# US 11,029,545 B2 · Thin film transistor liquid crystal display (TFT-LCD) and the driving circuit and switching power supply thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,545 B2 - Document ID: US11029545B2 - Status: Granted - Kind: B2 - Application number: 16/083,391 - Filed: 2018-07-06 - Published: 2020-10-29 - Granted: 2021-06-08 - Earliest claimed: 2018-05-18 - Assignees: Shenzhen China Star Optoelectronics Technology Co., Ltd. - Applicants: Shenzhen China Star Optoelectronics Technology Co., Ltd. - Inventors: Yuntao Li - Web page: https://patentgrep.com/patent/US11029545B2 ## CPC - G02F 1/13306: {Circuit arrangements or driving methods for the control of single liquid crystal cells (G02F1/132, G02F1/133382 take precedence)} - G02F 1/1368: in which the switching element is a three-electrode device {(G02F1/136277 takes precedence)} - G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)} - H02M 1/44: Circuits or arrangements for compensating for electromagnetic interference in converters or inverters - H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators - G09G 2310/08: Details of timing specific for flat panels, other than clock recovery - G09G 2330/021: Power management, e.g. power saving - G09G 2330/06: Handling electromagnetic interferences [EMI], covering emitted as well as received electromagnetic radiation - 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 - 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) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) ## Abstract The present disclosure relates to a TFT-LCD and the driving circuit and the switching power supply thereof. The switching power supply includes a PWM controller, an electronic signal generator, and a field effect transistor. The output pins of the electronic signal generator being configured to output voltage signals that vary periodically between multiple voltage ranges. The frequency selection pins of the PWM controller and the output pins of the electronic signal generator are connected to receive the voltage signals from the electronic signal generator, and the PWM controller outputs switching signals of a predetermined frequency through at least one output pin according to a voltage range of the voltage signals received by the frequency selection pins. A gate pin of the FET connects to output pins of the PWM controller, and a source pin of the FET is grounded. ## Claims ### Claim 1 A switching power supply, comprising: a pulse width modulation (PWM) controller, an electronic signal generator, and a field effect transistor (FET); wherein an output pin of the electronic signal generator is configured to output a voltage signal that varies periodically between multiple voltage ranges, such that the multiple voltage ranges are sequentially assigned to the voltage signal; wherein a frequency selection pin of the PWM controller and the output pin of the electronic signal generator are connected to receive the voltage signal from the electronic signal generator, and the PWM controller outputs a switching signal through at least one output pin according to the voltage signal of the electronic signal generator received by the frequency selection pin; wherein a gate pin of the FET connects to output pin of the PWM controller, and a source pin of the FET is grounded; wherein the switching signal output from the PWM controller varies periodically according to the periodic variation of the voltage signal output from the electronic signal generator and a frequency of the switching signal of the PWM controller varies periodically between multiple values respectively corresponding to the multiple voltage ranges of the voltage signal of the electronic signal generator, wherein a cycle of the multiple values of the frequency of the switch signal of the PWM controller is periodically repeated; wherein the multiple voltage ranges comprise a first voltage range and a second voltage range and the voltage signal varies periodically between the first voltage range and the second range and a cycle of the first voltage range and the second voltage periodically repeated; and wherein the first voltage range is 0 to 0.7V and the second voltage range is 2.7V to 3.3 V; the frequency of the switching signal of the PWM controller corresponding to the first voltage range is 500 kHz, and the frequency of the switching signal of the PWM controller corresponding to the second voltage range is 750 kHz. ### Claim 2 (depends on 1) The switching power supply as claimed in claim 1, wherein the voltage signal is a square wave signal. ### Claim 3 (depends on 2) The switching power supply as claimed in claim 2, wherein the voltage signal is a clock signal. ### Claim 4 (depends on 1) The switching power supply as claimed in claim 1, wherein the switching power supply further comprises an inductor connected in series between an input power source of the switching power supply and a drain pin of the FET. ### Claim 5 (depends on 1) The switching power supply as claimed in claim 1, wherein the switching power supply further comprises a crystal triode, wherein a collector pin and an emitter pin of the crystal triode are connected to a drain pin of the FET, and a base pin of the crystal triode is connected to an output pin of the switching power supply. ### Claim 6 (depends on 5) The switching power supply as claimed in claim 5, wherein the crystal triode is a PNP type crystal triode. ### Claim 7 A driving circuit of TFT-LCD, comprising: a switching power supply comprising a pulse width modulation (PWM) controller, an electronic signal generator, and a field effect transistor (FET); wherein an output pin of the electronic signal generator is configured to output a voltage signal that varies periodically between multiple voltage ranges, such that the multiple voltage ranges are sequentially assigned to the voltage signal; wherein a frequency selection pin of the PWM controller and the output pin of the electronic signal generator are connected to receive the voltage signal from the electronic signal generator, and the PWM controller outputs a switching signal through at least one output pin according to the voltage signal of the electronic signal generator received by the frequency selection pin; wherein a gate pin of the FET connects to output pin of the PWM controller, and a source pin of the FET is grounded; wherein the switching signal output from the PWM controller varies periodically according to the periodic variation of the voltage signal output from the electronic signal generator and a frequency of the switching signal of the PWM controller varies periodically between multiple values respectively corresponding to the multiple voltage ranges of the voltage signal of the electronic signal generator, wherein a cycle of the multiple values of the frequency of the switch signal of the PWM controller is periodically repeated; wherein the multiple voltage ranges comprise a first voltage range and a second voltage range and the voltage signal varies periodically between the first voltage range and the second range and a cycle of the first voltage range and the second voltage periodically repeated; and wherein the first voltage range is 0 to 0.7V and the second voltage range is 2.7V to 3.3 V; the frequency of the switching signal of the PWM controller corresponding to the first voltage range is 500 kHz, and the frequency of the switching signal of the PWM controller corresponding to the second voltage range is 750 kHz. ### Claim 8 (depends on 7) The driving circuit as claimed in claim 7, wherein the voltage signal is a square wave signal. ### Claim 9 (depends on 8) The driving circuit as claimed in claim 8, wherein the voltage signal is a clock signal. ### Claim 10 (depends on 7) The driving circuit as claimed in claim 7, wherein the switching power supply further comprises an inductor connected in series between an input power source of the switching power supply and a drain pin of the FET. ### Claim 11 (depends on 7) The driving circuit as claimed in claim 7, wherein the switching power supply further comprises a crystal triode, wherein a collector pin and an emitter pin of the crystal triode are connected to a drain pin of the FET, and a base pin of the crystal triode is connected to an output pin of the switching power supply. ### Claim 12 (depends on 11) The driving circuit as claimed in claim 11, wherein the crystal triode is a PNP type crystal triode. ### Claim 13 (depends on 7) A TFT-LCD, which comprises the driving circuit as claimed in claim 7.