Low-Voltage Level Shifter Circuit With OS-FET Leakage Suppression
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Solution Overview
Problem
Conventional level shifters face challenges in reducing power consumption due to high off-leakage current in standby mode, especially when using n-type Si-FETs, and struggle with controlling high-voltage circuits efficiently due to shoot-through current issues.
Innovation Solution
Incorporating an oxide semiconductor transistor (OS-FET) in series with an n-type Si-FET in the off-leakage current path and using capacitive coupling to raise the gate potential of the OS-FET, enhancing its on-state current characteristics to match or exceed those of the n-type Si-FET, thereby reducing power consumption and preventing shoot-through current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an n-type Si-FET is used in a level shifter, then the on-state current is sufficient for fast operation, but the off-leakage current increases power consumption in standby mode
Solution Approach 1:
The patent divides the transistor channel into two distinct segments: a silicon-based channel for fast switching operation and an oxide semiconductor channel for low leakage current. This segmentation allows each material to contribute its superior property to the overall transistor performance, resolving the contradiction between speed and power consumption.
Solution Approach 2:
The patent employs a composite channel structure combining silicon and oxide semiconductor materials. The silicon portion provides high mobility for fast on-state current, while the oxide semiconductor portion provides extremely low off-state leakage. This composite approach directly addresses the technical contradiction by integrating complementary material properties.
2Use of energy by moving object
If power supply of high-voltage circuit is stopped to reduce power consumption, then energy saving is achieved, but control of high-voltage circuit becomes difficult due to shoot-through current
Solution Approach 1:
The patent changes the electrical parameters of the transistor by utilizing the unique properties of oxide semiconductor material, which enables operation at lower voltages with reduced shoot-through current. This parameter change allows safe stopping of power supply while maintaining control 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
The solution effectively minimizes static leakage current and power consumption in standby mode while maintaining fast response speed, comparable to conventional level shifters, by leveraging the lower off-leakage current of OS-FETs and increased on-state current through capacitive coupling.
Implementation Method 1
Since the OS-FET has off-leakage current much lower than that of the n-type Si-FET, off-leakage current can be reduced even when an off-leakage current path is found in a standby mode
Implementation Method 2
The potential of a gate electrode of the OS-FET is raised to a potential higher than input signal voltage by capacitive coupling with the output signal line, so that Vgs, and on-state current of the OS-FET are increased
Data Source
AI summary
Leakage current in a standby mode of a level shifter capable of operating with low voltage is reduced. Provided is a level shifter circuit in which an n-channel silicon transistor and an oxide semiconductor transistor are provide in series between an output signal line and a low potential power supply line. The potential of a gate electrode of the oxide semiconductor transistor is raised to a potential higher than input signal voltage by capacitive coupling, so that on-state current of the oxide semiconductor transistor is increased.