Gamma Correction DAC Bulk-Biasing for Wider Output Range
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Solution Overview
Problem
Existing gamma correction digital-to-analog converters (DACs) for OLED display systems face challenges in occupying small area, adjusting output dynamic range, and minimizing internal resistance, which are crucial for efficient display performance.
Innovation Solution
A gamma correction DAC comprising a first and second DAC circuit, along with a voltage generator, dynamically adjusts output dynamic range by using adjustable bulk voltages and medium voltage transistors to reduce internal resistance and occupied area, while generating gamma correction analog signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a gamma correction DAC is designed to occupy small area, then the internal resistance increases and output dynamic range decreases
Solution Approach 1:
The gamma correction DAC is divided into two separate DAC circuits: a first DAC circuit for generating a first gamma voltage and a second DAC circuit for generating a second gamma voltage. This segmentation allows each circuit to be optimized independently, enabling small occupied area while maintaining adequate output dynamic range through the combined operation of both circuits.
Solution Approach 2:
The patent introduces a voltage generator that dynamically adjusts the bulk voltage supplied to the transistors based on the digital data input. This dynamic adjustment of bulk voltage allows the DAC to maintain small internal resistance and adequate output dynamic range even when occupying small area, as the bulk voltage is optimized in real-time according to the operating conditions.
2Area of moving object
If the DAC circuit is reduced in size, then internal resistance increases
Solution Approach 1:
The voltage generator dynamically adjusts the bulk voltage supplied to the transistors based on the digital data input and operating conditions. This dynamic bulk voltage adjustment compensates for the increased internal resistance that would normally result from reduced transistor size, allowing the DAC to maintain low internal resistance while occupying small area.
Solution Approach 2:
The patent changes the bulk voltage parameter dynamically to optimize the performance of the transistors. By adjusting the bulk voltage, the electrical characteristics of the transistors are optimized to maintain low internal resistance even when the transistor dimensions are reduced to minimize occupied area.
3Area of moving object
If medium voltage transistors are used to reduce occupied area, then output dynamic range may be compromised
Solution Approach 1:
The output dynamic range is distributed across two DAC circuits, each using medium voltage transistors. The first DAC circuit generates a first gamma voltage and the second DAC circuit generates a second gamma voltage, and their combined output achieves the required dynamic range without requiring large-area high-voltage transistors in a single circuit.
Solution Approach 2:
The dynamic bulk voltage adjustment compensates for the limitations of medium voltage transistors, enabling them to deliver adequate output dynamic range despite their smaller size. The bulk voltage is optimized to maximize the output swing and linearity of the medium voltage transistors.
Data Source
AI summary
A gamma correction digital-to-analog converter (DAC) includes a first DAC circuit, a second DAC circuit and a voltage generator. The first DAC circuit includes a plurality of first transistors and is configured to receive a plurality of first reference gamma voltages and 1 upper bits of k-bit digital data and generate a first gamma voltage based on the 1 upper bits of the k-bit digital data and the first reference gamma voltages. The second DAC circuit includes a plurality of second transistors and is configured to receive a plurality of second reference gamma voltages and m lower bits of the k-bit digital data and generate a second gamma voltage based on the m lower bits of the k-bit digital data and the second reference gamma voltages. The voltage generator is configured to generate a bulk voltage and supply the generated bulk voltage to a bulk terminal of each of the first transistors or supply the generated bulk voltage to a bulk terminal of each of the second transistors to generate a gamma correction analog signal according to the first gamma voltage and the second gamma voltage. A data driver including a gamma correction DAC and a method thereof are also introduced.