Display Driver Output Buffer Pre-Charge Circuit
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Solution Overview
Problem
Display devices face challenges in maintaining high slew rates and reducing power consumption as scan rates and resolutions increase, due to difficulties in controlling pre-charge circuits connected between output terminals and source lines, leading to feedback delays and increased input stage sizes.
Innovation Solution
A display driver with a pre-charge circuit connected between the input and output stages of output buffers, controlled by a pre-charge control unit that compares image data to adjust output voltages, allowing for rapid voltage changes without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scan rate and resolution of the display device are increased, then the image quality and performance are improved, but the slew rate of the output terminal decreases and power consumption increases
Solution Approach 1:
The pre-charge circuit performs preliminary action by pre-charging the output terminal to a predicted voltage level before the actual voltage transition is needed. The pre-charge control unit compares current image data with previous frame data to determine the required pre-charge voltage, allowing the output buffer to start from a closer voltage point and achieve faster transitions at high scan rates
2Adaptability or versatility
If the pre-charge circuit is connected between the output terminal and source line, then the output voltage can be adjusted, but feedback delays occur and the input stage size increases
Solution Approach 1:
The invention extracts the pre-charge function from the main feedback path and implements it as a separate parallel circuit. The pre-charge control unit independently determines pre-charge voltages based on image data comparison, bypassing the feedback delay issues of the main output stage while still achieving output voltage adjustment
3Adaptability or versatility
If the pre-charge circuit is connected between the output terminal and source line, then the output voltage can be adjusted, but the circuit area of the input stage increases
Solution Approach 1:
The invention segments the voltage control function into two independent parts: the main output stage for steady-state voltage control and the pre-charge circuit for transient voltage preparation. This segmentation allows each stage to be optimized independently, reducing the input stage area requirements while maintaining full output voltage control capability
Data Source
AI summary
A display driver includes a first latch storing first image data, a second latch storing second image data, and a buffer unit including a plurality of output buffers outputting a source voltage corresponding to the first image data. Each of the plurality of output buffers includes an input stage, an output stage, and a pre-charge circuit connected between the input stage and the output stage. A pre-charge control unit compares the first image data with the second image data to control the pre-charge circuit.