Display device and method for driving the same
Provided is a display device capable of switching a refresh rate while suppressing deterioration in display quality and degradation in liquid crystal. In the case of switching the refresh rate from 60 Hz to 7.5 Hz, a transition period for gradually changing the refresh rate from 60 Hz to 7.5 Hz is provided between a 60-Hz period and a 7.5-Hz period. This transition period is configured by sequentially arraying a 30-Hz period, a 20-Hz period, a 15-Hz period, a 12-Hz period and a 10-Hz period from a start point of the transition period. Hence the refresh rate gradually changes from 60 Hz to 7.5 Hz sequentially through 30 Hz, 20 Hz, 15 Hz, 12 Hz and 10 Hz. The number of positive-polarity frames and the number of negative-polarity frames are respectively 20 in the whole of the transition period, and are equal to each other.
1. A display device, comprising:
a display portion which includes a plurality of pixel formation portions;
a drive portion which drives the display portion; and
a display control portion which controls the drive portion based on data received from an external source, wherein
the display control portion controls an alternating current drive;
a refresh rate of a screen of the display portion is determined according to a proportion of a refresh period, during which the screen is refreshed, and a non-refresh period, during which the screen is not refreshed;
when the display control portion determines that the refresh rate of the screen is to be switched from a first refresh rate to a second refresh rate, the display control portion sets a transition period that includes a positive polarity period and a negative polarity period;
before the transition period, the drive portion drives the display portion based on the first refresh rate in a first drive period;
after the transition period, the drive portion drives the display portion based on the second refresh rate in a second drive period;
during the transition period, the drive portion drives the display portion based on at least one refresh rate having a value that falls between the first refresh rate and the second refresh rate;
the positive polarity period includes a positive refresh frame, during which the screen is refreshed in a positive polarity, and one or more positive non-refresh frames immediately following the positive refresh frame, during which the screen of the display portion is not refreshed;
the negative polarity period includes a negative refresh frame, during which the screen is refreshed in a negative polarity, and one or more negative non-refresh frames immediately following the negative refresh frame, during which the screen of the display portion is not refreshed; and
a total number of the one or more positive non-refresh frames is substantially the same as a total number of the one or more negative non-refresh frames, in a whole of the transition period.
2. The display device according to claim 1 , wherein the display control portion provides the positive polarity period and the negative polarity period in substantially the same proportion as each other with respect to each of the at least one refresh rate during the transition period.
3. The display device according to claim 1 , wherein the display control portion switches a potential supplied to the plurality of pixel formation portions according to the refresh rate of the screen.
4. The display device according to claim 1 , wherein the display control portion:
switches from the second drive period to the first drive period when the display control portion receives, from the external source, image data corresponding to the screen of the display portion during a non-refresh period of the second drive period, and
switches from the first drive period to the second drive period after the transition period.
5. The display device according to claim 1 , wherein the pixel formation portion includes a thin-film transistor in which:
a control terminal is connected to a scan line in the display portion,
a first conduction terminal is connected to a signal line in the display portion,
a second conduction terminal is connected to a pixel electrode in the display portion, which is supplied with a potential in accordance with an image to be displayed, and
a channel layer is formed of an oxide semiconductor.
6. A method for driving a display device having
a display portion which includes a plurality of pixel formation portions,
a drive portion which drives the display portion, and
a display control portion which controls the drive portion based on data received from an external source,
the method comprising:
a step of performing an alternating current drive; and
a step of determining a refresh rate of a screen according to a proportion of a refresh period, during which the screen is refreshed, and a non-refresh period, during which the screen is not refreshed;
a transition step of setting a transition period that includes a positive polarity period and a negative polarity period; wherein
the transition step is performed when the refresh rate of the screen is to be switched from a first refresh rate to a second refresh rate;
before the transition period, the method further comprises a step of driving the display portion based on the first refresh rate in a first drive period;
after the transition period, the method further comprises a step of driving the display portion based on the second refresh rate in a second drive period;
in the transition step, the display portion is driven based on at least one refresh rate having a value that falls between the first refresh rate and the second refresh rate;
in the transition step, the positive polarity period includes a positive refresh frame, during which the screen is refreshed in a positive polarity, and one or more positive non-refresh frames immediately following the positive refresh frame, during which the screen of the display portion is not refreshed;
in the transition step, the negative polarity period includes a negative refresh frame, during which the screen is refreshed in a negative polarity, and one or more negative non-refresh frames immediately following the negative refresh frame, during which the screen of the display portion is not refreshed; and
in the transition step, a total number of the one or more positive non-refresh frames is substantially the same as a total number of the one or more negative non-refresh frames.
7. The drive method according to claim 6 , wherein in the transition step, the positive polarity period and the negative polarity period are provided in substantially the same proportion as each other with respect to each of the at least one refresh rate during the transition period.
8. The display device according to claim 1 , wherein a number of the one or more positive non-refresh frames included in the positive polarity period and a number of the one or more negative non-refresh frames included in the negative polarity period increase as the refresh rate of the screen decreases.