Open student theses
The control of modern power electronic converters requires a broadband measurement of the current. Due to the steep current edges and high voltages, conventional measurement technology reaches its limits here. In addition to the precise measurement, this should also be as low-invasive as possible. In order to keep the power density as high as possible, the current measurement methods should be as compact as possible.
Type of Thesis:
BA ❌ FA ✅ MA ✅
Contact:
Modern wide bandgap semiconductor based power transistors, such as SiC power MOSFETs and GaN power HEMTs, allow for extremely fast voltage and current switching on the nanosecond scale, resulting in increased power densities in power converters.
The control of the switching waveforms of such fast-switching power electronic sub-systems becomes a major challenge, but is indispensible both for maintaining electro-magnetic compatibility and for the limitation of switching loss energies.
In this research work, several techniques in the design of the gate loop of power commutation cells based on GaN power transistors in view of waveform shaping for an optimum tradeoff between electro-magnetic emission and switching loss energy are investigated in theory, simulation and measurement and compared to the prevailing state of the art. The final work programme is determined in bilateral planification between the tutor and the student and can comprise: Survey of the prevailing state of the art, Theoretical investigation of gate-loop concepts for waveform shaping, including multi-level gate drivers such as Bosch EG120, nonlinear external gate resistance and novel proprietary GaN power transistors with custom gate structure, Circuit-level switching waveform simulations in ADS, On-wafer measurements of novel proprietary GaN power transistors with custom gate structure, Experimental validation of selected gate loop concepts in custom-designed breadboard demonstrators
Type of Thesis:
BA ✅ FA ✅ MA ✅
Relevant Experience:
- Theoretical expertise in power semiconductor devices and power electronics circuits is recommended.
Contact:
Together with the wide-bandgap semicondcutor based power transistors, such as SiC power MOSFETs and GaN power HEMTs, ceramic capacitors form the basic building blocks of fast-switching high current and voltage commutation cells and power modules in high power density switched-mode power converters. The power capacitors must follow suit with the power transistors in high-frequency capabilities, in order not to become the bottleneck for switching loss energy and thermal management, and accurate simulation models of the capacitors‘ high-frequency characteristcs must be developed for the reliable design of fast-switching power modules. Together with the wide-bandgap semicondcutor based power transistors, such as SiC power MOSFETs and GaN power HEMTs, ceramic capacitors form the basic building blocks of fast-switching high current and voltage commutation cells and power modules in high power density switched-mode power converters. The work is carried out in collaboration at University of Stuttgart, Germany, and at ENSI Caen, France. The final work programme is determined in trilateral planification between the tutors and the student and can comprise: Survey of the prevailing state of the art, Microwave characterisation of ceramic capacitors at ILH, including the design of dedicated test breadboards, Model development, implementation in VerilogA and verification at ENSI Caen, Optional: power module breadboard design and experimental validation at ILH.
Type of Thesis:
BA ✅ FA ✅ MA ✅
Relevant Experience:
- Theoretical expertise in power semiconductor devices and power electronics circuits is recommended.
Contact:
More Information:
The work is carried out in collaboration and joint tutorship with ENSI Caen, France. Parts of the work may be carried out at ENSI Caen.
In the development of power electronic applications, their behaviour must be examined in many different fault cases. In order to be able to estimate the effects of various short-circuit cases in an application, a precise characterisation of the individual transistors for a short-circuit is necessary, especially for new types of WBG transistors. Goal of this thesis is to develope, construct and test a test bench for investigating this behaviour.
Type of Thesis:
BA ❌ FA ✅ MA ✅
Relevant Experience:
- PE 1 und 2, RT 1 und 2, RPSS 1 und 2
Contact:
The current development of so-called bidirectional switches based on a GaN HEMT structure shows promising approaches. However, one obstacle to a large-scale market launch is the suitable termination of the substrate during a bidirectional switching process without reducing the blocking capability in the switched-off state. This work therefore aims to develop a circuit for active substrate termination of a bidirectional switch and to investigate its effect on the switching behaviour and dielectric strength.
Type of Thesis:
BA ✅ FA ❌ MA ✅
Relevant Experience:
- RPSS1+2, solid understanding of microelectronics and integrated circuit design, Measurement technique
Contact:
Gallium nitride (GaN)-based high electron mobility transistors (HEMTs) play a key role in modern power electronics, especially in applications such as high-frequency circuits, power converters and renewable energy systems. Precise modeling of these transistors is crucial to maximize their performance and efficiency. An established model for this is the ASM GaN HEMT model, which was developed specifically to describe the complex physical properties of GaN transistors. However, traditional approaches to parameter extraction, such as manual fitting, often reach their limits, especially for nonlinear systems such as HEMTs. Reinforcement learning (RL) offers a promising alternative by enabling adaptive, data-driven optimization strategies that could improve the accuracy and efficiency of parameter extraction for the ASM model.
Type of Thesis:
BA ❌ FA ✅ MA ✅
Relevant Experience:
- Basic knowledge of transistor modeling
- Experience with programming (ideally Python) and Machine Learning
- Interest in the application of modern AI methods in Power Electronics
Contact:
Contact
Dominik Koch
M.Sc.Group Leader Power Electronics / Research Assistant
Benjamin Schoch
M.Sc.Group Leader High Frequency Electronics / Research Assistant