OLED Pixel Driving Circuit With Capacitor Boost for Threshold Loss
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Solution Overview
Problem
The light-emitting brightness of sub-pixels in OLED display panels is reduced due to the threshold voltage of the driving transistor, which limits the driving current output to the sub-pixels.
Innovation Solution
A pixel driving circuit is designed with a first charging unit, a discharging unit, a second charging unit, and an energy storage capacitor, where the energy storage capacitor is pre-charged, discharged to a preset voltage, and then charged with a data voltage, increasing the voltage output to the gate electrode of the driving transistor, thereby enhancing the driving current and brightness of the sub-pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the driving transistor is used to drive sub-pixels, then the sub-pixels can emit light, but the threshold voltage of the driving transistor reduces the driving current output, resulting in dark brightness
Solution Approach 1:
The energy storage capacitor is pre-charged to a first voltage before the driving transistor operates. This preliminary charging ensures that when the driving transistor turns on, the capacitor can compensate for the threshold voltage drop and maintain sufficient driving current to the sub-pixels, preventing brightness degradation
Solution Approach 2:
The patent dynamically adjusts the voltage of the energy storage capacitor based on operational needs. The capacitor voltage is changed from a first voltage (when driving transistor is off) to a second voltage (when driving transistor is on), optimizing the driving current output and compensating for threshold voltage effects
2Illumination intensity
If the energy storage capacitor voltage is increased to compensate for threshold voltage, then the driving current increases and brightness improves, but the circuit complexity increases with additional charging and discharging units
Solution Approach 1:
The energy storage capacitor serves multiple functions: it stores energy for the driving transistor, compensates for threshold voltage drops, and provides voltage boosting. By making the capacitor multi-functional, the patent avoids adding separate compensation circuits, thus improving brightness without proportionally increasing circuit complexity
Solution Approach 2:
The patent combines the voltage compensation function with the existing energy storage capacitor in the pixel circuit. Instead of adding a separate compensation circuit, the capacitor's charging and discharging operations are integrated with the driving transistor control, merging multiple functions into a single component
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
The increased voltage output from the energy storage capacitor to the gate electrode of the driving transistor improves the driving current to the sub-pixels, enhancing their light-emitting brightness and reducing the influence of threshold voltage on current operation, leading to improved brightness uniformity in the display panel.
Implementation Method 1
an energy storage capacitor, wherein an input terminal of the first charging unit is configured for inputting a pre-charge voltage, and an output terminal of the first charging unit is connected to the energy storage capacitor, so as to charge the energy storage capacitor when the first charging unit is turned on
Data Source
AI summary
A pixel driving circuit, a method thereof, and a display panel, related to the field of display technology. The pixel driving circuit includes: a first charging unit, a discharging unit, a second charging unit, an energy storage capacitor and a driving transistor. The first charging unit is configured for pre-charging the energy storage capacitor. The discharge unit is configured for discharging the voltage of the pre-charged energy storage capacitor to a preset voltage. The second charging unit is configured for inputting the data voltage to the storage capacitor. After the second charging unit charges the energy storage capacitor, the voltage of the energy storage capacitor is equal to the sum of the preset voltage and the data voltage. The energy storage capacitor is connected to the gate electrode of the driving transistor.