TWI841343B - Brightness compensation method, display driver chip, display device, and information processing device - Google Patents

Abstract

The present invention mainly discloses a brightness compensation method, which is executed by a display driver chip, thereby performing a brightness compensation on an OLED display panel according to a current working temperature; the brightness compensation method includes the following steps: according to the current working temperature, looking up a current substrate compensation voltage from a lookup table, wherein the lookup table includes a plurality of working temperatures and a plurality of substrate compensation voltages corresponding to the plurality of working temperatures; and transmitting the current substrate compensation voltage to a substrate end of an OLED element driver element included in each of the pixel circuits. Thus, when the method of the present invention is applied, the higher the detected operating temperature, the higher the base compensation voltage used to adjust the driving current. In this way, the current density is controlled to achieve the beneficial effect of maintaining the brightness of the OLED display panel without becoming brighter as the operating temperature increases.

Description

Brightness compensation method, display driver chip, display device, and information processing device

The present invention relates to the technical field of display devices, and more particularly to a brightness compensation method that can perform voltage compensation on a plurality of light-emitting elements of a display panel according to the ambient temperature.

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.

FIG. 1 is a block diagram of a known OLED display device. As shown in FIG. 1 , the known OLED display device 1a mainly includes: an OLED display panel 11a and at least one display driver chip 12a, wherein the OLED display panel 11a includes M×N pixel circuits 111a, M×N OLED elements 112a, M gate lines 11Ga, and N source lines 11Sa. FIG. 2 is a block diagram of the pixel circuit shown in FIG. 1 . As shown in FIG. 1 and FIG. 2 , each of the pixel circuits 111a includes: a data writing unit 11Wa, a storage capacitor unit 11Ca, an OLED element driving unit 11Da, and a light emission duration control unit 11Ea.

FIG3 is a graph of brightness versus driving voltage. As shown in FIG2 and FIG3, when the operating temperature is 25°C, if the driving voltage is 8V, the brightness of the driven OLED element 112a is about 1500 cd/ ^cm2 . However, after the OLED element 112a is lit for a period of time, the operating temperature will continue to rise. As shown in FIG2 and FIG3, when the operating temperature is 65°C, even if the driving voltage is still maintained at 8V, the brightness of the driven OLED element 112a will rise to 3800 cd/ ^cm2 .

On the other hand, FIG4 is a graph of current density relative to driving voltage. As shown in FIG2 and FIG4, when the operating temperature is 25°C, if the driving voltage is 8V, the current density flowing through the driven OLED element 112a is about 25 mA/ ^cm2 . However, after the OLED element 112a is lit for a period of time, the operating temperature continues to rise. As shown in FIG2 and FIG4, when the operating temperature is 65°C, even if the driving voltage is still maintained at 8V, the current density flowing through the driven OLED element 112a rises to 65 mA/ ^cm2 .

In summary, due to its material properties, the brightness (current density) of the OLED element 112a increases with the increase of the operating temperature. Therefore, for the user operating the OLED display device 1a, he will obviously feel that the brightness of the OLED display panel 11a gradually becomes brighter with the increase of the use time, thereby reducing the user's experience of the OLED display device 1a.

From the above description, it can be seen that a brightness compensation method is urgently needed in the field.

The main purpose of the present invention is to provide a brightness compensation method, which is executed by a display driver chip, thereby performing a brightness compensation on an OLED display panel according to a current operating temperature. When the method of the present invention is applied, when the detected operating temperature is higher, the base compensation voltage used to adjust the driving current also becomes higher accordingly, thereby adjusting the current density to achieve the beneficial effect of maintaining the brightness of the OLED display panel without becoming brighter as the operating temperature increases.

To achieve the above-mentioned purpose, the present invention proposes an embodiment of the brightness compensation method, which is executed by a display driver chip to perform a brightness compensation on an OLED display panel including M×N pixel units; wherein each pixel unit includes a pixel circuit and an OLED element, and the brightness compensation method includes: Finding a current substrate compensation voltage from a lookup table according to a current operating temperature, wherein the lookup table includes a plurality of operating temperatures and a plurality of substrate compensation voltages corresponding to the plurality of operating temperatures; and Transmitting the current substrate compensation voltage to a substrate end of an OLED element driver element included in each pixel circuit.

In a feasible embodiment, the OLED element driving element is a P-type TFT element, and a substrate voltage received by the substrate end is the sum of a first driving voltage and the substrate compensation voltage.

In another feasible embodiment, the OLED element driving element is an N-type TFT element, and a substrate voltage received by the substrate end is the substrate compensation voltage.

In one embodiment, the OLED display panel further includes at least one temperature sensor, and the display driver chip is coupled to the at least one temperature sensor, and includes: A storage unit storing the lookup table; A low-dropout regulator (LDO); and A control unit coupling the temperature sensor, the storage unit and the low-dropout regulator; Wherein, the control unit completes the detection of the current working temperature through the temperature sensor, and finds the current substrate compensation voltage from the lookup table according to the current working temperature; Wherein, the control unit controls the low-dropout regulator to generate the current substrate compensation voltage and transmit it to the substrate end of each OLED element driver element.

Furthermore, the present invention also proposes an embodiment of a display driver chip, which is used to form a display device together with an OLED display panel including M×N pixel units, and each pixel unit includes a pixel circuit and an OLED element; its characteristic is that the display driver chip executes a brightness compensation method, thereby performing a brightness compensation on the OLED display panel according to a current operating temperature; the brightness compensation method includes the following steps: Finding a current substrate compensation voltage from a lookup table according to the current operating temperature, wherein the lookup table includes a plurality of operating temperatures and a plurality of substrate compensation voltages corresponding to the plurality of operating temperatures; and The current substrate compensation voltage is transmitted to a substrate end of an OLED element driving element included in each of the pixel circuits.

In a feasible embodiment, the OLED element driving element is a P-type TFT element, and a substrate voltage received by the substrate end is the sum of a first driving voltage and the substrate compensation voltage.

In another feasible embodiment, the OLED element driving element is an N-type TFT element, and a substrate voltage received by the substrate end is the substrate compensation voltage.

In one embodiment, the OLED display panel further includes at least one temperature sensor, and the display driver chip is coupled to the at least one temperature sensor, and includes: A storage unit storing the lookup table; A low-dropout regulator (LDO); and A control unit coupling the temperature sensor, the storage unit and the low-dropout regulator; Wherein, the control unit completes the detection of the current working temperature through the temperature sensor, and finds the current substrate compensation voltage from the lookup table according to the current working temperature; Wherein, the control unit controls the low-dropout regulator to generate the current substrate compensation voltage and transmit it to the substrate end of each OLED element driver element.

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

Furthermore, the present invention also provides an information processing device, which is characterized in that it has a display device, and the display device includes an OLED display panel and at least one display driver chip of the present invention as described above. In one embodiment, the information processing device is an electronic device selected from the group consisting of a smart phone, a smart watch, a tablet computer, a laptop computer, an all-in-one computer, a smart TV, a car entertainment device, an access control device, a clock-in device, and an electronic door lock.

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.

FIG5 is a block diagram of a display device to which a brightness compensation method of the present invention is applied. As shown in FIG5, the display device 1 mainly includes: an OLED display panel 11 and at least one display driver chip 12, wherein the OLED display panel 11 includes M×N pixel circuits 111, M×N OLED elements 112, M gate lines 11G, and N source lines 11S. FIG6 is a block diagram of the pixel circuit shown in FIG5. As shown in FIG5 and FIG6, each of the pixel circuits 111 includes: a data writing unit 11W, a storage capacitor unit 11C including a storage capacitor Cst, an OLED element driving unit 11D, and a light emission duration control unit 11E. In a feasible embodiment, the display device 1 can be integrated into an electronic device, and the electronic device can be but is not limited to a smart phone, a smart watch, a tablet computer, a laptop computer, an all-in-one computer, a smart TV, a car entertainment device, an access control device, a clock-in device, or an electronic door lock.

A brightness compensation method of the present invention is integrated into the display driver chip 12 in the form of a computer-readable program code or algorithm file, so that the display driver chip 12 is executed to perform a brightness compensation on the OLED display panel 11 according to a current operating temperature, thereby achieving the beneficial effect of maintaining the brightness of the OLED display panel 11 from becoming brighter as the operating temperature increases.

FIG7 is a flow chart of a brightness compensation method of the present invention. As shown in FIG6 and FIG7, the brightness compensation method of the present invention first performs step S1: according to a current operating temperature, a current substrate compensation voltage is found from a lookup table, wherein the lookup table includes a plurality of operating temperatures and a plurality of substrate compensation voltages corresponding to the plurality of operating temperatures. Further, the method flow is to perform step S2: the current substrate compensation voltage is transmitted to a substrate end of an OLED element driving element included in each of the pixel circuits 111.

FIG8 is a first circuit topology diagram of the OLED element driving unit shown in FIG6. As shown in FIG8, the OLED element driving unit 11D includes an OLED element driving element, and the OLED element driving element is a P-type TFT element. In addition, one end of the storage capacitor Cst is coupled to a common point between the gate terminal of the P-type TFT element and the data writing unit 11W, and the other end of the storage capacitor Cst is coupled to a first driving voltage ELVDD. On the other hand, the source terminal of the OLED element driving element is coupled to the first driving voltage ELVDD, and the drain terminal thereof is coupled to the OLED element 112. As can be seen from FIG. 8 , since the OLED element driving element is a P-type TFT element, after the current substrate compensation voltage is transmitted to a substrate end of the OLED element driving element included in the pixel circuit 111, a substrate voltage VBp received by the substrate end is the sum of a first driving voltage ELVDD and the substrate compensation voltage Vcp, for example: ELVDD+2V.

FIG9 is a second circuit topology diagram of the OLED element driving unit shown in FIG6. As shown in FIG9, the OLED element driving unit 11D includes an OLED element driving element, and the OLED element driving element is also a P-type TFT element. The difference is that one end of the storage capacitor Cst is coupled to the gate terminal of the P-type TFT element and a display data voltage VDATA, and the other end of the storage capacitor Cst is coupled to the ground. On the other hand, the source terminal of the OLED element driving element is coupled to the first driving voltage ELVDD, and its drain terminal is coupled to the OLED element 112. As can be seen from FIG. 9 , since the OLED element driving element is a P-type TFT element, after the current substrate compensation voltage is transmitted to a substrate end of the OLED element driving element included in the pixel circuit 111, a substrate voltage VBp received by the substrate end is the sum of a first driving voltage ELVDD and the substrate compensation voltage Vcp, for example: ELVDD+2V.

On the other hand, FIG10 is a third circuit topology diagram of the OLED element driving unit shown in FIG6. As shown in FIG10, the OLED element driving unit 11D includes an OLED element driving element, and the OLED element driving element is an N-type TFT element. In addition, one end of the storage capacitor Cst is coupled to a common connection point between the gate terminal of the N-type TFT element and the data writing unit 11W, and the other end of the storage capacitor Cst is coupled to a common connection point between the source terminal of the N-type TFT element and the OLED element 112. On the other hand, the drain terminal of the OLED element driving element is coupled to the first driving voltage ELVDD, and its source terminal is coupled to the OLED element 112. As can be seen from FIG. 10 , since the OLED element driving element is an N-type TFT element, after the current substrate compensation voltage is transmitted to a substrate end of the OLED element driving element included in the pixel circuit 111, a substrate voltage VBn received by the substrate end is the substrate compensation voltage Vcn, for example: -2V.

FIG11 is a fourth circuit topology diagram of the OLED element driving unit shown in FIG6. As shown in FIG11, the OLED element driving unit 11D includes an OLED element driving element, and the OLED element driving element is also an N-type TFT element. The difference is that one end of the storage capacitor Cst is coupled to between the gate terminal of the N-type TFT element and a display data voltage VDATA, and the other end of the storage capacitor Cst is coupled to the ground. On the other hand, the drain terminal of the OLED element driving element is coupled to the first driving voltage ELVDD, and its source terminal is coupled to the OLED element 112. As can be seen from FIG. 11 , since the OLED element driving element is an N-type TFT element, after the current substrate compensation voltage is transmitted to a substrate end of the OLED element driving element included in the pixel circuit 111, a substrate voltage VBn received by the substrate end is the substrate compensation voltage Vcn, for example: -2V.

To explain in more detail, as shown in FIG5 , the display driver chip 12 is internally provided with a storage unit 121 for storing the lookup table, a low-dropout regulator (LDO) 122, and a control unit 120 coupled to the storage unit 121 and the LDO 122. On the other hand, the control unit 120 is also coupled to at least one temperature sensor included in the OLED display panel 11. During normal operation, the control unit 120 completes the detection of a current operating temperature of the LED display panel 11 through the temperature sensor, and searches out a corresponding current substrate compensation voltage from the lookup table according to the detected current operating temperature. Then, the control unit 120 controls the LDO 122 to generate the current substrate compensation voltage and transmit it to the substrate end of each of the OLED device driving elements. This arrangement can ensure that the substrate compensation voltage is stably supplied to the substrate end of the OLED device driving element.

Thus, the brightness compensation method of the present invention has been fully and clearly described above; and, from the above, it can be known that the present invention has the following advantages:

(1) The present invention provides a brightness compensation method, which is executed by a display driver chip, thereby performing a brightness compensation on an OLED display panel according to a current operating temperature. When the method of the present invention is applied, when the detected operating temperature is higher, the base compensation voltage used to adjust the drive current also becomes higher accordingly, thereby regulating the current density to achieve the beneficial effect of maintaining the brightness of the OLED display panel without becoming brighter as the operating temperature increases.

(2) In addition, the present invention also provides a display device, which includes: an OLED display panel and at least one display driver chip; the display driver chip executes a brightness compensation method of the present invention as described above, thereby performing a brightness compensation on the OLED display panel according to a current working temperature. Furthermore, the present invention also provides an information processing device, which is characterized by having the display device of the present invention as described above.

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 technology 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 display panel 111a: pixel circuit 112a: OLED element 11Ga: gate line 11Sa: source line 12a: display driver chip 11Ca: storage capacitor unit 11Wa: data writing unit 11Da: OLED element driver unit 11Ea: luminescence duration control unit 1: display device 11: OLED display panel 111: pixel circuit 112: OLED element 11G: gate line 11S: source line 12: display driver chip 120: control unit 121: storage unit 122: LDO 11C: storage capacitor unit 11W: Data writing unit 11D: OLED element driving unit 11E: Luminous duration control unit S1: Find a current substrate compensation voltage from a lookup table according to a current working temperature S2: Transmit the current substrate compensation voltage to a substrate end of an OLED element driving element included in each of the pixel circuits

FIG. 1 is a block diagram of a known OLED display device; FIG. 2 is a block diagram of a pixel circuit shown in FIG. 1; FIG. 3 is a curve diagram of brightness relative to driving voltage; FIG. 4 is a curve diagram of current density relative to driving voltage; FIG. 5 is a block diagram of a display device applying a brightness compensation method of the present invention; FIG. 6 is a block diagram of a pixel circuit shown in FIG. 5; FIG. 7 is a flow chart of a brightness compensation method of the present invention; FIG. 8 is a first circuit topology diagram of the OLED element driving unit shown in FIG. 6; FIG. 9 is a second circuit topology diagram of the OLED element driving unit shown in FIG. 6; FIG. 10 is a third circuit topology diagram of the OLED element driving unit shown in FIG. 6; and FIG11 is a fourth circuit topology diagram of the OLED element driving unit shown in FIG6.

S1: Find a current base compensation voltage from a lookup table based on a current operating temperature

S2: Transmit the current substrate compensation voltage to a substrate end of an OLED element driving element included in each pixel circuit

Claims (4)

A brightness compensation method is implemented by a display driver chip to perform brightness compensation on an OLED display panel including M×N pixel units; wherein each pixel unit includes a pixel circuit and an OLED element, and the brightness compensation method includes: searching a current substrate compensation voltage from a lookup table according to a current operating temperature, wherein the lookup table includes a plurality of operating temperature values. The method comprises: determining a plurality of substrate compensation voltages corresponding to the plurality of operating temperatures; and transmitting the current substrate compensation voltage to a substrate end of an OLED element driving element included in each of the pixel circuits, wherein the OLED element driving element is a P-type TFT element, and a substrate voltage received by the substrate end is a sum of a first driving voltage and the substrate compensation voltage; or the OLED element driving element is connected to the substrate end of the pixel circuit; The LED element driving element is an N-type TFT element, and a substrate voltage received by the substrate end is the substrate compensation voltage; wherein the OLED display panel further includes at least one temperature sensor, and the display driving chip is coupled to the at least one temperature sensor, and includes: a storage unit storing the lookup table; a low voltage difference linear regulator; and a control unit coupled to the temperature sensor. The control unit comprises a temperature sensor, a storage unit and a low voltage difference linear regulator; wherein the control unit detects the current working temperature through the temperature sensor, finds the current substrate compensation voltage from the lookup table according to the current working temperature, and drives the low voltage difference linear regulator to generate the current substrate compensation voltage and transmit it to the substrate end of each OLED element driving element. A display driver chip is used to form a display device together with an OLED display panel including M×N pixel units, and each pixel unit includes a pixel circuit and an OLED element; the display driver chip executes a brightness compensation method, thereby performing a brightness compensation on the OLED display panel according to a current working temperature; the brightness compensation method includes the following steps: according to the current working temperature The method further comprises: finding a current substrate compensation voltage from a lookup table according to the operating temperature, wherein the lookup table includes a plurality of operating temperatures and a plurality of substrate compensation voltages corresponding to the plurality of operating temperatures; and transmitting the current substrate compensation voltage to a substrate end of an OLED element driving element included in each of the pixel circuits, wherein the OLED element driving element is a P-type TFT element, and a substrate voltage received by the substrate end is is the sum of a first driving voltage and the substrate compensation voltage; or the OLED element driving element is an N-type TFT element, and a substrate voltage received by the substrate end is the substrate compensation voltage; wherein the OLED display panel further includes at least one temperature sensor, and the display driving chip is coupled to the at least one temperature sensor, and includes: a storage unit storing the lookup table; a low voltage difference linear regulator; and a The control unit is coupled to the temperature sensor, the storage unit and the low voltage difference linear regulator; wherein the control unit detects the current working temperature through the temperature sensor, finds the current substrate compensation voltage from the lookup table according to the current working temperature, and drives the low voltage difference linear regulator to generate the current substrate compensation voltage and transmit it to the substrate end of each OLED element driving element. A display device, characterized in that it includes an OLED display panel and at least one display driver chip as described in claim 2. An information processing device is characterized in that it has a display device, and the display device includes an OLED display panel and at least one display driver chip as described in claim 2.

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