Output Circuit Stabilizes Voltage for High-Frequency Display Drivers
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Solution Overview
Problem
Existing data line drivers face challenges in maintaining uniform voltage distribution across display panels, leading to excessive overshoot and undershoot in output voltages, particularly when dealing with high load capacities and short driving periods, which results in luminance differences and image quality deterioration.
Innovation Solution
The proposed output circuit incorporates a differential amplifier with an inverting input terminal and multiple non-inverting input terminals, along with a delay circuit that generates a delay voltage with a predetermined time constant, to stabilize the output voltage and prevent overshoot and undershoot by adjusting the voltage change based on the weighted average of input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the frame frequency is increased to 120 Hz or more, then the image quality and moving picture characteristics are improved, but the data output period becomes approximately 1/N, making it difficult to charge and discharge the load capacity at high speed
Solution Approach 1:
The patent applies dynamics by making the amplification factor variable rather than fixed. The differential amplifier dynamically adjusts its amplification factor based on the required driving conditions, allowing the output circuit to adapt to different frame frequencies and load capacities. This dynamic adjustment enables the circuit to maintain high charging/discharging speeds even at 120 Hz or higher frame frequencies.
Solution Approach 2:
The patent changes the parameter of amplification factor from a fixed value to a variable parameter that can be adjusted according to driving conditions. By varying the amplification factor, the output circuit can optimize its performance for different frame frequencies and load capacities, resolving the contradiction between high frame frequency operation and sufficient charging/discharging speed.
2Speed
If the amplification factor is increased to charge the load capacity quickly, then the charging speed is improved, but excessive overshoot and undershoot occur in the output voltage
Solution Approach 1:
The patent implements feedback by using the delay circuit to feed back a portion of the output voltage to the inverting input terminal of the differential amplifier. This feedback mechanism allows the circuit to monitor its own output and automatically adjust the amplification factor to prevent excessive overshoot and undershoot, thereby maintaining output voltage stability while achieving fast charging speeds.
Solution Approach 2:
The delay circuit acts as an intermediary element between the output terminal and the inverting input terminal. It introduces a time delay in the feedback signal, which helps to stabilize the output voltage by preventing immediate feedback reactions that could cause overshoot and undershoot, while still enabling fast charging through controlled amplification.
3Device complexity
If the circuit configuration is simplified to reduce the circuit scale, then the manufacturing cost is reduced, but the driving capability to charge and discharge high load capacity may be insufficient
Solution Approach 1:
The patent achieves multi-functionality by designing a differential amplifier that can dynamically adjust its amplification factor based on different driving conditions. This single amplifier circuit can handle both high load capacity driving and maintain output stability, eliminating the need for separate circuits for different functions. The delay circuit also serves dual purposes by providing both feedback for stability and timing control for preventing overshoot.
Solution Approach 2:
The patent merges the amplification function and the stability control function into a single integrated circuit structure. The differential amplifier and delay circuit work together as a unified system, where the delay circuit's feedback directly controls the differential amplifier's operation. This merging reduces the overall circuit scale while maintaining sufficient driving capability for high load capacity applications.
Data Source
AI summary
An output circuit includes a differential amplifier including an inverting input terminal, non-inverting input terminals and an output terminal, and outputs, from the output terminal, a voltage having a level corresponding to a weighted average of respective input voltage levels of the non-inverting input terminals, when the output voltage level is equal to a input voltage level of the inverting input terminal, and outputs a voltage having a level corresponding to a difference between a level corresponding to a weighted average of the respective input voltage levels of the non-inverting input terminals and the input voltage level, when which the output voltage level is different from the input voltage level; and a delay circuit that generates a delay voltage responding with a predetermined time constant with respect to a change in the output voltage level and supplies the delay voltage to the inverting input terminal.