OLED Driving Circuit Isolates Threshold Voltage via Time-Multiplexed Switching
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Solution Overview
Problem
Current OLED display panels face challenges in maintaining consistent luminous intensity due to the influence of threshold voltage in the transistor, affecting the stability and performance of the display.
Innovation Solution
The OLED driving circuit incorporates a specific configuration of capacitors and switch units, including transistors, which manage voltage signals across different time periods to isolate the OLED current from the threshold voltage of the transistor, ensuring consistent luminance by using a formula IOLED=12β(Vint-Vdata)2, where β is a parameter related to process and feature sizes, and Vgs is the voltage difference between the source and gate of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional OLED driving circuit uses a transistor to drive the OLED, then the circuit structure is simple, but the luminous intensity is affected by the threshold voltage of the transistor, resulting in unstable display performance
Solution Approach 1:
The driving circuit is divided into multiple switch units (first, second, third, fourth switch units) that operate at different time periods. Each switch unit is controlled by independent control signals to sequentially charge capacitors and transfer voltages, separating the threshold voltage influence from the OLED driving current through time-multiplexed operations.
Solution Approach 2:
Capacitors (first and second capacitors) are charged in advance during specific time periods before the OLED is driven. The first capacitor is charged to a first voltage and the second capacitor to a second voltage through the switch units, preparing the voltage conditions needed to eliminate threshold voltage effects before the actual OLED activation occurs.
2Device complexity
If the OLED is driven by a current related to the transistor threshold voltage, then the driving circuit is simple, but the luminous intensity becomes unstable due to threshold voltage variations
Solution Approach 1:
The circuit uses dynamic voltage transfer through capacitors and switch units that operate at different time periods. The first capacitor transfers its charged voltage to influence the OLED gate, while the second capacitor provides additional voltage compensation. This dynamic, time-multiplexed voltage management eliminates the static threshold voltage dependency, making luminous intensity stable despite transistor variations.
Solution Approach 2:
The circuit changes the voltage parameters applied to the OLED by charging capacitors to specific voltages (first voltage and second voltage) at different time periods. By controlling the switch units to transfer these predetermined voltages, the circuit creates a driving voltage that is independent of the transistor threshold voltage, thereby stabilizing the luminous intensity.
Data Source
AI summary
Present disclosure provides OLED driving circuit, comprising: first switch unit, electrically connected between first end of first capacitor and data input end; second switch unit, electrically connected between second end of first capacitor and data input end; third switch unit, its first end electrically connected to voltage input end, its second end electrically connected to OLED, its third end electrically connected to first end of first capacitor, third switch unit configured to switch connection and disconnection between first and second ends of third switch unit; fourth switch unit, its first end electrically connected to first end of first capacitor, its second end electrically connected to second end of third switch unit; wherein first and second ends of second capacitor are electrically connected to voltage input end and second end of first capacitor, respectively. Present disclosure further provides OLED driving method, display substrate and display apparatus.