Segmented Current Source Driver for High-Bit Display Gradation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current current drive systems for organic luminous elements face challenges in controlling circuit size and reducing wiring complexity, especially when increasing the number of output bits, leading to increased costs and complexity in display devices.
Innovation Solution
A current output type semiconductor circuit is designed with first and second current source groups, where the second group outputs a current larger than the first, allowing for efficient gradation control and reduced circuit size, and a separate control circuit generates video and command signals to minimize wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of output bits is increased to improve gradation representation, then display quality is improved, but circuit size and wiring complexity increase
Solution Approach 1:
The current output circuit is segmented into multiple current source groups, where each group handles specific bit ranges. The first current source group outputs currents for lower-order bits while the second current source group outputs currents for higher-order bits. This segmentation allows the circuit to achieve high-resolution current output (8 bits or more) without requiring a single large complex circuit, thereby improving gradation representation while controlling circuit size and wiring complexity.
2Area of stationary object
If transistor size is reduced to decrease circuit area, then circuit size is reduced, but output current fluctuation increases
Solution Approach 1:
Different current source groups use transistors with different channel lengths and widths optimized for their specific functions. The first current source group uses transistors with channel length L1 and width W1 for lower-order bits, while the second current source group uses transistors with channel length L2 and width W2 for higher-order bits. This local optimization allows each transistor group to achieve appropriate current precision for its bit range while maintaining compact circuit area, thus reducing overall circuit size while controlling output current fluctuation.
Data Source
AI summary
To provide a current output type semiconductor circuit, a drive device for display, a display device, and a current output method that can control an increase in a circuit size to be lower even if the number of output bits of a current driver is increased.A current output type semiconductor circuit, including first current source groups 241a and 241b, includes first unit transistors of outputting a predetermined current and output lower order N (N is a natural number) bits; and second current source groups 242a, 242b, 242c, 242d, 242e, and 242f that include second unit transistors of outputting a current larger than that of the first unit transistors and output higher order M (M is a natural number, (N+M)≧3) bits.