Liquid Crystal Display Shift-Register Circuits with Periodic Current Reversal
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Solution Overview
Problem
Noise generation and malfunction in shift register circuits due to floating output terminals, leading to transistor deterioration and circuit unreliability in non-single-crystal semiconductor devices.
Innovation Solution
Implementing a circuit design where the direction of current flowing through transistors is periodically inverted by alternating the voltage levels applied to their terminals, using transistors with different potentials to prevent electric field concentration and reduce deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor continuously outputs signals having certain levels (e.g., L-level signals) in a shift register circuit, then the circuit can maintain stable operation during non-selection periods, but the transistor deteriorates due to continuous conduction and electric field concentration on the drain side
Solution Approach 1:
The patent applies periodic action by switching the transistor between two operational states: in the first state, the transistor conducts current in one direction during non-selection periods, and in the second state, the transistor conducts current in the opposite direction during selection periods. This periodic reversal of current direction prevents continuous stress on the same drain side, thereby reducing transistor deterioration while maintaining stable circuit operation.
2Device complexity
If the direction of current flowing through the transistor is fixed in a digital circuit such as a shift register circuit, then the circuit design is simple, but the electric field concentrates on the drain side and the transistor easily deteriorates
Solution Approach 1:
The patent implements dynamics by making the current direction through the transistor changeable rather than fixed. The transistor alternates between conducting current in the first direction during non-selection periods and conducting current in the opposite direction during selection periods. This dynamic current reversal prevents permanent electric field concentration on one side, reducing transistor deterioration without significantly complicating the circuit design.
3Object-affected harmful factors
If a transistor is kept on for most of the operating period to supply low potential to the output terminal, then noise in the output terminal is reduced, but the transistor deteriorates in accordance with the time during which the transistor is on
Solution Approach 1:
The patent applies periodic action by alternating the transistor's operational state: during non-selection periods (when noise suppression is critical), the transistor is turned on to supply low potential to the output terminal; during selection periods, the transistor is turned off and the current direction is reversed. This periodic operation maintains noise suppression when needed while allowing the transistor to rest and recover, thereby extending its operational lifespan.
Data Source
AI summary
To suppress a malfunction of a circuit due to deterioration in a transistor. In a transistor which continuously outputs signals having certain levels (e.g., L-level signals)in a pixel or a circuit, the direction of current flowing through the transistor is changed (inverted). That is, by changing the level of voltage applied to a first terminal and a second terminal (terminals serving as a source and a drain) every given period, the source and the drain are switched every given period. Specifically, in a portion which successively outputs signals having certain levels (e.g., L-level signals) in a circuitincluding a transistor, L-level signals having a plurality of different potentials (L-level signals whose potentials are changed every given period) are used as the signals having certain levels.