Power saving for oled displays with multiple refresh rates

Abstract

Rendering an image on an active area of an OLED includes rendering the image on the active area of the display panel at a plurality of different frame rates. For a plurality of the different frame rates that match or are higher than a threshold frame rate, a frame refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period. When rendering the image on the active area, for at least one of the different frame rates that is lower than the threshold frame rate, a frame refresh operation is performed once per frame period and at least one self-refresh operation is performed during the frame period.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 148,598, filed February 11, 2021, entitled “POWER SAVING IN OLED DISPLAYSWITH MULTIPLE REFRESH RATES,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This manual relates to displays on computing devices. Background Technology

[0004] A computing device's display can have a modifiable refresh rate, or the rate at which pixel content is updated or changed. Generally, a lower refresh rate reduces the display's power consumption and increases battery life, while a higher refresh rate can improve graphics output. Summary of the Invention

[0005] In general, the display panel includes a plurality of pixels arranged in an array, the array comprising rows and columns, each pixel in the array including at least one OLED light-emitting device. The display panel further includes a plurality of pixel circuits, each pixel circuit associated with and configured to drive its associated OLED light-emitting device. The display panel further includes a plurality of scan lines configured to select the pixel circuit associated with each row of pixels; a plurality of column data lines configured to control the pixel circuit associated with each column of pixels; and a plurality of emission lines configured to supply signals to the pixel circuit associated with each row of pixels, causing the pixel circuit to supply drive current to the anode of the OLED pixels in the row. The display panel further includes a device driver configured to supply signals to the scan lines, column lines, and emission lines to cause the display panel to render an image on an active region of the panel at a plurality of different frame rates. When rendering an image on the active region, for a plurality of different frame rates having a frame rate matching or higher than a threshold frame rate, an image refresh operation is performed once per frame period, and no self-refresh operation is performed during the frame period. When rendering an image on an active region, for at least one of different frame rates having a frame rate lower than a threshold frame rate, an image refresh operation is performed once per frame period and a self-refresh operation is performed at least once during the frame period.

[0006] The implementation scheme may include one or more of the following features individually or in any combination of them.

[0007] For example, each of the pixel circuits may include at least two metal-oxide-semiconductor transistors. The threshold rate may be 60 Hz or lower. Different frame rates having a frame rate lower than the threshold frame rate may have a rate as a factor of the threshold frame rate. The device driver may be configured to apply a first gamma correction value when rendering frames at frame rates at or below the threshold rate, and to apply a second gamma correction value different from the first gamma correction value when rendering frames at frame rates above the threshold rate.

[0008] When the threshold frame rate is N Hz, where N is a real value, each of the different frame rates with a frame rate lower than N can have a frame rate that is a factor of N. The number of self-refresh operations performed during a rendering frame at a different frame rate in MHz can be (N / M–1).

[0009] The device driver can be further configured to: when rendering an image on the active region at one of different frame rates having a frame rate lower than a threshold frame rate, supply signals to the scan lines, column lines, and emission lines to cause the display panel to: perform an image refresh operation once per frame period; perform a self-refresh operation at least once during the frame period when the brightness of the active region of the display panel is lower than a threshold brightness; and not perform a self-refresh operation during the frame period when the brightness of the active region of the display panel is lower than the threshold brightness. The device driver can be further configured to: when rendering an image on the active region, supply signals to the scan lines, column lines, and emission lines to cause the display panel to: apply a first gamma correction value to the rendering of the image when performing a self-refresh operation at least once during the frame period; and apply a second gamma correction value, different from the first gamma correction value, to the rendering of the image when not performing a self-refresh operation during the frame period.

[0010] The device driver can be further configured to supply signals to the scan lines, column lines, and emission lines to cause the display panel to: perform an image refresh operation once per frame period; perform a self-refresh operation at least once during the frame period when the gray level of the active area of ​​the display panel is below a threshold brightness; and not perform a self-refresh operation during the frame period when the gray level of the active area of ​​the display panel is below the threshold brightness. The gray level can be based on the average gray level of all pixels in the active area. The gray level can also be based on the percentage of pixels in the active area whose gray level is above a threshold gray level.

[0011] When rendering an image on an active region, the device driver can be further configured to supply signals to scan lines, column lines, and emission lines to cause the display panel to: apply a first gamma correction value to the rendering of the image when a self-refresh operation is performed at least once during a frame period; and apply a second gamma correction value, different from the first gamma correction value, to the rendering of the image when a self-refresh operation is not performed during a frame period.

[0012] The device driver can be further configured to supply signals to the scan lines, column lines, and emitter lines to cause the display panel to: render image frames on the active region of the panel at one of different frame rates having a rate lower than a threshold rate, wherein rendering includes: performing an image refresh operation once per frame period, and based on a function value of the luminance level of the active region of the display panel and the grayscale level of the rendered frame: when the value of the function is higher than a threshold, performing a self-refresh operation at least once during the frame period, and when the value of the function is lower than a threshold, not performing a self-refresh operation during the frame period. A first partial derivative of the function with respect to the grayscale value can be negative, and a second partial derivative of the function with respect to the panel luminance value can be positive. When rendering image frames on the active region, the device driver can be further configured to supply signals to the scan lines, column lines, and emitter lines to cause the display panel to: apply a first gamma correction value to the rendering of the image when a self-refresh operation is performed at least once during the frame period; and apply a second gamma correction value, different from the first gamma correction value, to the rendering of the image when a self-refresh operation is not performed during the frame period.

[0013] In another general aspect, the display panel includes a plurality of pixels arranged in an array, the array comprising rows and columns, each pixel in the array including at least one OLED light-emitting device. The display panel includes a plurality of pixel circuits, each pixel circuit associated with and configured to drive its associated OLED light-emitting device. The display panel includes a plurality of scan lines configured to select the pixel circuit associated with each row of pixels; a plurality of column data lines configured to control the pixel circuit associated with each column of pixels; and a plurality of emission lines configured to supply signals to the pixel circuit associated with each row of pixels, causing the pixel circuit to supply drive current to the anode of the OLED pixels in the row. The display panel includes a device driver configured to supply signals to the scan lines, column lines, and emission lines to cause the display panel to render an image on an active region of the panel at a plurality of different frame rates. When rendering an image on the active region, for a plurality of different frame rates having a frame rate matching or higher than a threshold frame rate, an image refresh operation is performed once per frame period, and no self-refresh operation is performed during the frame period. When rendering an image over an active region, an image refresh operation is performed once per frame period and a self-refresh operation is performed at least once during the frame period for at least one of different frame rates having a frame rate lower than a threshold frame rate. The device driver is configured to apply a single gamma correction value when rendering frames at one or more frame rates at or below the threshold rate and when rendering frames at a frame rate higher than the threshold rate.

[0014] The implementation may include one or more of the following features individually or in any combination thereof. For example, each of the pixel circuits may include at least two metal-oxide-semiconductor transistors. The threshold rate may be 60 Hz or lower. Different frame rates having a frame rate lower than the threshold frame rate may have a rate that is a factor of the threshold frame rate. When the threshold frame rate is N Hz, where N is a real value, each of the different frame rates having a frame rate lower than N may have a frame rate that is a factor of N. The number of self-refresh operations performed during a rendering frame at a different frame rate of M Hz may be (N / M–1).

[0015] In another general aspect, a method for rendering an image on an active region of a display panel, wherein the display panel includes: a plurality of pixels arranged in an OLED pixel array, each pixel of the array including at least one OLED light-emitting device; a plurality of pixel circuits, each pixel circuit being associated with and configured to drive its associated OLED light-emitting device, the method comprising: rendering the image on the active region of the display panel at a plurality of different frame rates; when rendering the image on the active region, performing an image refresh operation once per frame period for the plurality of different frame rates having a frame rate matching or higher than a threshold frame rate and not performing a self-refresh operation during the frame period; and when rendering the image on the active region, performing an image refresh operation once per frame period for at least one of the different frame rates having a frame rate lower than a threshold frame rate and performing a self-refresh operation at least once during the frame period.

[0016] The implementation scheme may include one or more of the following features individually or in any combination thereof. For example, the threshold rate may be 60 Hz or lower. Different frame rates having a frame rate lower than the threshold frame rate may have a rate that is a factor of the threshold frame rate.

[0017] The method may further include applying a first gamma correction value when rendering frames at frame rates at or below a threshold rate, and applying a second gamma correction value, different from the first gamma correction value, when rendering frames at a frame rate above the threshold rate. When the threshold frame rate is N Hz, where N is a real value, each of the different frame rates having a frame rate below N has a frame rate as a factor of N, and the number of self-refresh operations performed during rendering a frame at one of the different frame rates at M Hz can be (N / M–1).

[0018] When rendering an image on the active area at one of different frame rates having a frame rate lower than the threshold frame rate, an image refresh operation may be performed once per frame period, and a self-refresh operation may be performed at least once during the frame period when the brightness of the active area of ​​the display panel is lower than the threshold brightness, and a self-refresh operation may not be performed during the frame period when the brightness of the active area of ​​the display panel is lower than the threshold brightness.

[0019] When rendering an image on an active region, a first gamma correction value may be applied to the rendering of the image if a self-refresh operation is performed at least once during the frame period, and a second gamma correction value different from the first gamma correction value may be applied to the rendering of the image if a self-refresh operation is not performed during the frame period.

[0020] When rendering an image on the active region at one of different frame rates having a frame rate lower than a threshold frame rate, an image refresh operation can be performed once per frame cycle. A self-refresh operation is performed at least once during the frame cycle when the gray level of the active region of the display panel is lower than the threshold brightness, and no self-refresh operation is performed during the frame cycle when the gray level of the active region of the display panel is lower than the threshold brightness. The gray level can be based on the average gray level of all pixels in the active region. The gray level can also be based on the percentage of pixels in the active region whose gray level is higher than the threshold gray level.

[0021] When rendering an image on an active region, a first gamma correction value may be applied to the rendering of the image if a self-refresh operation is performed at least once during the frame period, and a second gamma correction value different from the first gamma correction value may be applied to the rendering of the image if a self-refresh operation is not performed during the frame period.

[0022] The method may further include rendering image frames on the active region of the panel at one of different frame rates having a rate lower than a threshold rate, wherein rendering includes performing an image refresh operation once per frame period, and based on a function value of the brightness level of the active region of the display panel and the grayscale level of the rendered frame: when the function value is higher than the threshold, a self-refresh operation may be performed at least once during the frame period, and when the function value is lower than the threshold, a self-refresh operation may not be performed during the frame period. A first partial derivative of the function with respect to the grayscale value may be negative, and a second partial derivative of the function with respect to the panel brightness value may be positive. The method may further include applying a first gamma correction value to the rendering of the image when a self-refresh operation is performed at least once during the frame period; and applying a second gamma correction value, different from the first gamma correction value, to the rendering of the frame when a self-refresh operation is not performed during the frame period.

[0023] In another general aspect, a method for rendering an image on an active region of a display panel, wherein the display panel includes: a plurality of pixels arranged in an OLED pixel array, each pixel of the array including at least one OLED light-emitting device; a plurality of pixel circuits, each pixel circuit associated with and configured to drive its associated OLED light-emitting device, the method comprising: rendering an image on the active region of the panel at a plurality of different frame rates; performing an image refresh operation once per frame period for the plurality of different frame rates having a frame rate matching or higher than a threshold frame rate and not performing a self-refresh operation during the frame period when rendering an image on the active region; performing an image refresh operation once per frame period for at least one of the different frame rates having a frame rate lower than a threshold frame rate and performing at least one self-refresh operation during the frame period when rendering an image on the active region; and applying a single gamma correction value when rendering a frame at one or more frame rates at or below a threshold rate and when rendering a frame at a frame rate higher than a threshold rate.

[0024] The implementation may include one or more of the following features individually or in any combination thereof. For example, each of the pixel circuits may include at least two metal-oxide transistors. The threshold rate may be 60 Hz or lower.

[0025] Different frame rates having a frame rate lower than the threshold frame rate can have a rate that is a factor of the threshold frame rate. When the threshold frame rate is N Hz, where N is a real value, each of the different frame rates having a frame rate lower than N can have a frame rate that is a factor of N, and the number of self-refresh operations performed during a rendering frame at a different frame rate of M Hz can be (N / M–1).

[0026] Details of one or more embodiments are set forth in the following figures and detailed description. Other features will become apparent from the detailed description, figures, and claims. As appropriate, any feature described herein with respect to an aspect, embodiment, example, or embodiment may be combined with any other feature described herein with respect to any other aspect, embodiment, example, or embodiment. Attached Figure Description

[0027] Figure 1 This is a view of a computing device according to an example implementation.

[0028] Figure 2 It can be included Figure 1 A schematic diagram of the display panel used in the display of a computing device.

[0029] Figure 3AThis is a schematic diagram of a circuit for a light-emitting device used to drive pixels in the active area of ​​a display panel.

[0030] Figure 3B It is used to pass Figure 3A A schematic timing diagram of the signals controlling the operation of the light-emitting device.

[0031] Figure 4A This is a schematic diagram of a circuit used to drive a light-emitting device when a self-refresh operation is applied to the circuit.

[0032] Figure 4B It is used for control Figure 4A A schematic timing diagram of the signals for the self-refresh operation of the circuit.

[0033] Figure 4C It is used for control Figure 4A Another schematic timing diagram of the signals for the self-refresh operation of the circuit.

[0034] Figure 5A This is a schematic diagram showing the instantaneous brightness of pixels across four frames as they change over time when the pixels operate at a frame rate of 120Hz and an image refresh rate of 120Hz.

[0035] Figure 5B This is a schematic diagram showing how the instantaneous brightness of a pixel changes over time when the pixel operates at a frame rate of 30Hz and an image refresh rate of 30Hz.

[0036] Figure 5C This is a diagram illustrating how the instantaneous brightness of a pixel changes over time when the pixel operates at a frame rate of 30Hz, refreshes the image once per frame, and performs a self-refresh operation three times per frame cycle.

[0037] Figure 5D It is used for control Figure 4A Another schematic timing diagram of the signals for the self-refresh operation of the circuit.

[0038] Figure 6 This is a schematic diagram illustrating an example relationship between the brightness level of the display panel and the system-level settings for controlling the brightness of the display panel.

[0039] Figure 7 This is a schematic diagram of the threshold curve used to determine whether to apply a self-refresh operation to a frame.

[0040] Figure 8A This is a schematic diagram showing the change in instantaneous brightness of a pixel over time across four frames when the pixel operates at a frame rate of 120Hz and an image refresh rate of 120Hz.

[0041] Figure 8BThis is a schematic diagram showing the change in instantaneous brightness of a pixel over time across two frames when the pixel operates at a frame rate of 60Hz and an image refresh rate of 120Hz.

[0042] Figure 8C This is a schematic diagram showing how the instantaneous brightness of a pixel changes over time when the pixel operates at a frame rate of 30Hz and an image refresh rate of 120Hz.

[0043] Figure 9A It is a schematic diagram of a light-emitting device for driving pixels in the active area of ​​a display panel, a device for supplying data signals, and a circuit for a refresh device to receive new data signals.

[0044] Figure 9B It is used when the frame rate is higher than the base frame rate, by Figure 9A A schematic timing diagram of the signals controlling the image refresh and anode discharge operation of the pixels.

[0045] Figure 9C This is a schematic diagram showing the change of instantaneous brightness of a pixel over time across multiple frames when the pixel operates at a frame rate of 120Hz and the anode of the pixel discharges at a rate of 60Hz.

[0046] Figure 10 This is a diagram illustrating the process of rendering an image on a display panel.

[0047] Figure 11 This is a diagram illustrating the process of rendering an image on a display panel.

[0048] The same reference numerals refer to the same elements. In the following description, when referring to displays, devices, systems, their features and / or otherwise using relative terms such as "top," "topmost," "bottom," "bottommost," "higher," and "lower," these may refer to the "top," "bottom," etc. of a display, device, system, its features, etc., in the orientation in which they are intended to be used and / or viewed by a user. Detailed Implementation

[0049] A display's refresh rate can be described as the rate at which rows of pixels in the display are refreshed (i.e., the amount of light or color emitted from the pixels has been updated) and / or the signals received that cause the pixels to generate an updated image on the display. Generally, in applications where the image changes, such as video applications or video games, higher refresh rates can improve image quality, while lower refresh rates can reduce the display's power consumption. However, when a display is configured to operate at both high and low refresh rates, technical issues may include the display's optical performance potentially differing at different refresh rates, which could distract or displease the viewer, and / or the power savings of operating the device at lower refresh rates may be compromised by attempting to achieve uniform optical performance across different refresh rates.

[0050] Figure 1 This is a view of a computing device 100 according to an example embodiment. The computing device 100 may include a display 102 and an input device 104. The display 102 may present, provide, output, and / or display graphical and / or visual output. In some examples, the display 102 may include a touchscreen display that receives touch input, such as a capacitive touchscreen display and / or a resistive touchscreen display. As a non-limiting example, the display 102 may include a light-emitting diode (LED) display, such as an organic LED (OLED) display and / or an active-matrix organic LED (AMOLED) display.

[0051] Input device 104 can receive input from a user. As a non-limiting example, input device 104 may include, for example, a keyboard, touchpad, or home button.

[0052] Figure 2 It is included as Figure 1 This is a schematic diagram of a portion of a display 102 in a computing device 100 and a display panel 200 used in the display. The display panel 200 may include a pixel array and pixel circuitry for driving pixels associated with each pixel, wherein the array has rows and columns. The display panel 200 may include a plurality of horizontal signal lines 210, 211 for providing signals to rows of pixel circuitry in the display panel. The horizontal signal lines may include a plurality of scan lines 210 for selecting pixel circuitry in each row of pixel circuitry, and a plurality of emitter lines for controlling current transmission to emitter devices (e.g., OLEDs) in the pixel circuitry.

[0053] For clarity, Figure 2The display panel 200 shows two horizontal signal lines (scan line 210 and emit line 211), but there are more horizontal signal lines in the display panel 200. Horizontal can refer to the position of the computing device 100 when it is in the orientation intended for use. The horizontal signal lines 210 and / or pixel rows can be numbered sequentially from the top portion 206 of the active area 207 of the display panel 200 to the bottom portion 208 of the active area 207 of the display panel 200. The top portion 206 of the active area 207 refers to the top portion of the active area 207 when the display panel 200 is in the orientation in which the user will view it.

[0054] During each frame of the display, horizontal signal lines 210, 211 may sequentially and / or continuously provide signals to the pixel rows, wherein the first and / or topmost rows of pixels receive signals at or near the start of the frame, and the last and / or bottommost rows of pixels receive signals at or near the end of the frame. The display panel 200 may include a scan line driver 214A and a transmitter line driver 214B that provide signals on the horizontal signal lines 210, 211. For example, when a new frame is provided to the display panel, the signals provided by the scan line driver 214A to the pixels via scan line 210 can be used to initialize and reset the pixels to receive new data signals, and the signals provided by the transmitter line driver 214B to the pixels via transmitter line 211 can be used to turn the drive current to the pixels on or off.

[0055] The display may include column data lines 212 for controlling the pixel circuits in each column of the pixel circuitry (e.g., by writing data voltages for driving the pixels to the pixel circuitry associated with the pixels). For clarity, Figure 2 Only one column data line is shown, but there are more column data lines in the display panel 200. Column data line 212 can provide signals to the pixel column in the active area 207 of the display panel 200. Horizontal signal lines 210, 211 and column data line 212 can be combined to provide signals to individual pixels on the display panel 200, causing each pixel to emit a specific amount and color of light as perceived by the user. The display panel 200 may include a column line driver 218 that provides signals to the column data line 212.

[0056] The display panel 200 may include a display driver 216 that can control the output of the display panel 200, such as providing input to the horizontal signal line 210 via the gate line driver 214A and the transmitter line driver 214B and providing input to the column data line 212 via the column line driver 218.

[0057] Display driver 216 may include timing controller 220. Timing controller 220 may generate signals and / or provide signals to horizontal signal lines 210 via gate line drivers 214A and emitter line drivers 214B, and to column data lines 212 via column line drivers 218. Signals may include clock signals and / or start pulses. Signals generated and / or provided by timing controller 220 may instruct and / or prompt horizontal signal lines 210 and / or column data lines 212, such as by sending signals to pixels to refresh and / or update the image rendered by the pixels. Timing controller 220 may send and / or provide signals to gate line drivers 214A, 214B. Display driver 216 may include memory 222 storing executable instructions for controlling pixels in the active region 207 of display panel 200. Display driver 216 may include gamma buffer 224 storing parameters for adjusting the signal values ​​provided to the pixels in the active region 207, such that the display panel 200 produces a desired optical output.

[0058] The display driver 216 of the display panel 200 can communicate with an external processor 230 (e.g., a GPU or a processor as part of a system-on-a-chip (SoC)), which can provide signals to the display driver to drive the pixels in the active area 207 of the panel.

[0059] When the display panel 200 operates to display video and / or still images, where frames of the video / image are refreshed in the active region 207, the display panel 200 consumes power. The LEDs in the pixels of the active region 207 themselves consume power, but a significant factor contributing to the total power consumption of the display panel 200 is the dynamic power consumption in the drive panel circuitry, including the row line drivers (e.g., gate line driver 214A, emitter line driver 214B, and column line driver 218) and the pixel circuitry in the active region 207 of the display panel 200. For example, due to the charging data line 212 (e.g., ... Figure 2 C DATA (indicated), charging scan line 210 (e.g.) Figure 2 C SCAN (representation), charging transmitter line 211 (e.g.) Figure 2 C EM (representation), supplies signals (e.g., clock signals) to the charging line 213 of the scan line driver (such as...) Figure 2 C SCLK (representation) and the charging line 215 that supplies signals (e.g., clock signals) to the transmitter line driver (as shown). Figure 2 C ECLKThe parasitic capacitance associated with the display panel 200 dissipates power. As high display refresh rates (e.g., 120Hz and 90Hz) become popular in high-quality displays, power consumption due to parasitic capacitance becomes a significant drain on the battery powering the computing device including the display panel 200. When the display panel operates at a relatively low refresh rate, the power consumed by the display panel 200 decreases. However, simply reducing the refresh rate of the display panel 200 may affect the optical performance of the active region 207 of the panel 200, as optical performance can be dependent on the refresh rate. Therefore, as described herein, the circuitry for supplying signals to the pixels in the active region 207 of the display and the techniques for the driving circuitry can ensure consistent optical performance of the active region 207 of the display panel 200 when the panel operates at different refresh rates.

[0060] Figure 3A This is a schematic diagram of a light-emitting device (e.g., an organic light-emitting diode (OLED)) 302 for driving pixels in the active region of a display panel, a circuit 300 for supplying data signals to the device 302, and a circuit 300 for refreshing the device 302 to receive new data signals. The light-emitting device 302 may have a capacitor (represented by capacitor 303) such that changing the voltage level across the light-emitting device 302 dissipates power. Figure 3B It is a schematic timing diagram for controlling the operation of the light-emitting device 302 through circuit 300.

[0061] Circuit 300 can be connected to supply initialization voltage V INIT The circuit 300 provides an initialization voltage supply line 309, a first power supply line 304 for supplying voltage ELVDD, and a data line 306 for supplying data voltage DATA[k]. Additionally, the circuit 300 can be connected to the (n-1)th scan line 308 for supplying signal SCAN[n-1], the pnth scan line 310 for supplying signal pSCAN[n], the nnth scan line 311 for supplying signal nSCAN[n], and the transmit line 312 for supplying signal EM[n].

[0062] Circuit 300 may include a driving transistor T1, second to seventh transistors T2 to T7 configured to drive the light-emitting device 302, and a storage capacitor C. ST Each of transistors T1 through T7 can be implemented using p-channel or n-channel thin-film transistor (TFT) technology. In an example embodiment, transistors T3 and T4 are implemented as n-channel transistors, while transistors T1, T2, T5, T6, and T7 are implemented as p-channel transistors. For example, transistors T1, T2, T5, T6, and T7 can be low-temperature polycrystalline silicon (LTPS) transistors, and transistors T3 and T4 can be metal-oxide-semiconductor transistors.

[0063] The light-emitting device (e.g., OLED) 302 may include an anode connected to a driving transistor T1 via a drive current-controlled switching transistor T6, a cathode connected to a low-voltage power supply voltage ELVSS, and a light-emitting layer between the anode and the cathode that generates light, wherein the amount of light generated is proportional to the amount of current supplied from the driving transistor T1.

[0064] Storage capacitor C of circuit 300 ST The first electrode can be connected to line 304, which supplies voltage EVLDD, and the storage capacitor C ST It can be connected to the gate electrode of the driving transistor T1, so that it can be charged by the driving voltage of the driving transistor T1. The driving transistor T1 can be charged by the voltage stored in the storage capacitor C. ST The driving voltage is used to control the current driving the light-emitting device (e.g., OLED) 302.

[0065] Transistor T3 can be controlled by the scan signal nSCAN[n] supplied on line 311, and the gate and drain electrodes of driving transistor T1 can be connected by transistor T3 to form a diode-connected driving transistor T1, so that the data voltage from DATA[k] supplied on line 306 can be stored in storage capacitor C after compensating for the threshold voltage during the sampling period of circuit 300. ST middle.

[0066] Transistor T2 can be controlled by the scan signal pSCAN[n] on line 310 to supply the data voltage DATA[k] from data line 306 to the source electrode of driving transistor T1 during the sampling period of circuit 300.

[0067] Transistor T5 can be controlled by the light emission control signal EM[n] on line 312 to supply a high-voltage power supply voltage ELVDD to the source electrode of driving transistor T1 during the light emission cycle of circuit 300.

[0068] Transistor T6 can be controlled by the light emission control signal EM[n] on line 312, such that during the light emission cycle of circuit 300, drive current is supplied from drive transistor T1 to light emission device (e.g., OLED) 302.

[0069] Transistor T4 can be controlled by the scan signal nSCAN[n-1] on line 308 to charge the storage capacitor C during the initialization cycle of circuit 300. ST The gate electrode of the driving transistor T1 is initialized to the initialization voltage V. INIT .

[0070] Transistor T7 can be controlled by the scan signal pSCAN[n] on line 310 to initialize the anode of the light-emitting device (e.g., OLED) 302. Transistor T7 can be turned on in response to the scan signal pSCAN[n] during the sampling period of circuit 300 to initialize the anode of device 302 to the initialization voltage V. INIT .

[0071] refer to Figure 3B When signal EM[n] is high, transistors T6 and T5 are disconnected and no drive current is supplied to device 302. When EM[n] is high, and nSCAN[n-1] is high, storage capacitor C... ST and the gate of the driving transistor T1 is driven by voltage V INIT Initialize. Then, when nSCAN[n-1] and pSCAN[n] are low and when nSCAN[n] is high, load the voltage DATA[k] onto the storage capacitor C. ST The above is used to set the brightness output of device 302 when EM[n] subsequently decreases.

[0072] exist Figure 3A In some embodiments shown, metal-oxide transistors (MOS transistors) may be used in T3 and T4 to reduce the effects of off-state leakage current in circuit 300, which could cause the brightness of the light-emitting device 302 to change during display cycles, especially over relatively long frame times (e.g., at low refresh rates). In some embodiments, even if MOS transistors are used in T3 and T4, LTPS transistors may be used in T1, T2, T5, T6, and T7 to handle other factors that affect optical artifacts (e.g., flicker) at low refresh rates and to maintain a small footprint for circuit 300.

[0073] While using metal-oxide-semiconductor transistors (MOS transistors) in pixel circuitry can reduce changes in pixel brightness over time and enable very low display refresh rates (e.g., 30Hz, 10Hz, 1Hz), some optical artifacts (e.g., flicker) can still occur at low frame rates or when switching to low frame rates. Therefore, to achieve acceptable low flicker artifacts at low frame rates in a display, the self-refresh operation in the display can be applied once or multiple times per frame cycle. Figure 3A The circuit 300. This self-refresh operation can be used to initialize the transistor hysteresis state and initialize / reset the anode electrode of the light-emitting device 302 in the pixel during the frame period. Without this self-refresh operation, it can exhibit flickering at a low frame rate when the active area of ​​the display panel displays a dim image (i.e., when a relatively low emission current is applied to the emission device 302 of the panel).

[0074] Figure 4AThis is a schematic diagram of circuit 300 when the self-refresh operation is applied to the circuit. Figure 4B This is a schematic timing diagram for the self-refresh operation of the control circuit 300.

[0075] During the self-refresh operation, the inputs nSCAN[n] and nSCAN[n-1] of lines 311 and 308 are low, so transistors T3 and T4 are off. When pSCAN[n] is low, transistor T7 is turned on, and the anode voltage is changed from V... INIT Initialization. Additionally, when the EM[n] signal is high, transmit control switches T5 and T6 are disconnected, and the bias voltage V is set via the DATA[k] signal. BIAS This is applied to line 306. Then, when pSCAN[n] is low to turn on transistor T2, V is applied to the source of transistor T1. BIAS This initializes the transistor hysteresis state so that when the data signal is applied to line 306 again, the brightness of the light-emitting device 302 increases to its expected value.

[0076] Figure 4C It is used for control Figure 4A Another schematic timing diagram of the signals for the self-refresh operation of the circuit. Specifically, Figure 4C The timing diagram illustrates the signals to the pixel circuitry associated with the pixel rows, where the pixel circuitry operates at a frame rate of 10Hz with a self-refresh rate of 120Hz, such that the optical characteristics of the display when rendering an image at a frame rate of 10Hz can appear similar to those when rendering an image at a frame rate of 120Hz. The diagonal lines in the upper part of the timing diagram illustrate the application of the nSCAN[n], pSCAN[n], and EM[n] signals to the pixel circuitry associated with the pixel rows (from the first row to the last row). Unfilled diagonal lines indicate the application of the EM[n] signal to the pixel circuitry. Dashed diagonal lines indicate the application of both the EM[n] and pSCAN[n] signals to the pixel circuitry. Dotted-dash diagonal lines indicate the application of the EM[n], pSCAN[n], and nSCAN[n] signals to the pixel circuitry.

[0077] During the image writing time window 412, the nSCAN[n], pSCAN[n], EM[n], and DATA[K] signals are written to the circuit to refresh the image data to be applied to pixels during the frame, such as... Figure 3B As shown, the signal is written within an 8.33ms time period, which corresponds to the image refresh time of the display at a refresh rate of 120Hz.

[0078] After the image data is refreshed during the image write time window 412, for the remaining 91.67 ms of the frame period, which may be called the self-refresh period 414, in response to the application of the pSCAN[n] signal to the pixel circuit at this rate (by... Figure 4C (As shown by the dashed line in the image), a self-refresh operation is applied to the pixel circuit at a rate of 120 Hz, where the pSCAN[n] signal initializes / resets the anode electrode of the light-emitting device in the pixel. See references herein. Figure 4A and 4B As explained, during the self-refresh operation, the EM[n] and pSCAN[n] signals are written to the pixel circuit and V is applied by the DATA[k] signal. BIAS The value of nSCAN[n] is set, but the nSCAN[n] signal remains low throughout the entire period 414. In this way, the optical performance of the display panel during low frame rate (e.g., 10 Hz) operation can be similar to that of the display panel operating at its maximum frame rate (e.g., 120 Hz), since the duration and rate of the light emission pulses can be the same for both frame rates.

[0079] pass Figure 5A , 5B Figures 5C and 5C show the effect of the self-refresh operation on the brightness output of the light-emitting device 302.

[0080] Figure 5A This is a schematic diagram illustrating the instantaneous brightness of a pixel over four frames when the pixel operates at a frame rate of 120Hz and an image refresh rate of 120Hz. Within a frame period, the pixel brightness gradually increases from a low level (e.g., zero) to a high level. However, at least for OLED device 302, the brightness does not immediately increase from zero at the start of a frame, especially when the pixel brightness is low and the pixel drive current is low. Instead, due to… Figure 3A The OLED capacitor 303 shown, the anode electrode voltage of the light-emitting device—OLED device—302 starts from the initial voltage level V. INIT The voltage level is increased relatively slowly to reach the desired brightness. Therefore, this is especially true when pixel brightness is low and pixel drive current is low. Figure 5AThe pixel brightness in the graph is not a series of closely spaced rectangular pulses (as shown by the dashed line in the first frame), but rather four pulses that are temporally separated and each includes an initial ramp of brightness that changes over time. Due to the time interval between the initial ramp of brightness and the brightness cycle, human viewers may perceive flicker in the display. At lower frame rates, flicker may be more noticeable compared to higher frame rates. Additionally, when pixel brightness is high and pixel drive current is high, then pixel brightness tends to rise from its minimum value earlier during the frame cycle, making the actual brightness curve (shown by the solid line) closer to the ideal curve (shown by the dashed line). Thus, flicker can be perceived more noticeably at low brightness levels than at high brightness levels. At some frame rates exceeding a threshold rate, flicker may be difficult to detect even at low brightness levels because the frame rate is high enough that the time-averaged brightness is perceived as constant.

[0081] Figure 5B This is a schematic diagram showing how the instantaneous brightness of a pixel changes over time when the pixel operates at a frame rate of 30Hz and an image refresh rate of 30Hz. Figure 5B The single frame shown in the figure is in relation to Figure 5A The graph shows four frames rendered within the same amount of time. However, the time-averaged light output from a pixel differs when the pixel operates at a frame rate of 30Hz compared to when the pixel operates at a frame rate of 120Hz. Therefore, when the display panel operates in modes using different frame rates, the different optical performance at these different frame rates causes unpleasant artifacts for the viewer of the device.

[0082] Figure 5C This is a schematic diagram illustrating the change in instantaneous brightness of a pixel over time when the pixel operates at a frame rate of 30Hz and refreshes the image once per frame (i.e., writes new data signals to the pixel) and performs a self-refresh operation three times per frame cycle, resulting in a pixel with a refresh rate of 120Hz. (See diagram from...) Figure 5C graphics and Figure 5A The graphical comparison shows that the optical performance of a pixel operating at a frame rate of 30 Hz with three self-refresh operations per frame cycle is the same as that of a pixel operating at a frame rate of 120 Hz. Therefore, generally speaking, when a display is designed and configured to operate at a maximum frame rate of N Hz, the display can operate at a lower frame rate of M Hz with an intra-frame self-refresh rate of (N / M–1), where N / M is an integer (i.e., where M is a factor of N).

[0083] However, due to the losses associated with parasitic capacitance when driving transistors to refresh the pixels of the display, operating a display panel at a 120Hz refresh rate and a 30Hz frame rate may increase the power consumption of the panel compared to operating the display panel at a 30Hz refresh rate and a 30Hz frame rate.

[0084] Therefore, in order to reduce the power consumption of the display panel while maintaining acceptable optical performance in the active area of ​​the panel, the panel's self-refresh operation can be retained for use when these self-refresh operations are needed to maintain optical performance, but not used when the self-refresh operation sacrifices the panel's effective power utilization.

[0085] In one implementation, for a display configured to operate at multiple different operating frame rates, a self-refresh operation may not be applied to multiple frame rates at or above a threshold frame rate and may be applied to frame rates below the threshold frame rate. The self-refresh operation may be based on an operating frame rate lower than the panel's maximum operating frame rate. For example, in a display panel configured to operate at frame rates such as 120Hz, 90Hz, 60Hz, 30Hz, 15Hz, 10Hz, 5Hz, and 1Hz, a self-refresh operation may not be performed for any frame rate above the threshold rate of 60Hz, while operation at a 30Hz frame rate may include one intra-frame self-refresh, operation at a 15Hz frame rate may include three intra-frame self-refreshes, operation at a 10Hz frame rate may include five intra-frame self-refreshes, operation at a 5Hz frame rate may include eleven intra-frame self-refreshes, and operation at a 1Hz frame rate may include fifty-nine intra-frame self-refreshes. When the threshold is high enough that the user cannot perceive flickering artifacts when using frame rates at or above the threshold, it may be acceptable to apply intra-frame refresh only when the frame rate is below the threshold, and not apply intra-frame refresh when the frame rate is at or above the threshold.

[0086] For a threshold frame rate of 60Hz, self-refresh operations are not used at frame rates of 120Hz, 90Hz, and 60Hz at or above the threshold frame rate. The 60Hz frame rate can be the base frame rate upon which the number of intra-frame self-refresh operations used at lower frame rates (e.g., 30Hz, 15Hz, 10Hz, 5Hz, and 1Hz) is based. By using a 60Hz frame rate instead of 120Hz or 90Hz as the base frame rate, the number of intra-frame self-refresh operations required at frame rates below the threshold frame rate can be reduced, thereby reducing the power consumption of the display panel.

[0087] Figure 5D It is used to control the self-refresh operation when the basic frame rate (e.g., 60Hz) is lower than the display panel's maximum operating frame rate (e.g., 120Hz). Figure 4AAnother schematic timing diagram of the signals for the self-refresh operation of the circuit. Specifically, Figure 5D The timing diagram is similar to Figure 4C The timing diagram differs in that the pSCAN[n] signal is applied at a rate of 60Hz, instead of as... Figure 4C At a rate of 120Hz, according to Figure 5D The signal shown is based on Figure 4C The signal shown performs the self-refresh operation at half the rate of the signal shown, thus reducing power consumption. Figure 4C and 5D When providing the EM[n] signal at the same rate, the optical performance of a display panel performing self-refresh operation at a rate of 60Hz during low frame rates (e.g., 10Hz) can be the same as the optical performance of the display panel operating at its basic frame rate (e.g., 60Hz), because the duration and rate of the light emission pulses can be the same for both frame rates, and the output of the OLED device refreshes at the same rate. The optical performance of a display panel performing self-refresh operation at a rate of 60Hz during low frame rates (e.g., 10Hz) can also be similar to the optical performance of the display panel operating at its maximum frame rate (e.g., 120Hz), because the duration and rate of the light emission pulses can be the same for both frame rates, although it may not be the same, as the refresh rate may differ for different frame rates.

[0088] Because of the self-refresh operation at a lower frame rate, which is used as a factor of the base frame rate, the optical performance at the lower frame rate can mimic the optical performance at the base frame rate, such as from... Figure 5C and Figure 5A As can be seen from the comparison, a single gamma correction value can be used for the base frame rate and for lower frame rates that are factors of the base frame rate. However, for frame rates above a threshold frame rate, different gamma correction values ​​can be used to ensure consistent optical performance of the display panel across all possible frame rates that the panel can use. (Reference) Figure 2 The gamma correction values ​​for different frame rates can be stored in the gamma buffer 224.

[0089] Table 1 provides example parameters for a display panel designed and configured to operate at a variety of different frame rates, with a threshold frame rate of 60Hz. Intra-frame refresh is not used for frame rates at and above the threshold frame rate (e.g., 120Hz, 90Hz, 60Hz); however, it is used for frame rates below the threshold frame rate that are factors of the threshold frame rate. Additionally, the same gamma correction value can be used for frame rates at and below the threshold frame rate, where the frame rate is a factor of the threshold frame rate.

[0090] Frame rate Self-refresh? Gamma settings 120Hz no Gamma A, 120Hz Gamma 90Hz no Gamma B, 90Hz Gamma 60Hz no Gamma C, 60Hz Gamma 30Hz yes Gamma C, 60Hz Gamma 15Hz yes Gamma C, 60Hz Gamma 10Hz yes Gamma C, 60Hz Gamma 5Hz yes Gamma C, 60Hz Gamma 1Hz yes Gamma C, 60Hz Gamma

[0091] In another implementation, for a display panel configured to operate at multiple different operating frame rates, when the display panel operates at a specific frame rate, a self-refresh operation can be applied to relatively dim frames but not to relatively bright frames because flicker artifacts are more noticeable on dim frames than on bright frames. In an example implementation, a threshold for enabling the self-refresh operation for a specific operating frame rate can be determined based on the system-level brightness of the active area of ​​the display. For example, the system-level brightness can be controlled by a user according to user preferences (e.g., by adjusting the brightness level of the display panel's output) or in response to a signal from an ambient light sensor that may be included in, incorporated into, or in another device within the display panel. For panel brightness levels exceeding the threshold brightness level, the self-refresh operation may not be applied when the display panel operates at a specific frame rate, while for panel brightness levels below the threshold brightness level, the self-refresh operation may be applied when the display panel operates at a specific frame rate. The threshold brightness level can differ for different frame rates. For example, the threshold brightness level may be higher for lower frame rates than for higher frame rates. The brightness level of a display panel does not need to be measured empirically; rather, it can be inferred from the system settings of the display panel used to control the monitor's brightness.

[0092] Figure 6 This is a schematic diagram 600 illustrating an example relationship between the brightness level of the display panel and the system-level settings for controlling the brightness of the display panel. A threshold brightness 602 can be identified; when the brightness is below the threshold brightness 602, an intra-frame refresh operation is applied to the panel at a specific frame rate; and a threshold 604 that generates the system setting value of the threshold brightness 602 can be determined. Then, for system setting values ​​below the threshold, an intra-frame refresh operation is applied to the panel at the specific frame rate.

[0093] In another implementation, for a display panel configured to operate at multiple different operating frame rates, when the display panel operates at a specific frame rate, determining whether to apply a self-refresh operation to a frame can be based on the determined gray level of the frame. For example, the self-refresh operation can be applied to frames with relatively low gray levels but not to frames with relatively high gray levels because such artifacts may be imperceptible for frames with high gray levels when flicker artifacts are more noticeable for frames with low gray levels. The determined gray level of the frame can be based on, for example, the average gray level of the pixels in the frame, the median gray level of the pixels in the frame, the proportion of pixels in the frame with gray levels below a threshold level, etc. The gray level of each pixel in the frame can be determined based on signals transmitted from the external processor 230 to the display panel 200 or from the device driver 216, wherein the signals are used to encode information for generating an image on the display panel 200.

[0094] In some implementations, determining whether to apply a self-refresh operation to a frame can be based on the frame's determined grayscale level and the brightness settings of the active area of ​​the display panel that renders the frame to the user. Figure 7 This is a schematic diagram 700 illustrating the threshold curve 702 used to determine whether a self-refresh operation should be applied to a frame. The threshold curve 702 can be a function of the frame's panel brightness value (shown on the X-axis of the graph) and grayscale value (shown on the Y-axis of the graph). Figure 7 As shown in Figure 700, the grayscale value of a frame on the Y-axis represents the percentage of pixels in the frame with grayscale values ​​less than a threshold. For example, if the possible grayscale values ​​of a pixel are in the range of 0 to 255, a threshold grayscale value 64 can be used as a parameter to determine the grayscale value of the frame based on the percentage of pixels in the frame with grayscale values ​​less than the threshold grayscale value. When parameterized in this way, the grayscale value of the frame is low when the percentage of pixels in the frame with grayscale values ​​less than the threshold grayscale value is high, and the grayscale value of the frame is high when the percentage of pixels in the frame with grayscale values ​​less than the threshold grayscale value is low. Therefore, as Figure 7 As shown in Figure 700, the gray level of the frame decreases from the origin of the figure as the percentage of pixels in the frame with gray values ​​below the threshold gray level increases.

[0095] In the implementation scheme, the threshold curve 702 can be a monotonically increasing function of the panel brightness value and a monotonically decreasing function of the grayscale value of the frame—that is, for any point on the threshold curve 702, the partial derivative of the curve 702 with respect to the grayscale value is negative, and the partial derivative of the curve 702 with respect to the panel brightness value is positive. As shown in Figure 700, for points above and to the left of the threshold curve 702, an intra-frame refresh operation can be applied to the frame, while for points below and to the right of the threshold curve 702, an intra-frame refresh operation is not applied to the frame.

[0096] refer to Figure 2 In some implementations, the determination of whether the panel brightness and grayscale values ​​of a frame are above or below threshold curve 702 can be performed by the display driver 216. In some implementations, the determination can be performed by an external processor 230 (e.g., a graphics processing unit or included in a SoC).

[0097] Refer again Figure 5B and Figure 5C Compared to rendering frames at a specific frame rate and disabling inter-frame refresh, rendering frames at a specific frame rate with intra-frame refresh enabled allows for the use of different gamma correction values. For example, as from... Figure 5B and 5CAs seen in the text, even if pixels can be programmed with the same DATA[k] voltage value to achieve the same maximum pixel brightness during the frame period, the perceived temporal average pixel brightness will differ due to the varying total blanking times (i.e., the time during which pixel brightness is zero or close to zero), depending on whether a self-refresh operation is applied. Specifically, when an intra-frame self-refresh operation is applied to a frame, the perceived pixel brightness decreases. Therefore, to prevent differences in perceived pixel brightness, a different gamma correction value can be used when rendering a frame with a self-refresh operation compared to rendering a frame without a self-refresh operation.

[0098] As described above, the display panel can be configured to operate at three or more different frame rates, which may include a maximum frame rate and two or more lower frame rates. When the display panel operates at each of the different frame rates, light pulses can be emitted from the pixels of the display panel at a rate equal to the maximum frame rate. A basic frame rate lower than the maximum frame rate can be used as the rate at which refresh operations are applied when using frame rates lower than the basic frame rate, including image refresh operations and one or more self-refresh operations. Figure 8A , 8B Figures 8C and 8C show the effect of the self-refresh operation on the brightness output of the light-emitting device 302.

[0099] Figure 8A This is a schematic diagram illustrating the instantaneous brightness of a pixel over four frames when the pixel operates at a frame rate of 120Hz and an image refresh rate of 120Hz. In this example, the 120Hz frame rate is the panel's maximum frame rate. Within one frame time period, the pixel's brightness scales up from a low level (e.g., zero) to a high level. Then, in an image refresh operation, the pixel is refreshed, new data is written, and a new frame is displayed in subsequent frame times. The image refresh operation occurs at a rate of 120Hz.

[0100] Figure 8B This is a schematic diagram illustrating the instantaneous brightness of a pixel over time across two frames when the pixel operates at a frame rate of 60Hz and an image refresh rate of 120Hz. Within the period of one frame time, the pixel's brightness gradually increases from a low level (e.g., zero) to a high level. Then, the light output is turned off and on again, causing two light pulses to be emitted at a rate of 120Hz during one frame time. After the frame ends, the pixel is refreshed in the image refresh operation, new data is written, and the new frame is displayed in subsequent frame times. Because the pixel is refreshed only at the beginning of a frame, rather than during the frame, the second light pulse does not include the pixel's slowly increasing brightness when it is emitted. Therefore, Figure 8A The temporal distribution of pixel brightness in Figure 8B The differences in the values ​​result in different gamma correction values ​​being used for the 120Hz maximum frame rate and the 60Hz base frame rate, excluding self-refresh operations.

[0101] Figure 8C This is a schematic diagram illustrating the change in instantaneous brightness of a pixel over time within a frame when the pixel operates at a frame rate of 30Hz and an image refresh rate of 120Hz. During the period of one frame time, the pixel brightness ramps up from a low level (e.g., zero) to a high level. Then, the light output is turned off and on again at a rate of 120Hz, causing four light pulses to be emitted at one rate during one frame time. After the end of the frame, the pixel is refreshed in an image refresh operation, new data is written, and a new frame is displayed in subsequent frame times. During the frame time, a self-refresh operation is applied to the pixel at a rate of 60Hz (to match the frame rate of the 60Hz base rate), and therefore... Figure 8C The temporal distribution of pixel brightness in Figure 8B The same applies, allowing a single gamma correction value to be either a 30Hz frame rate or a 60Hz base frame rate.

[0102] In order to enable a single gamma correction value to be used for each frame rate (e.g., 120Hz, 60Hz, and 30Hz), the pixel circuitry used to drive the pixels of the display panel can be configured and controlled to operate the display panel at each of the different frame rates using a single gamma correction value for all the different frame rates.

[0103] In one implementation, when the display panel operates at its maximum frame rate (e.g., 120Hz), the anode of the OLED in the panel can discharge at a rate of 60Hz, allowing... Figure 8A The temporal distribution of pixel brightness is changed to match Figure 8B The temporal distribution of pixel brightness.

[0104] Figure 9A This is a schematic diagram of a light-emitting device (e.g., an organic light-emitting diode (OLED)) 902 for driving pixels in the active region of a display panel, a circuit 900 for supplying data signals to the device 902, and a circuit 900 for refreshing the device 902 to receive new data signals. The circuit 900 can be used to drive the device 902 at a frame rate having a first frequency and to discharge the anode of the device at a second frequency of half the first frequency.

[0105] The light-emitting device 902 may have a capacitor (represented by capacitor 903) so that changing the voltage level across the light-emitting device 902 dissipates power.

[0106] Circuit 900 can be connected to supply initialization voltage V INITThe circuit 900 provides an initialization voltage supply line 909, a first power supply line 904 for supplying voltage ELVDD, and a data line 906 for supplying data voltage DATA[k]. Additionally, the circuit 900 can be connected to the n-(n-1)th scan line 908 for supplying signal nSCAN[n-1], the pnth scan line 910 for supplying signal pSCAN[n], the nnth scan line 911 for supplying signal nSCAN[n], and the transmit line 912 for supplying signal EM[n].

[0107] Circuit 900 may include a driving transistor T1, second to sixth transistors T2 to T7 configured to drive the light-emitting device 902, and a storage capacitor C. ST Each of transistors T1 through T7 can be implemented using p-channel or n-channel thin-film transistor (TFT) technology. In an example embodiment, transistors T3 and T4 are implemented as n-channel transistors, while transistors T1, T2, T5, T6, and T7 are implemented as p-channel transistors. For example, transistors T1, T2, T5, T6, and T7 can be low-temperature polycrystalline silicon (LTPS) transistors, and transistors T3 and T4 can be metal-oxide-semiconductor transistors.

[0108] The light-emitting device (e.g., OLED) 902 may include an anode connected to a driving transistor T1 via a drive current-controlled switching transistor T6, a cathode connected to a low-voltage power supply voltage ELVSS, and a light-emitting layer between the anode and the cathode that generates light, wherein the amount of light generated is proportional to the amount of current supplied from the driving transistor T1.

[0109] The storage capacitor C of circuit 900 ST The first electrode can be connected to line 904, which supplies voltage EVLDD, and the storage capacitor C ST It can be connected to the gate electrode of the driving transistor T1, so that it can be charged by the driving voltage of the driving transistor T1. The driving transistor T1 can be charged by the voltage stored in the storage capacitor C. ST The driving voltage is used to control the current driving the light-emitting device (e.g., OLED) 902.

[0110] Transistor T3 can be controlled by the scan signal nSCAN[n] supplied on line 911, and the gate and drain electrodes of driving transistor T1 can be connected by transistor T3 to become a diode-connected driving transistor T1, so that the data voltage from DATA[k] supplied on line 306 can be stored in storage capacitor C after compensating for the threshold voltage during the sampling period of circuit 900. ST middle.

[0111] Transistor T2 can be controlled by the scan signal pSCAN1[n] on line 910 to supply the data voltage DATA[k] from data line 906 to the source electrode of driving transistor T1 during the sampling period of circuit 900.

[0112] Transistor T5 can be controlled by the light emission control signal EM[n] on line 912 to supply the high-voltage power supply voltage ELVDD to the source electrode of driving transistor T1 during the light emission cycle of circuit 900.

[0113] Transistor T6 can be controlled by the light emission control signal EM[n] on line 912, such that during the light emission cycle of circuit 900, drive current is supplied from drive transistor T1 to light emission device (e.g., OLED) 902.

[0114] Transistor T4 can be controlled by the scan signal nSCAN[n-1] on line 908 to charge the storage capacitor C during the initialization cycle of circuit 900. ST The gate electrode of the driving transistor T1 is initialized to the initialization voltage V. INIT .

[0115] Transistor T7 can be controlled by scan signal pSCAN2[n] on line 909 to initialize the anode of light-emitting device (e.g., OLED) 902. Transistor T7 can be turned on in response to scan signal pSCAN2[n] during the sampling period of circuit 900 to initialize the anode of device 902 to initialization voltage V. INIT .

[0116] Because the pSCAN1[n] signal on line 910 can be different from the pSCAN2[n] signal on line 909, the discharge of the anode of OLED 902 can be controlled independently of the update of the DATA[k] signal supplied on line 906.

[0117] Figure 9B It is used when the frame rate is higher than the base frame rate (when the frame rate is 120Hz and the base frame rate is 60Hz). Figure 9A A schematic timing diagram of the signals controlling the image refresh and anode discharge operations of the pixels. Specifically, Figure 9B The timing diagram indicates that for each frame rendered on the display panel, the anode did not discharge. For example, in odd-numbered frames (from... Figure 9B Starting from the first frame on the left, in response to the nSCAN, pSCAN1, pSCAN2, and EM signals applied to the pixel circuitry, the image is refreshed and the anode discharges, as referenced in this document. Figure 9A This is explained. Figure 9B The middle line is represented by a solid diagonal line filled with double-dotted lines. In even-numbered frames (from... Figure 9BStarting from the second frame on the left, in response to the nSCAN, pSCAN1, and EM signals applied to the pixel circuitry, the image is refreshed, but the anode does not discharge, as referenced in this article. Figure 9A As explained, however, pSCAN2 remains high, preventing T7 from being activated. This is in Figure 9B The solid line in the middle is represented by a diagonal line filled with dashed lines.

[0118] Figure 9C This is a schematic diagram illustrating the change in instantaneous brightness of a pixel over time across multiple frames when the pixel operates at a frame rate of 120Hz and the pixel's anode discharges at a rate of 60Hz. (The last sentence appears to be incomplete and possibly refers to a different topic.) Figure 9C The pixel brightness curves show that every other frame includes a slowly tilting initial pixel brightness, while other frames include a step function for pixel brightness that begins. Therefore, the instantaneous brightness of a pixel changing over time matches the instantaneous brightness of a pixel operating at a 60Hz frame rate without a frame rate threshold, as shown below. Figure 8B As shown in the diagram. Therefore, a single gamma correction value can be used for frames rendered at 120Hz with skipped anode discharge, frames rendered at 60Hz with no self-refresh, and frames rendered at a rate that includes self-refresh as a factor of 60Hz.

[0119] In another implementation, instead of using separate pSCAN1 and pSCAN2 signals for transistors T2 and T7 respectively to force skipping the anode discharge when rendering multiple frames at 120Hz or at another frame rate higher than the base frame rate, the same signal can be applied as pSCAN[n] to... Figure 4A The pixel circuit 300 shown can control the voltage level of pSCAN[n] so that it turns on T2 for all frames but on T7 for fewer than all frames. For example, to render frames at a frame rate of 120Hz, the voltage level can be controlled to turn on T7 at a rate of 60Hz, so that the anode discharges only in alternating frames. See again Figure 4A The DATA[k] signal provided to the source of T2 can have a higher voltage than the V signal provided to the source of T7. INIT The voltage signal (e.g., -4V) has a high voltage level (e.g., +1V to +6V). Therefore, if the high voltage level (e.g., +7V) used for the pSCAN signal is higher than the highest data voltage, and if the first low voltage level (e.g., -8V) used for the pSCAN signal is lower than V... INIT Then, both T2 and T7 can be turned on via the first low voltage level to cause the anode of the pixel to discharge and refresh the image data used to drive the pixel. However, if the second low voltage level (e.g., -4V) used for the pSCAN signal is higher than V... INITHowever, if the voltage level is below the minimum DATA[k] voltage level, T2 can be turned on by the first low voltage level to refresh the image data used to drive the pixel, while T7 remains off to prevent the pixel from anodic discharge.

[0120] Figure 10 This is a schematic diagram of a process for rendering an image on a display panel according to the technology described herein. The process includes a method 1000 for rendering an image on an active area of ​​a display panel, wherein the display panel includes: a plurality of pixels arranged in an OLED pixel array, and each pixel in the array including an OLED light-emitting device; a plurality of pixel circuits, wherein each pixel circuit is associated with and configured to drive its associated OLED light-emitting device.

[0121] Method 1000 includes rendering an image on an active area of ​​a display panel at multiple different frame rates (1002). Additionally, method 1000 includes performing an image refresh operation once per frame period and not performing a self-refresh operation during the frame period when rendering an image on the active area, for multiple different frame rates having a frame rate matching or higher than a threshold frame rate (1004). Method 1000 also includes performing an image refresh operation once per frame period and performing at least one self-refresh operation during the frame period when rendering an image on the active area, for at least one of the different frame rates having a frame rate lower than a threshold frame rate (1006).

[0122] Figure 11 This is a schematic diagram of a process for rendering an image on a display panel according to the techniques described herein. The process includes method 1100 for rendering an image on an active area of ​​a display panel, wherein the display panel includes: a plurality of pixels arranged in an OLED pixel array, and each pixel in the array including an OLED light-emitting device; a plurality of pixel circuits, wherein each pixel circuit is associated with and configured to drive its associated OLED light-emitting device.

[0123] Method 1100 includes rendering an image on an active region of a panel at multiple different frame rates (1102). When rendering an image on the active region, for multiple different frame rates having a frame rate matching or higher than a threshold frame rate, an image refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period (1104). When rendering an image on the active region, for at least one of the different frame rates having a frame rate lower than the threshold frame rate, an image refresh operation is performed once per frame period and at least one self-refresh operation is performed during the frame period (1106). A single gamma correction value is applied when rendering frames at one or more frame rates at or below the threshold rate and when rendering frames at a frame rate higher than the threshold rate (1108).

[0124] Various implementations of the systems and techniques described herein can be implemented in digital electronic circuits, integrated circuits, specially designed ASICs (Application-Specific Integrated Circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be used for special or general purposes and is coupled to receive data and instructions from a storage system, at least one input device, and at least one output device, and to transfer data and instructions to the storage system, at least one input device, and at least one output device.

[0125] These computer programs (also referred to as programs, software, software applications, or code) include machine instructions for a programmable processor and can be implemented in high-level procedural and / or object-oriented programming languages, and / or in assembly / machine languages. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, device, and / or apparatus (e.g., disk, optical disk, memory, programmable logic device (PLD)) used to provide machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor.

[0126] To provide interaction with the user, the systems and techniques described herein can be implemented on a computer with a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) to display information to the user, as well as a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including sound, speech, or tactile input.

[0127] The systems and techniques described herein can be implemented in computing systems that include back-end components (e.g., as data servers), middleware components (e.g., application servers), front-end components (e.g., client computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and techniques described herein), or any combination of these back-end, middleware, or front-end components. The components of the system can be interconnected through any form or medium of digital data communication (e.g., communication networks). Examples of communication networks include local area networks (“LANs”), wide area networks (“WANs”), and the Internet.

[0128] A computing system may include clients and servers. Clients and servers are typically located far apart and usually interact through a communication network. The relationship between clients and servers is established by computer programs running on the respective computers and having a client-server relationship with each other.

[0129] Several embodiments have been described. However, it should be understood that various modifications can be made without departing from the spirit and scope of the invention.

[0130] Furthermore, the logical flow depicted in the accompanying drawings does not necessarily need to achieve the desired result in the specific order or sequence shown. Additionally, other steps may be provided, or steps may be removed from the described flow, and other components may be added to or removed from the described system. Therefore, other embodiments are within the scope of the appended claims.

[0131] Although certain features of the described embodiments have been illustrated herein, many modifications, substitutions, alterations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations falling within the true spirit of the embodiments of the invention.

Claims

1. A display panel, comprising: A plurality of pixels arranged in an array, the array comprising rows and columns, each pixel in the array comprising at least one OLED light-emitting device; Multiple pixel circuits, each pixel circuit being associated with one of the OLED light-emitting devices and configured to drive its associated OLED light-emitting device; Multiple scan lines, the multiple scan lines being configured to select the pixel circuitry associated with each row of the pixel; Multiple column data lines, the multiple column data lines being configured to control the pixel circuitry associated with each column of the pixel; Multiple emitter lines are configured to supply signals to pixel circuitry associated with each row of the pixels, such that the pixel circuitry supplies drive current to the anode of the OLED pixels in the row. A device driver configured to supply signals to the scan lines, the column data lines, and the transmit lines to cause the display panel to render images on an active area of ​​the display panel at multiple different frame rates, including: (i) For multiple frame rates that match or exceed the threshold frame rate, an image refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period; (ii) For lower frame rates than the threshold frame rate and when the brightness of the active area of ​​the display panel is lower than the threshold brightness, an image refresh operation is performed once per frame period and a self-refresh operation is performed at least once during the frame period; and (iii) For the lower frame rate which is lower than the threshold frame rate and when the brightness of the active area of ​​the display panel is higher than the threshold brightness, an image refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period.

2. The display panel according to claim 1, wherein, Each of the pixel circuits includes at least two metal-oxide transistors.

3. The display panel according to claim 1, wherein, The threshold frame rate is 60 Hz or lower.

4. The display panel according to claim 1, wherein, The first frame rate and the second frame rate have a rate that is a factor of the threshold frame rate.

5. The display panel according to claim 1, wherein, The device driver is configured to apply a first gamma correction value when rendering a frame at a frame rate lower than the threshold frame rate, and to apply a second gamma correction value different from the first gamma correction value when rendering a frame at a frame rate higher than the threshold frame rate.

6. The display panel according to claim 4, wherein, When the threshold frame rate is N Hz, where N is a real value, the first frame rate has a frame rate that is a factor of N.

7. The display panel according to claim 6, wherein, The number of self-refresh operations performed during the rendering of a frame at one of the different frame rates of M Hz is (N / M–1).

8. The display panel according to claim 1, wherein, The device driver is further configured for the lower frame rate: When the self-refresh operation is performed at least once during the frame period, a first gamma correction value is applied to the rendering of the image, and When no self-refresh operation is performed during the frame period, a second gamma correction value, different from the first gamma correction value, is applied to the rendering of the image.

9. The display panel according to claim 1, comprising: By identifying that the gray level of the active area of ​​the display panel is lower than a specific brightness, the brightness of the active area of ​​the display panel is identified as being lower than the threshold brightness; as well as By identifying that the gray level of the active area of ​​the display panel is greater than the specific brightness, it is identified that the brightness of the active area of ​​the display panel is higher than the threshold brightness.

10. The display panel according to claim 9, wherein, The gray level is based on the average gray level of all pixels in the active region.

11. The display panel according to claim 9, wherein, The gray level is based on the percentage of pixels in the active region whose gray level is higher than a threshold gray level.

12. The display panel according to claim 1, comprising: Based on the fact that the value of the function of the brightness level of the active area of ​​the display panel and the gray level of the rendered frame meets the standard, it is identified that the brightness of the active area of ​​the display panel is lower than the threshold brightness. as well as The brightness of the active area of ​​the display panel is identified as being higher than the threshold brightness if the value of the function of the brightness level of the active area of ​​the display panel and the gray level of the rendered frame fails to meet the standard.

13. The display panel according to claim 12, wherein, The first partial derivative of the function with respect to the gray level value is negative, and the second partial derivative of the function with respect to the panel brightness value is positive.

14. The display panel according to claim 1, in, The device driver is configured to apply a single gamma correction value when rendering a frame at a lower frame rate below the threshold frame rate and when rendering a frame at a frame rate above the threshold frame rate.

15. A method for rendering an image on an active area of ​​a display panel, the display panel comprising: A plurality of pixels arranged in an OLED pixel array, wherein each pixel in the array includes at least one OLED light-emitting device; a plurality of pixel circuits, wherein each pixel circuit is associated with and configured to drive its associated OLED light-emitting device, the method comprising: Rendering images on the active area of ​​the display panel at multiple different frame rates includes: (i) For multiple frame rates that match or exceed the threshold frame rate, an image refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period; (ii) For lower frame rates than the threshold frame rate and when the brightness of the active area of ​​the display panel is lower than the threshold brightness, an image refresh operation is performed once per frame period and a self-refresh operation is performed at least once during the frame period; and (iii) For the lower frame rate which is lower than the threshold frame rate and when the brightness of the active area of ​​the display panel is higher than the threshold brightness, an image refresh operation is performed once per frame period and no self-refresh operation is performed during the frame period.

16. The method according to claim 15, wherein, The threshold frame rate is 60 Hz or lower.

17. The method according to claim 15, wherein, The first frame rate and the second frame rate have a rate that is a factor of the threshold frame rate.

18. The method of claim 15, further comprising: When rendering a frame at a frame rate lower than the threshold frame rate, a first gamma correction value is applied; as well as When rendering a frame at a frame rate higher than the threshold frame rate, a second gamma correction value, different from the first gamma correction value, is applied.

19. The method of claim 17, wherein, When the threshold frame rate is N Hz, where N is a real value, the first frame rate has a frame rate that is a factor of N.

20. The method according to claim 19, wherein, The number of self-refresh operations performed during the rendering of a frame at one of the different frame rates of M Hz is (N / M–1).

21. The method of claim 15, further comprising, for the lower frame rate: when rendering an image over the active region: When the self-refresh operation is performed at least once during the frame period, a first gamma correction value is applied to the rendering of the image, and When no self-refresh operation is performed during the frame period, a second gamma correction value, different from the first gamma correction value, is applied to the rendering of the image.

22. The method of claim 15, further comprising: By identifying that the gray level of the active area of ​​the display panel is lower than a specific brightness, the brightness of the active area of ​​the display panel is identified as being lower than the threshold brightness; as well as By identifying that the gray level of the active area of ​​the display panel is greater than the specific brightness, it is identified that the brightness of the active area of ​​the display panel is higher than the threshold brightness.

23. The method according to claim 22, wherein, The gray level is based on the average gray level of all pixels in the active region.

24. The method according to claim 22, wherein, The gray level is based on the percentage of pixels in the active region whose gray level is higher than a threshold gray level.

25. The method of claim 22, further comprising: When rendering an image on the active region: When a self-refresh operation is performed at least once during the frame period, the first gamma correction value is applied to the rendering of the image; as well as When no self-refresh operation is performed during the frame period, a second gamma correction value, different from the first gamma correction value, is applied to the rendering of the image.

26. The method of claim 15, further comprising: Based on the fact that the value of the function of the brightness level of the active area of ​​the display panel and the gray level of the rendered frame meets the standard, it is identified that the brightness of the active area of ​​the display panel is lower than the threshold brightness. as well as The brightness of the active area of ​​the display panel is identified as being higher than the threshold brightness if the value of the function of the brightness level of the active area of ​​the display panel and the gray level of the rendered frame fails to meet the standard.

27. The method according to claim 26, wherein, The first partial derivative of the function with respect to the gray level value is negative, and the second partial derivative of the function with respect to the panel brightness value is positive.

28. The method of claim 26, further comprising: When a self-refresh operation is performed at least once during the frame period, the first gamma correction value is applied to the rendering of the image; as well as When no self-refresh operation is performed during the frame period, a second gamma correction value, different from the first gamma correction value, is applied to the rendering of the frame.

29. The method of claim 15, comprising: A single gamma correction value is applied when rendering a frame at a lower frame rate below the threshold frame rate and when rendering a frame at a frame rate above the threshold frame rate.

Images