# US 7,609,256 B2 · Power supply circuit, display driver, electro-optical device, electronic instrument, and method of controlling power supply circuit

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

- Number: US 7,609,256 B2
- Document ID: US7609256B2
- Status: Granted
- Kind: B2
- Application number: 11/313,172
- Filed: 2005-12-20
- Published: 2006-06-22
- Granted: 2009-10-27
- Earliest claimed: 2004-12-21
- Assignees: Seiko Epson Corporation
- Inventors: Akira Morita
- Web page: https://patentgrep.com/patent/US7609256B2

## CPC

- G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)}
- G09G 3/3614: {Control of polarity reversal in general}
- G09G 3/3655: {Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors}
- G09G 3/3688: {suitable for active matrices only}
- G09G 3/3696: {Generation of voltages supplied to electrode drivers}
- G09G 2310/027: Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
- G09G 2320/0271: Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
- G09G 2330/025: Reduction of instantaneous peaks of current
- 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 power supply circuit including: a high-potential-side voltage generation circuit which generates a high-potential-side voltage; a low-potential-side voltage generation circuit which generates a low-potential-side voltage; and a switch circuit which alternately supplies the high-potential-side voltage and the low-potential-side voltage to the common electrode as a common electrode voltage. The power supply circuit performs supply capability control of the common electrode voltage which changes at least one of current drive capability of the high-potential-side voltage generation circuit, an output voltage level of the high-potential-side voltage generation circuit, current drive capability of the low-potential-side voltage generation circuit, and an output voltage level of the low-potential-side voltage generation circuit according to a total value generated based on grayscale data for the number of dots of one scan line. The total value is a value obtained by sequentially adding a converted voltage value obtained by converting each piece of the grayscale data for the number of dots of one scan line according to a given grayscale characteristic.

## Claims

### Claim 1

A power supply circuit which supplies voltage to a common electrode which is opposite to a pixel electrode, an electro-optical substance being interposed between the common electrode and the pixel electrode, the power supply circuit comprising:
a first voltage generation circuit which generates a first voltage supplied to the common electrode;
a second voltage generation circuit which generates a second voltage supplied to the common electrode, the second voltage being lower than the first voltage; and
a switch circuit which alternately supplies the first voltage and the second voltage to the common electrode as a common electrode voltage,
wherein the power supply circuit performs supply capability control of the common electrode voltage which changes at least one of current drive capability of the first voltage generation circuit, an output voltage level of the first voltage generation circuit, current drive capability of the second voltage generation circuit, and an output voltage level of the second voltage generation circuit according to a total value generated based on grayscale data for the number of dots of one scan line, each dot corresponding to voltage applied to the pixel electrode; and
wherein the total value is a value obtained by adding at least part of converted values obtained by converting each piece of the grayscale data for the number of dots of one scan line according to a given grayscale characteristic.

### Claim 2 (depends on 1)

The power supply circuit as defined in claim 1, comprising:
a first conductivity type first auxiliary transistor to which a first power supply voltage of the first voltage generation circuit is supplied at a source and which is electrically connected to an output of the switch circuit at a drain,
wherein the supply capability control is performed by controlling a gate voltage of the first auxiliary transistor corresponding to the total value.

### Claim 3 (depends on 1)

The power supply circuit as defined in claim 1, comprising:
a second conductivity type second auxiliary transistor to which a second power supply voltage of the second voltage generation circuit is supplied at a source and which is electrically connected to an output of the switch circuit at a drain,
wherein the supply capability control is performed by controlling a gate voltage of the second auxiliary transistor corresponding to the total value.

### Claim 4 (depends on 1)

The power supply circuit as defined in claim 1,
wherein the first voltage generation circuit includes a first operational amplifier which outputs the first voltage based on a first input voltage.

### Claim 5 (depends on 4)

The power supply circuit as defined in claim 4,
wherein the supply capability control is performed by changing at least one of current drive capability and a slew rate of the first operational amplifier according to the total value.

### Claim 6 (depends on 4)

The power supply circuit as defined in claim 4,
wherein the supply capability control is performed by changing the first input voltage according to the total value.

### Claim 7 (depends on 4)

The power supply circuit as defined in claim 4,
wherein the supply capability control is performed by stopping or limiting an operating current of the first operational amplifier and electrically connecting an input and an output of the first operational amplifier according to the total value.

### Claim 8 (depends on 1)

The power supply circuit as defined in claim 1, comprising:
a first charge-pump circuit which generates a first power supply voltage of the first voltage generation circuit by a charge-pump operation in synchronization with a first charge clock signal,
wherein the supply capability control is performed by stopping the first charge clock signal or reducing frequency of the first charge clock signal according to the total value.

### Claim 9 (depends on 1)

The power supply circuit as defined in claim 1,
wherein the second voltage generation circuit includes a second operational amplifier which outputs the second voltage based on a second input voltage.

### Claim 10 (depends on 9)

The power supply circuit as defined in claim 9,
wherein the supply capability control is performed by changing at least one of current drive capability and a slew rate of the second operational amplifier according to the total value.

### Claim 11 (depends on 9)

The power supply circuit as defined in claim 9,
wherein the supply capability control is performed by changing the second input voltage according to the total value.

### Claim 12 (depends on 9)

The power supply circuit as defined in claim 9,
wherein the supply capability control is performed by stopping or limiting an operating current of the second operational amplifier and electrically connecting an input and an output of the second operational amplifier according to the total value.

### Claim 13 (depends on 1)

The power supply circuit as defined in claim 1, comprising:
a second charge-pump circuit which generates a second power supply voltage of the second voltage generation circuit by a charge-pump operation in synchronization with a second charge clock signal,
wherein the supply capability control is performed by stopping the second charge clock signal or reducing frequency of the second charge clock signal according to the total value.

### Claim 14 (depends on 1)

The power supply circuit as defined in claim 1,
wherein the supply capability control is performed in a period determined based on the total value.

### Claim 15 (depends on 1)

The power supply circuit as defined in claim 1,
wherein the supply capability control is performed according to an amount of change between the total value in a present horizontal scan period and the total value in a horizontal scan period immediately before the present horizontal scan period, instead of the total value.

### Claim 16 (depends on 15)

The power supply circuit as defined in claim 15,
wherein the supply capability control is performed in a period corresponding to the amount of change between the total value in the present horizontal scan period and the total value in the horizontal scan period immediately before the present horizontal scan period.

### Claim 17 (depends on 16)

The power supply circuit as defined in claim 16,
wherein, when performing a field inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one vertical scan period, the amount of change is calculated based on a value obtained by subtracting the total value in the horizontal scan period immediately before the present horizontal scan period from the total value in the present horizontal scan period; and
wherein, when performing a line inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one horizontal scan period, the amount of change is calculated based on a value obtained by adding the total value in the present horizontal scan period and a correction value corresponding to the total value.

### Claim 18 (depends on 15)

The power supply circuit as defined in claim 15,
wherein, when performing a field inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one vertical scan period, the amount of change is calculated based on a value obtained by subtracting the total value in the horizontal scan period immediately before the present horizontal scan period from the total value in the present horizontal scan period; and
wherein, when performing a line inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one horizontal scan period, the amount of change is calculated based on a value obtained by adding the total value in the present horizontal scan period and a correction value corresponding to the total value.

### Claim 19 (depends on 1)

The power supply circuit as defined in claim 1,
wherein, when the grayscale data of each dot is j bits (j is an integer greater than one), the total value is a value obtained by adding converted values obtained by converting higher-order k-bit data (k<j, k is a natural number) of each of the grayscale data for the number of dots of one scan line according to the given grayscale characteristic.

### Claim 20 (depends on 19)

The power supply circuit as defined in claim 19, wherein k is one.

### Claim 21 (depends on 1)

The power supply circuit as defined in claim 1,
wherein, when the value obtained by adding the at least part of the converted values is p bits (p is an integer greater than one), the total value is a value indicated by higher-order q bits (q<p, q is a natural number) of the value obtained by adding the at least part of the converted values.

### Claim 22 (depends on 1)

The power supply circuit as defined in claim 1,
wherein the number of bits of the grayscale data is smaller than the number of bits of data indicating the converted values.

### Claim 23 (depends on 1)

A display driver comprising:
a voltage value conversion circuit which generates converted values obtained by converting grayscale data of each dot corresponding to voltage applied to a pixel electrode according to a given grayscale characteristic;
a total value calculation circuit which generates a total value based on the converted values for the number of dots of one scan line;
a driver circuit which supplies a drive voltage corresponding to the grayscale data to a data line electrically connected to the pixel electrode; and
the power supply circuit as defined in claim 1 which performs the supply capability control by using the total value generated by the total value calculation circuit.

### Claim 24 (depends on 1)

An electro-optical device comprising:
a plurality of scan lines;
a plurality of data lines;
a plurality of pixel electrodes, each of the pixel electrodes being specified by one of the scan lines and one of the data lines;
a common electrode which is opposite to the pixel electrodes, an electro-optical substance being interposed between the common electrode and the pixel electrodes;
a data driver which drives the data lines; and
the power supply circuit as defined in claim 1 which alternately supplies the first voltage and the second voltage to the common electrode.

### Claim 25 (depends on 1)

An electronic instrument comprising the power supply circuit as defined in claim 1.

### Claim 26

A power supply circuit which supplies voltage to a common electrode which is opposite to a pixel electrode, an electro-optical substance being interposed between the common electrode and the pixel electrode, the power supply circuit comprising:
a circuit which alternately supplies a first voltage and a second voltage to the common electrode,
wherein the power supply circuit performs supply capability control of the common electrode voltage which changes at least one of current drive capability of a first voltage generation circuit generating the first voltage, an output voltage level of the first voltage generation circuit, current drive capability of a second voltage generation circuit generating the second voltage lower than the first voltage, and an output voltage level of the second voltage generation circuit according to a total value generated based on grayscale data for the number of dots of one scan line, each dot corresponding to voltage applied to the pixel electrode; and
wherein the total value is a value obtained by adding at least part of converted values obtained by converting each of the grayscale data for the number of dots of one scan line according to a given grayscale characteristic.

### Claim 27 (depends on 26)

The power supply circuit as defined in claim 26,
wherein the supply capability control is performed in a period determined based on the total value.

### Claim 28 (depends on 26)

The power supply circuit as defined in claim 26,
wherein the supply capability control is performed according to an amount of change between the total value in a present horizontal scan period and the total value in a horizontal scan period immediately before the present horizontal scan period, instead of the total value.

### Claim 29 (depends on 28)

The power supply circuit as defined in claim 28,
wherein the supply capability control is performed in a period corresponding to the amount of change between the total value in the present horizontal scan period and the total value in the horizontal scan period immediately before the present horizontal scan period.

### Claim 30 (depends on 29)

The power supply circuit as defined in claim 29,
wherein, when performing a field inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one vertical scan period, the amount of change is calculated based on a value obtained by subtracting the total value in the horizontal scan period immediately before the present horizontal scan period from the total value in the present horizontal scan period; and
wherein, when performing a line inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one horizontal scan period, the amount of change is calculated based on a value obtained by adding the total value in the present horizontal scan period and a correction value corresponding to the total value.

### Claim 31 (depends on 28)

The power supply circuit as defined in claim 28,
wherein, when performing a field inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one vertical scan period, the amount of change is calculated based on a value obtained by subtracting the total value in the horizontal scan period immediately before the present horizontal scan period from the total value in the present horizontal scan period; and
wherein, when performing a line inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one horizontal scan period, the amount of change is calculated based on a value obtained by adding the total value in the present horizontal scan period and a correction value corresponding to the total value.

### Claim 32 (depends on 26)

The power supply circuit as defined in claim 26,
wherein, when the grayscale data of each dot is j bits (j is an integer greater than one), the total value is a value obtained by adding converted values obtained by converting higher-order k-bit data (k<j, k is a natural number) of each of the grayscale data for the number of dots of one scan line according to the given grayscale characteristic.

### Claim 33 (depends on 32)

The power supply circuit as defined in claim 32, wherein k is one.

### Claim 34 (depends on 26)

The power supply circuit as defined in claim 26,
wherein, when the value obtained by adding the at least part of the converted values is p bits (p is an integer greater than one), the total value is a value indicated by higher-order q bits (q<p, q is a natural number) of the value obtained by adding the at least part of the converted values.

### Claim 35 (depends on 26)

The power supply circuit as defined in claim 26,
wherein the number of bits of the grayscale data is smaller than the number of bits of data indicating the converted values.

### Claim 36 (depends on 26)

A display driver comprising:
a voltage value conversion circuit which generates converted values obtained by converting grayscale data of each dot corresponding to voltage applied to a pixel electrode according to a given grayscale characteristic;
a total value calculation circuit which generates a total value based on the converted values for the number of dots of one scan line;
a driver circuit which supplies a drive voltage corresponding to the grayscale data to a data line electrically connected to the pixel electrode; and
the power supply circuit as defined in claim 26 which performs the supply capability control by using the total value generated by the total value calculation circuit.

### Claim 37 (depends on 26)

An electro-optical device comprising:
a plurality of scan lines;
a plurality of data lines;
a plurality of pixel electrodes, each of the pixel electrodes being specified by one of the scan lines and one of the data lines;
a common electrode which is opposite to the pixel electrodes, an electro-optical substance being interposed between the common electrode and the pixel electrodes;
a data driver which drives the data lines; and
the power supply circuit as defined in claim 26 which alternately supplies the first voltage and the second voltage to the common electrode.

### Claim 38 (depends on 26)

An electronic instrument comprising the power supply circuit as defined in claim 26.

### Claim 39

A method of controlling a power supply circuit including a first voltage generation circuit and a second voltage generation circuit, the first voltage generation circuit generating a first voltage to be supplied to a common electrode which is opposite to a pixel electrode, an electro-optical substance being interposed between the common electrode and the pixel electrode, the second voltage generation circuit generating a second voltage lower than the first voltage to be supplied to the common electrode, and the method comprising:
converting each of grayscale data for the number of dots of one scan line into converted values according to a given grayscale characteristic, each dot corresponding to voltage applied to the pixel electrode;
changing at least one of current drive capability of the first voltage generation circuit, an output voltage level of the first voltage generation circuit, current drive capability of the second voltage generation circuit, and an output voltage level of the second voltage generation circuit according to a total value obtained by adding at least part of the converted values; and
alternately supplying the first voltage and the second voltage to the common electrode.

### Claim 40 (depends on 39)

The method of controlling a power supply circuit as defined in claim 39,
wherein at least one of the current drive capability of the first voltage generation circuit, the output voltage level of the first voltage generation circuit, the current drive capability of the second voltage generation circuit, and the output voltage level of the second voltage generation circuit is changed in a period determined based on the total value.

### Claim 41 (depends on 39)

The method of controlling a power supply circuit as defined in claim 39,
wherein at least one of the current drive capability of the first voltage generation circuit, the output voltage level of the first voltage generation circuit, the current drive capability of the second voltage generation circuit, and the output voltage level of the second voltage generation circuit is changed according to an amount of change between the total value in a present horizontal scan period and the total value in a horizontal scan period immediately before the present horizontal scan period.

### Claim 42 (depends on 41)

The method of controlling a power supply circuit as defined in claim 41,
wherein at least one of the current drive capability of the first voltage generation circuit, the output voltage level of the first voltage generation circuit, the current drive capability of the second voltage generation circuit, and the output voltage level of the second voltage generation circuit is changed in a period corresponding to the amount of change between the total value in the present horizontal scan period and the total value in the horizontal scan period immediately before the present horizontal scan period.

### Claim 43 (depends on 41)

The method of controlling a power supply circuit as defined in claim 41,
wherein, when performing a field inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of one vertical scan period, the amount of change is calculated based on a value obtained by subtracting the total value in the horizontal scan period immediately before the present horizontal scan period from the total value in the present horizontal scan period; and
wherein, when performing a line inversion drive in which polarity of the common electrode voltage is changed based on a given reference potential in units of at least one horizontal scan period, the amount of change is calculated based on a value obtained by adding the total value in the present horizontal scan period and a correction value corresponding to the total value.

### Claim 44 (depends on 39)

The method of controlling a power supply circuit as defined in claim 39,
wherein, when the grayscale data of each dot is j bits (j is an integer greater than one), the total value is a value obtained by adding converted values obtained by converting higher-order k-bit data (k<j, k is a natural number) of each of the grayscale data for the number of dots of one scan line according to the given grayscale characteristic.

### Claim 45 (depends on 44)

The method of controlling a power supply circuit as defined in claim 44, wherein k is one.

### Claim 46 (depends on 39)

The method of controlling a power supply circuit as defined in claim 39,
wherein, when the value obtained by adding the at least part of the converted values is p bits (p is an integer greater than one), the total value is a value indicated by higher-order q bits (q<p, q is a natural number) of the value obtained by adding the at least part of the converted values.

### Claim 47 (depends on 39)

The method of controlling a power supply circuit as defined in claim 39,
wherein the number of bits of the grayscale data is smaller than the number of bits of data indicating the converted values.