BACKGROUND

Field of Invention

The present invention relates to a device for driving a backlight assembly of a display device and a device for driving the display device.

Description of Related Art

The traditional backlight sources of the LCD device are at full brightness. The display of a dark frame is achieved by reducing the transmittance of liquid crystal, which has no help for reducing the power consumption. By contrast, the backlight local dimming allows the brightness of backlight source to be varied with dark and light frames, so the brightness of backlight source is reduced when a dark frame is displayed. Thus, the entire amount of power consumption of the backlight is reduced. In addition to the power consumption reduction, the backlight local dimming can also improve the frame quality of the LCD device.

A typical backlight local dimming can increase the frame contrast and reduce the power consumption, but the inappropriate backlight decision and image compensation may reduce the image quality. Therefore, it is desirable to provide an improved backlight local dimming to improve the aforementioned problems.

SUMMARY

The present invention provides a device for driving a backlight assembly of a display device. The device includes: an image receiver for receiving an input image, a block division unit for dividing the input image into plural blocks, a duty cycle determination unit for determining a duty cycle of a driving signal of each of the blocks, and a driving unit for driving the backlight assembly of the display device with the driving signal of each of the blocks. The duty cycle determination unit is used for: generating a histogram of gray levels of pixels of each of the blocks; obtaining a high gray level and a median gray level of each of the blocks according to the histogram; obtaining a high gray quantity based on the high gray level and a median gray quantity of the median gray level of each of the blocks according to the histogram; obtaining a weight value of each of the blocks according to the high gray level, the high gray quantity, the median gray quantity, and a lookup table; and calculating the duty cycle of the driving signal of each of the blocks according to the weight value, the high gray level, and the median gray level.

In accordance with one or more embodiments of the invention, in which obtaining the high gray level of each of the blocks includes: setting a quantity threshold (X); statistically analyzing top X brightest pixels of the pixels; and determining a gray level of Xth brightest pixel is the high gray level.

In accordance with one or more embodiments of the invention, the median gray level of each of the blocks is an average value of gray levels of pixels of each of the blocks.

In accordance with one or more embodiments of the invention, the high gray quantity is a number of the pixels with brightness from a maximum gray level to the high gray level.

In accordance with one or more embodiments of the invention, the weight value of each of the blocks is obtained by inputting the high gray level and a normalized value of a ratio of the high gray quantity to the median gray quantity into the lookup table.

In accordance with one or more embodiments of the invention, as the high gray level or the normalized value is greater, the weight value is greater.

In accordance with one or more embodiments of the invention, the duty cycle is a sum of a product of the high gray level and the weight value and a product of the median gray level and a difference between 1 and the weight value.

The present invention further provides a device for driving a display device. The device includes: an image receiver for receiving an input image, a block division unit for dividing the input image into plural blocks, a duty cycle determination unit, a gain value determination unit, and a compensation unit. The duty cycle determination unit is used for: generating a histogram of gray levels of pixels of each of the blocks; obtaining a high gray level and a median gray level of each of the blocks according to the histogram; calculating an image high gray level and an image median gray level of the input image according to the high gray level and the median gray level of each of the blocks; inputting a difference between the image high gray level and the image median gray level into a gain lookup table to obtain a duty gain; obtaining an updated duty cycle of a driving signal of each of the blocks according to the duty gain. The gain value determination unit is used for obtaining a gain value of each of the blocks according to the updated duty cycle. The compensation unit is used for compensating the input image by using the gain value of each of the blocks.

In accordance with one or more embodiments of the invention, in which obtaining the high gray level of each of the blocks includes: setting a quantity threshold (X); statistically analyzing top X brightest pixels of the pixels; and determining a gray level of Xth brightest pixel is the high gray level.

In accordance with one or more embodiments of the invention, the median gray level of each of the blocks is an average of gray levels of pixels of each of the blocks.

In accordance with one or more embodiments of the invention, the image high gray level is a maximum value of the high gray levels of the blocks.

In accordance with one or more embodiments of the invention, the image median gray level is an average value of the median gray levels of the blocks.

In accordance with one or more embodiments of the invention, as the difference between the image high gray level and the image median gray level is closer to 191, the duty gain is closer to 1.

In accordance with one or more embodiments of the invention, the updated duty cycle is obtaining by adding a first duty cycle to a product of the duty gain and a difference between a second duty cycle and the first duty cycle.

In accordance with one or more embodiments of the invention, the second duty cycle is not less than the first duty cycle.

In accordance with one or more embodiments of the invention, the duty cycle determination unit is further used for: obtaining a high gray quantity based on the high gray level and a median gray quantity of the median gray level of each of the blocks according to the histogram; obtaining a weight value of each of the blocks according to the high gray level, the high gray quantity, the median gray quantity, and a lookup table; and calculating a duty cycle of the driving signal of each of the blocks according to the weight value, the high gray level. The device further includes a driving unit for driving a backlight assembly of the display device with the updated duty cycle of the driving signal of each of the blocks.

In accordance with one or more embodiments of the invention, the high gray quantity is a number of the pixels with brightness from a maximum gray level to the high gray level.

In accordance with one or more embodiments of the invention, the weight value of each of the blocks is obtained by inputting the high gray level and a normalized value of a ratio of the high gray quantity to the median gray quantity into the lookup table.

In accordance with one or more embodiments of the invention, as the high gray level or the normalized value is greater, the weight value is greater.

In accordance with one or more embodiments of the invention, the duty cycle is a sum of a product of the high gray level and the weight value and a product of the median gray level and a difference between 1 and the weight value.

