Congratulations Dr. Ali Saket! 🎉
Many years of sustained research productivity and a solid thesis defense is what it takes to become a world-class #powerelectronics PhD graduate. Congratulations Dr. Ali Saket!
A month ago, Ali defended his thesis on:
"High-Efficiency and Low Noise Planar Transformers for Power Converters: Paired Layers Interleaving"
at The University of British Columbia, giving a grand finale to this key stage of his career.
Achievements
- 18 peer-reviewed IEEE publications, 3 IEEE presentations (3 under review)
- Industrial collaborations with Delta-Q Technologies on #Magnetic #EMI, #ResonantConverters, and #BatteryChargers
- Mentor for 10+ undergraduate co-ops
Awards and Fellowships
- 2nd Best Paper Award of 2018: IEEE Transactions on Power Electronics
- Faculty of Applied Science Graduate Award (2016–2018)
- UBC J.K. ZEE Memorial Fellowship in Electrical Engineering
We are grateful to have had Ali contributing to the success of #martinordonezlab all of these years and wish him the best with his new job at @SMPCT.
We would also like to thank:
- Chair: Matthew Choptuik
- Supervisory Committee: Martin Ordonez, Bill Dunford, Wilson Eberle
- Examiner Committee: Shahriar Mirabbasi, Bhushan Gopaluni
- External Examiner: Praveen Jain
Abstract: Mohammad Ali Saket’s PhD Thesis
Title:
"High-Efficiency and Low Noise Planar Transformers for Power Converters: Paired Layers Interleaving"
Abstract
Magnetic components of any switching power supply are usually the bulkiest part of the circuit and determine the overall height of the converter. The design and/or selection of magnetics can affect the selection and cost of all the other associated power components, besides determining the overall performance, size, and form factor of the converter itself.
Nowadays, many applications, such as consumer electronics, the automotive industry, and telecoms, require high power density and low-profile power converters. However, the height of traditional magnetic cores often causes the form factor of power converters to be plump and bulky, making them unsuitable for such applications.
To implement slim-profile converters, the Planar Transformer (PT) has emerged, featuring low height, simple reproducibility, lower leakage inductance, and low thermal resistance. Despite these benefits, PTs are known for their large parasitic capacitance due to the significant overlap and proximity of planar layers, degrading power converter performance.
Capacitive effects in transformers are divided into two types:
- Inter-winding capacitance: Generates Common-Mode (CM) noise, causing EMI problems.
- Intra-winding capacitance: Affects converter efficiency and voltage regulation in LLC resonant converters.
Reducing inter-winding capacitance by separating primary and secondary windings can increase leakage inductance and AC resistance. Conversely, interleaved structures minimize AC resistance and leakage inductance but significantly increase inter-winding capacitance. This results in a design trade-off between minimizing parasitic elements.
This dissertation presents new design methods to address these challenges by focusing on the root cause of parasitic capacitance. A detailed parasitic capacitance model is developed to connect the distributed capacitance of layers with the transformer’s equivalent circuit.
The Paired Layers Interleaving concept introduced in this thesis provides criteria to achieve zero CM noise generation in PTs. Using this method, overlapping layers of primary and secondary windings are designed so that no CM noise is generated. These "paired layers" allow for highly interleaved structures with low AC resistance and leakage inductance while maintaining minimal CM noise.
The model is applicable to various power converters, divided into three categories. Multiple examples demonstrate the method’s generality across different winding types, turn ratios, and topologies. The proposed method is validated through analysis, Finite Element Method (FEM) simulations, and experiments.
Additionally, this dissertation investigates the negative effects of PT’s large intra-winding capacitance on LLC resonant converter voltage regulation under light load conditions. It shows that intra-winding capacitance distorts the transformer’s voltage, resulting in loss of regulation.
To address this issue, six new winding layouts with minimal intra-winding capacitance are presented. These layouts ensure proper voltage regulation even under no-load conditions and enable the design of wide-range planar inductors with high self-resonant frequency, ideal for high-frequency operation.