Current Sensing Device for OLED Display Noise Reduction
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Solution Overview
Problem
Current sensing devices in organic light emitting display devices are vulnerable to noise and have long sensing times, which distort sensing results and hinder accurate compensation for changes in driving characteristics of OLEDs or driving TFTs, leading to inconsistent image brightness.
Innovation Solution
A current sensing device with a sensing unit that includes a comparator, MOS transistors, and resistors, which compares pixel current with a reference current to minimize noise and reduce sensing time by operating in a saturation region, ensuring accurate and high-resolution sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current integrator is used to sense low current, then sensing capability for low current is improved, but noise resistance deteriorates and sensing time increases
Solution Approach 1:
The patent changes the operating parameters of the sensing circuit by using a comparator instead of an integrator, operating MOS transistors in saturation region, and adjusting reference current levels to achieve both low current sensing capability and noise resistance simultaneously
2Measurement precision
If a current integrator is used to sense low current, then sensing capability for low current is improved, but sensing time increases
Solution Approach 1:
The patent replaces the integrator-based sensing mechanism with a comparator-based mechanism, fundamentally changing the sensing approach from integration over time to direct comparison, thereby reducing sensing time while maintaining capability
3Reliability
If reference voltage changes occur, then noise is generated, but compensation for driving characteristic changes is required
Solution Approach 1:
The patent introduces a comparator as an intermediary device that compares the pixel current with reference current, and uses MOS transistors operating in saturation region as intermediaries to transfer currents, isolating the sensing circuit from noise generated by reference voltage changes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces noise amplification and shortens sensing time, enabling precise compensation for changes in driving characteristics, thus maintaining consistent image brightness and improving overall display performance.
Implementation Method 1
a comparator having an inverting input terminal connected to a third node, a non-inverting input terminal connected to a fourth node, comparing a reference voltage charged at the third node when the reference current is input and a pixel voltage charged at the fourth node when the pixel current is input, and outputting a comparison result
Implementation Method 2
A current sensing device with a sensing unit that includes a comparator, MOS transistors, and resistors, which compares pixel current with a reference current to minimize noise and reduce sensing time by operating in a saturation region
Data Source
AI summary
A current sensing device and an organic light emitting display device including the same are disclosed. The current sensing device includes a sensing unit selectively connected to a pixel and a reference current source through a sensing line. The sensing unit includes a plurality of resistors connected to a first node and setting a divided voltage according to a pixel current input from the pixel and a reference current input from the reference current source, a first MOS transistor connected between the first node and a second node, a second MOS transistor diode-connected to the second node, and a comparator having an inverting input terminal connected to a third node, a non-inverting input terminal connected to a fourth node, comparing a reference voltage charged at the third node when the reference current is input and a pixel voltage charged at the fourth node when the pixel current is input, and outputting a comparison result.