TFT Threshold Voltage Shift Correction in Organic EL Displays
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Solution Overview
Problem
The threshold voltage shift in thin-film transistors (TFTs) used in organic EL displays causes fluctuations in electric current supply, leading to deteriorated display quality due to differences between calculated and actual threshold voltage shifts over time.
Innovation Solution
A display device with a control circuit that calculates the threshold voltage shift during both deterioration and recovery periods, correcting the signal voltage to match the actual shift, thereby ensuring consistent electric current supply to the light-emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the threshold voltage shift is calculated based only on deterioration period, then the calculation is simple, but the calculated amount differs from the actual amount of threshold voltage shift
Solution Approach 1:
The control circuit calculates the threshold voltage shift by incorporating feedback from both the deterioration period (when signal voltage is applied) and the recovery period (when signal voltage is zero). This dual-period feedback mechanism ensures that the calculated threshold voltage shift accurately reflects the actual shift, resolving the contradiction between calculation simplicity and accuracy.
2Device complexity
If the signal voltage is not corrected for threshold voltage shift, then the drive circuit is simple, but the luminance control deteriorates over time
Solution Approach 1:
The control circuit performs preliminary correction of the signal voltage based on the calculated threshold voltage shift before the voltage is applied to the drive transistor. This preliminary action compensates for the anticipated threshold voltage shift, ensuring stable luminance control over time without requiring complex drive circuitry.
3Device complexity
If the threshold voltage shift is not corrected, then the signal processing is simple, but the electric current supply to light-emitting element fluctuates
Solution Approach 1:
The control circuit uses feedback from both deterioration and recovery periods to calculate the threshold voltage shift, then applies this information to correct the signal voltage. This feedback-based correction stabilizes the electric current supply to the light-emitting element, resolving the contradiction between signal processing simplicity and current stability.
Data Source
AI summary
A display is provided that includes a display having a light-emitting element and a drive transistor, which supplies a current to the light-emitting element causing the light-emitting element to emit light. The display also includes a signal line driving circuit that supplies a signal voltage applied between a gate and a source of the drive transistor, and a control circuit that calculates an amount of threshold voltage shift of the drive transistor on the basis of an amount of deterioration of a threshold voltage of the drive transistor during a deterioration period, and corrects the signal voltage in accordance with the amount of threshold voltage shift.