Display Panel Current Detection Using VCO-Based Readout
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Solution Overview
Problem
Existing semiconductor devices for detecting drain current in driving transistors of display panels face challenges due to noise and variability in operational amplifiers and comparators, leading to reduced accuracy in luminance compensation across pixels.
Innovation Solution
A semiconductor device incorporating an error amplifier, voltage-controlled oscillator, counter, and specific switch circuits to accurately detect and convert current into digital signals, minimizing noise and ensuring consistent voltage supply for precise current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operational amplifiers and comparators are used in the current detection circuit, then the circuit can detect drain current, but noise and variation are introduced that reduce detection accuracy
Solution Approach 1:
The patent removes operational amplifiers and comparators from the current detection circuit, extracting the noise-generating components. Instead, it uses a capacitor to integrate the drain current signal directly, converting current to voltage without amplification stages that introduce noise and variation.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element between the drain current source and the measurement point. The capacitor integrates the current signal over time, providing a noise-free conversion from current to voltage that can be measured by standard voltmeters without requiring noisy active components.
2Manufacturing precision
If the number of pixels in display panel is increased to achieve higher resolution, then display quality improves, but variations in electrical characteristics of driving transistors increase making accurate detection more difficult
Solution Approach 1:
The patent employs a self-measuring approach where each pixel's driving transistor characteristics are automatically detected through its own drain current measurement. The capacitor-integration method provides inherent noise rejection that works uniformly across all pixels regardless of transistor variations, enabling accurate per-pixel measurement without requiring external calibration or complex compensation circuits.
Data Source
AI summary
A semiconductor device capable of current detection accurately is provided. The semiconductor device includes an error amplifier, a voltage controlled oscillator (VCO), a counter, a first circuit, and a terminal. The terminal is electrically connected to a non-inverting input terminal of the error amplifier. An inverting input terminal of the error amplifier is supplied with first voltage. An output terminal of the error amplifier is electrically connected to the VCO. An output terminal of the VCO is electrically connected to the counter. The first circuit is electrically connected to the output terminal of the VCO and the terminal. The circuit supplies current in accordance with the frequency of a signal output from the VCO.