# US 8,786,305 B2 · Test circuit and test method for detecting electrical defect in TFT-LCD > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,305 B2 - Document ID: US8786305B2 - Status: Granted - Kind: B2 - Application number: 13/297,711 - Filed: 2011-11-16 - Published: 2012-05-17 - Granted: 2014-07-22 - Earliest claimed: 2010-11-17 - Assignees: Beijing Boe Optoelectronics Technology Co., Ltd. - Applicants: Yun Dong - Inventors: Yun Dong - Web page: https://patentgrep.com/patent/US8786305B2 ## CPC - G09G 3/006: {Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays (testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309)} - G02F 1/1309: {Repairing; Testing} - G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)} - 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) - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract The present disclosure discloses a test circuit and a test method for detecting a TFT-LCD electrical defect, which relates to the field of liquid crystal display and is able to distinguish effectively between a capacitive defect and a TFT defect. The test circuit for detecting a TFT-LCD electrical defect includes: a test apparatus connected with the input terminals of a first reference voltage and a second reference voltage corresponding to the same gray scale, the test apparatus controls the output terminals of the first reference voltage and the second reference voltage to output a constant voltage to a data line. The present disclosure can be applied to a liquid crystal display. ## Claims ### Claim 1 A test circuit for detecting a thin film transistor liquid crystal display (TFT-LCD) electrical defect, comprising a test apparatus connected with the input terminals of a first reference voltage and a second reference voltage corresponding to the same gray scale, the test apparatus controlling the output terminals of the first reference voltage and the second reference voltage to output a constant voltage to a data line. ### Claim 2 (depends on 1) The test circuit according to claim 1, wherein the test apparatus comprises: a first switch controlled by a first control signal, the first switch being connected with the input terminal of the first reference voltage or the second reference voltage; and a second switch controlled by a second control signal, the two terminals of the second switch being connected between the input terminals of the first reference voltage and the second reference voltage respectively. ### Claim 3 (depends on 2) The test circuit according to claim 2, wherein when testing, the first control signal controls the first switch to be open so as to disconnect the circuit of the input terminal of the first reference voltage or the second reference voltage; the second control signal controls the second switch to be closed so as to connect the circuit between the input terminals of the first reference voltage and the second reference voltage. ### Claim 4 (depends on 1) The test circuit according to claim 1, wherein the test apparatus comprises a selection switch controlled by a selection control signal, a fixed connection terminal of the selection switch being connected with the input terminal of the first reference voltage or the second reference voltage, and a selection connection terminal of the selection switch selecting to connect the circuit between the input terminal of the first reference voltage or the second reference voltage and the fixed connection terminal of the selection switch, or selecting to connect the circuit between the input terminals of the first reference voltage and the second reference voltage. ### Claim 5 (depends on 4) The test circuit according to claim 4, wherein when testing, the selection connection terminal of the selection switch connects the circuit between the input terminals of the first reference voltage and the second reference voltage. ### Claim 6 A test method of detecting a thin film transistor liquid crystal display (TFT-LCD) electrical defect, comprising: in each frame of picture, controlling both output terminals of a first reference voltage and a second reference voltage corresponding to the same gray scale to output a constant voltage to a data line. ### Claim 7 (depends on 6) The test method according to claim 6, after said controlling both output terminals of the first reference voltage and the second reference voltage corresponding to the same gray scale to output the constant voltage to the data line, further comprising: obtaining pictures in different gray scales by adjusting a common electrode voltage Vcom to adjust gray scales. ### Claim 8 (depends on 7) The test method according to claim 7, wherein the range of the gray scales is in L40˜L80 or L100˜L150. ### Claim 9 (depends on 6) The test method according to claim 6, wherein in each frame of picture, said controlling both output terminals of the first reference voltage and the second reference voltage corresponding to the same gray scale to output the constant voltage to the data line comprises: at the current frame, the numerical value of the voltage output to the data line is equal to that of the first reference voltage or the second reference voltage corresponding to the same gray scale; and at the next frame, the voltage output to the date line is the same as the voltage output to the data line at the previous frame. ### Claim 10 (depends on 7) The test method according to claim 7, wherein in each frame of picture, said controlling both output terminals of the first reference voltage and the second reference voltage corresponding to the same gray scale to output the constant voltage to the data line comprises: at the current frame, the numerical value of the voltage output to the data line is equal to that of the first reference voltage or the second reference voltage corresponding to the same gray scale; and at the next frame, the voltage output to the date line is the same as the voltage output to the data line at the previous frame. ### Claim 11 (depends on 8) The test method according to claim 8, wherein in each frame of picture, said controlling both output terminals of the first reference voltage and the second reference voltage corresponding to the same gray scale to output the constant voltage to the data line comprises: at the current frame, the numerical value of the voltage output to the data line is equal to that of the first reference voltage or the second reference voltage corresponding to the same gray scale; and at the next frame, the voltage output to the date line is the same as the voltage output to the data line at the previous frame.