Display Driver Segmentation for High-Precision Gradation
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Solution Overview
Problem
Existing display drivers face challenges in achieving high-precision gradation voltages for multiple gradation levels, leading to increased layout area requirements due to the need for higher breakdown voltage components in the switch circuit, particularly in the second D/A converter circuit.
Innovation Solution
A display driver configuration that includes a first D/A converter circuit for upper-bit data conversion, a second D/A converter circuit with a reference voltage ladder resistance circuit and switch elements for varying the reference voltage based on lower-bit data, and an inverting amplifier circuit for amplifying gradation voltages, allowing for reduced breakdown voltage requirements and a smaller layout area by using transistors with lower breakdown voltages for the switch circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second D/A converter circuit with switch elements is added to achieve multiple gradation levels, then gradation precision is improved, but layout area increases due to higher breakdown voltage requirements
Solution Approach 1:
The patent segments the D/A converter into two separate circuits: a first D/A converter that outputs a basic gradation voltage, and a second D/A converter that outputs a reference voltage for fine adjustment. This segmentation allows each circuit to be optimized independently, with the second converter using lower breakdown voltage transistors for the switch elements, thereby reducing the layout area while maintaining high gradation precision.
Solution Approach 2:
The patent introduces an inverting amplifier circuit as an intermediary between the first D/A converter and the output. This amplifier receives the basic gradation voltage from the first D/A converter and adjusts it based on the reference voltage from the second D/A converter, enabling precise gradation control without requiring the switch elements to handle high breakdown voltages directly.
2Reliability
If transistors with higher breakdown voltage are used in the switch circuit, then reliability is improved, but layout area increases
Solution Approach 1:
The patent applies local quality by using different transistor breakdown voltage specifications in different parts of the circuit. The first D/A converter and inverting amplifier use transistors with higher breakdown voltage for reliability, while the switch elements in the second D/A converter use lower breakdown voltage transistors, optimizing the trade-off between reliability and area for each specific component based on its functional requirements.
Data Source
AI summary
A display driver includes a first D/A converter circuit configured to output a gradation voltage corresponding to upper-bit data of display data, a second D/A converter circuit configured to output a reference voltage corresponding to lower-bit data of the display data, and an inverting amplifier circuit configured to amplify the gradation voltage with reference to the reference voltage, and to drive a data line of an electro-optical panel. The second D/A converter circuit includes a first resistor provided between a node of a high potential-side power source and an output node of the reference voltage, a second resistor provided between the output node and a first node, a reference voltage ladder resistance circuit provided between the first node and a node of a low potential-side power source, and a switch circuit.