Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
In Active Matrix Organic Light Emitting Diode (AMOLED) displays, the heterogeneity in threshold voltages of driving transistors leads to variations in driving currents across pixels, affecting image homogeneity.
Innovation Solution
A pixel driving circuit with a specific configuration of transistors and connections, including a data line, scan lines, signal controlling lines, storage capacitor, and light emitting device, that compensates for threshold voltage drifts by controlling voltage differences, ensuring consistent driving currents through the use of N-type and P-type switch transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional pixel driving circuit with two transistors and one storage capacitor is used, then the circuit structure is simple, but the threshold voltage heterogeneity of driving transistors causes driving current variations and poor image homogeneity
Solution Approach 1:
The patent applies preliminary action by introducing a compensation phase before the normal display phase. During the compensation phase (first time period), the circuit pre-adjusts the voltage on the storage capacitor to compensate for threshold voltage variations. This preliminary adjustment ensures that when the display phase begins, the driving current is already corrected for transistor heterogeneity, thereby improving image homogeneity without requiring a complete redesign of the basic circuit structure
Solution Approach 2:
The patent implements dynamics by making the circuit operation multi-phase and time-dependent. The circuit switches between different operational states (compensation phase and display phase) using scan signals, allowing the circuit characteristics to dynamically adapt to threshold voltage variations. This dynamic operation enables the same circuit structure to achieve both simplicity and improved image homogeneity through temporal separation of compensation and display functions
2Ease of operation
If the driving current is directly controlled by Vdata voltage without compensation, then the circuit operation is simple, but threshold voltage drift affects driving current stability
Solution Approach 1:
The patent implements feedback by using the threshold voltage variation itself as the basis for compensation. During the compensation phase, the circuit measures the actual threshold voltage effect on the driving transistor and uses this information to adjust the storage capacitor voltage accordingly. This feedback mechanism ensures that the driving current remains stable despite threshold voltage drift, while maintaining relatively simple circuit operation through the use of existing circuit elements in a multi-phase configuration
Data Source
AI summary
The embodiments of the present disclosure provide a pixel driving circuit and a driving method thereof, an array substrate and a display apparatus, which is able to avoid an influence on a driving current of an active light emitting device caused by a drift in a threshold voltage of a driving transistor. The pixel driving circuit comprises a data line, a first scan line, a second scan line, a signal controlling line, a light emitting device, a storage capacitor, a driving transistor, a first switch transistor, a second switch transistor, a third switch transistor, a fourth switch transistor and a fifth switch transistor. The embodiments of the present disclosure may be applied to a display manufacture.