Segmented DAC Circuit for AMOLED Source Drivers With Lower Switching Area
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Solution Overview
Problem
Current digital-to-analog conversion circuits in AMOLED source drivers face challenges in reducing switching area while maintaining accuracy, particularly due to high power consumption and limited precision in high-definition display applications.
Innovation Solution
A digital-to-analog conversion circuit comprising a first digital-to-analog converter for high bits and a second digital-to-analog converter for low bits, utilizing a voltage division module, voltage selection modules, and operation amplifiers to generate reference voltages and reduce the number of switches required, thereby optimizing the DAC structure and minimizing chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current steering DAC is used to drive video transmission, then high speed and high precision are achieved, but power consumption increases due to doubled source current
Solution Approach 1:
The patent divides the (m+n)-bit DAC into two separate converters: a first DAC handling m high bits and a second DAC handling n low bits. This segmentation allows each converter to operate more efficiently, reducing the overall current requirement while maintaining high precision conversion capability.
2Device complexity
If resistor string voltage division type DAC is used, then structure is simple with small glitches and good linearity, but accuracy is limited to about 8 bits
Solution Approach 1:
The patent segments the DAC function into two parts: the first DAC uses voltage division for the high bits (simpler structure), while the second DAC handles the low bits with higher precision requirements. This segmentation allows the system to achieve >10 bit accuracy while keeping parts of the structure simple.
Solution Approach 2:
The patent merges the outputs of two separate DACs (first DAC for high bits, second DAC for low bits) to achieve the final (m+n)-bit conversion. This combination allows the system to overcome the 8-bit limitation of individual voltage division DACs while avoiding the complexity and high current requirements of full-resolution current steering DACs.
3Measurement precision
If conventional DAC structure is used in large-size AMOLED source driver, then conversion function is provided, but chip area is greatly increased with 60%-70% occupied by DACs
Solution Approach 1:
By segmenting the DAC into two functional units (first DAC for high bits, second DAC for low bits), the patent reduces the overall area requirement. The voltage division module generates reference voltages that are reused by both DACs, further reducing the area occupied by reference voltage generation circuitry.
Solution Approach 2:
The voltage division module serves multiple functions: it generates reference voltages for the first DAC, provides reference voltages for the second DAC, and enables both high-bit and low-bit conversions. This multi-functionality reduces the total component count and chip area while maintaining high conversion accuracy.
Data Source
AI summary
Embodiments of the present disclosure relate to a digital-to-analog conversion circuit and method, a source driver, and a display apparatus. The digital-to-analog conversion circuit includes a first digital-to-analog converter corresponding to m high bits of (m+n)-bit digital signal and a second digital-to-analog converter corresponding to n low bits, where m and n are integers greater than 0. The first digital-to-analog converter comprises a voltage division module configured to generate 2m reference voltages at equal intervals in voltage; a first voltage selection module configured to select, from the 2m reference voltages, a first voltage corresponding to the m bits; and an operation module configured to generate a second voltage higher than the first voltage by the interval in voltage based on two adjacent reference voltages of the 2m reference voltages and the first voltage. The second digital-to-analog converter is configured to generate a third voltage corresponding to the n bits by using the first voltage and the second voltage as reference voltages, and to generate the sum of the third voltage and the first voltage.