High-Voltage Selector Circuit for Close Input Voltage Switching
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Solution Overview
Problem
Existing high voltage selectors fail to accurately select the higher voltage between internal and external supply voltages when their magnitudes are close, leading to abnormal voltage drops.
Innovation Solution
A high voltage selector with a detecting stage, clamping stage, and selecting stage that includes transistors to control the output voltage based on the relative magnitudes of input voltages, using a detection signal to activate or deactivate the clamping stage and switching transistors to ensure the higher voltage is selected without drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional high voltage selector with two switching transistors is used, then the circuit structure is simple, but it fails to accurately select the higher voltage when input voltages are close in magnitude, causing abnormal voltage drops
Solution Approach 1:
The high voltage selector is divided into three functional stages: detecting stage, clamping stage, and selecting stage. Each stage performs a specific function in the voltage selection process, improving accuracy by breaking down the complex selection task into manageable segments that work sequentially.
Solution Approach 2:
A clamping stage is introduced as an intermediary between the detecting stage and the selecting stage. This clamping stage acts as a mediator that prepares the voltage signal by clamping it to appropriate levels before the final selection, ensuring accurate voltage comparison and selection without abnormal drops.
2Reliability
If the conventional two-transistor selector is used, then the number of components is minimized, but the reliability of voltage selection deteriorates when input voltages are similar
Solution Approach 1:
The selector is segmented into three distinct stages with five transistors total, where each stage handles a specific aspect of voltage selection. This segmentation improves reliability by ensuring that each stage can be optimized for its specific function, particularly the clamping stage which ensures stable voltage levels for accurate comparison.
Solution Approach 2:
The detecting stage performs preliminary detection of the voltage relationship between inputs before the final selection occurs. This preliminary action allows the circuit to prepare appropriate control signals for the clamping and selecting stages, ensuring reliable voltage selection before the actual selection takes place.
Data Source
AI summary
A high voltage selector includes a first input terminal to receive a first input voltage, a second input terminal to receive a second input voltage and an output terminal to generate an output voltage. The higher one of the first input voltage and the second input voltage is selected as the output voltage by the high voltage selector. Even if the magnitude of the first input voltage and the magnitude of the second input voltage are close, the output voltage from the high voltage selector will not produce an abnormal voltage drop.