PMOS Shift Registers Using Two Clock Signals
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Solution Overview
Problem
The high cost of CMOS shift register circuits in LCDs due to the requirement of multiple masks and the increased expense of ASICs needed for PMOS shift registers, which require four clock signals, poses a challenge for cost reduction in display technologies.
Innovation Solution
A signal driving circuit comprising PMOS shift registers connected in series and controlled by only two clock signals, where the shift registers output driving pulses in turn after receiving a start pulse, reducing the complexity and cost by eliminating the need for additional clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMOS shift registers require four clock signals, then the shift registers can operate reliably, but the ASIC cost increases
Solution Approach 1:
The patent combines the functions of multiple clock signals into two clock signals (CLK1 and CLK2) by strategically assigning them to different shift registers. Specifically, odd-numbered shift registers (1st, 3rd, 5th, etc.) receive CLK1 while even-numbered shift registers (2nd, 4th, 6th, etc.) receive CLK2, allowing the system to maintain reliable operation with reduced signal complexity
Solution Approach 2:
The patent segments the shift register array into odd and even positioned registers, assigning different clock signals to each segment. This segmentation allows independent clocking of alternating registers, enabling reliable sequential operation while reducing the total number of clock signals required from four to two
2Manufacturing precision
If CMOS shift register circuits are used, then image display quality is improved, but manufacturing cost increases due to multiple masks
Solution Approach 1:
The patent replaces expensive CMOS shift register circuits with cheaper PMOS shift register circuits. While PMOS circuits have different characteristics, they provide sufficient functionality for the application at lower manufacturing cost, with the trade-off being accepted in exchange for the significant reduction in mask requirements and fabrication complexity
Data Source
AI summary
Systems for displaying images are provided. In this regard, a representative system incorporates a signal driving circuit that includes a plurality of PMOS shift registers connected in series and controlled only by a first clock signal and a second clock signal, wherein the PMOS shift registers are operative to output corresponding driving pulses in turn after receiving a start pulse.