Dual Transistor Pixel Circuit for OLED Power Reduction
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Solution Overview
Problem
Organic electroluminescence display panels face high power consumption due to current-driven luminescence production, especially with increasing screen size and high-definition requirements, and existing solutions complicate pixel circuit configurations with additional components and switching circuits.
Innovation Solution
The implementation of an organic EL display panel with two drive transistors (P-type and N-type) and a capacitor, where the first drive transistor supplies a first drain current for low voltage and the second drive transistor supplies a second drain current for high voltage, allowing selective use of power source lines based on data voltage, reducing the need for additional switching circuits and components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive transistor is used in the pixel circuit, then the circuit configuration is simple, but power consumption is high due to current-driven luminescence production
Solution Approach 1:
The pixel circuit is segmented into two drive transistors (first drive transistor and second drive transistor) with different functions. The first drive transistor supplies drive current during the light emission period, while the second drive transistor supplies current during the non-light emission period. This segmentation allows the circuit to reduce power consumption by controlling current flow more efficiently, addressing the contradiction between circuit simplicity and power consumption reduction.
Solution Approach 2:
The patent introduces dynamic control mechanisms including a selection transistor that switches between different drive transistors based on the light emission state, and a holding capacitor that dynamically adjusts voltage levels. This dynamic adaptation enables the circuit to optimize power consumption while maintaining simple overall configuration, resolving the contradiction between circuit complexity and energy efficiency.
2Use of energy by moving object
If additional switching circuits and components are added to reduce power consumption, then power consumption decreases, but the pixel circuit configuration becomes complicated
Solution Approach 1:
The patent merges multiple functions into the two drive transistors and their associated components. The first and second drive transistors serve both as current sources and as part of the switching mechanism, while the holding capacitor serves both voltage storage and switching control functions. This merging reduces the need for separate switching circuits, achieving power consumption reduction without significant increase in circuit complexity.
Solution Approach 2:
The drive transistors are designed with multi-functionality: they act as current sources for the organic EL element, as switching elements controlled by the selection transistor, and as part of the voltage regulation system through the holding capacitor. This universal design allows the circuit to reduce power consumption using existing components rather than adding dedicated switching circuits, thus avoiding increased complexity.
3Illumination intensity
If high current is supplied to achieve high luminance, then display brightness is improved, but power consumption increases significantly
Solution Approach 1:
The patent implements periodic action by controlling the organic EL element to emit light only during specific periods (light emission period) rather than continuously. The first drive transistor supplies current during the light emission period, while the second drive transistor handles the non-light emission period. This periodic operation allows high luminance when needed while reducing average power consumption, resolving the contradiction between brightness and energy consumption.
Solution Approach 2:
The patent changes the electrical parameters (current and voltage) dynamically based on the operational state. The holding capacitor stores voltage at different levels, and the drive transistors adjust current supply accordingly. During light emission, higher current is supplied for high luminance, while during non-emission periods, current is reduced or stopped, lowering power consumption. This parameter modulation resolves the contradiction between achieving high luminance and reducing overall power 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 configuration reduces power consumption and simplifies the pixel circuit while maintaining high-definition capabilities without significantly increasing the number of circuit elements, enabling efficient luminescence production across various grayscale levels.
Implementation Method 1
organic electroluminescence (EL) elements are known as display panels that use current-driven luminescence elements
Implementation Method 2
a capacitor that includes a first electrode and a second electrode, and holds a voltage corresponding to a data voltage
Data Source
AI summary
An organic EL display panel includes: a P-type drive transistor having a gate connected to a capacitor and a drain connected to an organic EL element; an N-type drive transistor having a gate connected to the capacitor and a source connected to the organic EL element; a first power source line for applying a first voltage to the P-type drive transistor; a second power source line for applying, to the N-type drive transistor, a second voltage higher than the first voltage. The P-type drive transistor has characteristics such that a first gate voltage value corresponding to a predetermined current value in current-voltage characteristics of the organic EL element is a minimum voltage of the data voltage, and the N-type drive transistor has characteristics such that a second gate voltage value corresponding to the predetermined current value is greater than a third gate voltage value corresponding to a minimum current value of the organic EL element.