1. Field of the Invention
The present invention relates to method for driving a flat panel displays, and particularly to a method for driving a flat panel display for reducing power consumption of a source driver by modified scan signals, and therefore for reducing the system power consumption.
2. Description of Related Art
In order to catch up with the modern lifestyle, video and image devices are becoming slimmer and lighter. Despite of advantages it may have, a conventional cathode-ray tube (CRT) display not only is large in bulk that occupies too much room because of its intrinsic structure of the electronic cavity, but also radiates rays which may hurt human eyes. Therefore, accompanying the development of optoelectronic technology and semi-conductor processing technology, flat panel displays including liquid crystal display (LCD), organic light-emitting diode (OLED) display and plasma display panel (PDP) are gradually becoming a mainstream in the display market.
Resolutions and refreshing frequencies of flat panel displays are continuously improving. Consequently, refreshing frequencies of scan lines are demanded to be more and more rapid, which contradicts the designs for power saving by system engineers. As a result, a technology for eliminating the contradiction therebetween called “smart charge sharing” technology is developed thereby.
FIGS. 1A and 1B are schematic diagrams of a conventional charge sharing technology provided by Dr. Craig Zajac of the US National Semiconductor Incorporation. Referring to FIG. 1A, first, a flat panel display 100 includes a source driver 110 and a pixel array 130. The pixel array 130 includes a plurality of data lines DL0 through DLm electrically connected to the source driver 110.
The source driver 110 includes a plurality of output amplifiers A1 through Am. Each of the output terminals of the amplifiers is respectively connected to a corresponding data line. The source driver 110 further includes a plurality of switches SW1 through SWm−1 for connecting adjacent two data lines. For example, a switch SW1 is adapted for connecting the adjacent data lines DL0 and DL1. As shown in FIG. 1A, each data line is taken as a sum of loads of resistance and capacitance of a corresponding output amplifier.
Before the source driver 110 driving the pixel array 130, voltages of each pair of the adjacent data lines are respectively higher or lower than a common voltage. Meanwhile, all of the switches SW1 through SWm−1 are at turn-off status. At the instance that the source driver 110 starts to drive the pixel array 130, all of the switches SW1 through SWm−1 will be switched to turn-on status as shown in FIG. 1B. At this certain instance, all amplifiers A1 through Am are at disable status, which is called Hi-Z mode during which the output amplifiers A1˜Am without current consumption. However, as the switches SW1 through SWm−1 are at turn-on status, there will be a current flowing from a data line having a voltage higher than the common voltage to a data line having a voltage lower than the common voltage, the path of which is as illustrated of the arrowheads in FIG. 1B. Thus, charges can be neutralized therein. After experiencing a Hi-Z mode, the switches SW1 through SWm−1 will go back to the turn-off status, while the source driver 110 can the drive pixel array 130 as usual.
In summary, the principle of the charge sharing technology is to reallocate energy (charges) stored in the data lines and whereby to drive the scan lines to a half of the final value without power consumption. Such technology is enough for those small flat panel displays taking little loads and providing a lower resolution. Unfortunately, whenever an overall slew rate of the source driver 110 slows down, an efficiency of the source driver 110 will drop down accordingly. Therefore, such a source driver can not satisfy the requirements of the new generation flat panel displays which demand higher resolution, higher load and larger size.