Shift Register with Separate Scan and Carry Outputs
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Solution Overview
Problem
Existing shift registers in flat panel display devices are prone to incorrect operation due to short-circuits between scan lines, which disrupt the transmission of carry signals, and require a mechanism to change shift direction based on panel structure or driving method.
Innovation Solution
A shift register design that includes stages supplied with sequentially delayed gate shift clocks, forward and reverse gate start pulses, carry signals, gate high voltage, and gate low voltage, featuring a scan pulse output unit, carry signal output unit, and shift direction changing switch circuit to manage Q node voltages in both forward and reverse shift modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scan lines are connected to output nodes of stages, then scan pulses can be applied to scan lines, but short-circuits between scan lines disrupt carry signal transmission and cause wrong operation
Solution Approach 1:
The patent segments the output functions by providing separate output nodes: one for scan pulses and another for carry signals. This segmentation allows the scan pulse output node to be short-circuited without affecting the carry signal transmission through the dedicated carry signal output node, thus resolving the reliability issue caused by short-circuit interference.
Solution Approach 2:
The patent introduces a level shifter as an intermediary component between the carry signal output node and the next stage input. This level shifter mediates the voltage level conversion and isolation, protecting the carry signal transmission from the harmful effects of short-circuits at the scan pulse output node.
2Adaptability or versatility
If shift direction needs to vary based on panel structure or driving method, then the shift register must have direction changing capability, but this increases device complexity
Solution Approach 1:
The patent implements multi-functionality by designing the switch circuit to serve dual purposes: it controls both the charge/discharge paths of the Q node and the selection of carry signal input sources. This single switch circuit enables bidirectional shifting (forward and reverse) without requiring separate circuits for each direction, thus achieving adaptability while minimizing complexity increase.
Solution Approach 2:
The patent introduces dynamic control through switch circuits that can change their connection states based on the desired shift direction. The switch circuits dynamically reconfigure the signal paths and charge/discharge routes, allowing the same hardware to adapt to different operating modes (forward or reverse shifting) without physical reconfiguration.
Data Source
AI summary
A shift register comprises a plurality of stages, which includes a (n−3)-th (where n is a positive integer) stage to a (n+3)-th stage, supplied with gate shift clocks which are sequentially delayed, a forward gate start pulse, a reverse gate start pulse, a carry signal, a gate high voltage, and a gate low voltage lower than the gate high voltage, and connected to each other in cascade, wherein the n-th stage, supplied with a (n−1)-th gate shift clock, an n-th gate shift clock, and a (n+1)-th gate shift clock, includes a scan pulse output unit, a carry signal output unit, and a shift direction changing switch circuit.