Source Driver DAC Switching to Block Gamma Coupling
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) experience transient gamma coupling during data conversion, leading to unstable image output in display panels, with binary DACs being more prone to this issue than ROM-type DACs.
Innovation Solution
Incorporating a switch unit with multiple switches between the reference voltage generation unit and the selection unit, which are turned off during data conversion periods, and a control unit that increases the pulse width of the line latch signal to control the switch unit, preventing gamma coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DAC structure (ROM-type or binary) is used, then the DAC can convert digital data to analog voltage, but transient gamma coupling occurs during data conversion causing unstable image output
Solution Approach 1:
The patent extracts and removes the harmful coupling path by introducing a switch unit that disconnects the connection between the reference voltage generation unit and selection unit during data conversion. This isolates the harmful gamma coupling effect from the signal path, eliminating the transient interference that causes image instability.
Solution Approach 2:
The patent applies preliminary action by controlling the switch unit to be in a specific state (turned off) before and during the data conversion period. This preliminary disconnection prevents the gamma coupling from occurring in the first place, rather than attempting to correct it after it occurs.
2Reliability
If the switch unit is added to prevent gamma coupling, then image stability is improved, but device complexity increases
Solution Approach 1:
The switch unit serves multiple functions: it acts as a normal signal transmission path during non-conversion periods, and simultaneously serves as a gamma coupling prevention mechanism during data conversion. This multi-functionality reduces the need for separate components and minimizes overall device complexity.
Solution Approach 2:
The patent merges the gamma coupling prevention function with the existing DAC structure by integrating the switch unit into the signal path between the reference voltage generation unit and selection unit. This combination approach adds minimal complexity while achieving the desired image stability.
Data Source
AI summary
A source driver and a digital-to-analog converter (DAC) thereof are provided. The DAC converts an input data into an analog voltage. The DAC includes a reference voltage generation unit, a switch unit, and a selection unit. The reference voltage generation unit provides a plurality of voltage levels. The switch unit is coupled to the reference voltage generation unit and determines whether to output the voltage levels, wherein the switch unit is turned off during a data conversion period of the input data. The selection unit is coupled to the reference voltage generation unit via the switch unit, and the selection unit selects one of the voltage levels output by the switch unit according to the input data, wherein the selected voltage level is served as the analog voltage output by the DAC.