Display Driver Current Compensation for Precise Gradation Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing display drivers using inverting amplifier circuits with resistor or capacitor feedback face challenges in maintaining high gain across fluctuating bias points, leading to errors in gradation voltage due to current flow through the ladder resistance circuit and noise sensitivity.
Innovation Solution
A display driver design incorporating an inverting amplifier circuit with resistor feedback, supplemented by first and second current compensating circuits that adjust compensation currents based on the difference between the output voltage and reference voltage, reducing errors in gradation voltage and enhancing noise resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an inverting amplifier circuit with resistor feedback is used, then the bias point fluctuation is reduced, but current flows through the ladder resistance circuit causing gradation voltage error
Solution Approach 1:
A current compensating circuit is introduced as an intermediary component between the inverting amplifier circuit and the ladder resistance circuit. This compensating circuit measures the current flowing through the ladder resistance circuit and generates a compensation signal that cancels out the error current, thereby eliminating the gradation voltage error while maintaining the stability benefits of resistor feedback
2Measurement precision
If capacitor feedback is used in inverting amplifier circuit, then gradation voltage error is avoided, but initialization time is required and drive time is shortened
Solution Approach 1:
The patent replaces the capacitor feedback mechanism with a resistor feedback mechanism combined with an active current compensating circuit. This substitution eliminates the need for periodic initialization that characterizes capacitor-based systems, allowing continuous operation without interrupting the drive cycle, thereby maximizing productivity while maintaining precision
3Measurement precision
If capacitor feedback is used in inverting amplifier circuit, then gradation voltage error is avoided, but noise sensitivity increases
Solution Approach 1:
The current compensating circuit employs a feedback mechanism that continuously monitors the current through the ladder resistance circuit and adjusts the compensation signal accordingly. This active feedback approach provides stable, low-noise compensation compared to passive capacitor feedback, reducing noise sensitivity while maintaining precision
4Device complexity
If forward amplifier circuit is used, then circuit configuration is simple, but gain decreases as bias point approaches power supply voltage
Solution Approach 1:
The patent adopts an inverting amplifier configuration with current compensation instead of a forward amplifier. While the inverting configuration itself is not inherently more complex, the addition of the current compensating circuit creates a systematic approach that maintains consistent gain across the full bias point range, overcoming the limitation of forward amplifiers where gain degrades near power supply rails
Data Source
AI summary
A display driver includes a digital-to-analog (D/A) converting circuit, an inverting amplifier circuit, and current compensating circuits. The D/A converting circuit converts display data into a gradation voltage. The inverting amplifier circuit includes an operational amplifier, a resistor provided between an input node to which the gradation voltage is input and an inverting input terminal of the operational amplifier, and a resistor provided between an output terminal of the operational amplifier and the inverting input terminal. The current compensating circuit causes a compensation current to flow from a first node of a first supply voltage to an input node. The current compensating circuit causes a compensation current to flow from the input node to a second node of a second supply voltage.