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:
By using fast-switching GaN HEMTs, it is possible to make both the power supply and the amplifier stage in an audio amplifier more efficient and perform better. Current amplifiers based on silicon and other linear amplifier topologies often exhibit low electrical efficiency and performance. By using a class-D amplifier stage in combination with a multiphase boost converter, the efficiency, performance and installation space can be optimized. The multiphase design of the boost stage means that both the inductances and the required transistors can be made smaller and more cost-effective. Furthermore, the voltage provided in this way should be converted into an audible audio signal with as little distortion as possible using a clocked full-bridge configuration.
Type of Thesis:
BA ✅ FA ✅ MA ✅
Preliminary experience
- LE 1+2 und RT 1+2
- RPSS 1+2
- µController
Contact:
A T-type inverter is a so-called 3-level topology. Compared to a classic half-bridge, three discrete potentials can be set at the switching node. This has the advantage of a significantly reduced THD of the output current with a simultaneously higher efficiency. By using GaN HEMTs, this topology can in theory be operated at comparatively high switching frequencies. However, in order to achieve clean switching behavior, a PCB design is required that keeps parasitic elements such as the line inductance and the switching node capacitance low. This should ensure that the full potential of GaN HEMTs is utilized.
The aim of this work is to use FEM simulation to compare different PCB concepts and then optimize them.
Type of Thesis:
BA ❌ FA ✅ MA ✅
Relevant Experience:
- Power electronics 1
- Ideally KiCAD and/or Altium
- Basic understanding of FEM simulations
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.
Contact
Dominik Koch
M.Sc.Group Leader Power Electronics / Research Assistant
Benjamin Schoch
M.Sc.Research Assistant