# US 7,746,330 B2 · Circuit and method for improving image quality of a liquid crystal display > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,330 B2 - Document ID: US7746330B2 - Status: Granted - Kind: B2 - Application number: 11/317,814 - Filed: 2005-12-22 - Published: 2007-06-28 - Granted: 2010-06-29 - Earliest claimed: 2005-12-22 - Assignees: Au Optronics Corporation - Inventors: Chia-Wei Yu; Hung-Min Shih - Web page: https://patentgrep.com/patent/US7746330B2 ## CPC - G09G 3/3406: {Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336)} - G09G 2310/08: Details of timing specific for flat panels, other than clock recovery - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - 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 circuit and method of reducing noises for improving quality of display in a liquid crystal display (LCD) system. The LCD system includes an LCD panel and at least one lamp. In operation the LCD system is supplied with a vertical synchronization signal and a horizontal synchronization signal. In one embodiment, the method comprises the steps of determining a lamp driving frequency for the at least one lamp responsive to the horizontal synchronization signal, and generating a lamp driving signal with the lamp driving frequency to be received by the at least one lamp for producing light, wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) and ⁢ ⁢ H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ## Claims ### Claim 1 A method of reducing noises for improving quality of display in a liquid crystal display (LCD) system, wherein the LCD system includes an LCD panel, at least one lamp for producing light to illuminate the LCD panel, and wherein in operation the LCD system is supplied with a video signal, a vertical synchronization signal and a horizontal synchronization signal, comprising the steps of: a. determining a lamp driving frequency for the at least one lamp responsive to the horizontal synchronization signal; and b. generating a lamp driving signal with the lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal, wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ### Claim 2 (depends on 1) The method of claim 1, wherein the determining step comprises the step of calculating the lamp driving frequency, flamp, from the formulae (1) and (2). ### Claim 3 (depends on 1) The method of claim 1, wherein the lamp driving frequency, flamp, is determinable in a range of flamp(min) to flamp(max), flamp(min) being a minimum driving frequency for the at least one lamp, and flamp(max) being a maximum driving frequency for the at least one lamp, respectively. ### Claim 4 (depends on 3) The method of claim 3, wherein the determining step comprises the steps of: a. obtaining a first number, n1, from the formula n1=(m flamp(min)/Hsync+1)2; b. obtaining a second number, n2, from the formula n2=(m flamp(max)/Hsync+1)/2; c. obtaining an integer N that is the smallest integer between the first number n1 and the second number n2; and d. determining the lamp driving frequency, flamp, for δ=0 from the formula flamp=((2N−1)Hsync)/m. ### Claim 5 (depends on 4) The method of claim 4, wherein the LCD system has a clock with a crystal oscillation frequency, fcrystan, and the determining step further comprises the steps of: a. obtaining an intermediate counting number, fcnt, from the formula fcnt=Integer[(fcrystal/flamp)/2]; and b. determining a real time lamp driving frequency, flamp, from the formula flamp=(fcrystal/fcnt)/2. ### Claim 6 (depends on 4) The method of claim 4, further comprises the step of constructing a predetermined table, wherein the predetermined table contains a first row of data, each element of the first row of data representing a possible frequency of the horizontal synchronization signal in unit of (Hz), and a second row of data, each element of the second row of data representing a corresponding lamp driving frequency, flamp, for δ=0 from the formula flamp=((2N−1)Hsync)/m. ### Claim 7 (depends on 1) The method of claim 1, wherein the determining step comprises the step of finding the lamp driving frequency, flamp, from the predetermined table for a given horizontal synchronization signal. ### Claim 8 A liquid crystal display (LCD) system, comprising: a. an LCD panel; b. at least one lamp for producing light to illuminate the LCD panel; and c. an inverter, wherein in operation the LCD system is supplied with a video signal, a vertical synchronization signal and a horizontal synchronization signal; wherein in response to the horizontal synchronization signal, the inverter generates a lamp driving signal with a lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal; and wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ### Claim 9 (depends on 8) The LCD system of claim 8, further comprising a control circuit for controlling the inverter, wherein the control circuit is capable of calculating the lamp driving frequency, flamp, from the formulae (1) and (2). ### Claim 10 (depends on 9) The LCD system of claim 9, wherein the control circuit comprises a complex programmable logic device. ### Claim 11 (depends on 8) The LCD system of claim 8, wherein the lamp driving frequency, flamp, is determinable in a range of flamp(min) to flamp(max), flamp(min) being a minimum driving frequency for the at least one lamp, andf flamp(max) being a maximum driving frequency for the at least one lamp, respectively. ### Claim 12 (depends on 8) The LCD system of claim 8, further comprising a clock with a crystal oscillation frequency, fcrystal, from which an intermediate counting number, fcnt, is obtainable from the formula fcnt=Integer[(fcrystal/flamp)/2], and a real time lamp driving frequency, flamp, is obtainable from the formula flamp=(fcrystal/fcnt)/2. ### Claim 13 (depends on 8) The LCD system of claim 8, further comprising a memory for containing a predetermined table, wherein the predetermined table contains a first column of data, each element of the first column of data representing a possible frequency of the horizontal synchronization signal in unit of (Hz), and a second column of data, each element of the second column of data representing a corresponding lamp driving frequency, flamp, for δ=0 from the formula flamp=((2N−1)Hsync)/m. ### Claim 14 (depends on 8) The LCD system of claim 8, wherein the inverter comprises a DC-to-AC inverter. ### Claim 15 (depends on 8) The LCD system of claim 8, wherein the LCD panel comprises a plurality of pixel elements arranged in a matrix for receiving the video signal. ### Claim 16 A circuit to be used in a liquid crystal display (LCD) system, wherein the LCD system includes an LCD panel, and at least one lamp for producing light to illuminate the LCD panel, comprising: a. an inverter; and b. a control circuit for controlling the inverter, wherein in operation the control circuit receives a horizontal synchronization signal and outputs a control signal to the inverter so as to generate a lamp driving signal with a lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal; and wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ### Claim 17 (depends on 16) The circuit of claim 16, wherein the inverter comprises a DC-to-AC inverter. ### Claim 18 (depends on 16) The circuit of claim 16, wherein the control circuit comprises a complex programmable logic device. ### Claim 19 A circuit to be used in a liquid crystal display (LCD) system, wherein the LCD system includes an LCD panel, and at least one lamp for producing light to illuminate the LCD panel, comprising: a. an inverter, wherein in operation and in response to a horizontal synchronization signal, the inverter generates a lamp driving signal with a lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal; and wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ### Claim 20 (depends on 19) The circuit of claim 19, wherein the inverter comprises a DC-to-AC inverter. ### Claim 21 A circuit to be used in a liquid crystal display (LCD) system, wherein the LCD system includes an LCD panel, and at least one lamp for producing light to illuminate the LCD panel, comprising an inverter, wherein in operation and in response to a horizontal synchronization signal, the inverter generates a lamp driving signal with a lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal; and wherein the lamp driving frequency is not a harmonic of the frequency of the horizontal synchronization signal; and wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency. ### Claim 22 (depends on 21) The circuit of claim 21, wherein the inverter comprises a DC-to-AC inverter. ### Claim 23 A method of reducing noises for improving quality of display in a liquid crystal display (LCD) system, wherein the LCD system includes an LCD panel, at least one lamp for producing light to illuminate the LCD panel, and wherein in operation the LCD system is supplied with a video signal, a vertical synchronization signal and a horizontal synchronization signal, comprising the step of generating a lamp driving signal with a lamp driving frequency to be received by the at least one lamp for producing light responsive to the lamp driving signal, wherein the lamp driving frequency is not a harmonic of the frequency of the horizontal synchronization signal; and wherein the following formulae (1) and (2) are satisfied: f lamp = 2 ⁢ n - 1 m ⁢ H sync + δ ( 1 ) H sync / m ≥ δ ≥ 0 ( 2 ) where Hsync is the frequency of the horizontal synchronization signal in unit of (Hz); flamp is the lamp driving frequency for the lamp driving signal in unit of (Hz); m, n=1, 2, 3, . . . , an integer; and δ indicates the permissible error of the lamp driving frequency.