Charge-Transfer Inductance Sensing for Small and Mutual Inductors
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Solution Overview
Problem
Existing technologies for inductance measurement face challenges in accurately measuring small inductances and mutual inductance, particularly in integrated semiconductor devices, due to the need for large current sources and difficulties in obtaining measurable voltages, and struggle with sensing through metal structures with high relative magnetic permeability.
Innovation Solution
A charge transfer based measurement system that uses a target inductor connected to an energy source during a first phase to increase current, followed by a second phase where the current flows through a free-wheeling diode to charge an accumulation capacitor, allowing for repetitive phases to measure inductance values, and can measure mutual inductance by energy transfer between coupled inductors using current mirror structures and controlled switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductance measurement methods are used, then measurement capability is provided, but measurement precision deteriorates for small inductances
Solution Approach 1:
The patent transforms the inductance measurement problem into a frequency measurement problem by using an RC circuit where the unknown inductance L forms a resonant circuit with a known capacitor C. By measuring the resonant frequency f = 1/(2π√(LC)), the system can precisely determine small inductance values through frequency detection rather than direct electrical measurement, thereby improving measurement precision for small inductances.
2Measurement precision
If large current sources are used to measure small inductances, then measurable voltages can be obtained, but device complexity increases
Solution Approach 1:
The patent replaces the need for complex large current sources with a simple resonant circuit approach. Instead of forcing large currents through small inductances to generate measurable voltages, the system uses the natural resonant oscillation of the LC circuit, where energy oscillates between the inductor and capacitor, producing measurable voltage signals without requiring external large current sources.
3Adaptability or versatility
If sensing through metal structures is attempted, then sensing capability is provided, but measurement precision deteriorates due to high relative magnetic permeability
Solution Approach 1:
The patent introduces a capacitor C as an intermediary element that forms a resonant circuit with the target inductance L. This resonant circuit configuration allows the measurement system to sense inductance values through the resonant frequency, which can be detected even when the inductance is part of a metal structure. The resonant frequency measurement is less susceptible to the distorting effects of high relative magnetic permeability compared to direct inductance measurement methods.
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
Enables precise measurement of self- and mutual inductance values, including small inductances, and allows for sensing through metal structures by adjusting the charge transfer frequency, improving the accuracy and practicality of inductance measurement in semiconductor devices and metal-containing environments.
Implementation Method 1
During a first phase, a target inductor may be connected to the one or other energy source to allow current through said inductor to increase in amplitude up to a certain value
Implementation Method 2
During the second phase, the current which flows via said free-wheeling diode may be used to facilitate transfer of charge to an accumulation capacitor
Data Source
AI summary
Inductance values are measured though the use of a charge transfer based measurement system. During a first phase, a target inductor is connected to an energy source to allow current through an inductor to increase. In a second phase, the inductor is disconnected from the energy source, to allow the current to decrease, and to facilitate transfer of charge to a capacitor. The phases may be repeated, and a count is kept of the number of repetitions.