OLED Threshold Voltage Sensing Circuit with Charge Sharing Compensation
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices face challenges in maintaining constant brightness due to changes in threshold voltage over time, necessitating a compensation process to account for parasitic capacitor offsets and improve sensitivity and reliability in threshold voltage sensing.
Innovation Solution
A circuit configuration that includes sample and hold units with capacitors and amplifiers to accurately sense and compensate for threshold voltage changes, utilizing charge sharing and switching mechanisms to reduce parasitic capacitor offsets and enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional sample and hold circuit is used to sense threshold voltage, then the circuit structure is simple, but parasitic capacitor offsets reduce measurement precision
Solution Approach 1:
The patent introduces a compensation capacitor as an intermediary element that mirrors and cancels the parasitic capacitance effect. By placing a compensation capacitor in parallel with the sampling capacitor and using switch control to connect it during the hold phase, the circuit compensates for parasitic offsets without fundamentally changing the sample and hold structure, thus improving measurement precision while maintaining reasonable circuit complexity
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing adjustable compensation capacitors with specific capacitance values. These compensation capacitors are tuned to match the parasitic capacitance values, allowing the circuit to dynamically adjust and cancel parasitic effects. This parameter-based approach enables precision improvement without requiring complete circuit redesign
2Stability of the object's composition
If threshold voltage sensing is performed without compensation, then the device complexity is low, but OLED brightness varies over time due to threshold voltage drift
Solution Approach 1:
The patent implements a feedback mechanism where the threshold voltage sensing circuit continuously monitors OLED threshold voltage changes and feeds this information back to the driving circuit. The compensation capacitor stores the sensed threshold voltage information, which is then used to adjust the driving signal, creating a closed-loop system that maintains stable OLED brightness despite threshold voltage drift over time
Solution Approach 2:
The patent performs preliminary threshold voltage sensing and compensation before the OLED driving operation. By using the sample and hold circuit to capture and store the threshold voltage information in advance, and pre-charging the compensation capacitor with the correct value, the system prepares the compensation data beforehand, ensuring stable brightness from the start of operation without requiring complex real-time adjustment mechanisms
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 solution effectively maintains constant OLED brightness by accurately sensing and compensating for threshold voltage changes, improving reliability and sensitivity in OLED display devices.
Implementation Method 1
a first sampling capacitor between the first input terminal and a first reference voltage
Implementation Method 2
a first charge sharing capacitor having a first terminal connected to the first sampling capacitor and a second terminal connected to a second reference voltage
Data Source
AI summary
A circuit configured to sense a threshold voltage of an organic light emitting diode (OLED) of a display panel includes a sample and hold unit configured to receive the threshold voltage of the OLED, a first sampling capacitor between the first input terminal and a first reference voltage, and a first charge sharing capacitor having a first terminal connected to the first sampling capacitor and a second terminal connected to a second reference voltage, a second sample and hold unit including a second input terminal connected to the first reference voltage, a second sampling capacitor between the second input terminal and the first reference voltage, and a second charge sharing capacitor having a first terminal connected to the second sampling capacitor and a second terminal connected to a third reference voltage, and an amplifier including first and second amplifier input terminals connected to the first and second output terminals, respectively.