# US 10,770,011 B2 · Buffer circuit, panel module, and display driving method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,011 B2 - Document ID: US10770011B2 - Status: Granted - Kind: B2 - Application number: 15/969,763 - Filed: 2018-05-02 - Published: 2018-09-06 - Granted: 2020-09-08 - Earliest claimed: 2014-02-11 - Assignees: Novatek Microelectronics Corp. - Applicants: Novatek Microelectronics Corp. - Inventors: Chieh-An Lin; Chun-Yung Cho; Jhih-Siou Cheng - Web page: https://patentgrep.com/patent/US10770011B2 ## CPC - G09G 3/3614: {Control of polarity reversal in general} - G09G 3/3685: {Details of drivers for data electrodes} - G09G 2310/027: Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters - G09G 2310/0291: Details of output amplifiers or buffers arranged for use in a driving circuit - 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 buffer circuit, a display module, and a display driving method are disclosed. The buffer circuit comprises a first polarity buffer, a negative polarity buffer. The first polarity buffer receives a first supply voltage and a second supply voltage to output a first reference voltage to a first resistance string. The second supply voltage is less than the first supply voltage. The negative polarity buffer receives the second supply voltage and a third supply voltage to output a negative reference voltage to a negative resistance string. The third supply voltage is less than the second supply voltage. ## Claims ### Claim 1 A gamma circuit, comprising: a first polarity gamma buffer having a first power receiving terminal for receiving a first supply voltage, and having a second power receiving terminal for receiving a second supply voltage which is different from a ground voltage, to output a first reference voltage to a plurality of first resistance strings; a supply voltage output circuit for providing the second supply voltage; and a second polarity gamma buffer having a third power receiving terminal for receiving the second supply voltage and having a fourth power receiving terminal for receiving a third supply voltage lower than the second supply voltage, to output a second reference voltage to a plurality of second resistance strings, wherein the supply voltage output circuit comprises a medium voltage gamma buffer having an output terminal and a capacitor coupled to the output terminal of the medium voltage gamma buffer, the medium voltage gamma buffer comprises a first power supply for receiving the first supply voltage, a second power supply for receiving the third supply voltage and an output supply that outputs the second supply voltage, and each of the second power receiving terminal and the third power receiving terminal is coupled to the output terminal of the medium voltage gamma buffer, and wherein the output terminal of the medium gamma buffer is connected to an inverting input terminal of the medium voltage gamma buffer. ### Claim 2 (depends on 1) The gamma circuit according to claim 1, wherein the first polarity gamma buffer comprises: a first power supply for receiving the first supply voltage; a second power supply for receiving the second supply voltage; and a first output supply coupled to one of the first resistance strings. ### Claim 3 (depends on 2) The gamma circuit according to claim 2, wherein the second polarity gamma buffer comprises: a third power supply for receiving the second supply voltage; a fourth power supply for receiving the third supply voltage; and a second output supply coupled to one of the second resistance strings. ### Claim 4 (depends on 3) The gamma circuit according to claim 3, wherein the first polarity gamma buffer further comprises a first input stage and a first output stage; the first input stage is coupled to the first output stage; the first power supply and the second power supply are coupled to the first output stage; the second polarity gamma buffer comprises a second input stage and a second output stage; the second input stage is coupled to the second output stage; the third power supply and the fourth power supply are coupled to the second output stage. ### Claim 5 (depends on 4) The gamma circuit according to claim 4, wherein the first output stage comprises a first output transistor and a second output transistor; the second output transistor is coupled to the first output transistor; the first power supply is coupled to a source of the first output transistor; the second power supply is coupled to a source of the second output transistor; the second output stage comprises a third output transistor and a fourth output transistor; the fourth output transistor is coupled to the third output transistor; the third power supply is coupled to a source of the third output transistor; the fourth power supply is coupled to a source of the fourth output transistor. ### Claim 6 (depends on 3) The gamma circuit according to claim 3, wherein the first polarity gamma buffer further comprises a first input stage and a first output stage; the first input stage is coupled to the first output stage; the first power supply and the second power supply are coupled to the first input stage; the second polarity gamma buffer comprises a second input stage and a second output stage; the second input stage is coupled to the second output stage; the third power supply and the fourth power supply are coupled to the second input stage. ### Claim 7 (depends on 6) The gamma circuit according to claim 6, wherein the first input stage comprises a first current source, a second current source, a first input resistor, a second input resistor, a third input resistor and a fourth input resistor; the first input resistor and the second input resistor are coupled to a first current source; the third input resistor and the fourth input resistor are coupled to a second current source; the second power supply is coupled to the first current source; the first power supply is coupled to the second current source; the second input stage comprises a third current source, a fourth current source, a fifth input resistor, a sixth input resistor, a seventh input resistor and an eighth input resistor; the fifth input resistor and the sixth input resistor are coupled to a third current source; the seventh input resistor and the eighth input resistor are coupled to a fourth current source; the fourth power supply is coupled to the third current source; the third power supply is coupled to the fourth current source. ### Claim 8 (depends on 1) The buffer circuit according to claim 1, wherein the first resistance strings, the second resistance strings, the first polarity gamma buffer and the second polarity gamma buffer are in-built in a source driver chip. ### Claim 9 (depends on 1) The gamma circuit according to claim 1, wherein the first resistance strings and the second resistance strings are in-built in a source driver chip; the first polarity gamma buffer and the second polarity gamma buffer are not in-built in the source driver chip. ### Claim 10 (depends on 1) The gamma circuit according to claim 1, wherein the supply voltage output circuit is a low drop out (LDO) linear voltage regulator. ### Claim 11 (depends on 1) The gamma circuit according to claim 1, wherein the supply voltage output circuit is a back converter. ### Claim 12 (depends on 1) The gamma circuit according to claim 1, wherein resistance values of each of the first resistance strings are equivalent to resistance values of each of the second resistance strings. ### Claim 13 (depends on 1) The gamma circuit according to claim 1, wherein the first resistance string has different bias points from the second resistance string. ### Claim 14 (depends on 1) The gamma circuit according to claim 1, wherein a current deficiency is compensated by one of the first and second supply voltages. ### Claim 15 (depends on 1) The gamma circuit according to claim 1, wherein the first resistance strings are disposed in parallel and the second resistance strings are disposed in parallel, the first resistance strings comprise a plurality of resistance dividers, each of the resistance dividers has a first terminal and a second terminal, the first terminals of ith resistance dividers are connected with each other, the second terminals of ith resistance dividers are connected with each other, the second resistance strings comprise a plurality of resistance dividers, each of the resistance dividers has a first terminal and a second terminal, the first terminals of jth resistance dividers are connected with each other, the second terminals of jth resistance dividers are connected with each other. ### Claim 16 (depends on 1) The gamma circuit according to claim 1, wherein the medium voltage gamma buffer outputs the second supply voltage to an inversion terminal of the medium voltage buffer. ### Claim 17 (depends on 1) The gamma circuit according to claim 1, wherein resistance values of each of the first resistance strings are asymmetric to resistance values of each of the second resistance strings. ### Claim 18 (depends on 1) The gamma circuit according to claim 1, wherein the plurality of first resistance strings only receive the first reference voltage, and the plurality of second resistance strings only receive the second reference voltage. ### Claim 19 A buffer circuit, comprising: a first polarity gamma buffer having a first power receiving terminal for receiving a first supply voltage and having a second power receiving terminal for receiving a second supply voltage, to output a first reference voltage to at least one first resistance string; a supply voltage output circuit; and a second polarity gamma buffer having a third power receiving terminal for receiving the second supply voltage and having a fourth power receiving terminal for receiving a third supply voltage, to output a second reference voltage to a second resistance string, wherein the third supply voltage is less than the second supply voltage; wherein the supply voltage output circuit comprises a medium voltage gamma buffer having an output terminal and a capacitor coupled to the output terminal of the medium voltage gamma buffer, and the medium voltage gamma buffer comprises a first power supply for receiving the first supply voltage, a second power supply for receiving the third supply voltage and an output supply that outputs the second supply voltage, and each of the second power receiving terminal and the third power receiving terminal is coupled to the output terminal of the medium voltage gamma buffer, wherein the supply voltage output circuit provides the second supply voltage which is different from a ground voltage, and wherein the output terminal of the medium gamma buffer is connected to an inverting input terminal of the medium voltage gamma buffer. ### Claim 20 (depends on 19) The buffer circuit according to claim 19, wherein the second supply voltage is less than the first supply voltage, the first supply voltage is larger than the ground voltage, the second supply voltage is larger than the ground voltage, and the third supply voltage is equal to the ground voltage. ### Claim 21 (depends on 19) The buffer circuit according to claim 19, wherein the first polarity gamma buffer comprises: a first power supply for receiving the first supply voltage; a second power supply for receiving the second supply voltage; and a first output supply coupled to the first resistance string. ### Claim 22 (depends on 19) The buffer circuit according to claim 19, wherein the second polarity gamma buffer comprises: a third power supply for receiving the second supply voltage; a fourth power supply for receiving the third supply voltage; and a second output supply coupled to the second resistance string. ### Claim 23 (depends on 19) The buffer circuit according to claim 19, wherein the at least one first resistance string only receives the first reference voltage, and at least one second resistance string only receives the second reference voltage. ### Claim 24 A driving device, comprising: a first resistance string; a second resistance string; a first polarity gamma buffer having a first power receiving terminal for receiving a first supply voltage and having a second power receiving terminal for receiving a second supply voltage, to output a first reference voltage to the first resistance string, wherein the second supply voltage is different from a ground voltage; a supply voltage output circuit for providing the second supply voltage; a second polarity gamma buffer having a third power receiving terminal for receiving the second supply voltage and having a fourth power receiving terminal for receiving a third supply voltage, to output a second reference voltage to the second resistance string, wherein the third supply voltage is less than the second supply voltage; and a driving circuit for driving a panel according to the first reference voltage and the second reference voltage; wherein the supply voltage output circuit comprises a medium voltage gamma buffer having an output terminal and a capacitor coupled to the output terminal of the medium voltage gamma buffer, and the medium voltage gamma buffer comprises a first power supply for receiving the first supply voltage, a second power supply for receiving the third supply voltage and an output supply that outputs the second supply voltage, and each of the second power receiving terminal and the third power receiving terminal is coupled to the terminal of the medium voltage gamma buffer, and wherein the output terminal of the medium gamma buffer is connected to an inverting input terminal of the medium voltage gamma buffer. ### Claim 25 (depends on 24) The driving device according to claim 24, wherein the first resistance string only receives the first reference voltage, and the second resistance string only receives the second reference voltage.