OLED Display Circuit with Feedback Control for Luminous Flux Stability
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Solution Overview
Problem
Current light-emitting displays with organic LEDs face challenges in maintaining consistent luminous flux due to aging and production-related changes in current/voltage characteristics, leading to reduced active periods and increased complexity in current control methods, which affect image quality and efficiency.
Innovation Solution
A circuit with a current control means and switching mechanisms allows for independent control of currents and voltages, enabling accurate setting of desired luminous flux through correction values stored in memory, and measuring electrical properties to adapt driving conditions, reducing parasitic capacitance effects and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If individual current control means are permanently driven by control signals, then the active period of light-emitting elements is extended, but the number of control lines increases reducing the area available for light emission
Solution Approach 1:
The patent implements periodic scanning of control lines where each control line sequentially controls multiple light-emitting elements over time. Instead of permanently connecting each element to a dedicated control line, the system periodically activates control lines to drive elements in groups, thereby extending the active period through repeated scanning cycles while minimizing the number of physical control lines required
Solution Approach 2:
Each control line is designed to serve multiple functions by sequentially controlling different light-emitting elements during different time periods. The control lines are reused across multiple elements and scanning cycles, making a single control line perform the work of multiple dedicated control lines, thus reducing the total number of control lines while maintaining extended active periods through persistent memory storage
2Reliability
If the forward voltage of OLED is compensated for aging by increasing control voltage, then the luminous flux remains stable, but the current increases causing higher energy consumption and reduced lifespan
Solution Approach 1:
The patent incorporates feedback mechanisms where the actual current flowing through each light-emitting element is measured and used to adjust the control voltage dynamically. This closed-loop control ensures that the luminous flux remains stable by compensating for aging effects through precise voltage adjustment rather than blanket voltage increases, thereby minimizing energy consumption while maintaining reliability
Solution Approach 2:
The system dynamically changes the control voltage parameter based on measured current values and aging characteristics of individual light-emitting elements. Instead of using a fixed or uniformly increased voltage, the control voltage is precisely adjusted for each element and time period to maintain stable luminous flux output, optimizing the balance between reliability and energy consumption
3Use of energy by moving object
If small control currents are used for setting small luminous flux values, then energy consumption is reduced, but the setting precision deteriorates due to poor reproducibility and parasitic capacitance effects
Solution Approach 1:
The patent introduces current control means (such as current mirrors or transistor-based current sources) as intermediary devices between the control voltage and the light-emitting elements. These intermediaries convert small control voltages into precise, stable control currents with high reproducibility, enabling accurate setting of small luminous flux values while maintaining low energy consumption. The intermediary circuitry compensates for parasitic capacitance effects and improves current setting precision
Solution Approach 2:
The system replaces direct current control with voltage-based control through electronic current control means. Instead of directly manipulating small control currents that are difficult to set precisely, the system uses voltage signals that are easier to generate and control, which are then converted to precise currents through electronic circuits. This substitution improves setting precision while maintaining low energy consumption
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
This solution improves the reproducibility of small luminous flux settings, extends active periods, and reduces energy usage by optimizing voltage supply based on aging effects, resulting in enhanced image quality and longer display lifespan.
Implementation Method 1
In organic light-emitting diodes, light is generated by passing a direct current through the organic diode material
Data Source
AI summary
A circuit for an element of a light-emitting display is proposed. The element comprises a current control means, first and second switching means and a light-emitting means. In one embodiment, a signal holding means is provided. The arrangement of the first and second switching means of the element makes it possible to measure the electrical parameters of the current control means and of the light-emitting means during operation. A light-emitting display having a plurality of elements is furthermore proposed. The light-emitting display has a control circuit and a memory. The measured values of the electrical parameters of the current control means (4) and of the light-emitting means of the elements are used to correct the control signal S that is used to drive the elements. This enables a uniform brightness distribution in the case of voltage actuation and makes it possible to compensate for temporal changes in the light-emitting means. In addition, a method for actuating the elements and the light-emitting display is proposed.