Electro-optical device and electronic apparatus

Patent metadata

Field	Value
Publication number	US-11562695-B2
Application number	US-202117559083-A
Country	US
Kind code	B2
Filing date	Dec 22, 2021
Priority date	Dec 23, 2020
Publication date	Jan 24, 2023
Grant date	Jan 24, 2023

Abstract

An electro-optical device includes a plurality of digital scanning lines, a digital signal line, and a plurality of pixel circuits. Each of the pixel circuits includes a light emitting element and a digital driving circuit. The digital driving circuit performs digital driving to turn the light emitting element ON-state or OFF-state based on a grayscale value. The digital driving circuit keeps the light emitting element ON-state by supplying a drive current to the light emitting element, in a period in which an enable signal is active, of a grayscale display period having a length corresponding to the grayscale value. The control line driving circuit sets a period in which the enable signal is active. A ratio, with respect to the grayscale display period, of an ON-state period in which the light emitting element is ON-state changes in accordance with the period in which the enable signal is active.

First claim

What is claimed is:

1. An electro-optical device comprising:
a plurality of digital scanning lines;
a digital signal line;
a plurality of pixel circuits; and
a control line driving circuit configured to output an enable signal, wherein
each pixel circuit of the plurality of pixel circuits includes
a light emitting element, and
a digital driving circuit configured to perform digital driving in which display data is set through the digital signal line when the digital driving circuit is selected through one of the digital scanning lines of the plurality of digital scanning lines, and the light emitting element is ON-state or OFF-state based on a grayscale value of the display data,
each pixel circuit is electrically connected to a digital scanning line included in the plurality of digital scanning lines, and to the digital signal line,
the digital driving circuit keeps the light emitting element ON-state by supplying a drive current to the light emitting element, in a period in which the enable signal is active, of a grayscale display period having a length corresponding to the grayscale value of the display data,
the control line driving circuit variably sets the period in which the enable signal is active, and
a ratio, with respect to the grayscale display period, of an ON-state period in which the light emitting element is ON-state changes in accordance with the period in which the enable signal is active.

2. The electro-optical device according to claim 1 , comprising:
a scanning line driving circuit configured to drive the plurality of digital scanning lines, wherein
a field constituting one image includes first to n-th scanning line selection periods in which first to n-th bits of the display data are set to the pixel circuit, n being an integer of 2 or more, and first to n-th display periods in which the light emitting element is ON-state or OFF-state in accordance with the first to n-th bits set to the pixel circuit, and
the grayscale display period having the length corresponding to the grayscale value of the display data is a display period, of the first to n-th display periods, corresponding to the scanning line selection period in which is set one bit of the first to n-th bits indicating ON-state of the light emitting element.

3. The electro-optical apparatus according to claim 2 , wherein
in each display period of the first to n-th display periods, the control line driving circuit causes the enable signal to be active at the ratio.

4. The electro-optical apparatus according to claim 2 , comprising:
a digital signal line driving circuit configured to output the first to n-th bits to the digital signal line, wherein
in each scanning line selection period of the first to n-th scanning line selection periods, the digital signal line driving circuit changes, in accordance with the ratio, an allocation of which one of the bits, of the first to n-th bits, is set to the pixel circuit, and
in each display period of the first to n-th display periods, the control line driving circuit causes the enable signal to be active in a period having a length corresponding to the allocation.

5. The electro-optical device according to claim 2 , wherein
the field includes a plurality of subfields,
in a subfield included in the plurality of subfields, the scanning line driving circuit selects, one time, a scanning line group as a selection target, among the plurality of digital scanning lines, and
the scanning line group includes a digital scanning line electrically connected to a pixel circuit to which an i-th bit is to be set, of the first to n-th bits of the display data in the subfield, i being an integer from 1 to n, and a digital scanning line electrically connected to a pixel circuit to which a j-th bit is to be set, of the first to n-th bits of the display data in the subfield, j being an integer of 1 to n and different from i.

6. The electro-optical device according to claim 5 , wherein
each subfield of the plurality of subfields is a period of the same length.

7. The electro-optical device according to claim 5 , wherein
in the subfield, the scanning line driving circuit selects, as the scanning line group, n digital scanning lines from a digital scanning line electrically connected to a pixel circuit to which the first bit is to be set, to a digital scanning line electrically connected to a pixel circuit to which the n-th bit is to be set.

8. The electro-optical device according to claim 5 , wherein
the first to n-th bits of the display data are set to each pixel circuit by the scanning line driving circuit selecting each digital scanning line, of the plurality of digital scanning lines, n times each in the field.

9. The electro-optical apparatus according to claim 1 , comprising:
a plurality of analog scanning lines; and
an analog signal line, wherein
each pixel circuit is electrically connected to an analog scanning line included in the plurality of analog scanning lines, and to the analog signal line,
each pixel circuit includes an analog driving circuit configured to perform analog current setting in which an analog data voltage is set from the analog signal line when the analog driving circuit is selected by the analog scanning line, and a current value of the drive current is variably set based on the analog data voltage, and
in the ON-state period, the digital driving circuit supplies the drive current from the analog driving circuit to the light emitting element.

10. The electro-optical device according to claim 9 , wherein
in a period in which an s-th pixel circuit, of the plurality of pixel circuits, electrically connected to an s-th digital scanning line and an s-th analog scanning line performs the analog current setting, a t-th pixel circuit, of the plurality of pixel circuits, electrically connected to a t-th digital scanning line and a t-th analog scanning line performs the digital driving, s being an integer of 1 or more, t being an integer of 1 or more and different from s.

11. The electro-optical device according to claim 1 , wherein
the digital driving circuit includes
a storage circuit configured to store the display data, and
a first drive transistor and a second drive transistor provided in series between a supply node of the drive current and an end of the light emitting element,
the first drive transistor is ON-state or OFF-state based on an output signal from the storage circuit,
the second drive transistor is ON-state or OFF-state based on the enable signal, and
when the first drive transistor and the second drive transistor are ON-state, the drive current is supplied to the light emitting element.

12. The electro-optical apparatus according to claim 1 , wherein
the control line driving circuit, to which ratio setting information based on luminance information of environment is input, sets the ratio based on the ratio setting information, the ratio setting information being configured to cause the ratio to be smaller the lower the luminance of the environment.

13. An electronic apparatus comprising:
the electro-optical device according to claim 12 ; and
a sensor configured to measure the luminance information.

14. An electronic apparatus comprising:
the electro-optical device according to claim 1 .

Assignees

• Seiko Epson Corp

Inventors

• Momose Yoichi
• Miyasaka Mitsutoshi

Classifications

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title

• G09G3/2007 Primary

  Display of intermediate tones · CPC title

• G09G3/204

  the sub-frames being organized in consecutive sub-frame groups · CPC title

• G09G2300/0842

  forming a memory circuit, e.g. a dynamic memory with one capacitor · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title