OLED Pixel Circuit Voltage Divider for High Contrast
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Solution Overview
Problem
OLED displays face limitations in achieving high contrast due to restricted voltage differences between electrodes, leading to low contrast and limited bright-dark change ranges, especially in low-voltage processes.
Innovation Solution
A pixel circuit with a voltage divider sub-circuit that regulates equivalent resistance values based on control signals, allowing for adjustable drive currents and voltages to maintain luminance in bright pixels while reducing voltage in dark pixels, thereby enhancing contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If low-voltage process is used for OLED display, then power consumption is reduced and device safety is improved, but voltage difference between electrodes is restricted leading to low contrast ratio
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: current source sub-circuit for drive current generation, voltage divider sub-circuit for voltage regulation, storage sub-circuit for voltage storage, and switch sub-circuit for signal control. This segmentation allows each module to perform its specific function optimally while working together to achieve high contrast ratio under low voltage conditions.
Solution Approach 2:
The voltage divider sub-circuit acts as an intermediary between the current source sub-circuit and the light-emitting device. It receives the drive voltage from the current source, regulates it through adjustable equivalent resistance, and outputs the controlled voltage to the light-emitting device, thereby enabling precise control of voltage difference to achieve high contrast ratio.
2Reliability
If voltage difference between electrodes is restricted, then device reliability is improved, but bright-dark change range is limited
Solution Approach 1:
The voltage divider sub-circuit employs dynamic resistance adjustment through the voltage division control signal terminal. The equivalent resistance value can be dynamically regulated based on the stored drive voltage, allowing the circuit to adaptively optimize the voltage difference across the light-emitting device within the safe operating range, thereby achieving wide bright-dark change range while maintaining device reliability.
Solution Approach 2:
The circuit changes the resistance parameter of the voltage divider sub-circuit based on the stored drive voltage. By adjusting the equivalent resistance value in response to different drive voltage levels, the circuit optimizes the voltage distribution to maximize the bright-dark change range while keeping the voltage difference within reliable limits.
3Illumination intensity
If voltage divider sub-circuit is added to regulate equivalent resistance, then contrast ratio is improved, but device complexity increases
Solution Approach 1:
The voltage divider sub-circuit is designed with multi-functionality: it regulates equivalent resistance to control voltage output, stores drive voltage through the storage sub-circuit, and responds to control signals from the voltage division control signal terminal. This multi-functional design achieves contrast ratio improvement while minimizing the increase in device complexity by consolidating functions into a single integrated sub-circuit.
Data Source
AI summary
A display substrate and a display device are provided. The display substrate includes a plurality of driving circuits, wherein each of the driving circuits includes: a first sub-circuit, respectively coupled to a gate signal terminal, a data signal terminal and a light-emitting power source terminal, and configured to store a drive voltage based on a voltage at the data signal terminal when the gate signal terminal receives a gate drive signal, and output a drive current to a light-emitting device based on the stored drive voltage under power supply provided by the light-emitting power source terminal; and a second sub-circuit, configured to regulate an equivalent resistance value of the second sub-circuit in an output path through which the drive current is output to the light-emitting device, based on a voltage division control signal received by the voltage division control signal terminal.