Data Driver Reset Unit for Display Device Ramp Linearity
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Solution Overview
Problem
Current data drivers face high current consumption and instability in sampling/holding operations, particularly when large voltage differences occur, leading to broken linearity of ramp signals, especially when transitioning between high and low gray levels in display devices.
Innovation Solution
A data driver design that includes a signal generator producing staircase waveform gray voltage signals using gamma reference voltages and a reset unit to supply a reset voltage corresponding to the intermediate value between previous and current selected gray voltage signals, reducing the number of ramp signals needed and stabilizing the sampling/holding operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If grouped ramp signals are supplied to reduce decoder area, then device complexity is reduced, but current consumption increases during sampling/holding operations when large voltage differences occur
Solution Approach 1:
The reset unit performs preliminary action by resetting the output circuit to an intermediate gray level voltage before the sampling/holding operation when a large voltage difference is detected. This preliminary reset prevents excessive current consumption during the subsequent sampling phase by avoiding large voltage transitions, thus resolving the contradiction between using grouped ramp signals for area reduction and the resulting current consumption increase.
2Use of energy by moving object
If current consumption is reduced by supplying fewer ramp signals, then energy efficiency improves, but the sampling/holding operation becomes unstable and ramp signal linearity is broken
Solution Approach 1:
The reset unit changes the voltage parameter of the output circuit by resetting it to an intermediate gray level voltage (corresponding to gray level 128) before the sampling/holding operation. This parameter change stabilizes the sampling process and maintains ramp signal linearity while allowing current consumption to be reduced through fewer ramp signals, thus resolving the contradiction between energy efficiency and operation stability.
3Device complexity
If the number of ramp signals is reduced to fewer than the number of gray voltages, then device complexity is reduced, but maintaining linearity of ramp signals becomes difficult
Solution Approach 1:
The reset unit acts as an intermediary by introducing an intermediate gray level voltage (gray level 128) as a reset level. This intermediary voltage level serves as a reference point that maintains the linearity of the reduced number of ramp signals (16 ramp signals for 256 gray levels) by providing a stable starting point for each horizontal period, thus resolving the contradiction between reducing device complexity and maintaining signal linearity.
Data Source
AI summary
A data driver includes: a signal generator which includes a staircase waveform gray voltage signal generator which generate a plurality of staircase waveform gray voltage signals using a lowest gamma reference voltage, a highest gamma reference voltage, and a plurality of gamma voltages having a magnitude between the lowest gamma reference voltage and the highest gamma reference voltage; and a channel driver which includes a decoder which output one staircase waveform gray voltage signal selected from the staircase waveform gray voltage signals, an output circuit which output a gray voltage corresponding to the selected staircase waveform gray voltage signal, and a reset unit which supplies one of the gamma voltages to the output circuit as a reset voltage.