Shift Register Circuit Node Potential Control
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Solution Overview
Problem
The high potential at internal nodes in shift register circuits, caused by the self-boosting effect, leads to unstable operation and degraded gate scanning signals in display devices, especially when the gate scan signal exceeds 25 V.
Innovation Solution
A shift register circuit design that includes a set circuit, a reset circuit, an output circuit, and control circuits to manage node potentials, using transistors and capacitors to maintain active and inactive potentials, and restrict changes in node potentials based on reference voltages, preventing excessive potential increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate scan signal high level reaches 25 V or more to fully turn on transistors, then transistor switching performance is improved, but the potential at internal nodes becomes excessively high (above 50 V), causing large transistor characteristic changes and threshold voltage drift
Solution Approach 1:
The patent introduces a first control circuit as an intermediary component between the self-boosting capacitor and the transistor gate. This control circuit includes a capacitor connected in parallel with the self-boosting capacitor and a control transistor that regulates the voltage at the first node. The control circuit mediates the voltage relationship, preventing the internal node potential from reaching excessively high levels while still enabling sufficient gate drive voltage to turn on transistors completely.
Solution Approach 2:
The patent changes the voltage parameter at the first node by introducing a control mechanism that limits the maximum voltage to a predetermined value. The control circuit adjusts the voltage parameter dynamically, ensuring it remains within a safe range (below 50 V) while still providing enough drive capability (above 25 V) for transistor operation. This parameter control prevents threshold voltage drift and maintains shift register stability.
2Productivity
If the gate scan signal high level is increased to ensure complete transistor turn-on, then switching completeness is improved, but threshold voltage drift increases due to excessive internal node potential
Solution Approach 1:
The first control circuit serves as an intermediary that decouples the relationship between gate drive voltage and internal node potential. The control transistor and associated capacitor work together to mediate the voltage transfer, allowing the gate to receive sufficient voltage for complete turn-on while preventing the internal node from reaching excessively high potentials that would cause threshold voltage drift.
Solution Approach 2:
The control circuit dynamically adjusts the voltage parameter at the first node, changing it from an uncontrolled high voltage (above 50 V) to a controlled voltage within a predetermined range. This parameter change ensures transistor turn-on completeness while maintaining threshold voltage stability, as the controlled voltage prevents excessive electric field effects that would otherwise cause drift.
3Power
If the self-boosting effect of the storage capacitor is utilized to increase gate scan signal amplitude, then gate drive capability is improved, but internal node potential becomes excessively high, causing transistor characteristic changes
Solution Approach 1:
The first control circuit acts as an intermediary that manages the self-boosting effect of the storage capacitor. The control transistor and parallel capacitor work together to mediate the voltage amplification, allowing the gate drive capability to be enhanced while preventing the internal node potential from becoming excessively high. The control circuit transforms the harmful uncontrolled self-boosting into a beneficial controlled voltage amplification.
Solution Approach 2:
The patent converts the potentially harmful self-boosting effect into a beneficial controlled voltage amplification. By introducing the control circuit, the uncontrolled self-boosting that caused excessive internal node potential is transformed into a controlled mechanism that provides sufficient gate drive capability while keeping internal node voltage within safe limits. The harmful effect is disguised as a beneficial feature through proper control.
Data Source
AI summary
A shift register circuit includes a set circuit, a first reset circuit, a first control circuit, and an output circuit. The output circuit is configured to change an active potential at the first node further away from an inactive potential in response to a first clock signal transferred to a signal output terminal being active, and the first control circuit is further configured to, responsive to the first clock signal transferred to the signal output terminal being active, restrict a change in the active potential at the first node based on a second reference voltage from a second reference voltage, the second reference voltage having a magnitude between an active input pulse and the inactive potential.