# US 10,311,825 B2 · Display driver

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,311,825 B2
- Document ID: US10311825B2
- Status: Granted
- Kind: B2
- Application number: 15/044,090
- Filed: 2016-02-15
- Published: 2016-06-09
- Granted: 2019-06-04
- Earliest claimed: 2007-06-01
- Assignees: National Semiconductor Corporation
- Applicants: National Semiconductor Corporation
- Inventors: Christopher Ludden; Imre Knausz
- Web page: https://patentgrep.com/patent/US10311825B2

## CPC

- G09G 3/3696: {Generation of voltages supplied to electrode drivers}
- G09G 3/3607: {for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels (display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127)}
- G09G 3/3688: {suitable for active matrices only}
- H04N 9/69: for modifying the colour signals by gamma correction (controlling camera response for colour signals H04N23/83)
- G09G 2310/0297: Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
- G09G 2320/0276: for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
- G09G 2320/0673: for control of gamma adjustment, e.g. selecting another gamma curve
- G09G 2330/021: Power management, e.g. power saving
- 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)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An LC display driver including a gamma reference circuit to generate N gamma-compensated reference voltages based on at least one pre-defined gamma curve divided into M regions defined by M+1 breakpoint voltages, each generated by a range-region DAC coupled to a subset of voltage taps of a range resistor string (some subsets overlapping). An output circuit generates the N gamma-compensated reference voltages, and includes a reference resistor string with N reference voltage taps, and M+1 breakpoint locations to receive respective breakpoint voltages, the N reference voltage taps divided into M subsets corresponding to the M regions of the gamma curve, each of the M subsets of reference voltage taps forming a voltage divider. N output selector circuits output a corresponding one of the N gamma-compensated reference voltages based on a respective reference voltage tap and the associated voltage divider.

## Claims

### Claim 1

A circuit suitable for use in a system with an LCD (liquid crystal display), comprising:
an LCD display driver integrated circuit(IC),including multiple LCD source driver circuits and a gamma reference circuit;
each LCD source driver circuit to
convert video image data input to the LCD display driver integrated circuit into N analog gray-level gamma-adjusted source voltage signals, each based on a respective one of N gamma reference voltages, and
drive out the gamma-adjusted source voltage signals;
the gamma reference circuit to generate the N gamma reference voltages based on at least one pre-defined gamma curve that includes the N (0 to N−1) gamma reference voltages divided into M−1 regions defined by M breakpoint voltages corresponding to M−1 segments of the gamma curve, including
a gamma-breakpoint circuit, including
a range resistor string with a sequence of voltage taps;
M breakpoint digital-to-analog converters (DACs), designated DAC(1) to DAC(M),
each breakpoint DAC including inputs coupled to a respective subset of the voltage taps of the range resistor string, where at least some of the M subsets of voltage taps overlap, and
each breakpoint DAC to output a respective breakpoint voltage based on the respective subset of voltage taps, including
a breakpoint voltage BP(1) from breakpoint DAC(1) and a breakpoint voltage BP(M) from a breakpoint DAC (M), and
intermediate breakpoint voltages BP(2) to BP(M−1) from respectively breakpoint DAC(2) to DAC(M−1);
a gamma-reference output circuit to generate the N gamma reference voltages, including
a reference resistor string having a set of reference voltage taps, and
N reference multiplexers, designated MUX(0) to MUX(N−1) each to select from a subset of the reference voltage taps of the reference resistor string, and to generate at an output a respective one of the N gamma reference voltages,
the reference resistor string including a first end point provided by the breakpoint voltage BP(1) from DAC(1), and a second end point provided by the breakpoint voltage BP(M) from DAC(M),
M−2 selected reference multiplexers designated MUX(2) to MUX(M−1) each having its output coupled respectively to the intermediate breakpoint voltages BP(2) to BP(M−1) from DAC(2) to DAC(M−1).

### Claim 2 (depends on 1)

The circuit of claim 1, wherein N=64, M=4 and the M breakpoint voltages correspond to reference voltages N=0, 7, 24, 56, 63.

### Claim 3 (depends on 1)

The circuit of claim 1, wherein the gamma reference circuit to generate the N gamma reference voltages selectively for each of multiple pre-defined gamma curves, and, for each selected gamma curve,
the gamma-breakpoint circuit to generate respective M breakpoint voltages corresponding to M−1 segments for the selected gamma curve;
the gamma-reference output circuit to generate the N gamma reference voltages from the N reference multiplexers, including the M−2 selected reference multiplexers having respective outputs coupled respectively to the intermediate breakpoint voltages BP(2) to BP(M−1)from the gamma-breakpoint circuit.

### Claim 4 (depends on 3)

The circuit of claim 3,
wherein gamma-breakpoint circuit includes polarity inversion circuitry to selectively invert a polarity of the voltages at respective endpoints of the range resistor string corresponding to positive and negative pre-defined gamma curves; and
wherein the multiple pre-defined gamma curves are for at least one of (a) red, green and blue, and (b) positive and negative inversion polarity.

### Claim 5 (depends on 1)

The circuit of claim 1, further comprising:
M buffer amplifiers coupled to respective breakpoint DACs, to output respective buffered breakpoint voltages BP(1) to BP(M).

### Claim 6 (depends on 1)

The circuit of claim 1, the gamma-breakpoint circuit further including
first and second inversion buffers coupled to the range resistor string respectively at first and second endpoints;
the first and second inversion buffers switched between high/low and low/high voltage outputs to invert a polarity of the voltages at the first and second endpoints.

### Claim 7 (depends on 1)

The circuit of claim 1, wherein spacings between the reference voltage taps of the reference resistor string are selectively non-uniform, to provide programmable nonlinearity for the pre-defined gamma curve.

### Claim 8

An LCD display system, comprising:
an LCD (liquid crystal display);
an LCD display driver including,
multiple LCD source driver circuits, and
a gamma reference circuit;
each LCD source driver circuit to
convert video image data input to the LCD display driver into N analog gray-level gamma-adjusted source voltage signals output to the LCD, each based on a respective one of N gamma reference voltages, and
drive out the gamma-adjusted source voltage signals to the LCD;
the gamma reference circuit to generate the N gamma reference voltages based on at least one pre-defined gamma curve that includes the N (0 to N−1) gamma reference voltages divided into M−1 regions defined by M breakpoint voltages corresponding to M−1 segments of the gamma curve, including
a gamma-breakpoint circuit, including
a range resistor string with a sequence of voltage taps;
M breakpoint digital-to-analog converters (DACs), designated DAC(1) to DAC(M), wherein
each breakpoint DAC including inputs coupled to a respective subset of the voltage taps of the range resistor string, where at least some of the M subsets of voltage taps overlap, and
each breakpoint DAC to output a respective breakpoint voltage based on the respective subset of voltage taps, including
a breakpoint voltage BP(1) from breakpoint DAC(1) and a breakpoint voltage BP(M) from a breakpoint DAC (M), and
intermediate breakpoint voltages BP(2) to BP(M−1) from respectively breakpoint DAC(2) to DAC(M−1); and
a gamma-reference output circuit to generate the N gamma reference voltages, including
a reference resistor string having a set of reference voltage taps, and
N reference multiplexers, designated MUX(0) to MUX(N−1) each to select from a subset of the reference voltage taps of the reference resistor string, and to generate at an output a respective one of the N gamma reference voltages,
the reference resistor string including a first end point provided by the breakpoint voltage BP(1) from DAC(1), and a second end point provided by the breakpoint voltage BP(M) from DAC(M),
M−2selected reference multiplexers designated MUX(2) to MUX(M−1) each having its output coupled respectively to the intermediate breakpoint voltages BP(2) to BP(M−1) from DAC(2) to DAC(M−1).

### Claim 9 (depends on 8)

The system of claim 8, wherein N=64, M=4 and the M breakpoint voltages correspond to reference voltages N=0, 7, 24, 56, 63.

### Claim 10 (depends on 8)

The system of claim 8, wherein the gamma reference circuit to generate the N gamma reference voltages selectively for each of multiple pre-defined gamma curves, and, for each selected gamma curve,
the gamma-breakpoint circuit to generate respective M breakpoint voltages corresponding to M−1 segments for the selected gamma curve;
the gamma-reference output circuit to generate the N gamma reference voltages from the N reference multiplexers, including the M−2 selected reference multiplexers having respective outputs coupled respectively to the intermediate breakpoint voltages BP(2) to BP(M−1) from the gamma-breakpoint circuit.

### Claim 11 (depends on 10)

The system of claim 10,
wherein gamma-breakpoint circuit includes polarity inversion circuitry to selectively invert the polarity of the voltages at respective endpoints of the range resistor string corresponding to positive and negative pre-defined gamma curves; and
wherein the multiple pre-defined gamma curves are for at least one of (a) red, green and blue, and (b) positive and negative inversion polarity.

### Claim 12 (depends on 8)

The system of claim 8 further comprising:
M buffer amplifiers coupled to respective breakpoint DACs, to output respective buffered breakpoint voltages BP(1) to BP(M).

### Claim 13 (depends on 8)

The system of claim 8, the gamma-breakpoint circuit further including
first and second inversion buffers coupled to the range resistor string respectively at first and second endpoints;
the first and second inversion buffers switched between high/low and low/high voltage outputs to invert a polarity of the voltages at the first and second endpoints.

### Claim 14 (depends on 8)

The system of claim 8, wherein spacings between the reference voltage taps of the reference resistor string are selectively non-uniform, to provide programmable nonlinearity for the pre-defined gamma curve.

### Claim 15

A method for use in a system with an LCD (liquid crystal display), comprising:
converting video image data into N analog gray-level gamma-adjusted source voltage signals for input to the LCD, each based on a respective one of N gamma reference voltages, and
generating the N gamma reference voltages based on at least one pre-defined gamma curve that includes the N (0 to N−1) gamma reference voltages divided into M−1 regions defined by M breakpoint voltages corresponding to M−1 segments of the gamma curve, including generating the M breakpoint voltages designated BP(1) to BP(M) using M respective range decoders with inputs coupled to a respective subset of voltage taps of a range resistor string, where at least some of the M subsets of voltage taps overlap;
generating the N gamma reference voltages using N reference multiplexers, each to select from a respective subset of reference voltage taps of a reference resistor string,
the reference resistor string including a first end point provided by the breakpoint voltage BP(1), and a second end point provided by the breakpoint voltage BP(M),
the N reference multiplexers including M−2 selected reference multiplexers with outputs respectively couple to intermediate breakpoint voltages BP(2) to BP(M−1).

### Claim 16 (depends on 15)

The method of claim 15, wherein N=64, M=4 and the M breakpoint voltages correspond to reference voltages N=0, 7, 24, 56, 63.

### Claim 17 (depends on 15)

The method of claim 15, wherein N gamma reference voltages are selectively generated for each of multiple pre-defined gamma curves.

### Claim 18 (depends on 15)

The method of claim 15, further comprising:
selectively inverting a polarity of the voltages at respective endpoints of the range resistor string corresponding to positive and negative pre-defined gamma curves.

### Claim 19 (depends on 18)

The method of claim 18, wherein multiple pre-defined gamma curves are generated for at least one of (a) red, green and blue, and (b) positive and negative inversion polarity.

### Claim 20 (depends on 15)

The method of claim 15, wherein spacings between the reference voltage taps of the reference resistor string are selectively non-uniform, to provide programmable nonlinearity for the pre-defined gamma curve.