OLED Current Drive System with Automatic Selector
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Solution Overview
Problem
Existing multi-line addressing techniques for liquid crystal displays are not suitable for organic light emitting diode (OLED) displays due to fundamental differences in technology and response characteristics, and there is a need for methods to improve the lifetime of passive matrix OLED displays by reducing peak drive levels.
Innovation Solution
A current drive system for multi-line addressing OLED displays that uses a plurality of current mirrors with automatic selectors to divide column current drive signals between row electrodes based on row drive signals, and a selection circuit to control current drive, allowing for reduced peak brightness and increased pixel lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multi-line addressing techniques from LCDs are applied to OLED displays, then power consumption can be reduced, but the technique is unsuitable due to fundamental differences in technology and response characteristics
Solution Approach 1:
The patent adapts multi-line addressing for OLEDs by changing the driving parameters from voltage-based (LCD) to current-based (OLED). The system uses current mirrors to replicate and divide column current signals across multiple row periods, with row drive signals controlling the duration and intensity of current application to each row, thereby achieving OLED-compatible multi-line addressing.
2Illumination intensity
If high peak drive levels are used in passive matrix OLED displays, then display brightness can be achieved, but pixel lifetime is reduced
Solution Approach 1:
The patent segments the column current drive signal across multiple row periods using current mirrors. Instead of applying the full column current in a single period, the current is divided and applied to different rows in successive periods, with each row receiving a portion of the total current. This segmentation reduces peak current density at each pixel while maintaining overall display brightness through cumulative effect.
Solution Approach 2:
The patent implements periodic multi-row scanning where column current drive signals are applied in successive row periods rather than simultaneously. Row drive signals selectively enable current flow to specific rows in each period, creating a time-multiplexed periodic action that reduces peak brightness requirements while maintaining perceived display brightness through persistence of vision.
3Speed
If column current drive signals are applied to all rows simultaneously, then display refresh rate can be maintained, but peak brightness and power consumption increase
Solution Approach 1:
The patent segments the display refresh operation into multiple row periods, with each period dedicated to driving a specific row or group of rows. This temporal segmentation allows the column current drive signals to be reused across multiple periods through current mirrors, maintaining overall refresh rate while reducing peak brightness requirements for each individual row activation.
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 peak brightness and increases the lifetime of OLED pixels by dividing column drive current between rows, achieving a significant reduction in peak luminance and extending the display's operational life.
Implementation Method 1
a plurality of current mirrors having a plurality of current mirror outputs for driving a plurality of row electrodes of the display
Implementation Method 2
a layer of light emitting material such as a light emitting polymer (LEP), oligomer or a light emitting low molecular weight material
Data Source
Figure 1a~1b
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AI summary
This invention relates to systems, methods and apparatus for driving organic light emitting diodes (OLED) displays, in particular those using multi-line addressing (MLA) techniques. Embodiments of the invention are particularly suitable for use with so-called passive matrix OLED displays. A current drive system for an electroluminescent display, the system comprising: a plurality of current mirrors having a plurality of outputs for driving a plurality of drive electrodes of said display, each said current mirror having a reference signal input; and an automatic selector coupled to said current mirror outputs to automatically select a said output for providing reference signal inputs to said current mirrors.