Reducing power consumption in a liquid crystal display

摘要

Embodiments of the invention relate to a method and apparatus to reduce power consumption in a passive matrix LCD driver circuit by using a plurality of drive buffers and active power management of sub-blocks in the passive matrix LCD drive circuit. Each drive buffer may operate in a first phase, which may include a high-drive mode to drive an LCD voltage to a threshold voltage level and a low-drive mode to modify the LCD voltage to approximate an input voltage of the drive buffer, and to maintain a constant LCD voltage level. The low-drive buffer consumes less current than the high-drive buffer, thus reducing power consumption. The drive buffer may also operate in a second phase, also a no-drive mode, in which the drive buffer and the bias voltage generator may be completely turned off, to further reduce power consumption. The drive buffer may be used to drive capacitive loads, as well as partially-resistive loads and inductive loads.

主权项

1. An apparatus, comprising:
a bias voltage generator to generate a plurality of bias voltages; and a drive buffer to drive a passive liquid crystal display (LCD) pixel or segment from a particular one of the bias voltages, wherein the drive buffer actively drives the passive LCD segment or pixel in a first phase, and wherein the drive buffer comprises:
a first buffer configured to actively drive a voltage, applied to the passive LCD pixel or segment, to a threshold level that is different from the particular one of the bias voltages, wherein the first buffer includes a current source that is configured to drive the voltage applied to the passive LCD pixel or segment to the threshold level; anda second buffer in parallel with the first buffer configured to actively further modify the voltage, applied to the passive LCD pixel or segment, from the threshold level to approximate the particular one of the bias voltages; wherein the drive buffer is configured to actively drive the passive LCD segment or pixel by adjusting the voltage, applied to the passive LCD pixel or segment, to approximate the particular one of the bias voltages, and by compensating a leakage associated with the passive LCD pixel or segment to provide a constant voltage at the passive LCD pixel or segment in a low-drive mode; and wherein the second buffer is activated during the low-drive mode.