# US 11,114,024 B2 · Method for maintaining LED brightness, LED driving circuit and display device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,114,024 B2 - Document ID: US11114024B2 - Status: Granted - Kind: B2 - Application number: 17/120,556 - Filed: 2020-12-14 - Published: 2021-06-17 - Granted: 2021-09-07 - Earliest claimed: 2019-12-17 - Assignees: Xianyang Caihong Optoelectronics Technology Co., Ltd - Applicants: Xianyang Caihong Optoelectronics Technology Co.,Ltd - Inventors: Yuyeh Chen - Web page: https://patentgrep.com/patent/US11114024B2 ## CPC - G09G 3/32: semiconductive, e.g. using light-emitting diodes [LED] - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - G09G 5/10: Intensity circuits - G09G 2300/0426: Layout of electrodes and connections - G09G 2300/0819: used for counteracting undesired variations, e.g. feedback or autozeroing - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - G09G 2320/0633: by amplitude modulation of the brightness of the illumination source - G09G 2360/142: the light being detected by light detection means within each pixel - G09G 2360/148: the light being detected by light detection means within each pixel - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A method for maintaining LED brightness is provided and exemplarily includes steps of: providing a LED driving circuit capable of performing current detection and compensation; performing a detection based on the LED driving circuit to obtain mapping relationships among current, brightness and voltage; and monitoring a current flowing through a LED driven by the LED driving circuit, and performing a compensation according to the monitored current and the mapping relationships to maintain brightness of the LED. Moreover, a LED driving circuit is also provided and includes first through fourth transistors and a capacitor. In addition, a display device adopting the method for maintaining LED brightness or the LED driving circuit is also provided. ## Claims ### Claim 1 A LED driving circuit comprising: a first transistor, a second transistor, a third transistor, a fourth transistor and a capacitor; wherein a drain of the first transistor and one terminal of the capacitor are electrically connected to a first reference node; a source of the second transistor, a gate of the first transistor and the other terminal of the capacitor are electrically connected to a second reference node; a source of the first transistor, a source of the third transistor and a source of the fourth transistor are electrically connected to a third reference node; a gate of the second transistor and a gate of the third transistor are electrically connected to a fourth reference node; a drain of the second transistor is electrically connected to a data signal input terminal; a drain of the third transistor is electrically connected to a detection signal receiving terminal; a drain of the fourth transistor is electrically connected to a detection current input terminal, and a gate of the fourth transistor is electrically connected to a detection control voltage terminal; the fourth reference node is electrically connected to a scan signal input terminal; and a LED is driven by the first transistor. ### Claim 2 (depends on 1) The LED driving circuit as claimed in claim 1, wherein a brightness detector is arranged beside the LED, the LED is a mini-LED, the LED driving circuit is applied to a mini-LED based display device, and the mini-LED based display device comprises a mini-LED display panel or a mini-LED backlight module of a liquid crystal display device. ### Claim 3 (depends on 2) The LED driving circuit as claimed in claim 2, wherein the first reference node is electrically connected to a voltage signal input terminal, the third reference is electrically connected to an anode of the LED, and a cathode of the LED is electrically connected to a common ground electrode. ### Claim 4 (depends on 3) The LED driving circuit as claimed in claim 3, wherein the LED driving circuit is performed with a current detection before leaving factory to obtain a mapping relationship between current and brightness; the current detection comprises: after the mini-LED based display device is produced, the fourth transistor of the LED driving circuit is used to acquire the mapping relationship between current and brightness; during the brightness detector is used to detect brightness of the LED, signals on the detection control voltage terminal and the scan signal input terminal are at logic high levels respectively, a signal on the data signal input terminal is at a logic low level, the fourth transistor is turned on, the LED driving circuit controls a current source outputs currents to flow through the LED, and meanwhile the brightness detector measures data of brightness of the LED, and thereby the mapping relationship between current and brightness and a mapping relationship between voltage and current are obtained. ### Claim 5 (depends on 3) The LED driving circuit as claimed in claim 3, wherein the LED driving circuit is performed with a real-time monitoring and compensation when it is normally working; the real-time monitoring and compensation comprise: during the mini-LED based display device is in normal use, the third transistor is used to acquire data of currents of the LED; during the LED driving circuit is normally working, signals on the scan signal input terminal, the data signal input terminal and the voltage signal input terminal are at logic high levels respectively, the first transistor, the second transistor and the third transistor all are turned on, the detection signal receiving terminal pulls out a voltage for calculating brightness of the LED, a controller of the mini-LED based display device meanwhile calculates instant brightness according to a mapping relationship between current and brightness and a mapping relationship between brightness and time, and the controller calculates a target voltage by reading and referring to a mapping relationship between voltage and current and considering the instant brightness and then adjusts a voltage on the voltage signal input terminal according to the target voltage to achieve the compensation. ### Claim 6 (depends on 2) The LED driving circuit as claimed in claim 2, wherein the first reference node, the source of the third transistor and the source of the fourth transistor are electrically connected to the third reference node; the third reference node is electrically connected to a cathode of the LED, and an anode of the LED is electrically connected to a voltage signal input terminal; and the source of the first transistor is electrically connected to a common ground electrode. ### Claim 7 (depends on 6) The LED driving circuit as claimed in claim 6, wherein the LED driving circuit is performed with a current detection before leaving factory to obtain a mapping relationship between current and brightness; the current detection comprises: after the mini-LED based display device is produced, the fourth transistor of the LED driving circuit is used to acquire the mapping relationship between current and brightness; during the brightness detector is used to detect brightness of the LED, signals on the detection control voltage terminal and the scan signal input terminal are at logic high levels respectively, a signal on the data signal input terminal is at a logic low level, the fourth transistor is turned on, the LED driving circuit controls a current source outputs currents to flow through the LED, and meanwhile the brightness detector measures data of brightness of the LED, and thereby the mapping relationship between current and brightness and a mapping relationship between voltage and current are obtained. ### Claim 8 (depends on 6) The LED driving circuit as claimed in claim 6, wherein the LED driving circuit is performed with a real-time monitoring and compensation when it is normally working; the real-time monitoring and compensation comprise: during the mini-LED based display device is in normal use, the third transistor is used to acquire data of currents of the LED; during the LED driving circuit is normally working, signals on the scan signal input terminal, the data signal input terminal and the voltage signal input terminal are at logic high levels respectively, the first transistor, the second transistor and the third transistor all are turned on, the detection signal receiving terminal pulls out a voltage for calculating brightness of the LED, a controller of the mini-LED based display device meanwhile calculates instant brightness according to a mapping relationship between current and brightness and a mapping relationship between brightness and time, and the controller calculates a target voltage by reading and referring to a mapping relationship between voltage and current and considering the instant brightness and then adjusts a voltage on the voltage signal input terminal according to the target voltage to achieve the compensation. ### Claim 9 A display device comprising a LED driving circuit and a LED, wherein the LED driving circuit comprises: a first transistor, a second transistor, a third transistor, a fourth transistor and a capacitor; a drain of the first transistor and one terminal of the capacitor are electrically connected to a first reference node; a source of the second transistor, a gate of the first transistor and the other terminal of the capacitor are electrically connected to a second reference node; a source of the first transistor, a source of the third transistor and a source of the fourth transistor are electrically connected to a third reference node; a gate of the second transistor and a gate of the third transistor are electrically connected to a fourth reference node; a drain of the second transistor is electrically connected to a data signal input terminal; a drain of the third transistor is electrically connected to a detection signal receiving terminal; a drain of the fourth transistor is electrically connected to a detection current input terminal, and a gate of the fourth transistor is electrically connected to a detection control voltage terminal; the fourth reference node is electrically connected to a scan signal input terminal; and the LED is driven by the first transistor. ### Claim 10 (depends on 9) The display device as claimed in claim 9, wherein a brightness detector is arranged beside the LED, the LED is a mini-LED, the display device is a mini-LED based display device, and the mini-LED based display device comprises a mini-LED display panel or a mini-LED backlight module of a liquid crystal display device. ### Claim 11 (depends on 10) The display device as claimed in claim 10, wherein the first reference node is electrically connected to a voltage signal input terminal, the third reference is electrically connected to an anode of the LED, and a cathode of the LED is electrically connected to a common ground electrode. ### Claim 12 (depends on 11) The display device as claimed in claim 11, wherein the LED driving circuit is performed with a current detection before leaving factory to obtain a mapping relationship between current and brightness; the current detection comprises: after the mini-LED based display device is produced, the fourth transistor of the LED driving circuit is used to acquire the mapping relationship between current and brightness; during the brightness detector is used to detect brightness of the LED, signals on the detection control voltage terminal and the scan signal input terminal are at logic high levels respectively, a signal on the data signal input terminal is at a logic low level, the fourth transistor is turned on, the LED driving circuit controls a current source outputs currents to flow through the LED, and meanwhile the brightness detector measures data of brightness of the LED, and thereby the mapping relationship between current and brightness and a mapping relationship between voltage and current are obtained. ### Claim 13 (depends on 11) The display device as claimed in claim 11, wherein the LED driving circuit is performed with a real-time monitoring and compensation when it is normally working; the real-time monitoring and compensation comprise: during the mini-LED based display device is in normal use, the third transistor is used to acquire data of currents of the LED; during the LED driving circuit is normally working, signals on the scan signal input terminal, the data signal input terminal and the voltage signal input terminal are at logic high levels respectively, the first transistor, the second transistor and the third transistor all are turned on, the detection signal receiving terminal pulls out a voltage for calculating brightness of the LED, a controller of the mini-LED based display device meanwhile calculates instant brightness according to a mapping relationship between current and brightness and a mapping relationship between brightness and time, and the controller calculates a target voltage by reading and referring to a mapping relationship between voltage and current and considering the instant brightness and then adjusts a voltage on the voltage signal input terminal according to the target voltage to achieve the compensation. ### Claim 14 (depends on 10) The display device as claimed in claim 10, wherein the first reference node, the source of the third transistor and the source of the fourth transistor are electrically connected to the third reference node; the third reference node is electrically connected to a cathode of the LED, and an anode of the LED is electrically connected to a voltage signal input terminal; and the source of the first transistor is electrically connected to a common ground electrode. ### Claim 15 (depends on 14) The display device as claimed in claim 14, wherein the LED driving circuit is performed with a current detection before leaving factory to obtain a mapping relationship between current and brightness; the current detection comprises: after the mini-LED based display device is produced, the fourth transistor of the LED driving circuit is used to acquire the mapping relationship between current and brightness; during the brightness detector is used to detect brightness of the LED, signals on the detection control voltage terminal and the scan signal input terminal are at logic high levels respectively, a signal on the data signal input terminal is at a logic low level, the fourth transistor is turned on, the LED driving circuit controls a current source outputs currents to flow through the LED, and meanwhile the brightness detector measures data of brightness of the LED, and thereby the mapping relationship between current and brightness and a mapping relationship between voltage and current are obtained. ### Claim 16 (depends on 14) The display device as claimed in claim 14, wherein the LED driving circuit is performed with a real-time monitoring and compensation when it is normally working; the real-time monitoring and compensation comprise: during the mini-LED based display device is in normal use, the third transistor is used to acquire data of currents of the LED; during the LED driving circuit is normally working, signals on the scan signal input terminal, the data signal input terminal and the voltage signal input terminal are at logic high levels respectively, the first transistor, the second transistor and the third transistor all are turned on, the detection signal receiving terminal pulls out a voltage for calculating brightness of the LED, a controller of the mini-LED based display device meanwhile calculates instant brightness according to a mapping relationship between current and brightness and a mapping relationship between brightness and time, and the controller calculates a target voltage by reading and referring to a mapping relationship between voltage and current and considering the instant brightness and then adjusts a voltage on the voltage signal input terminal according to the target voltage to achieve the compensation.