# US 9,439,252 B1 · Driving LEDs in LCD backlight > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,252 B1 - Document ID: US9439252B1 - Status: Granted - Kind: B1 - Application number: 14/589,926 - Filed: 2015-01-05 - Granted: 2016-09-06 - Earliest claimed: 2011-09-07 - Assignees: IML International - Applicants: Integrated Memory Logic International - Inventors: Alberto Viviani - Web page: https://patentgrep.com/patent/US9439252B1 ## CPC - H05B 45/3725: Switched mode power supply [SMPS] - G02F 1/133603: {with LEDs} - G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines} - H05B 45/20: Controlling the colour of the light - H05B 45/46: having LEDs disposed in parallel lines - G09G 2330/021: Power management, e.g. power saving - G09G 2330/028: Generation of voltages supplied to electrode drivers in a matrix display other than LCD - H05B 45/375: using buck topology - H05B 45/38: using boost topology - H05B 45/385: using flyback topology - Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL - 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) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A backlight driver includes current sources that are connected between LED strings and a number of bias voltages. There can be any number of different bias voltages, each at a ground potential or higher voltage. The bias voltage is selected for a particular LED string in order to reduce a current drop across the current source. This reduces the power consumption of the current source and LED string. Heat dissipation is also reduced. ## Claims ### Claim 1 A system comprising: a first voltage input, second voltage input, and third voltage input; a first voltage generator circuit, coupled to the first voltage input and generating a first voltage output, wherein the first voltage output is at a higher voltage level than the first voltage input; a first source block comprising a first source node, coupled to a first end of a first plurality of serially-connected light emitting diodes; and a first multiplexing block coupled to the second and third voltage inputs, and a first multiplexing block output is coupled to the first source block, wherein the first voltage output and the first source node are configured to be coupled to a second end of the first plurality of serially-connected light emitting diodes. ### Claim 2 (depends on 1) The system of claim 1 comprising: a second source block comprising a second source node, coupled to a first end of a second plurality of serially-connected light emitting diodes; and a second multiplexing block coupled to the second and third voltage inputs, and a second multiplexing block output is coupled to the second source block, wherein the first voltage output and the second source node are configured to be coupled to a second end of the second plurality of serially-connected light emitting diodes. ### Claim 3 (depends on 2) The system of claim 2 wherein the first plurality of serially-connected light emitting diodes is coupled to the first voltage output, and the second plurality of serially-connected light emitting diodes is coupled to the first voltage output. ### Claim 4 (depends on 1) The system of claim 1 comprising a backlight for an display panel, wherein the backlight comprises the first plurality of serially-connected light emitting diodes. ### Claim 5 (depends on 1) The system of claim 1 wherein the first voltage generator circuit, first current source block, second current source block, first multiplexing block, and second multiplexing block reside on a single integrated circuit substrate. ### Claim 6 (depends on 3) The system of claim 3 wherein the first voltage generator circuit, first current source block, second current source block, first multiplexing block, and second multiplexing block reside on a single integrated circuit substrate, and the first and second plurality of serially-connected light emitting diodes do not reside on the same integrated circuit substrate where the first voltage generator circuit, first current source block, second current source block, first multiplexing block, and second multiplexing block reside. ### Claim 7 (depends on 1) The system of claim 1 wherein each light emitting diode in the first plurality of serially-connected light emitting diodes illuminates a white color only. ### Claim 8 (depends on 1) The system of claim 1 comprising: a first logic block coupled to the first multiplexing block, wherein the first logic block controls selection of the first multiplexing block. ### Claim 9 (depends on 8) The system of claim 8 comprising: a second logic block comprising inputs coupled to the first source node, and a second logic block output coupled to the first voltage generator circuit. ### Claim 10 (depends on 1) The system of claim 1 wherein the first voltage generator circuit comprises a boost converter circuit. ### Claim 11 (depends on 1) The system of claim 1 comprising: a second voltage generator circuit, coupled to the first voltage input and generating at least a second voltage output and a third voltage output, wherein the first voltage output is coupled to the second voltage input, and the second voltage output is coupled to the third voltage input. ### Claim 12 (depends on 11) The system of claim 11 wherein the second voltage generator circuit comprises a buck converter circuit. ### Claim 13 (depends on 1) A smartphone comprising the system of claim 1. ### Claim 14 (depends on 1) A television comprising the system of claim 1. ### Claim 15 A method comprising: providing a first voltage input, second voltage input, and third voltage input; using a first voltage generator circuit, coupled to the first voltage input and generating a first voltage output, wherein the first voltage output is at a higher voltage level than the first voltage input; coupling a first source block comprising a first source node to a first end of a first plurality of light emitting diodes coupled in series; and coupling a first multiplexing block to the second and third voltage inputs, and a first multiplexing block output is coupled to the first source block, wherein the first voltage output and the first source node are configured to be coupled to a second end of the first plurality of light emitting diodes coupled in series. ### Claim 16 (depends on 15) The method of claim 15 comprising: coupling a second source block comprising a second source node to a first end of a second plurality of light emitting diodes coupled in series; and coupling a second multiplexing block to the second and third voltage inputs, and coupling a second multiplexing block output to the second source block, wherein the first voltage output and the second source node are configured to be coupled to a second end of the second plurality of light emitting diodes coupled in series. ### Claim 17 (depends on 15) A method of operating a smartphone backlight comprising the method of claim 15, wherein the backlight comprises the first plurality of light emitting diodes. ### Claim 18 (depends on 15) A method of operating a television backlight comprising the method of claim 15, wherein the backlight comprises the first plurality of light emitting diodes. ### Claim 19 A system comprising: a backlight comprising a first plurality of light emitting diodes coupled in series; a first voltage input, second voltage input, and third voltage input; a first voltage generator circuit, coupled to the first voltage input and generating a first voltage output, wherein the first voltage output is at a higher voltage level than the first voltage input; a first source block comprising a first source node, coupled to a first end of the first plurality of light emitting diodes; and a first multiplexing block coupled to the second and third voltage inputs, and a first multiplexing block output is coupled to the first source block, wherein the first voltage output and the first source node are configured to be coupled to a second end of the first plurality of light emitting diodes. ### Claim 20 (depends on 19) The system of claim 19 wherein the backlight comprises a second plurality of light emitting diodes coupled in series, and the system comprises: a second source block comprising a second source node, coupled to a first end of a second plurality of light emitting diodes; and a second multiplexing block coupled to the second and third voltage inputs, and a second multiplexing block output is coupled to the second source block, wherein the first voltage output and the second source node are configured to be coupled to a second end of the second plurality of light emitting diodes.