Method for power level control of a display and apparatus for carrying out the method

Method for power level control in a display device having a plurality of luminous elements corresponding to the pixels of a picture, wherein the time duration of a video frame or video field is divided into a plurality of sub-fields during which the luminous elements can be activated for light emission in small pulses corresponding to a sub-filed code word which is used for brightness control, wherein a set of power level modes is provided for sub-field coding, wherein to each power level mode a characteristic sub-field organization belongs defining a characteristic power level value, the sub-field organization being variable in respect to one or more of the following characteristics:

• the number of sub-fields;
• the sub-field type;
• the sub-field position;
• the sub-filed weight;
• the sub-field pre-scaling;
• and
• a factor for the sub-field weights which is used to vary the amount of small pulses generated during each sub-filed;
• said method comprising steps of:
• determining a value which is characteristic for the power level of a video picture;
• selecting a corresponding power level mode for the sub-field coding wherein the switching between power level modes corresponding to the characteristic value for the power level of the video picture is controlled with an hysteresis like switching which is implemented for the dynamic control of the power level mode selection as a function of the measured picture average power.