Pixel Bypass Circuit for OLED Hotspot Prevention
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Solution Overview
Problem
Display devices with light emitting elements face issues of hotspot phenomenon and deterioration due to concentrated driving current, leading to inefficiencies and reduced lifespan.
Innovation Solution
Incorporation of a bypass unit within the pixel circuit that allows selective bypassing of driving current to prevent overcurrent flow through non-conductive light emitting elements, utilizing a compensation transistor and diode to distribute current among conductive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If driving current is supplied to light emitting elements without bypass unit, then light emitting elements can emit light, but current concentrates in fewer elements causing hotspot phenomenon and deterioration
Solution Approach 1:
A bypass unit is introduced as an intermediary component connected in parallel with the light emitting elements. This bypass unit includes a compensation transistor that acts as a mediator to divert excess current away from the light emitting elements, preventing current concentration and hotspot formation while maintaining normal light emission function.
Solution Approach 2:
The bypass unit dynamically changes the electrical parameters (current distribution) based on the conduction state of light emitting elements. When some elements become non-conductive, the bypass transistor adjusts its conduction state to redistribute current, changing the current flow parameters to prevent overload on remaining elements.
2Reliability
If bypass unit is added to prevent current concentration, then current distribution is improved, but device complexity increases
Solution Approach 1:
The bypass unit is designed to be integrated within the existing pixel circuit structure, sharing common electrodes and control mechanisms. The compensation transistor utilizes the same voltage signals already present in the pixel circuit, allowing the bypass function to be achieved without adding independent control circuits, thus minimizing the increase in device complexity.
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
Prevents hotspot formation and subsequent deterioration of light emitting elements by ensuring even current distribution, thereby enhancing the reliability and longevity of the display device.
Implementation Method 1
a compensation transistor connected to the first electrode of the some of the light emitting elements and configured to allow a part of the driving current to pass therethrough based on a voltage of a second electrode of the some of the light emitting elements
Implementation Method 2
an amplifier configured to compare a voltage of the second electrode of the some of the light emitting elements with a reference voltage to supply an output voltage
Implementation Method 3
a compensation diode connected between the compensation transistor and the second electrode of the some of the light emitting elements
Data Source
AI summary
A display device includes a plurality of pixels on a substrate, each of the plurality of pixels including a pixel circuit to drive a plurality of light emitting elements, wherein the pixel circuit of each of the plurality of pixels includes: a first transistor configured to supply a driving current to a first electrode of the light emitting elements; and a plurality of light emitting groups, each of the light emitting groups including some of the light emitting elements and a bypass unit connected between the first electrode and a second electrode of the some of the light emitting elements to selectively bypass a part of the driving current.