Wide-Range Level Shifter With Fewer Transistors and Lower Power
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Solution Overview
Problem
Conventional voltage level shift circuits require a large number of transistors, leading to increased size and power consumption, especially when transforming digital control signals from 0-3.3 volts to -15-20 volts for liquid crystal display applications.
Innovation Solution
A wide range level shift system utilizing a specific configuration of NMOS and PMOS transistors, along with an impedance circuit, to reduce the number of transistors required, optimizing power consumption and circuit size by employing a novel transistor connection and impedance circuit arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage level shift circuits use multiple transistors to transform voltage levels, then the voltage transformation function is achieved, but the circuit size and power consumption increase significantly
Solution Approach 1:
The patent merges the functions of multiple transistors into a compact configuration where NMOS and PMOS transistors are combined in a shared structure. The source of the NMOS transistor is connected to the drain of the PMOS transistor, and their gates are connected together, creating a unified circuit block that performs voltage level shifting with fewer components while maintaining the transformation function from 0-3.3V to -15-20V
Solution Approach 2:
The patent designs a universal voltage level shifter that can handle both positive and negative voltage transformations simultaneously. The circuit configuration allows it to transform input signals from 0-3.3V to output signals in the range of -15-20V, covering both VGH and VGL voltage levels required for liquid crystal display driving, thereby reducing the need for separate transformation circuits
2Power
If conventional voltage level shift circuits add output buffer stages to drive next stage, then the driving capability is improved, but rush current occurs when input voltage changes
Solution Approach 1:
The patent introduces an impedance circuit as an intermediary element connected between the output nodes. This impedance circuit acts as a mediator that limits and controls the current flow when input voltage transitions occur, preventing rush current from flowing directly between the output buffer stages while still allowing the circuit to maintain its voltage transformation and driving functions
3Object-generated harmful factors
If conventional voltage level shift circuits add inverter sets to prevent rush current, then the harmful current is avoided, but the number of transistors increases to twelve or more
Solution Approach 1:
The patent combines the rush current prevention function directly into the existing transistor configuration rather than adding separate inverter sets. By connecting the gates of NMOS and PMOS transistors together and using their source-drain connections strategically, the circuit inherently prevents rush current without requiring additional transistor sets, thereby reducing the total transistor count while maintaining protection against harmful currents
Data Source
AI summary
A wide range level shift system receives an input signal with a first voltage level and a second voltage level. The wide range level shift system transforms the input signal to an output signal with a third voltage level and a fourth voltage level, wherein the first voltage level is smaller than the second voltage level, the second voltage level is smaller than the third voltage level, and the fourth voltage level is smaller than the first voltage level. The wide range level shift system reduces the number of transistors required, the layout area of the transistors, and the power consumption.