Display driver

Abstract

In a display driver, a first backlight control unit using a histogram and a second backlight control unit using an optical sensor can be used in combination. The display driver includes a PWM generating unit setting a control signal value consisting of a product of a luminance rate of X % and a luminance rate of Y % as a luminance rate of a control signal for controlling a backlight with respect to maximum backlight luminance when a luminance rate of a control signal obtained by first backlight control with respect to the maximum backlight luminance is X % and a luminance rate of a control signal obtained by second backlight control with respect to the maximum backlight luminance is Y %.

1 . A display driver comprising:
 a first control unit switching brightness of a display image based on a display data value at a predetermined position of a histogram of inputted display data and switching backlight luminance based on the display data value, wherein an object of detection of the histogram is a data range from a brightest level to an N-th level of gray-scale (N is a positive integer and is not 0) of the display data;   a second control unit performing backlight luminance control different from the first control unit; and   a generating unit setting a backlight control signal value consisting of a product of a luminance rate of X % and a luminance rate of Y % as a luminance rate of a backlight control signal for controlling a backlight with respect to maximum backlight luminance when a luminance rate of a backlight control signal obtained by a processing of the first control unit with respect to the maximum backlight luminance is defined as X % (0<X≦100) and a luminance rate of a backlight control signal obtained by a processing of the second control unit with respect to the maximum backlight luminance is defined as Y % (0<Y<100).   
     
     
         2 . The display driver according to  claim 1 ,
 wherein when stopping the processing of the first control unit, one operation of setting the luminance rate of X % of the backlight control signal obtained by the processing of the first control unit to 100% and selecting 100% as the luminance rate of the backlight control signal in place of X % obtained by the processing of the first control unit is performed so that the luminance rate for controlling the backlight is set to the luminance rate of Y % obtained by the processing of the second control unit.   
     
     
         3 . The display driver according to  claim 1 ,
 wherein when stopping the processing of the first control unit, the first control unit is stopped by register setting from outside and the luminance rate for controlling the backlight is set to the luminance rate of Y % obtained by the processing of the second control unit.   
     
     
         4 . The display driver according to  claim 1 ,
 wherein when stopping the processing of the second control unit, one operation of setting the luminance rate of Y % of the backlight control signal obtained by the processing of the second control unit to 100% and selecting 100% as the luminance rate of the backlight control signal in place of Y % obtained by the processing of the second control unit is performed so that the luminance rate for controlling the backlight is set to the luminance rate of X % obtained by the processing of the first control unit.   
     
     
         5 . The display driver according to  claim 1 ,
 wherein when stopping the processing of the second control unit, the second control unit is stopped by register setting from outside and the luminance rate for controlling the backlight is set to the luminance rate of X % obtained by the processing of the first control unit.   
     
     
         6 . The display driver according to  claim 1 ,
 wherein the backlight control signal for controlling the backlight is outputted as a PWM signal of one bit.   
     
     
         7 . The display driver according to  claim 1 ,
 wherein the backlight luminance control of the second control unit is performed by sensing external-light luminance with an optical sensor and adjusting the backlight luminance.   
     
     
         8 . A display driver comprising:
 a first control unit switching brightness of a display image based on a display data value at a predetermined position of a histogram of inputted display data and switching backlight luminance based on the display data value, wherein an object of detection of the histogram is a data range from a brightest level to an N-th level of gray-scale (N is a positive integer and is not 0) of the display data;   a second control unit performing backlight luminance control different from the first control unit; and   a generating unit setting a backlight control signal value of a luminance rate of Y % as a luminance rate of a backlight control signal for controlling a backlight with respect to backlight maximum luminance when a luminance rate of a backlight control signal obtained by a processing of the second control with respect to the backlight maximum luminance is Y % and the luminance rate of Y % is smaller than a luminance rate of Q % with respect to the backlight maximum luminance set as a threshold,   wherein when the luminance rate of Y % is smaller than the luminance rate of Q % with respect to the backlight maximum luminance set as a threshold, a processing of the first control unit is stopped.   
     
     
         9 . The display driver according to  claim 8 ,
 wherein the threshold can be set from outside.   
     
     
         10 . The display driver according to  claim 8 ,
 wherein when stopping the processing of the first control unit without using the threshold, the first control unit is stopped by register setting from outside, and the luminance rate of Y % obtained by the processing of the second control unit is set as the luminance rate for controlling the backlight.   
     
     
         11 . The display driver according to  claim 8 ,
 wherein when stopping the processing of the second control unit, one operation of setting the luminance rate of Y % of the backlight control signal obtained by the processing of the second control unit to 100% and selecting 100% as the luminance rate of the backlight control signal in place of Y % obtained by the processing of the second control unit is performed so that the luminance rate for controlling the backlight is set to a luminance rate of X % obtained by the processing of the first control unit.   
     
     
         12 . The display driver according to  claim 8 ,
 wherein when stopping the processing of the second control unit, the second control unit is stopped by register setting from outside and a luminance rate of X % obtained by the processing of the first control unit is set as the luminance rate for controlling the backlight.   
     
     
         13 . The display driver according to  claim 8 ,
 wherein the backlight control signal for controlling the backlight is outputted as a PWM signal of one bit.   
     
     
         14 . The display driver according to  claim 8 ,
 wherein the backlight luminance control of the second control unit is performed by sensing external-light luminance with an optical sensor and adjusting the backlight luminance.   
     
     
         15 . A display driver comprising:
 a first control unit switching brightness of a display image based on a display data value at a predetermined position of a histogram of inputted display data and switching backlight luminance based on the display data value, wherein an object of detection of the histogram is a data range from a brightest level to an N-th level of gray-scale (N is a positive integer and is not 0) of the display data; and   second to K-th (K is an integer equal to or larger than 3) control units performing backlight luminance control different from the first control unit,   wherein one of the second to K-th control units and the first control unit are used in combination.   
     
     
         16 . A display driver for driving a display device including a backlight comprising:
 a first control unit outputting a first control signal for controlling luminance of the backlight based on a histogram of inputted display data;   a second control unit outputting a second control signal for controlling the luminance of the backlight based on a luminance signal detected by a sensor; and   a generating unit including a circuit multiplying the first control signal and the second control signal together and controlling the luminance of the backlight based on a third control signal from the circuit.   
     
     
         17 . The display driver according to  claim 16 ,
 wherein the generating unit includes a first circuit switching between the first control signal and a signal of a first predetermined value and a second circuit switching between the second control signal and a signal of a second predetermined value.   
     
     
         18 . The display driver according to  claim 17 ,
 wherein the generating unit includes a third circuit dividing the second control signal by the second predetermined value.   
     
     
         19 . A display driver for driving a display device including a backlight comprising:
 a generating unit generating a plurality of gray-scale voltages;   a decoder decoding a gray-scale voltage from inputted display data with reference to the plurality of gray-scale voltages from the generating unit; and   a control unit controlling luminance of the backlight based on a control signal obtained by multiplying a first control signal based on a histogram of the inputted display data and a second control signal based on a luminance signal detected by a sensor.   
     
     
         20 . The display driver according to  claim 19 ,
 wherein the control unit includes:   a first control unit outputting the first control signal based on the histogram of the inputted display data;   a second control unit outputting the second control signal based on the luminance signal detected by the sensor; and   a generating unit including a circuit multiplying the first control signal and the second control signal together and controlling the luminance of the backlight based on a third control signal from the circuit.