TWI869067B - Display brightness stabilization method, display driver chip, display device and information processing device - Google Patents

Abstract

The present invention discloses a display brightness stabilization method, which is executed by a display driver chip when the display brightness value (DBV) and/or the frame rate changes, so that the display brightness of the display panel remains stable and unchanged. When the DBV value increases, the driving voltage ELVSS transmitted to the display panel by the power management chip will be pulled down due to the IR drop effect, causing the display brightness to decrease due to the negative feedback effect. Therefore, the method of the present invention adopts a method of tracking ELVSS, and is designed to maintain a constant value between the voltage difference between ELVSS and the initialization voltage Vinit output by the display driver chip to the display panel, thereby solving the problem of negative feedback of display brightness. On the other hand, when the frame rate is switched, the display brightness will change instantaneously due to the asynchrony between Vinit output by the display driver chip and ELVSS output by the power management chip. The problem of Vinit and ELVSS asynchrony can also be solved by the method of tracking ELVSS proposed by the present invention.

Description

Display brightness stabilization method, display driver chip, display device and information processing device

The present invention relates to the technical field of OLED displays, and more particularly to a method for stabilizing display brightness performed by a display driver chip.

It is known that flat panel displays include non-self-luminous flat panel displays and self-luminous flat panel displays, wherein liquid crystal displays are a type of non-self-luminous flat panel displays that have been used for a long time, while organic light-emitting diode (OLED) displays and light-emitting diode (LED) displays are self-luminous flat panel displays that are currently in mainstream applications. FIG1 is a block diagram of a known OLED display device. As shown in FIG1 , the known OLED display device 1a mainly includes: an OLED panel 11a, at least one display driver chip 12a, and a power management chip 13a, wherein the OLED panel 11a includes a plurality of sub-pixel units 111a, and each of the sub-pixel units 111a is composed of an OLED element and a pixel circuit. As shown in FIG1 , the pixel circuit of each sub-pixel unit 111a receives a first driving voltage ELVDD and a second driving voltage ELVSS provided by the power management chip 13a, and receives an initialization voltage Vinit provided by the display driver chip 12a. Furthermore, during normal operation, the display driver chip 12a generates a voltage adjustment signal (i.e., Swire pulse) to the power management chip 13a according to the display brightness value (DBV) and/or the frame rate, thereby controlling the power management chip 13a to increase/decrease the output second driving voltage ELVSS. At the same time, according to the DBV and/or the frame rate, the display driver chip 12a increases/decreases the output initialization voltage Vinit.

It should be known that the average picture level (APL) is used to define the proportion of the white window of the OLED display on the black background. For example, the images shown in FIG. 2A, FIG. 2B, and FIG. 2C are APL=10%, APL=40%, and APL=80%, respectively. According to market specifications, when the OLED display device 1a displays an image with APL=10%, the brightness of the white window must reach 3000nit. In an ideal case, this can be achieved by operating the pixel circuit to increase the driving current flowing into the OLED element. Unfortunately, in practice, since there is a line between the input end of the second driving voltage ELVSS and the cathode end of the OLED element, when the driving current increases, the driving current and the IR drop generated by the line will cause the second driving voltage ELVSS to be pulled down, causing the brightness of the OLED element to decrease, resulting in the brightness of the white window failing to meet 3000nit.

It is also known that the frame rate of the OLED display device 1a will be adjusted according to different application scenarios. For example, the frame rates of the game mode, web mode and text reading mode are 144Hz, 60Hz and 10Hz respectively. As shown in FIG3 , the market specification requires that there must be a corresponding second driving voltage ELVSS and initialization voltage Vinit in different frame rate modes to ensure brightness stability when the frame rate is switched. In actual situations, the application processor (AP) sends a frame rate switching command to the display driver chip 12a in the Nth frame, and the display driver chip 12a outputs the adjusted initialization voltage Vinit in the N+1th frame. However, since the power management chip 13a increases/decreases the second driving voltage ELVSS only after receiving the voltage adjustment signal transmitted by the display driver chip 12a, as shown in FIG. 3 , the adjusted initialization voltage Vinit and the adjusted second driving voltage ELVSS are out of sync in the N+1th frame, resulting in a brief brightness difference when the frame rate is switched.

In summary, the conventional method of directly increasing the driving current to improve the brightness of the OLED element and adjusting Vinit and ELVSS according to the frame rate obviously has defects and needs to be improved. Therefore, it is necessary to consider designing a method that can stabilize and maintain the display brightness during the frame rate switching process and/or when the driving current increases.

From the above description, it can be seen that a display brightness stabilization method is urgently needed in the art.

The main purpose of the present invention is to provide a display brightness stabilization method, which is executed by a display driver chip when the display brightness value (DBV) and/or the frame rate changes, so that the display brightness of the display panel remains stable and unchanged. When the DBV value increases, the driving voltage ELVSS transmitted to the display panel by the power management chip will be pulled down due to the IR drop effect, causing the display brightness to decrease due to the negative feedback effect. Therefore, the method of the present invention adopts a method of tracking ELVSS, and is designed to maintain a constant value between the voltage difference between ELVSS and the initialization voltage Vinit output by the display driver chip to the display panel, thereby solving the problem of negative feedback of display brightness. On the other hand, when the frame rate is switched, the display brightness will change instantaneously due to the asynchrony between Vinit output by the display driver chip and ELVSS output by the power management chip. The problem of Vinit and ELVSS asynchrony can also be solved by the method of tracking ELVSS proposed by the present invention.

To achieve the above-mentioned purpose, the present invention proposes an embodiment of the display brightness stabilization method, which is executed by a display driver chip and includes: When a display brightness value (DBV) changes from a first DBV value to a second DBV value or a frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information is generated; and Based on the driving voltage information, an initialization voltage is generated and transmitted to a display panel, and a voltage adjustment signal (Swire pulse) is generated and transmitted to a power management chip, so that the power management chip performs a voltage adjustment process on a driving voltage transmitted to the display panel, so that the initialization voltage and the driving voltage differ by a voltage offset value (offset).

In one embodiment, the display driver chip has a storage unit that pre-stores a lookup table and the voltage offset value, and the lookup table includes: a plurality of frequency values of the frame rate, a plurality of DBV values of the display brightness value, and a plurality of voltage values of the driving voltage.

In one embodiment, when the frame rate is fixed, when the display brightness value is adjusted from the first DBV value to the second DBV value, the display driver chip searches the lookup table for a voltage value corresponding to the frame rate and the second DBV value, and then generates the voltage adjustment signal to the power management chip based on the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value.

In one embodiment, when the frame rate is adjusted from the first frame rate value to the second frame rate value while fixing the display brightness value, the display driver chip searches the lookup table for a voltage value corresponding to the display brightness value and the second frame rate value, and then generates the voltage adjustment signal to the power management chip based on the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value.

Furthermore, the present invention also proposes an embodiment of a display driver chip, which is used to form a display together with a display panel; its characteristic is that when a display brightness value (DBV) and/or a frame rate of the display changes, the display driver chip executes a display brightness stabilization method to stabilize the display brightness of the display panel; the display brightness stabilization method includes: When the display brightness value changes from a first DBV value to a second DBV value or the frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information is generated; and An initialization voltage is generated based on the driving voltage information and transmitted to a display panel, and a voltage adjustment signal is generated and transmitted to a power management chip, so that the power management chip performs a voltage adjustment process on the driving voltage transmitted to the display panel, thereby making the initialization voltage and the driving voltage differ by a voltage offset value.

In one embodiment, the display driver chip has a storage unit that pre-stores a lookup table and the voltage offset value, and the lookup table includes: a plurality of frequency values of the frame rate, a plurality of DBV values of the display brightness value, and a plurality of voltage values of the driving voltage.

In one embodiment, when the frame rate is fixed, when the display brightness value is adjusted from the first DBV value to the second DBV value, the display driver chip searches the lookup table for a voltage value corresponding to the frame rate and the second DBV value, and then generates the voltage adjustment signal to the power management chip based on the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value.

In one embodiment, when the frame rate is adjusted from the first frame rate value to the second frame rate value while fixing the display brightness value, the display driver chip searches the lookup table for a voltage value corresponding to the display brightness value and the second frame rate value, and then generates the voltage adjustment signal to the power management chip based on the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value.

Furthermore, the present invention also provides a display device, which is characterized in that it includes a display panel and at least one display driver chip of the present invention as described above.

In addition, the present invention also provides an information processing device having at least one display device; the display device includes a display panel and at least one display driver chip of the present invention as described above. In a feasible embodiment, the information processing device is an electronic device selected from the group consisting of a head-mounted display device, a smart TV, a smart phone, a smart watch, a tablet computer, an all-in-one computer, a notebook computer, a car entertainment device, a digital camera, and a video door phone.

In order to enable the Review Committee to further understand the structure, features, purpose, and advantages of the present invention, the following are attached with drawings and detailed descriptions of preferred specific embodiments.

FIG. 4 is a block diagram of a display device applying a display brightness stabilization method of the present invention. As shown in FIG. 4 , the display device 1 mainly includes: a display panel 11 , at least one display driver chip 12 and a power management chip 13 . The display panel 11 includes a plurality of sub-pixel units 111 , and each of the sub-pixel units 111 consists of a light-emitting element and a pixel circuit. In possible embodiments, the light-emitting element may be, but is not limited to, an OLED element, a QLED element or a Micro-LED element. As shown in FIG. 4 , the pixel circuit of each sub-pixel unit 111 receives two signals provided by the power management chip 13 . drive voltages ELVSS and ELVDD, and receive an initialization voltage Vinit provided by the display driving chip 12 .

FIG5 is a flow chart of a display brightness stabilization method of the present invention. As shown in FIG4 and FIG5, the display brightness stabilization method of the present invention is integrated into the display driver chip 12 in the form of a voltage adjustment unit 121. Thus, when a display brightness value (DBV) and/or a frame rate of the display device 1 changes, the display driver chip 12 activates the voltage adjustment unit 121 to control the power management chip 13 to adjust the voltage value of the drive voltage ELVSS, and at the same time, the voltage adjustment unit 121 adjusts the initialization voltage Vinit in a manner of tracking ELVSS, thereby maintaining the display brightness of the display panel 11 stable and unchanged.

As shown in FIG5 , the display brightness stabilization method of the present invention includes the following steps: S1: When a display brightness value (DBV) changes from a first DBV value to a second DBV value or a frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information is generated; and S2: Based on the driving voltage information, an initialization voltage Vinit is generated and transmitted to a display panel 11, and a voltage adjustment signal is generated and transmitted to a power management chip 13, so that the power management chip 13 performs a voltage adjustment process on a driving voltage ELVSS transmitted to the display panel 11, so that the initialization voltage and the driving voltage differ by a voltage offset value (offset).

In one embodiment, a file including a lookup table and a voltage offset value (offset) can be stored in a storage unit of the display driver chip 12, so that the driving voltage information in step S1 can be obtained by looking up the table. Specifically, when the display driver chip 12 is powered on, the lookup table and the voltage offset value are loaded into at least one register of the display driver chip 12, so that the display driver chip 12 can access relevant data at any time. The lookup table is exemplarily shown in the following table (1). Table (1) 60Hz 120Hz DBV ELVSS (V) Offset (V) ELVSS (V) Offset (V) 0xFFF -4.4 0.2 -4.2 0.2 0x7FF -3 0.2 -2.8 0.2 ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． 0x333 -2.4 0.2 -2.2 0.2 0x147 -2.0 0.2 -1.8 0.2

To explain in more detail, when the frame rate is fixed (e.g., fixed at 60Hz), when the display brightness value is adjusted from the first DBV value to the second DBV value (e.g., 0xFFF=4095à0x7FF=2047), the display driver chip 12 finds a voltage value (i.e., -3V) corresponding to the frame rate and the second DBV value from the lookup table, and then generates a voltage adjustment signal (Swire pulse) to the power management chip 13 based on the voltage value, thereby controlling the power management chip 13 to adjust the drive voltage ELVSS to -3V. At the same time, the display driver chip 12 adjusts the initialization voltage Vinit in a manner of tracking the driving voltage by making Vinit=ELVSS+offset, that is, -2.8V=-3V+0.2V.

In contrast, when the display brightness value is fixed (e.g., fixed at 0x7FF=2047), when the frame rate is adjusted from the first frame rate value to the second frame rate value (e.g., 60Hzà120Hz), the display driver chip 12 searches the lookup table for a voltage value (i.e., -2.8V) corresponding to the display brightness value and the second frame rate value, and then generates a voltage adjustment signal to the power management chip 13 based on the voltage value, thereby controlling the power management chip 13 to adjust the drive voltage ELVSS to -2.8V. At the same time, the display driver chip 12 adjusts the initialization voltage Vinit in a manner of tracking the driving voltage by making Vinit=ELVSS+offset, that is, -2.6V=-2.8V+0.2V.

Thus, the above description has completely and clearly explained the display brightness stabilization method of the present invention; and, from the above description, it can be known that the present invention has the following advantages:

(1) The present invention discloses a method for stabilizing display brightness, which is executed by a display driver chip when the display brightness value (DBV) and/or the frame rate changes, so as to maintain the display brightness of a display panel stable and unchanged. When the DBV value increases, the driving voltage ELVSS transmitted by the power management chip to the display panel will be pulled down due to the IR drop effect, causing the display brightness to decrease due to the negative feedback effect. Therefore, the method of the present invention adopts a method of tracking ELVSS, and is designed to maintain a constant value between the voltage difference between ELVSS and the initialization voltage Vinit output by the display driver chip to the display panel, thereby solving the problem of negative feedback of display brightness. On the other hand, when the frame rate is switched, the display brightness will change instantaneously due to the asynchrony between Vinit output by the display driver chip and ELVSS output by the power management chip. As shown in the working timing diagram of FIG6 , the problem of Vinit and ELVSS asynchrony can also be solved by the method of tracking ELVSS proposed by the present invention.

(2) The present invention also discloses a display driver chip, which is used to form a display together with a display panel; its characteristic is that when a display brightness value (DBV) and/or a frame rate of the display changes, the display driver chip executes the display brightness stabilization method of the present invention as described above to make the display brightness of the display panel stable and unchanged.

(3) Furthermore, the present invention also provides a display device, which is characterized in that it includes a display panel and at least one display driver chip of the present invention as described above.

(4) Furthermore, the present invention also provides an information processing device having at least one display device; the display device includes a display panel and at least one display driver chip of the present invention as described above. In a feasible embodiment, the information processing device is an electronic device selected from the group consisting of a head-mounted display device, a smart TV, a smart phone, a smart watch, a tablet computer, an all-in-one computer, a notebook computer, a car entertainment device, a digital camera, and a video door phone.

It must be emphasized that what is disclosed in the above-mentioned case is a preferred embodiment. Any partial changes or modifications that are derived from the technical ideas of this case and are easily inferred by people familiar with the art do not deviate from the scope of the patent rights of this case.

In summary, this case shows that its purpose, means and effects are very different from the known technology, and it is the first invention that is practical and indeed meets the patent requirements for invention. We sincerely request the review committee to examine this carefully and grant a patent as soon as possible to benefit the society. This is our utmost prayer.

1a: OLED display device 11a: OLED panel 111a: sub-pixel unit 12a: display driver chip 13a: power management chip 1: display device 11: display panel 111: sub-pixel unit 12: display driver chip 121: voltage adjustment unit 13: power management chip S1: when a display brightness value changes from a first DBV value to a second DBV value or a frame rate changes from a first frame rate value to a second frame rate value, a corresponding drive voltage information is generated S2: Generate an initialization voltage based on the driving voltage information and transmit it to a display panel, and at the same time generate a voltage adjustment signal and transmit it to a power management chip, so that the power management chip performs a voltage adjustment process on the driving voltage transmitted to the display panel, so that the initialization voltage and the driving voltage differ by a voltage offset value

FIG1 is a block diagram of a known OLED display device; FIG2A is a diagram of a display image of APL=10%; FIG2B is a diagram of a display image of APL=40%; FIG2C is a diagram of a display image of APL=80%; FIG3 is a working timing diagram of a vertical synchronization signal Vsync, a frame rate, a second driving voltage ELVSS, and an initialization voltage Vinit; FIG4 is a block diagram of a display device to which a display brightness stabilization method of the present invention is applied; FIG5 is a flow chart of a display brightness stabilization method of the present invention; and FIG6 is a working timing diagram of a vertical synchronization signal Vsync, a frame rate, a second driving voltage ELVSS, and an initialization voltage Vinit.

S1: When a display brightness value changes from a first DBV value to a second DBV value or a frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information is generated

S2: Generate an initialization voltage based on the driving voltage information and transmit it to a display panel, and generate a voltage adjustment signal and transmit it to a power management chip, so that the power management chip performs a voltage adjustment process on the driving voltage transmitted to the display panel, so that the initialization voltage and the driving voltage differ by a voltage offset value.

Claims (10)

A display brightness stabilization method is performed by a display driver chip and includes: when a display brightness value (DBV) changes from a first DBV value to a second DBV value or a frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information is generated; and according to the driving voltage information, an initialization voltage is generated and transmitted to a display panel, and a voltage adjustment signal is generated and transmitted to a power management chip, so that the power management chip performs a voltage adjustment process on a driving voltage transmitted to the display panel, so that the initialization voltage and the driving voltage differ by a voltage offset value (offset). The display brightness stabilization method as described in claim 1, wherein the display driver chip has a storage unit that pre-stores a lookup table and the voltage offset value, and the lookup table includes: a plurality of frequency values of the frame rate, a plurality of DBV values of the display brightness value, and a plurality of voltage values of the drive voltage. The display brightness stabilization method as described in claim 2, wherein, when the display brightness value is adjusted from the first DBV value to the second DBV value under the condition of fixing the frame rate, the display driver chip finds a voltage value corresponding to the frame rate and the second DBV value from the lookup table, and then generates the voltage adjustment signal to the power management chip according to the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value. The display brightness stabilization method as described in claim 2, wherein, when the display brightness value is fixed, when the frame rate is adjusted from the first frame rate value to the second frame rate value, the display driver chip finds a voltage value corresponding to the display brightness value and the second frame rate value from the lookup table, and then generates the voltage adjustment signal to the power management chip according to the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value. A display driver chip is used to form a display together with a display panel; its characteristic is that when a display brightness value (DBV) and/or a frame rate of the display changes, the display driver chip executes a display brightness stabilization method to stabilize the display brightness of the display panel; the display brightness stabilization method comprises: when the display brightness value changes from a first DBV value to a second DBV value or the frame rate changes from a first frame rate value to a second frame rate value, a corresponding driving voltage information; and generating an initialization voltage according to the driving voltage information and transmitting it to the display panel, and generating a voltage adjustment signal and transmitting it to a power management chip, so that the power management chip performs a voltage adjustment process on the driving voltage transmitted to the display panel, thereby making the initialization voltage and the driving voltage differ by a voltage offset value (offset). A display driver chip as described in claim 5, wherein the display driver chip has a storage unit that pre-stores a lookup table and the voltage offset value, and the lookup table includes: a plurality of frequency values of the frame rate, a plurality of DBV values of the display brightness value, and a plurality of voltage values of the drive voltage. The display driver chip as described in claim 6, wherein, when the frame rate is fixed, when the display brightness value is adjusted from the first DBV value to the second DBV value, the display driver chip looks up a voltage value corresponding to the frame rate and the second DBV value from the lookup table, and then generates the voltage adjustment signal to the power management chip according to the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value. The display driver chip as described in claim 6, wherein, when the display brightness value is fixed, when the frame rate is adjusted from the first frame rate value to the second frame rate value, the display driver chip finds a voltage value corresponding to the display brightness value and the second frame rate value from the lookup table, and then generates the voltage adjustment signal to the power management chip according to the voltage value, thereby controlling the power management chip to adjust the drive voltage to have the voltage value. A display device, characterized in that it includes a display panel and at least one display driver chip as described in any one of claim 5 to claim 8. An information processing device having at least one display device, characterized in that the display device includes a display panel and at least one display driver chip as described in any one of claim 5 to claim 8.