Organic EL Display Driving Method Synchronizes Power Supply Voltage
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Solution Overview
Problem
Passive matrix organic EL display devices face challenges in achieving desired brightness due to insufficient charge supply to unselected pixels, leading to increased power consumption and reduced operational life, as existing driver circuits struggle to manage the charging and discharging of capacitor components efficiently.
Innovation Solution
The implementation of a driving method that synchronizes the voltage of the second power supply with the voltage waveform of the light emitting current, allowing the selected electrode to be connected to a ground or power supply while unselected electrodes are prevented from emitting current, thereby reducing unnecessary charging and discharging in unselected pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a push-pull type driver circuit is used to drive passive matrix organic EL display devices, then the display device can be operated with scanning electrode elements, but unnecessary charging and discharging of capacitor components occurs in unselected pixels, leading to increased power consumption
Solution Approach 1:
The patent applies preliminary action by resetting the potential of scanning electrode elements to a reference potential before the light emitting period begins. This preliminary reset prevents unnecessary charging and discharging of capacitor components in unselected pixels, thereby reducing power consumption while maintaining the push-pull driver circuit operation
Solution Approach 2:
The patent implements equipotentiality by connecting unselected scanning electrode elements to a reference potential during the light emitting period. This creates an equipotential state that prevents potential differences from causing unnecessary charging and discharging currents in unselected pixels, thus reducing power consumption
2Reliability
If voltage is applied to unselected scanning electrode elements during operation, then the display device can maintain electrode functionality, but charge supply to unselected pixels increases power consumption
Solution Approach 1:
The patent applies equipotentiality by maintaining unselected scanning electrode elements at a reference potential during the light emitting period. This prevents potential differences that would cause charge supply to unselected pixels, thereby reducing power consumption while keeping the electrodes functional and ready for subsequent scanning operations
3Device complexity
If conventional driver circuits are used without voltage synchronization, then circuit design is simpler, but brightness is insufficient due to inadequate charge supply to pixels
Solution Approach 1:
The patent implements dynamics by making the voltage of the second power supply variable and synchronized with the voltage waveform of the light emitting current from the first power supply. This dynamic voltage adjustment ensures adequate charge supply to selected pixels for improved brightness while maintaining manageable driver circuit complexity through coordinated control
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 approach enhances brightness and reduces power consumption by ensuring effective charge supply to lighting pixels while minimizing power loss, thereby extending the operational life of the display device.
Implementation Method 1
The light emitting mechanism of an organic EL light emitting element is considered as follows. An exciton is generated in a fluorescent dye molecule of the light emitting layer with an electron injected from a cathode and a hole injected from an anode. Light emission occurs in a process of irradiating recombination of the exciton.
Data Source
AI summary
An organic EL display device is disclosed that prevents charging and discharging that do not contribute to light emission, thereby reducing power consumption. The organic EL display device comprises a plurality of first electrode elements, a plurality of second electrode elements crossing the first electrode elements, and organic light emitting layers sandwiched by the first electrode elements and the second electrode elements. A first driving unit passes light emitting current through the first electrode elements. A second driving unit connects the second electrode elements to the ground to pass the light emitting current and to a second power supply not to pass the light emitting current. The voltage of the second power supply is varied in synchronism with the voltage waveform of output of the light emitting current from the first driving unit.