Hybrid DAC Architecture for High-Bit LCD Source Drivers
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Solution Overview
Problem
Conventional digital to analog converters in LCD devices experience exponential size increases with the number of digital bits for RGB data, leading to inefficient circuit size and image quality enhancement.
Innovation Solution
A hybrid digital to analog converter is introduced, comprising a resistor string type DAC unit for high bits and a binary-weighted current type DAC unit for low bits, along with a gamma voltage generation unit and a voltage-to-current converter, to reduce circuit size while maintaining high image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of digital bits of RGB data is increased to enhance image quality, then the quality of images is improved, but the size of the decoder and digital to analog converter increases exponentially
Solution Approach 1:
The patent divides the digital data into high bits and low bits, processing them through separate DAC paths. The high bits are processed by a first DAC unit while low bits are processed by a second DAC unit, allowing the system to handle high-resolution data without requiring a single exponentially large converter structure
Solution Approach 2:
The patent transitions from a single-dimensional voltage output approach to a two-dimensional approach by generating both voltage and current outputs. The first DAC unit outputs voltage corresponding to high bits, while the second DAC unit outputs current corresponding to low bits, which are then combined through a voltage-to-current converter to achieve the full resolution without exponential area growth
2Ease of operation
If a conventional digital to analog converter uses a resistor string to provide gray voltages, then gray voltage selection is achieved, but the converter size increases greatly when RGB data bits increase
Solution Approach 1:
The patent segments the gray voltage generation into two parts: a first DAC unit that generates gray voltages for high bits and a second DAC unit that generates gray voltages for low bits. This segmentation allows each unit to use fewer switches, avoiding the exponential growth of switch count while maintaining complete gray voltage selection capability
Solution Approach 2:
The patent adds a current output dimension to complement the voltage output. The second DAC unit outputs current that is converted to voltage through a voltage-to-current converter, creating an additional dimension for data representation that reduces the complexity of the resistor string and switch network
Data Source
AI summary
A hybrid digital to analog converter (DAC) includes a first digital to analog converting unit (DACU) and a second DAC unit. The first DAC unit provides an analog voltage corresponding to Q-bit upper data of P-bit gray data, in response to a plurality of gamma voltages, where P is a natural number equal to or greater than 10 and Q is a natural number less than 10. The second DAC unit provides an analog current having a magnitude according to each bit level of R-bit lower data of the P-bit gray data, based on a rated current generated from a reference voltage, where R is a natural number corresponding to P-Q.