Dual-Amplifier Current Sensing With Offset Calibration
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Solution Overview
Problem
Current sensing in wireless power systems is prone to inaccuracies due to various sources, which can lead to inefficiencies in power measurement and potential overheating from foreign objects.
Innovation Solution
An integrated circuit with a current sense circuit featuring dual amplifier paths, including an always-on analog channel and a switched amplifier for offset measurement, along with symmetrically arranged polysilicon resistors to minimize stress and temperature differentials, ensuring high accuracy across a wide range of currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single amplifier is used for current sensing, then the device complexity is reduced, but the measurement precision deteriorates due to inability to perform offset measurement without disrupting analog control loops
Solution Approach 1:
The patent divides the current sensing function into two separate amplifier paths: an always-on analog amplifier for continuous current measurement and a switched amplifier for periodic offset measurement. This segmentation allows both functions to operate independently without mutual interference, achieving high measurement precision while managing device complexity through functional separation.
Solution Approach 2:
The switched amplifier is designed to serve multiple functions: it performs offset measurement during calibration phases and can be activated for specific measurement scenarios. This multi-functionality allows a single component to handle diverse tasks, improving measurement precision without proportionally increasing device complexity.
2Measurement precision
If resistors are placed close to the amplifier inputs, then the wiring complexity is reduced, but the measurement precision deteriorates due to stress and temperature differentials
Solution Approach 1:
The patent employs symmetric layout design where resistors are positioned equidistantly from the amplifier inputs and mirrored across the circuit axis. This symmetric arrangement ensures that stress and temperature differentials affect both sides equally, causing errors to cancel out and thereby improving measurement precision while maintaining manageable layout complexity.
Solution Approach 2:
The patent implements localized temperature compensation by placing identical resistors in symmetric positions around the amplifier, ensuring that local temperature variations affect matching pairs equally. This local quality approach maintains measurement precision by ensuring uniform environmental impact across critical circuit elements.
Data Source
AI summary
A structure is described which includes two amplifiers in parallel. A first amplifier is considered an always-on amplifier. The always on amplifier provides continual measurements of a current (Isns) across an integrated polysilicon resistor for one or more analog control loops. A second amplifier is considered a switched amplifier. The switched amplifier provides measurements of the current (Isns) for one or more digital control loops. The switched amplifier is switched by one or more switches for performing offset measurements with high accuracy.