the enable signal may be, for example, a gate enable voltage sent to each of the gates of the subpixels in the row via row enable link 156. For ease of presentation, subpixels R171, G172, B173, R174, G175, and B176 in FIG. 1 constitute two pixels of one exemplary row. An exemplary array with three rows, each containing two pixels and therefore six sub-pixels, and thus similar to the single row of FIG. 1, is illustrated in FIG. 2, which will now be described.

[0044] FIG. 2 illustrates an exemplary pixel array 165 of an exemplary display panel 160 of a display device 100 according to one or more embodiments. The pixel array 165 is disposed on the display panel 160 along with MUX A 151A and MUX B 153B. The boundaries of the display panel 160 are indicated in FIG. 2 by a dashed rectangle. The pixel array 165 includes at least three rows, each having six subpixels. The three rows are row A 166, row B 167, and row C 168, respectively. Row A 166 is the row of subpixels illustrated in FIG. 1, and rows B 167 and C 168 are each equivalent to row A 166. In the exemplary pixel array of FIG. 2, similar to the example of FIG. 1, a pixel is a subpixel of two actual pixels. Thus, each row of the pixel array 165 includes subpixels R1, G1, B1, R2, G2, and B2. For ease of illustration, all red subpixels are shown as dotted rectangles, all green subpixels are shown as white rectangles, and all blue subpixels are shown as white rectangles containing black grid lines.

[0045] As described above, the gates of the subpixels in each row of pixel array 165 may all be connected together and may receive an enable signal that selects the entire row to be refreshed. The enable signal turns on each subpixel's transistor during a refresh period, as shown in FIG. 1 and described above, allowing the subpixel to receive a source voltage that determines its luminance value from a corresponding amplifier during the refresh period, known as the horizontal period. Thus, continuing with reference to FIG. 2, for row A 166, there is gate driver A that provides an enable signal via gate line 1 155. Similarly, for row B 167, there is gate driver B that provides an enable signal via gate line 2 156, and finally, for row C 167, there is gate driver C that provides an enable signal via gate line 3 157. The gate drivers thus enable the display device's display driver to sequentially activate all of the rows of display panel 160 (e.g., from top row to bottom, or bottom row to top, or in some other row-interleaved manner) to generate the image that is displayed on display panel 160. Individual rows are enabled by their corresponding gate drivers, and the signals provided by the amplifiers connected to each of the columns of that row are thus passed to the sub-pixels of the enabled rows in an order determined by the display driver and its timing controller, which is effected by switching on and off the MUX switches in MUX A 151A and MUX B 153B, respectively.

[0046] 1 and 2, each source voltage signal for each group of three subpixels is provided by a single amplifier, either amplifier 1 151 or amplifier 2 153. Amplifiers 151, 153 as well as gate driver 159 may be provided, for example, in display driver circuitry, which may be, for example, an IC or part of an IC. Amplifiers 151 and 153 are therefore shown as being external to display panel 160.

[0047] Continuing with reference to FIG. 2 , as described above, each row of pixel array 165 includes three subpixels, each driven by a single amplifier, that are individually driven with a source voltage such that they display a desired luminance during each horizontal refresh period. In addition, in one or more embodiments, a pre-charge voltage may also be applied at the beginning of each horizontal refresh period, where the onset of each individual pre-charge voltage is delayed in time from the onset of the pre-charge voltage preceding it. Thus, for example, in one or more embodiments, amplifier 1 151, which provides source voltages to each of sub-pixels R1, G1, and B1, sends the pre-charge voltage to sub-pixel R1 of row A 166 under the control of the display driver at the beginning of a horizontal refresh period. After a predetermined delay, amplifier 1 151 sends the pre-charge voltage to sub-pixel G1 of row A 166, and after another predetermined delay, sends the pre-charge voltage to sub-pixel B1 of row A 166. In one or more embodiments, the predefined delays have the same duration, while in other embodiments, two or more, or even all, of the predefined delays may have different durations. In one or more embodiments, the duration of the pre-charge voltage is sufficient to charge the source line of the associated subpixel.

[0048] 3A and 3B, described next, illustrate conventional methods for driving a set of subpixels with and without precharge. As noted above, each of these methods generates significant EMI noise and is therefore particularly problematic in displays used in cars, trucks, etc., which, as noted above, have strict limits on EMI.

[0049] FIG. 3A illustrates an exemplary set of conventional drive signals for each of the red, green, and blue subpixels over four exemplary conventional horizontal periods 305 of a display device. The plots illustrated in FIG. 3A may collectively be referred to as a "timing diagram" for a set of pixels, in this case, for a set of subpixels. The signals shown are voltage signals supplied to MUX switches connected to each of the red, green, and blue subpixels, as illustrated in FIG. 1 and described above. Each of the signals illustrated in FIG. 3A therefore controls whether the corresponding MUX switch is closed (and thus on) or open (and thus off). In one or more embodiments, each MUX switch may be controlled by, for example, a metal-oxide semiconductor (MOS) transistor. In one or more embodiments, the transistors may be PMOS or NMOS transistors.

[0050] Continuing with reference to FIG. 3A, the timing diagram includes three signal plots, one for each of the three MUX switches in this exemplary embodiment. Accordingly, the three plots are labeled with the corresponding switch names: MUX1 (connected to the red subpixel), MUX2 (connected to the green subpixel), and MUX3 (connected to the blue subpixel). In each of the three plots, the x-axis is time and the y-axis is voltage. As shown, the signals provided during each horizontal period are similar for each of the three switches, which respectively turn on the respective MUX switches for the pixel drive signals provided by the amplifiers (wherein the pixel drive signals correspond to the desired brightness levels for each subpixel). Thus, when a MUX switch is turned on, the voltage subsequently provided by the amplifiers is passed to the source lines of the subpixels, as illustrated above in FIGS. 1 and 2. As shown in FIG. 3A, at the beginning of each horizontal period, MUX1 turns on, enabling the amplifiers connected to each of the red, green, and blue subpixels via a set of MUX switches to provide a pixel drive signal to the red subpixel while the MUX1 switch is connected. Such a pixel drive signal is illustrated by pixel signal 307 in the timing diagrams of FIG. 3A and all subsequent figures. Pixel signal 307 is, for example, a voltage pulse that goes high, thereby turning on the MUX1 switch, lasts for a certain duration, and then goes low, thereby turning off the MUX1 switch. Following the red subpixel signal, MUX2 turns on by its own pixel signal in the middle of the horizontal period after MUX1 is turned off, so that the amplifier can provide the pixel drive signal to the green subpixel. Finally, after MUX2 turns off, a third pixel signal 307 turns on MUX3, which then passes the pixel drive signal from the amplifier to the blue subpixel.

[0051] Thus, the waveforms illustrated in FIG. 3A (along with FIG. 3B and other figures herein) represent control signals that turn the MUX switches on and off. In the example shown, a high voltage level indicates that the switch is on, and therefore that the source line of that subpixel is connected to its amplifier, and a low level indicates that they are disconnected. This is because, in the example of FIG. 3A, the MUX switches are opened and closed by NMOS transistors that require a "high" gate voltage to turn on. In other examples where the MUX switches are controlled by PMOS transistors that require a "low" gate voltage to turn on, the high and low polarities would be opposite to those shown in the various figures.

[0052] FIG. 3B illustrates an exemplary set of conventional drive signals from FIG. 3A with an additional precharge signal 309 applied to each subpixel over four exemplary horizontal periods of a conventional display device. Referring to FIG. 3B, as shown, in this example, three precharge signals are applied simultaneously to all three subpixels at the beginning of each horizontal period 305. For ease of illustration, each precharge signal is shown in FIG. 3B shaded lighter than the rest of the signal line for that MUX switch. As with FIG. 3A, the timing diagram in FIG. 3B illustrates when each MUX switch is turned on and off. As shown, each precharge signal 309 is applied for a duration and then goes low, the duration of the precharge signal being the same for each MUX switch and shorter than the duration of the pixel signal 307. To implement this exemplary timing, the MUX initially simultaneously turns on all three of its switches, e.g., MUX1, MUX2, and MUX3, passing the precharge voltage generated by the amplifier to each subpixel for the duration of the precharge signal 309. Because all three switches are on and therefore all pass the signal provided by the amplifier, the precharge voltage is the same for each subpixel. Then, for example, the MUX turns off switches MUX2 and MUX3 but continues to leave MUX1 on, passing it the pixel signal for the red subpixel, in turn, for its pixel signal 309. Thus, as shown, MUX1 remains closed, and therefore on, in the "precharge and pixel composite signal" 311, for the entire duration of the sum of the individual durations of signals 307 and 309. Using the precharge and pixel composite signal as shown provides advantages in terms of noise and power consumption.However, in other instances, as shown in FIGS. 4C and 4D and described below, the precharge signal 309 may go low just before the immediately following pixel signal 307 goes high; thus, in such instances, there is no precharge and pixel composite signal; rather, the MUX switch first turns on for the precharge signal, then turns off, and then essentially immediately turns on again and remains on while the amplifier provides that pixel signal to the corresponding subpixel.

[0053] It should be noted here that because a precise voltage charge of a given pixel or subpixel is not necessarily required for the precharge signal, but rather for the actual charge time (e.g., between each pixel signal 307), in some embodiments the duration of the precharge signal 309 may be shorter than the duration of the actual charge signal 307, as shown. However, in other embodiments the duration of the precharge signal 309 may be the same as or even longer than the duration of the pixel signal 307.

[0054] Additionally, although FIG. 3B illustrates the durations of all of the individual precharge signals 309 as being the same for all subpixels, this is not required and in other embodiments different pixels or subpixels of a display device, or pixels or subpixels of one or more rows of a display device, may have different precharge signal 309 durations.

[0055] As noted above, and as described below with reference to FIGS. 5A and 5B, each of the exemplary conventional drive signals illustrated in FIGS. 3A and 3B, respectively, generates noise when the MUX switches are turned on. Therefore, in one or more embodiments, to minimize or otherwise reduce noise, the precharge signals 309 are not applied as illustrated in FIG. 3B, but rather are time-delayed from one another. As explained, using delays between the onset of successive precharge signals for a given MUX switch in this manner may be referred to as "shifting" or "staggering" the precharge signals. Examples of staggered precharge signals, according to one embodiment, are illustrated in FIGS. 4A and 4B, described next.

[0056] 4A illustrates a set of drive signals, including staggered precharge signals for each of the red, green, and blue subpixels, over four exemplary horizontal periods of a display device, according to one or more embodiments. As noted above, as illustrated in FIG. 4A, at the beginning of a horizontal period 305, a precharge signal 309 is first applied to a first subpixel, in this example, the red subpixel, by turning on (closing) MUX1. After a first delay time interval Δt 315, MUX2 is turned on, and the precharge signal 309 is applied to the green subpixel. After a second delay Δt 315, as illustrated, while MUX1 and MUX2 are still on, MUX3 is turned on, and the precharge signal 309 is applied to the blue subpixel. This staggered sequence of precharge signals 309 occurs at the beginning of each horizontal period 305, as illustrated. To more clearly illustrate the signals and their respective start times and durations, a single horizontal period of FIG. 4A is shown in expanded view in FIG. 4B, which will now be described.

[0057] Figure 4B is an enlarged portion of one of the horizontal periods 305 shown in Figure 4A, in accordance with one or more embodiments. As shown in Figure 4B, the horizontal period 305 begins at time t = t0 321. At that time, the MUX1 red switch 326 is turned on for the precharge signal 309, and the precharge voltage generated by the amplifier (which in Figure 4B powers all three of the subpixels) is passed to the red subpixel. While the precharge voltage is still high for the red subpixel and the amplifier continues to supply the precharge voltage signal to the red subpixel, after a delay Δt, for example, at time t = t0 + Δt 323, the MUX2 green switch 327 is turned on, and the precharge voltage generated by the amplifier is then passed to the green subpixel as its precharge signal 309. Then, while the precharge signal is still high for both the red and green subpixels, after another delay Δt, at time t=t0+2Δt 325, the MUX3 blue switch 328 is turned on, and the precharge voltage generated by the amplifier is now passed to the blue subpixel as its precharge signal. In the example of FIG. 4B , the intervals during which the three precharge signals are shifted or offset from one another are illustrated as a single delay time interval Δt. However, this is by no means necessary, and in other examples, the MUX3 blue switch 328 may be turned on at a time other than t=t0+2Δt. Thus, in general, the second MUX switch may be turned on at time t=t0+Δt1, and the third MUX switch may be turned on at time t=t0+Δt1+Δt2, where Δt1 is not the same as Δt2. For the general case of a pixel set of more than three pixels, for example, a first precharge signal may be applied to the first pixel of the pixel set, followed by subsequent precharge signals applied to each remaining pixel in the pixel set in sequence, such that the onset of the precharge signal for the Kth pixel is delayed from the onset of the corresponding precharge signal for the (K-1)th (or previous) pixel by a time Δt, where each time Δt may be different for each pixel (except for the first pixel in the pixel set, which has no delay).In FIG. 4B, the precharge signal 309 is shown as a dashed line, and the pixel signal 307 is shown as a solid line.

[0058] Continuing with reference to FIG. 4B , as shown, following time t=t0+2Δt 325, the precharge voltage continues to be applied to MUX1 until the end of precharge signal 309, at which point pixel signal 307 for the red subpixel is applied. Thus, the total signal applied to the red subpixel is actually the combined precharge signal 309 and pixel signal 311. This combined signal 311 begins at time t=t0 and ends when both signals 309 and 307 complete. For the other two subpixels in this pixel set, their respective precharge signals end some time before the end of pixel signal 307 for the red subpixel. When the MUX1 red 326 switch is turned off, the MUX2 green 327 switch is turned on for the duration of that pixel signal 307, allowing the amplifier to drive the green subpixel. When the MUX2 Green 327 switch is turned off, the MUX3 Blue 328 switch is turned on for the blue subpixel's pixel signal 307, allowing the amplifier to drive the blue subpixel at its appropriate brightness voltage. Shortly thereafter, the horizontal period 305 ends and the process repeats. As explained, staggering the start of each precharge signal 309 from one subpixel to the next reduces EMI noise.

[0059] 4B, MUX1 Red 326 is turned off before the actual charging of MUX2 Green 327 is turned on. Generally, as shown, the precharge voltage 309 of MUX2 327 is turned off before the longer precharge of MUX1 326 and pixel composite signal 311 terminates. However, this is not necessary, and in other embodiments (not shown), the precharge signal 309 of MUX2 327 may remain on at the time MUX1 326 is turned off.

[0060] In FIG. 4B , there is a time overlap of 2Δt between the time the precharge voltage 309 on the red subpixel ends and the time the precharge signal 309 on the blue subpixel ends, as shown at 312. A similar overlap of Δt occurs between the end of the precharge signal for the green subpixel and the start of the pixel signal for the red subpixel. During these overlapping times, the red subpixel is driven with the actual pixel signal voltage (that causes it to emit light at the desired brightness determined by the image being displayed at the time) and therefore receives its pixel signal 307. However, as described above, because all three subpixels are connected to a single amplifier that outputs only one voltage at a time, during this overlapping period 312, the precharge voltage being output by the amplifier (to each of the green and blue subpixels) will be the same as the actual pixel signal voltage supplied to the red subpixel. This voltage can be higher or lower than the actual pixel voltage later supplied to each of the green and blue subpixels in their respective pixel signals. In such a case, during the overlap, the precharge signals 309 for each of the green and blue subpixels may be different from the required voltages applied to them during their actual pixel signals 307. If this persists for a significant amount of time, the green and blue subpixels may appear too bright (if the red subpixel's luminance is higher than their luminance during that horizontal period) or too dark (if the red subpixel's luminance is lower than their luminance during that horizontal period), distorting the image. In one or more embodiments, this is not a problem because the precharge signals persist for such a short period of time that the human eye cannot detect the voltage difference between a higher (or lower) precharge signal and a lower (or higher) pixel signal for the same subpixel during a horizontal period, and therefore no degradation in the image is visible.

[0061] 3A through 4E, the first subpixel to be driven in each row is shown as being the "red" subpixel, but this is understood to be by no means required and is merely exemplary. Thus, in any given embodiment, the three red, green, and blue subpixels may be driven in any order, and any one of them may be the first subpixel to be driven in a given horizontal period of the display device.

[0062] In one example, the periods illustrated in FIG. 4B can have the following values: Note that these values ​​are understood to be illustrative and not limiting, as many other values ​​are possible, all within the scope of the present disclosure. The horizontal period 305 may be, for example, 16 microseconds, and the pixel signal 307 may have a duration of, for example, 3.0 microseconds. The precharge signal 309 may last for 2.5 microseconds, resulting in a composite signal 311 duration of, for example, 5.5 microseconds. The delay Δt may be, for example, anywhere between 0.5 and 1.5 microseconds. As discussed above, to achieve the EMI improvement benefits of various embodiments, the precharge signals for a set of subpixels are shifted / staggered, and thus applied with a small delay Δt from one precharge signal to the next. However, if the delay Δt is too long, the effect will be similar to that of conventional driving, as shown in FIG. 3A, where MUX1, MUX2, and MUX3 are each turned on sequentially, and the effect of the precharge signal will not be felt by the corresponding subpixel. On the other hand, if the delay Δt is too short, the effect will be similar to that of conventional precharge timing, as shown in FIG. 3B, where the effect of the staggering is not felt. Therefore, according to various embodiments, the optimal delay will be somewhere between these two extremes. As explained above, for the example given above, with a horizontal period of 16 microseconds, a precharge signal duration of 2.5 microseconds, and a pixel signal duration of 3.0 microseconds, an exemplary delay may be between 0.5 and 1.5 microseconds. In other embodiments, other delay intervals may be appropriate.

[0063] As noted above, the delay Δt need not be uniform between any two switches connected to a given amplifier. Thus, for example, in a general sense, Δt may differ between two or more, or even all, of the delays. Thus, for a set of N pixels connected to a single amplifier, referencing the N pixels as an index by an integer K, the start of the precharge signal for the Kth pixel is delayed by a time Δt from the start of the precharge signal for the (K-1)th (or previous) pixel of the set, where each delay Δt is different for each pixel or subpixel.

[0064] According to various embodiments, the precharge signal 309 for a pixel reduces noise generated when the same switch is turned on later in the horizontal period. This is because charge remains on the source line and, as the case may be, on the pixel or subpixel even after the switch corresponding to each pixel is turned off. Thus, for example, the precharge signal 309 applied to each of the green and blue MUX switches at the beginning of a horizontal period reduces switching noise when the same switches are turned on again later in the same horizontal period, such as when the MUX2 green 327 and MUX3 blue 328 switches are later turned on for their pixel signals. In some embodiments, the overall duration of the pixel signal period 307 may be shortened because the precharge signal serves to precharge the capacitance of each source line and pixel (subpixel).

[0065] Figure 4C illustrates another example of the timing diagram illustrated in Figure 4B, in accordance with one or more other embodiments, in which for the first subpixel, i.e., the red subpixel, the precharge signal 309 falls low before the pixel signal 307 goes high. Thus, as illustrated in Figure 4C, for the MUX1 Red 326 signal, the precharge signal 309 ends and falls low before the pixel signal 309 begins to go high. This example is a variation of the timing diagram illustrated in Figure 4B, but illustrates that it is possible, and perhaps convenient, not to couple the precharge signal 309 to the subsequent pixel signal 307 for any pixel in a set whose pixel drive signal 309 immediately follows the corresponding precharge signal 307. In this regard, it should be noted that Figures 4D and 4E, described next, include several examples of pixels (other than the first pixel) whose pixel signals immediately follow the end of the precharge signal, which in one or more embodiments may be connected as shown in Figure 4B, or may not be coupled, for example, as shown in Figure 4C.

[0066] FIGS. 4D and 4E illustrate other timing diagrams for precharge signals and pixel signals in other exemplary embodiments. The embodiments illustrated in FIGS. 4D and 4E, respectively, do not use time shifting or staggering of precharge signals; rather, they use different durations for precharge signals in sets of pixels (or subpixels) to reduce EMI noise. However, with reference to the exemplary timing diagrams illustrated in FIGS. 4D and 4E, in yet other embodiments that are variations of the examples illustrated in FIGS. 4D and 4E, the timing diagrams may be further modified to stagger or shift the precharge signals 309 illustrated in FIGS. 4D and 4E, respectively, between successive pixels or subpixels by a delay Δt, which would also contribute to reducing EMI. As explained, the delay Δt need not be uniform between any two switches connected to a given amplifier, and therefore between any two consecutive pixels. Thus, with reference to FIG. 4D, the precharge signals 309D have different durations for the MUX2 switches, which in this example are for green subpixels. The precharge signal 309D lasts approximately three times as long as the precharge signals for the MUX1 and MUX3 switches, which are the same in this example. However, note that the exemplary precharge timing scheme of FIG. 4D has a drawback in that the load capacitance will double during charging of the red subpixel (MUX1) because the MUX2 switch for the green subpixel is also on for the entire duration of the pixel signal for the red subpixel that the MUX1 switch is on. Also note that, as discussed above with reference to FIG. 4C, the precharge signal 309D on MUX2 for the green subpixel goes low just before the immediately following pixel signal 307D for the same green subpixel goes high. Thus, this is an example without the precharge and pixel composite signals, as discussed above with reference to FIG. 4C.

[0067] Referring to FIG. 4E , yet another alternative exemplary timing diagram, according to another alternative embodiment, is similarly illustrated. In this exemplary timing scheme, for each subpixel, each precharge signal operates from the beginning of the horizontal period until the start of the corresponding pixel signal (which, as noted above, is not shifted or staggered in this example) so that there are increasingly longer precharge and pixel composite signals for each successive pixel in the set. Thus, for example, the last subpixel of the set, i.e., the blue subpixel, has a MUX3 precharge signal 309E that lasts longer than each of the precharge and pixel composite signals for the red and green subpixels, respectively. Similarly, the MUX2 precharge signal 309D lasts longer than the entire precharge and pixel composite signal for the red subpixel. Understood another way, in the exemplary timing diagram of FIG. 4E , each MUX switch remains closed from the beginning of the horizontal period until the end of its respective subpixel's pixel signal. As a result, as shown, each precharge signal is longer than the precharge signal for the previous subpixel, and therefore, overall, the MUX switches are closed, and therefore on, for a much longer time per horizontal period than in any of the exemplary timing diagrams described above. This implies a potential drawback of the alternative timing approach of FIG. 4E : during charging of the red subpixel (MUX1), the load capacitance of the amplifier would triple because both the MUX2 switch for the green subpixel and the MUX3 switch for the blue subpixel are also on during the entire composite signal for the red subpixel (MUX1). Furthermore, during charging of the green subpixel (MUX2), the MUX3 switch for the blue subpixel is also on, so the load capacitance of the amplifier would double. In some cases, the increased load capacitance can degrade the luminance supplied to each subpixel, thereby reducing image quality.However, in one or more embodiments that may use the timing diagram of Figure 4E, if the amplifiers driving the sets of subpixels have sufficient capacity to drive the increased load capacitance, the example timing illustrated in Figure 4E may be used without image degradation, and its benefits for EMI mitigation may be realized, as described. As mentioned above, in other examples that use variations of the timing diagram of Figure 4E, the precharge signal may also be staggered / shifted to reduce EMI.

[0068] FIG. 5A is an exemplary plot of conventional drive signals for three subpixels and corresponding surface noise for a single exemplary horizontal period of a display device. The pixel drive signals do not have corresponding precharge signals, and therefore, FIG. 5A illustrates the conventional case shown in FIG. 3A. As shown in FIG. 5A, there is a spike in the noise signal just as each MUX switch is turned on. In the exemplary plot of FIG. 5A, the y-axis for each of the voltage plots of MUX1 601, MUX2 602, and MUX3 603 is in 10V, and the y-axis for noise plot 620 is in 100mV. Thus, for example, there are spikes in the noise at time 620A when MUX1 turns on, time 620B when MUX2 turns on, and finally, time 620C when MUX3 turns on. As shown at the left edge of the figure, there is an additional spike in the noise signal 620 at time 620D when the MUX1 switch turns on for a second time at the beginning of the second horizontal period. Note that the noise signal 620 as plotted in Figure 5A increases in the downward direction, so the lower the peaks, the more noise there is. It is these noise spikes that are mitigated by one or more embodiments.

[0069] Similarly, Figure 5B is an example plot of conventional drive signals for the same three subpixels shown in Figure 5A, using the same timing for the pixel signals as shown in Figure 5A. However, in the timing diagram of Figure 5B, simultaneous conventional precharge signals, such as those shown in Figure 3B above, are also applied to each subpixel as shown at the beginning of the horizontal period (at time 620A). As shown in Figure 5B, the noise at points 620B and 620C in Figure 5A, where MUX2 and MUX3 are turned on, respectively, is now reduced, as shown within ellipses 604 and 605 in Figure 5B. However, as also shown in Figure 5B, the spikes in noise immediately after time 620A, when all three switches MUX1, MUX2, and MUX3 are turned on due to the conventional simultaneous precharge signals, and immediately after time 620D, when the same three switches MUX1, MUX2, and MUX3 are turned on a second time at the beginning of the next horizontal period, remain large and are not reduced. In fact, by comparing the noise signals 620 in Figures 5A and 5B, it can be seen that the noise at times 620A and 620D shown in Figure 5B for the conventional simultaneous precharge approach is even larger than either of the noise spikes seen in Figure 5A, where there is no precharge at all. To address this issue, in one or more embodiments, this noise may be significantly reduced using exemplary staggered / shifted timing protocols such as those shown in Figures 4A, 4B, and 4C. Figure 6 illustrates the reduced noise seen when using the exemplary staggered timing diagrams of Figures 4A and 4B, as described next.

[0070] FIG. 6 is an exemplary plot of the same drive signals for the same three subpixels shown in FIGS. 5A and 5B, respectively, and the corresponding surface noise when the three precharge signals are staggered, as shown in FIGS. 4A and 4B and described above, in accordance with one or more embodiments. For the precharge signals, each beginning after a predetermined time delay from the previous precharge signal, as illustrated within oval 620E, the noise signal when each of MUX2 and MUX3 is first turned on is significantly reduced from the noise generated when each MUX switch is turned on simultaneously, as illustrated at point 620A in FIG. 5B. Thus, with reference to FIG. 6, at time t0 621, the first precharge signal for MUX1 goes high, turning the switch on. At time t=t0+ΔMUX2 622, a second precharge signal is applied, turning MUX2 on. Finally, at time t=t0+ΔMUX2+ΔMUX3 623, a third precharge signal is applied to MUX3 to turn it on. In this example, there are only three switches connected to the same amplifier, and therefore only three subpixels. However, it is understood that in other embodiments with two or more MUX switches per amplifier, each MUX switch in the series will be turned on after a predefined delay. This delay may or may not be the same as any other delay in the staggering scheme. In examples with more than two switches, as described, in some embodiments, ΔMUX2, ΔMUX3... ΔMUXN may be the same. In other embodiments, they may be different. In this example, the delays between successive pixels, i.e., ΔMUX2 and ΔMUX3, may not be the same, for example. In other embodiments, they may be the same; therefore, in such embodiments, there is a single delay Δt applied to the start of each successive precharge signal. In other embodiments, such as those illustrated in Figures 4D and 4E, there is no delay at all, but the length of the precharge signal may be different for any two given pixels.In still other embodiments, some of the precharge signals may have the same time duration, while other precharge signals may have different values. Thus, for example, referring again to FIG. 4D, the precharge signals on MUX1 and MUX3 are substantially identical, while the precharge signal 309D on MUX2 is approximately three times as long as the other two precharge signals. In other embodiments that use variations of the timing diagrams illustrated in each of FIGs. 4D and 4E, but also stagger / shift the precharge signals to reduce EMI, the delays between successive pixels (or subpixels) may be the same, or the delays from one pixel to the next may not be the same.

[0071] FIG. 7 is an exemplary plot of noise level versus frequency for an exemplary display panel implementing two different pixel drive schemes. Plot 710, the lighter shaded plot, is for a timing scheme referred to as "RevT25," in accordance with one or more embodiments, which uses the exemplary timing diagrams illustrated in FIGS. 4A and 4B. Plot 711, the darker shaded plot, is for a timing scheme referred to as "RevT24," which uses conventional simultaneous precharge signaling, as illustrated in FIG. 3B. As illustrated in FIG. 7, the noise level corresponding to plot 711 for the RevT24 simultaneous precharge signaling has significant noise at points 701 (293 kHz), 703 (352 kHz), 705 (411 kHz), and 707 (470 kHz), which represent the fifth, sixth, seventh, and eighth harmonics of the noise over one horizontal period, which in this example is 58.7 kHz. However, for these same frequencies, plot 710, which represents a shifted / displaced precharge signal in accordance with one or more embodiments, shows that the noise is significantly reduced, as expected.

[0072] FIG. 8 illustrates a method of driving subpixels in a display device to minimize or otherwise reduce EMI noise generation, according to one or more embodiments. For example, the display device may be installed in an automobile. For example, the display device may include a display panel having a pixel array, which may be divided into M rows with L pixels per row. For example, as shown in the first three columns of pixel array 165 in FIG. 2 (representing a single pixel in each of the three rows shown), each row of the pixel array may be driven by, and therefore connected to, a single amplifier. The exemplary method of FIG. 8 uses the timing scheme illustrated in FIGS. 4A and 4B, although, as described above, other methods may be implemented using the timing schemes of any of FIGS. 4C, 4D, or 4E in other examples.

[0073] Method 800 includes blocks 810 through 840. In other embodiments, method 800 may have more or fewer blocks. Method 800 begins at block 810. In block 810, a gate line signal is provided to gate on each pixel in a row. For example, the row may be any of M rows of a pixel array. For example, the pixel array may be pixel array 165 of FIG. 2, and the row may be row B 167 of pixel array 165. Thus, for example, the gate line signal may be provided via gate line 2 156 by gate line driver B.

[0074] Method 800 proceeds from block 810 to block 820. In block 820, a source line precharge signal is sequentially applied for each of the L pixels in the row, with the start of each source line precharge signal being shifted in time by a delay ΔT from the start of the precharge signal for the previous pixel in the row. For example, the delay ΔT may be uniform across the row, and for a row of three pixels, the precharge signals may be those illustrated in FIGS. 4A and 4B. A first precharge period for, e.g., a red subpixel may begin at time t=t0, a second precharge period for, e.g., a green subpixel may begin at time t=t0+ΔT, and a third precharge period for, e.g., a blue subpixel may begin at time t=t0+2ΔT.

[0075] Method 800 proceeds from block 820 to block 830. In block 830, for the first of the L pixels in the row, at the end of the precharge signal, but before it can drop to a low voltage, a pixel drive signal is applied that continues until after the end of the precharge signal applied to the last (e.g., Lth) pixel in the row. For example, as shown in FIG. 4B , the pixel drive signal 307 applied to the red subpixel by turning on switch MUX1 Red 326 remains high for a time interval following the end of the precharge signal 309 applied to the blue subpixel, the last subpixel of the set. As noted above, this feature is illustrative only and need not be implemented in other embodiments. The precharge signal on one or more subsequent pixels or subpixels in the row (or any other set of pixels) may last longer than the pixel signal for an earlier pixel or subpixel in the row (or other set).

[0076] From block 830, the method 800 proceeds to block 840, where pixel drive signals are provided to the remaining pixels in the row. For example, referring again to FIG. 4B, after the pixel drive signal for the red subpixel is applied, the MUX2 Green 327 and MUX3 Blue 328 switches are sequentially turned on, followed by application of pixel drive signals to each of the green and blue subpixels to complete a horizontal period.

[0077] In one or more embodiments, a calibration process may be performed to determine the optimal shift / shift timing of the precharge signal to meet a given maximum allowable EMI noise, or, for example, a preferred maximum EMI noise specification according to various embodiments. Thus, for example, a first precharge timing is set for a source line precharge scheme such as that illustrated in FIGS. 4A and 4B. The EMI noise level is measured using the first precharge timing. After measuring the EMI noise level, it is determined whether the specification is met. If so, the calibration process ends. However, if it is determined that the first precharge timing does not meet the specification, the precharge signal shift is adjusted to a second precharge timing, and the EMI level is measured again. This process may be repeated, if necessary, for a third, fourth, or Nth precharge timing scheme until the desired specification is met, and then the process ends.

[0078] In one or more embodiments, a given display device may be provided in a handheld electronic device, a vehicle, a public booth, a personal kitchen, or the like. In one or more embodiments, a display panel may include an array of pixels, e.g., M rows and N columns. In each row, several pixels, e.g., L pixels, where L is 1, 2, 3, 6, or 12, may be connected to a single amplifier or signal source via a switch, e.g., a MUX switch. When a row of the pixel array is enabled, the L pixels, or possibly all of the subpixels, connected to the single amplifier may be driven with both a precharge signal and a pixel signal during each horizontal period of the display. In one or more embodiments, the precharge signals are applied at the beginning of the horizontal period but are shifted or offset from one another. In one or more embodiments, shifting / shifting the precharge voltages from one another by a predefined delay reduces EMI noise. Note that any examples above in which rows of pixels are used are merely illustrative and not limiting. Thus, in one or more embodiments, any set of pixels connected to a single amplifier can be driven using the disclosed techniques, where the pixels are not limited to any row or any other structure of a given display panel.

[0079] The embodiments and examples set forth herein are presented to best explain embodiments of the present technology and specific applications thereof, and thereby enable those skilled in the art to make and use the present disclosure. However, those skilled in the art will recognize that the foregoing description and examples have been presented for purposes of illustration and example only. The description set forth is not intended to be exhaustive or to limit the disclosure to the precise form disclosed.

[0080] In view of the foregoing, the scope of the present disclosure is determined by the claims that follow.

Claims

1. 1. A method of driving pixels of a display device, comprising: for a set of N pixels connected to an amplifier via a multiplexer, the N pixels to be driven during one horizontal period, the method comprising: turning on a first switch connected between a first pixel of the set of the multiplexer and the amplifier to apply a precharge signal generated by the amplifier to the first pixel; applying a first pixel drive signal generated by the amplifier to the first pixel while keeping the first switch on following application of the precharge signal; sequentially turning on second to N-th switches of the multiplexer while the precharge signal is passed to the first pixel through the first switch; Including, a K-th switch among the second to N-th switches is connected between the K-th pixel of the set and the amplifier (K ​​is an integer between 2 and N); The start of turning on the K switch is delayed by a time Δt K−1 from the start of turning on the (K−1)th switch among the second to Nth switches. method.

2. applying second through N-th pixel drive signals to the second through N-th pixels of the set, respectively, after applying the first pixel drive signal to the first pixel. The method of claim 1.

3. The application of the precharge signal to the first pixel and the turning on of the second to Nth switches have the same duration. The method of claim 2.

4. the first through Nth pixels of the set each include a MOSFET, and the precharge signal is applied to a source input of the MOSFET; The first to Nth pixel driving signals are applied to the source inputs of the MOSFETs of the first to Nth pixels, respectively. The method of claim 2.

5. At least one of the time Δt K−1 is different for two or more of the second to N-th switches, or two or more of the second to N-th switches are turned on for different durations. The method of claim 1.

6. The time Δt K−1 is the same for K that is 2 or more and N or less. The method of claim 1.

7. The time ΔtK-1 is shorter than the on duration of the (K-1) switch. The method of claim 1.

8. A display panel having N sets of pixels; a gate driver configured to enable the set of N pixels in a horizontal period; a display driver comprising an amplifier coupled via a multiplexer to each of the set of N pixels; a processor coupled to the gate driver and the display driver; Equipped with The processor controls the display driver to: turning on a first switch connected between a first pixel of the multiplexer and the amplifier to apply a precharge signal generated by the amplifier to the first pixel; applying a first pixel drive signal generated by the amplifier to the first pixel while keeping the first switch on continuously with application of the precharge signal; The second to N-th switches of the multiplexer are sequentially controlled to be turned on while the precharge signal is passed to the first pixel via the first switch; a K-th switch among the second to N-th switches is connected between the K-th pixel of the set and the amplifier (K ​​is an integer between 2 and N); The start of turning on the K switch is delayed by a time Δt K−1 from the start of turning on the (K−1)th switch among the second to Nth switches. Display device.

9. A method for calibrating a display device according to claim 8, comprising: staggering the start of turning on the first to Nth switches so that there is a minimum delay between turning on any two of the first to Nth switches; driving said set of N pixels for one or more predefined periods; measuring the level of electromagnetic interference (EMI) generated when driving the set of N pixels; Contains method.

10. In response to determining that the measured level of EMI does not conform to a maximum EMI level, further recursively reducing the measured level of EMI until the measured level of EMI is less than the maximum EMI level. increasing the minimum delay; and measuring the level of EMI produced by driving the set of N pixels with the increased minimum delay; Contains 10. The method of claim 9.

Images