Display device and method for driving display device
A display device includes: luminance converter that converts an input gradation value into a target luminance value corresponding to the input gradation value; correction calculator that calculates an output gradation value from the target luminance value and calculates a corrected luminance value from the output gradation value using an efficiency residual rate; cumulative stress calculator that updates the efficiency residual rate using a cumulative stress amount obtained by converting a stress amount on the light emitting element calculated from the corrected luminance value into a first stress amount at a reference current and accumulating a second stress amount obtained by converting the converted first stress amount according to a frame rate; and stress amount converter that converts the first stress amount into the second stress amount by multiplying the first stress amount by a conversion coefficient corresponding to the frame rate obtained from the video signal.
1. A display device including a display screen in which a plurality of pixels each including a light emitting element are arranged in a matrix, the display device comprising:
a correction circuit that corrects an input gradation value indicated by a luminance signal included in a video signal,
wherein the correction circuit includes:
a luminance converter that converts the input gradation value into a target luminance value corresponding to the input gradation value;
a correction calculator that calculates an output gradation value obtained by correcting the input gradation value from the target luminance value and calculates a corrected luminance value obtained by correcting the target luminance value from the output gradation value using an efficiency residual rate which is an index indicating a degree of deterioration of the light emitting element and which indicates a residual rate of a luminous efficiency of the light emitting element;
a cumulative stress calculator that updates the efficiency residual rate using a cumulative stress amount obtained by converting a stress amount on the light emitting element calculated from the corrected luminance value into a first stress amount indicating the stress amount when a reference current flows through the light emitting element and accumulating a second stress amount obtained from the first stress amount converted and obtained by converting the first stress amount according to a frame rate obtained from the video signal; and
a stress amount converter that converts the first stress amount into the second stress amount by acquiring the frame rate obtained from the video signal and multiplying the first stress amount by a conversion coefficient corresponding to the frame rate acquired.
2. The display device according to claim 1 ,
wherein the stress amount calculated from the corrected luminance value is a stress amount at a first current flowing through the light emitting element when the light emitting element is made to emit light with the corrected luminance value,
the stress amount at the first current is a time during which the first current flows through the light emitting element,
the stress amount at the reference current is a time during which the reference current flows through the light emitting element,
the cumulative stress calculator converts the stress amount calculated from the corrected luminance value into the first stress amount by converting the time during which the first current flows through the light emitting element into the time during which the reference current flows through the light emitting element, and calculates the cumulative stress amount by calculating a cumulative time obtained by accumulating a time corresponding to the frame rate, the time being the time during which the reference current flows through the light emitting element and being the second stress amount.
3. The display device according to claim 2 ,
wherein the efficiency residual rate is represented by a ratio of an emission luminance after deterioration of the light emitting element to an initial emission luminance of the light emitting element, and
the cumulative stress calculator updates the efficiency residual rate by setting the efficiency residual rate to a new efficiency residual rate calculated from the cumulative time calculated as the cumulative stress amount by using a relationship between a luminance of the light emitting element and the cumulative time during which the reference current flows through the light emitting element.
4. The display device according to claim 1 ,
wherein the stress amount converter includes:
a look-up table that stores a plurality of frame rates and a conversion coefficient associated with each of the plurality of frame rates in advance; and
a frame rate converter that converts the first stress amount into the second stress amount by acquiring the frame rate obtained from the video signal, selecting, from the lookup table, the conversion coefficient corresponding to the frame rate acquired, and multiplying the first stress amount by the conversion coefficient.
5. The display device according to claim 1 ,
wherein the stress amount converter includes:
a storage that stores a calculation formula for calculating the conversion coefficient, the calculation formula expressed by a ratio having the frame rate as a denominator; and
a conversion coefficient calculator that converts the first stress amount into the second stress amount by acquiring the frame rate obtained from the video signal, obtaining the conversion coefficient corresponding to the frame rate by applying the frame rate acquired to the calculation formula, and multiplying the first stress amount by the conversion coefficient.
6. A method for driving a display device including a display screen in which a plurality of pixels each including a light emitting element are arranged in a matrix, the method comprising:
correcting an input gradation value indicated by a luminance signal included in a video signal,
wherein the correcting includes:
converting the input gradation value into a target luminance value corresponding to the input gradation value;
calculating an output gradation value obtained by correcting the input gradation value from the target luminance value and calculates a corrected luminance value obtained by correcting the target luminance value from the output gradation value using an efficiency residual rate which is an index indicating a degree of deterioration of the light emitting element and which indicates a residual rate of a luminous efficiency of the light emitting element;
updating the efficiency residual rate by converting a stress amount on the light emitting element calculated from the corrected luminance value into a first stress amount indicating the stress amount when a reference current flows through the light emitting element, and accumulating a second stress amount obtained from the first stress amount converted and obtained by converting the first stress amount according to a frame rate obtained from the video signal; and
converting the first stress amount into the second stress amount by acquiring the frame rate obtained from the video signal and multiplying the first stress amount by a conversion coefficient corresponding to the frame rate acquired.