Display Driver Voltage Generator Circuit Design
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Solution Overview
Problem
Existing display drivers for liquid crystal or organic EL display devices require multiple systems of drivers for generating reference voltages for different color components, leading to increased device scale and power consumption due to the need for amplifiers and switches, which complicates the generation of gradation voltages along gamma characteristics.
Innovation Solution
A display driver with a gradation reference voltage generator that uses a combination of ladder resistors, input amplifiers, and a selector to generate and switch gradation reference voltages for different color components, reducing the need for multiple driver systems and minimizing power consumption by eliminating the response delay of amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple systems of drivers are used to generate reference voltages for different color components, then the required reference voltages can be supplied to DA conversion circuits, but the device scale and power consumption increase
Solution Approach 1:
The patent merges multiple reference voltage generation functions into a single driver circuit. One driver circuit generates all reference voltages for red, green, and blue color components by sequentially switching between different gamma characteristics, eliminating the need for separate driver systems for each color component.
Solution Approach 2:
The patent employs dynamic switching of gamma characteristics within a single driver circuit. The driver can switch between first gamma characteristic (for red and green) and second gamma characteristic (for blue) based on the color component being driven, allowing one circuit to perform multiple functions dynamically.
2Reliability
If amplifiers are added between the switch output and single wiring to supply reference voltages, then the reference voltages can be supplied to all DA conversion circuits, but the response delay increases due to amplifier response time
Solution Approach 1:
The patent extracts the amplifier from the critical signal path. Instead of placing amplifiers between the switch and the wiring that distributes reference voltages to DA conversion circuits, the design uses the switch output directly, eliminating the amplifier response delay from the reference voltage generation path.
Solution Approach 2:
The patent introduces a buffer circuit as an intermediary between the switch output and the DA conversion circuits. This buffer circuit can drive multiple loads without requiring high slew rate amplifiers, thus reducing response delay while maintaining the ability to supply reference voltages to all DA conversion circuits.
3Speed
If the slew rate of amplifiers is increased to cope with large screen and high-definition display, then the response speed improves, but power consumption increases
Solution Approach 1:
The patent removes amplifiers from the reference voltage generation path entirely, eliminating the need for high slew rate amplifiers and their associated power consumption. The switch output is used directly or through a buffer to supply reference voltages to DA conversion circuits.
Solution Approach 2:
The switch circuit is designed to directly output reference voltages with sufficient drive capability to supply multiple DA conversion circuits without requiring additional amplification stages, making the system self-sufficient and reducing power consumption.
Data Source
AI summary
A display driver and a display device are provided. The driver includes a first ladder resistor receiving a first potential at one end and a higher second potential at the other end to generate voltages obtained by dividing a voltage between first and second potentials; a second ladder resistor receiving first potential at one end, a second potential at the other end, and each of partial voltages among the voltages generated by the first ladder resistor at a connection point between the resistors to generate gradation reference voltages; first to k-th input amplifiers individually amplifying first to k-th DC bottom potentials respectively corresponding to first to k-th gamma correction characteristics to generate first to k-th amplified bottom potentials; and a first selector sequentially selecting one of the first to k-th amplified bottom potentials and supplying the selected one to one end of the first ladder resistor as a first potential.