Pixel Precharge Circuit for Faster Uniform Current Writing
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Solution Overview
Problem
In active matrix display devices, variations in transistor characteristics lead to inconsistent current supply to light emitting elements, affecting luminance and requiring longer times to achieve a steady state, with existing solutions either wasting time or being inefficient in charge supply.
Innovation Solution
A precharge circuit with a comparison control circuit and precharge switch is used to detect potential differences and control charge supply, optimizing the precharge operation to rapidly achieve a predetermined potential and reduce the effect of transistor variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current write type pixel circuit is used to prevent current variations due to TFT characteristic variations, then luminance uniformity is improved, but the write time is extended due to prolonged charge accumulation period
Solution Approach 1:
The invention applies preliminary action by performing a precharge operation before the main write operation. The precharge circuit supplies charge to the signal line in advance, bringing it closer to the target potential. This preliminary charge supply reduces the time required for the subsequent write operation to complete, while still achieving the desired current accuracy and luminance uniformity.
Solution Approach 2:
The invention introduces a precharge circuit as an intermediary component between the voltage source and the pixel circuit. This precharge circuit includes a precharge switch and a comparison control circuit that mediates the charge supply process, enabling faster potential adjustment without compromising the final current precision required for uniform luminance.
2Device complexity
If a fixed period charge supply method is used, then the circuit structure is simplified, but the write speed is reduced due to inefficient charge supply timing
Solution Approach 1:
The invention implements feedback control through a comparison control circuit that monitors the potential of the signal line and compares it with a reference potential. Based on this feedback, the precharge switch is controlled to supply charge only when needed, optimizing the charge supply timing. This feedback mechanism enables faster write speeds without significantly increasing circuit complexity.
3Productivity
If the precharge period is extended to achieve steady state faster, then write speed is improved, but energy consumption increases due to prolonged charge supply
Solution Approach 1:
The invention applies dynamics by making the precharge period variable rather than fixed. The comparison control circuit dynamically adjusts the precharge duration based on the actual potential state of the signal line, stopping the precharge operation as soon as the target potential is reached. This dynamic control achieves fast write speeds while minimizing energy consumption by avoiding unnecessary prolonged charge supply.
Data Source
AI summary
In the case of reducing an effect of variations in current characteristics of transistors by inputting a signal current to a transistor in a pixel, a potential of a wiring is detected by using a precharge circuit. In the case where there is a difference between a predetermined potential and the potential of the wiring, a charge is supplied to the wiring to perform a precharge by charging rapidly. When the potential of the wiring reaches the predetermined potential, the supply of charge is stopped and a signal current only is supplied. Thus, a precharge is performed only in a period until the potential of the wiring reaches the predetermined potential, therefore, a precharge can be performed for an optimal period.