Shift Register Eliminates DC Source to Reduce Transistor Stress
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Solution Overview
Problem
Conventional shift registers in LCDs require a DC voltage source, which induces stress on transistors and increases manufacturing costs, necessitating a design without this dependency.
Innovation Solution
A shift register design utilizing resident charges stored in transistors through parasitical capacitors for AC coupling, eliminating the need for a DC voltage source by using switching circuits to manage voltage levels and maintain transistor states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a DC voltage source VDD is connected to transistors 18 and 20, then the transistors can be turned on rapidly and voltage levels can be pulled down quickly, but stress is induced on the transistors and manufacturing costs increase
Solution Approach 1:
The patent removes the DC voltage source VDD from the circuit, extracting the problematic element that causes transistor stress while maintaining the voltage pull-down function through alternative means (transistor 20 acting as a switch with AC coupling)
Solution Approach 2:
The patent introduces AC coupling as an intermediary mechanism between the clock signal and the transistor gate, allowing voltage level control without direct DC connection, thereby reducing stress on transistors while maintaining switching speed
2Ease of operation
If a DC voltage source VDD is provided in the shift register, then transistor switching can be controlled, but manufacturing costs increase and device performance deteriorates
Solution Approach 1:
The patent eliminates the DC voltage source VDD from the circuit design, removing the component that increases manufacturing complexity and cost while maintaining transistor control functionality through AC coupling and clock signal manipulation
Solution Approach 2:
The patent makes the clock signal serve multiple functions: it both drives the switching operation and provides the voltage levels needed for transistor control, eliminating the need for separate DC voltage sources and simplifying the overall circuit design
3Stability of the object's composition
If DC voltage source VDD is used for all the time, then transistors 18 and 20 can be turned on, but stress is continuously induced on the transistors
Solution Approach 1:
The patent employs periodic AC coupling through clock signals to control transistor switching, replacing continuous DC voltage application with periodic voltage transitions that maintain transistor stability only when needed, thereby reducing continuous stress accumulation
Solution Approach 2:
The patent transitions from a static DC voltage connection to a dynamic AC coupling scheme where voltage levels change periodically with the clock signal, allowing transistors to be turned on only during required periods rather than continuously, reducing stress while maintaining operational stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces transistor stress and manufacturing costs while improving device performance by maintaining high voltage levels and controlling transistor states without additional DC power, enhancing AC coupling efficiency.
Implementation Method 1
The first switching circuit holds electric charges by the parasitical capacitor resident in the transistor in order to keep the first switching circuit in a turn-on state
Data Source
AI summary
A shift register includes a plurality of register stages. Each register stage includes an output circuit, a first switching circuit and a second switching circuit. The output circuit is capable of outputting a first driving signal. The first switching circuit is used to pull down the output circuit into a low voltage level when the output circuit is not outputting the first driving signal. The second switching circuit is capable of receiving an input signal. The first switching circuit holds electric charges by the parasitical capacitor resident in the transistor in order to keep the first switching circuit in a turn-on state when the output circuit is not outputting the first driving signal.