PMOS Shift Register for Positive-Logic LTPS AMOLED Scanning
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Solution Overview
Problem
Existing shift registers cannot output positive logic signals, limiting their application in LTPS AMOLED displays, as they typically use PMOS structures that are designed for negative logic signals.
Innovation Solution
A shift register design incorporating an input switch unit, inverting unit, output switch unit, and voltage maintaining units, including leakage protection and lock switch units, all implemented using P-channel transistors and capacitors, allowing for the shifting and outputting of positive-logic scanning signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a PMOS structure is used in the shift register, then the device can be manufactured with standard processes and good reliability, but it cannot output positive logic signals and is limited to negative logic applications
Solution Approach 1:
The shift register is divided into distinct functional modules: input switch unit, inverting unit, output switch unit, and voltage maintaining unit. Each module performs a specific function, allowing the PMOS structure to handle positive logic signals through coordinated operation of these segmented components rather than requiring a complete circuit redesign.
Solution Approach 2:
The inverting unit acts as an intermediary component between the input and output switch units. It converts the logic level to enable the PMOS-based output switch unit to properly output positive logic signals, serving as a mediating element that resolves the compatibility issue between PMOS structure and positive logic requirement.
2Reliability
If voltage levels are maintained during switch off states, then signal integrity is improved, but leakage current increases and power consumption rises
Solution Approach 1:
The voltage maintaining units operate periodically rather than continuously. They maintain voltage levels during critical periods when switches are off to ensure signal integrity, then discharge or reset during active periods. This periodic operation reduces continuous power consumption while maintaining signal stability when needed.
Solution Approach 2:
The voltage maintaining units pre-charge or pre-discharge capacitors before the switching operation occurs. By preparing the voltage levels in advance, the actual switching transition requires less energy and maintains signal integrity without continuous power consumption during the off state.
Data Source
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AI summary
Provided are a shift register and a driving method thereof, a shift scanning circuit, and a display apparatus. The shift register comprises an input switch unit, an inverting unit, an output switch unit, and a first node voltage maintaining unit. The input switch unit has an output terminal (O) connected to a first node (N1). The first node voltage maintaining unit has a voltage stabilizing terminal connected to the first node (N1), and is adapted to record a level at the first node (N1) when the input switch unit is turned on, and to maintain the recorded level at an input terminal (I) of the inverting unit when the input switch unit is turned off. The inverting unit has an output terminal (O) connected to a second node (N2). The output switch unit has a control terminal (CON) connected to the second node (N2), and is turned on according to a state of a level at the second node. The shift register provided by the solution can adopt a PMOS structure to realize shifting positive-logic scanning signals and outputting positive-logic scanning signals, so that the PMOS structure can be used for the scan driving of the LTPS AMOLED.