Pull-Down Control Circuit Reducing Transistor Stress
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Solution Overview
Problem
Conventional shift registers in LCD gate drivers experience reliability issues due to prolonged high voltage stress on transistors, leading to transistor deterioration and reduced performance.
Innovation Solution
A pull-down control circuit with a release circuit and transistors T4, T5, T6, and T7, where the transistors are designed to alternate between high and low voltage levels, reducing stress on transistor T5 and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional pull-down control circuit configuration is used, then the circuit structure is simple, but the transistor T5 experiences prolonged high voltage stress leading to deterioration and reduced reliability
Solution Approach 1:
The invention makes the pull-down control circuit dynamic by introducing a release circuit that periodically releases the high voltage stress on transistor T5. The circuit transitions from a static configuration where T5 continuously bears high voltage to a dynamic one where the voltage stress is periodically relieved through the release circuit's controlled activation, thereby improving reliability without excessive complexity increase
Solution Approach 2:
The release circuit is designed to operate periodically, alternating between releasing and non-releasing states. This periodic action allows transistor T5 to experience intervals of reduced voltage stress, preventing continuous deterioration while maintaining the overall circuit functionality. The periodic release mechanism addresses the reliability issue without requiring a complete redesign of the entire pull-down control circuit
2Reliability
If transistor T5 is continuously turned on for high voltage level, then the pull-down control function is maintained, but the transistor characteristics deteriorate due to prolonged stress
Solution Approach 1:
The release circuit introduces periodic action by alternately releasing and non-releasing high voltage to transistor T5. During the releasing period, T5 is protected from high voltage stress, while during the non-releasing period, the normal pull-down control function is maintained. This periodic modulation of voltage application duration prevents continuous stress accumulation and extends transistor lifespan
Solution Approach 2:
The release circuit performs preliminary anti-action by proactively releasing high voltage stress on transistor T5 before significant deterioration can occur. The circuit anticipates the harmful effect of prolonged high voltage exposure and counteracts it by periodically removing the stress, thereby preventing transistor degradation rather than merely responding to it after damage occurs
Data Source
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Figure 2(a)~2(b)
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AI summary
The present invention relates to a pull-down control circuit and a shift register of using same. In one embodiment, the pull-down control circuit includes a release circuit and four transistors T4, T5, T6 and T7 electrically coupled to each other. The release circuit is adapted for causing the transistor T5 to be turned on and off alternately, thereby substantially reducing the stress thereon, improving the reliability and prolonging the lifetime of the shift register.