Spiral Transformer Layout to Reduce Interwinding Capacitance

Solution Overview

Problem

Existing spiral planar inductors and transformers suffer from limited Q-factor and increased resistance due to additional turns, along with capacitive coupling between coils, leading to inefficiencies in energy storage and transfer.

Innovation Solution

Implementing a width-modulated spiral inductor design where each turn has a varying width, with a predetermined ratio, and offsetting primary and secondary spiral inductors to reduce inter-winding capacitance and maintain consistent resistance per turn.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the number of turns is increased to increase inductance, then inductance increases, but resistance increases and Q-factor decreases

Engineering Contradiction:

ImproveinductanceVSAvoidresistance

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The patent applies local quality by varying the track width at different positions along the spiral inductor. The track width is increased at outer turns where the path length is longer, compensating for the increased resistance in those regions. This localized adjustment optimizes the resistance distribution without changing the overall inductance, thereby improving the Q-factor.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameter of the track width along the spiral path. By modulating the track width as a function of the radial position or turn number, the resistance per unit length is adjusted to compensate for the varying path lengths, optimizing the overall resistance while maintaining the required inductance value.

Inventive Principle:

Principle #35Parameter changes

2Area of stationary object

If additional turns are added to increase inductance, then inductance increases, but Q-factor decreases due to increased resistance

Engineering Contradiction:

ImproveinductanceVSAvoidQ-factor

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent applies local quality by varying the track width at different positions along the spiral inductor. The track width is increased at outer turns where the path length is longer, compensating for the increased resistance in those regions. This localized adjustment optimizes the resistance distribution without changing the overall inductance, thereby improving the Q-factor.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameter of the track width along the spiral path. By modulating the track width as a function of the radial position or turn number, the resistance per unit length is adjusted to compensate for the varying path lengths, optimizing the overall resistance while maintaining the required inductance value, thus improving Q-factor.

Inventive Principle:

Principle #35Parameter changes

3Power

If spiral inductors are stacked vertically to form transformer, then coupling is achieved, but capacitive coupling between coils increases

Engineering Contradiction:

Improvemagnetic couplingVSAvoidcapacitive coupling

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by varying the track width at different positions along the spiral inductor. The track width is increased at outer turns where the path length is longer, compensating for the increased resistance in those regions. This localized adjustment optimizes the resistance distribution without changing the overall inductance, thereby improving the Q-factor.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the geometric parameter of the track width along the spiral path. By modulating the track width as a function of the radial position or turn number, the resistance per unit length is adjusted to compensate for the varying path lengths, optimizing the overall resistance while maintaining the required inductance value, thus improving Q-factor.

Inventive Principle:

Principle #35Parameter changes

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

The width-modulated design significantly improves the Q-factor and reduces capacitive coupling, enhancing energy efficiency and performance by maintaining inductance while minimizing resistance and capacitive interference.

Implementation Method 1

The inductance L (μH) of the spiral planar inductor may be estimated according to the following known Wheeler's Equation

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

capacitive coupling between the planar coils of the inductor thereby causing undesired effect

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS20250279236A1Transformer with spiral inductors

Publication Date: 2025.09.04 UNIVERSITY OF LIMERICK

AI summary

Disclosed is a transformer that includes a primary spiral inductor, and a secondary spiral inductor magnetically coupled to the primary spiral inductor, wherein a physical location of the secondary spiral inductor is at an offset relative to the primary spiral inductor to reduce interwinding capacitance between the primary and secondary spiral inductors, while decreasing a magnetic coupling between the primary and secondary spiral inductors to a lesser extent.