Active matrix display devices and methods of driving the same

摘要

An active matrix display device has a column driver circuit for providing pixel drive signals to columns of pixels, and comprising current source circuits. Each current source circuit has a supply switch (78) for controlling the time during which the current source supplies current to or drains current from the column. A mapping means (74) derives from a pixel drive level a digital value which represents a time period for the control of the supply switch (78) of each current source circuit. The mapping means (74) implements a single mapping function for use in providing the digital values for all current source circuits. Having a current source circuit for each column facilitates the application of inversion patterns. The conversion of pixel drive levels to values representing time is carried out in a shared manner, so that the required area is kept to a minimum.

主权项

1. An active matrix liquid crystal display device comprising:
an array of pixels arranged in rows and columns, each pixel comprising a liquid crystal cell; a column driver circuit for providing pixel drive signals to the columns of pixels, wherein the column driver circuit comprises an array of current source circuits, a respective current source circuit being provided for each column of pixels, wherein each current source circuit comprises: a current source; and a supply switch for controlling the time during which the current source supplies current to or drains current from the column, and wherein the device further comprises a mapping means for deriving a digital value from the transmittance of the liquid crystal cell, wherein the digital value represents a time period for the control of the supply switch of each current source circuit, the mapping means implementing a single mapping function for use in providing the digital values for all current source circuits; wherein the column driver circuit is adapted to apply a polarity inversion scheme such that the current source is controlled to supply current to or drain current from the column thereby generating a voltage corresponding to a positive gamma curve and a voltage corresponding to a negative gamma curve on a capacitor of the liquid crystal cell alternately.