Negative Level Shifter Using Medium-Voltage Shielding Circuit
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Solution Overview
Problem
Existing negative level shifters fail to operate normally when the drain-body voltage of elements in shielding circuits exceeds the medium voltage operating region, leading to ineffective voltage transformation between the logic region and the negative voltage signal in display driver circuits.
Innovation Solution
A negative level shifter design that includes a first level shifter with an input circuit, a shielding circuit, and a load circuit, utilizing NMOS transistors connected to the source terminal and body region, and a second level shifter to generate a level difference, ensuring the voltage between the drain terminal and body region operates within the medium voltage range by applying a first voltage to the body regions of PMOS transistors and connecting the source terminal and body region of NMOS transistors to maintain the voltage within the medium voltage operating region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the maximum medium voltage is used as the negative voltage in the shielding circuit, then the voltage transformation capability is improved, but the drain-body voltage of the NMOS transistor exceeds the medium voltage operating region causing malfunction
Solution Approach 1:
The patent divides the level shifter into two separate level shifters: a first level shifter that transforms input voltage to intermediate voltage, and a second level shifter that transforms intermediate voltage to negative voltage. This segmentation allows each stage to operate within its safe voltage range, preventing any single element from experiencing excessive drain-body voltage that would exceed the medium voltage operating region.
Solution Approach 2:
The patent introduces an intermediate voltage level as a mediator between the input voltage and the final negative voltage. The first level shifter produces this intermediate voltage, which then serves as the input for the second level shifter. This intermediary voltage stage prevents direct exposure of medium voltage elements to the full voltage differential, ensuring they remain within their operating regions.
2Device complexity
If additional negative voltage is used to drive the display panel device, then the voltage transformation is simplified, but the driver IC size increases
Solution Approach 1:
The patent employs a shielding circuit that enables medium voltage elements to operate in a medium voltage operating region while performing negative level shifting functionality. The shielding circuit uses a small number of elements (two PMOS transistors and two NMOS transistors) to achieve multi-functional operation: it provides both the voltage transformation capability and the shielding function necessary for negative level shifting, thereby reducing the overall driver IC area.
Solution Approach 2:
The patent changes the operating voltage parameters of the shielding circuit elements to medium voltage range, allowing them to operate efficiently without requiring additional negative voltage supplies. By adjusting the voltage operating region parameters and using the body terminal connection technique, the circuit achieves negative level shifting with reduced component count and smaller area.
Data Source
AI summary
A negative level shifter that connects a source terminal and a body region of an element included in a shielding circuit so that the element operates within a medium voltage operating region. The negative level shifter of the present disclosure connects the source terminal and the body region of the shielding circuit so that the voltage between the drain terminal of the shielding circuit and the body region required for negative level shifting is operated in the medium voltage operating region. In addition, the negative level shifter may be able to use a medium voltage transistor rather than a high voltage transistor element provided in the input circuit so that the design area will be reduced compared to the conventional art. Also, the present disclosure suggests a display device with a negative level shifter.