Emission Driving Circuit With Bootstrapped Pull-Up Gate Stability
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Solution Overview
Problem
The stability of emission driving circuits is compromised due to unstable turn-on levels of pull-up transistors, leading to flicker issues, as the level of the clock signal changes under load, affecting the emission driving circuit's performance.
Innovation Solution
The emission driving circuit incorporates a pull-up controller and pull-down controller with transistors and capacitors to stabilize the voltage levels, reducing the load on the clock signal and ensuring stable operation by applying a second voltage directly to the pull-up transistor's gate electrode and connecting a second gate electrode to prevent threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clock signal is applied to the gate electrode of the pull-up transistor, then the pull-up transistor can be turned on, but the level of the clock signal changes due to load, causing unstable turn-on level and decreasing stability
Solution Approach 1:
The control of the pull-up transistor is segmented into two independent control nodes: a first pull-up control node receiving the clock signal and a second pull-up control node receiving a bootstrapped voltage. This segmentation isolates the clock signal from direct loading effects while maintaining transistor control functionality.
Solution Approach 2:
A bootstrapping circuit is introduced as an intermediary mechanism that transfers the clock signal level to the second pull-up control node through a capacitor. This intermediary approach prevents direct loading of the clock signal while ensuring stable voltage level at the transistor gate.
2Reliability
If the clock signal level changes due to load, then the pull-up transistor turn-on level becomes unstable, but adding more transistors and control nodes increases device complexity
Solution Approach 1:
The first pull-up control node serves multiple functions: it receives the clock signal, provides feedback through the capacitor to the second pull-up control node, and maintains voltage stability during the emission signal period. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The bootstrapping circuit performs preliminary action by pre-charging the second pull-up control node to the appropriate voltage level before the pull-up transistor needs to be activated. This preliminary voltage establishment ensures stable turn-on characteristics without requiring continuous clock signal intervention.
Data Source
AI summary
An emission driving circuit includes: a pull-up controller configured to transmit a first voltage to a first pull-up control node in response to an input signal, to control a voltage of a second pull-up control node in response to a voltage of the first pull-up control node and a clock signal, and to transmit a second voltage to a third pull-up node in response to the voltage of the second pull-up control node; a pull-down controller configured to transmit the input signal to a second pull-down node in response to the input signal and the clock signal; and an output circuit configured to output an emission signal from an output node in response to a voltage of the third pull-up control node and a voltage of the second pull-down control node.