The present disclosure relates generally to power management and refreshing the pixels of a liquid crystal display.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art
Electronic devices increasingly include display screens as part of the user interface of the device. As may be appreciated, the display screens may be employed in a wide array of devices, including desktop computer systems, notebook computers, handheld computing devices, cellular phones and portable media players. Liquid crystal display (LCD) panels have become increasingly popular for use in these devices. This popularity can be attributed to their light weight and thin profile, as well as the relatively low power it takes to operate the pixels of the LCD's to generate images on the LCD.
For any given pixel of an LCD monitor, the amount of light that is viewable on the LCD depends on the voltage applied to the pixel. However, applying a single direct current (DC) voltage could eventually damage the pixels of the display. Thus, in order to prevent such possible damage, LCD's typically alternate, or invert, the voltage applied to the pixels between positive and negative DC values for each pixel. This inversion results in an overall average DC voltage of zero over time, with no loss in brightness because the root mean square of the voltage can be chosen to be the same for both the positive and negative DC values.
This inversion may be done on a line-by-line basis to refresh the voltage of the LCD, creating line inversion refreshes for the LCD. Similarly, LCDs typically refresh the panel by switching the polarity for each line and transmitting the necessary voltage to each pixel, in effect, redrawing the panel on a line by line basis for each cycle of refresh (typically 60 Hz). In other types of LCD's, the inversion may be done on a “frame” basis so that the entire frame is held at one polarity for one cycle, such that all lines (rows) are redrawn from the first line to the last line, and then switched to the opposite polarity for the next cycle, again redrawing from the first line of the panel to the last line. In a frame refresh, the polarity of the “frame” is switched every cycle (e.g., 60 times per second for a 60 Hz refresh rate). Depending on the type of LCD panel, some refresh techniques may result in undesirable artifacts or visual effects. Further, as the demand for portable devices continues to grow, there is a need for LCD inversion techniques and image refreshing techniques that consume less power.