Selected problems from power electronics and electrical drives
FEKT-DKC-VE1Acad. year: 2020/2021
Ringning problems of fast switching semiconductors MOS-FET, SiC MOS-FET and GaN MOS-FET, circuit realization of gate-drivers for these transistors, snubber circuits for the turn-off process (lossy and lossless), parasitic effects in power circuits of DC/DC converters with fast switching semiconductors - influence of the transformer leakage, transformer parasitic capacitance and transistor parasitic capacitance C-E, forward and reverse recovery of diodes and their ellimination. Skin-effect and proximity effect in the windings, problems of geometrical design of the power circuit and gate-driver, problems of EMC.
Learning outcomes of the course unit
The graduate understands the ringing effect and knows the mechanisms of its appearing.
The graduate is able to eliminate the ringing by the construction of power circuit and gate-driver.
The graduate can construct power-stages of gate-drivers for SiC MOS-FET and GaN MOS-FET transistors.
The graduate knows the snubber circuits.
The graduate understands selected resonant and quasi-resonant converters in detail.
The graduate is able to design the pulse transforemsr and a choke inductor taking into account the problems of skin-effect and proximity effects.
The graduate is able to construct power circuits with extremely fast semiconductors and is able to elliminate the forced parasitic effects appearing in these cases.
The graduate can correctly read the distorted measurement results of power circuits.
The graduate can design EMC filters and is able to construct control circuits with high immunity to the interference of power circuits.
1. Basic knowledge of power circuits of DC/DC and DC/AC converters.
2. Basic knowledge of turn-on and turn-off processes of a switching transistor.
3. Basic knowledge of gate-driver problems.
4. Basic knowledge of pulse transformers and choke-inductor design.
Recommended optional programme components
Recommended or required reading
Patočka, M.: Magnetické jevy a obvody ve výkonové elektronice, měřicí technice a silnoproudé elektrotechnice. V Brně: VUTIUM, 2011. ISBN 978-80-214-4003-6. (CS)
Patočka, M.: Vybrané statě z výkonové elektroniky, svazek 1, skriptum FEKT VUT Brno (CS)
Patočka, M.: Vybrané statě z výkonové elektroniky, svazek 2, skriptum FEKT VUT Brno (CS)
Bose, B.K.: Power electronics and AC Drives. Prentice Hall 1986 (CS)
Planned learning activities and teaching methods
Teaching methods depend on the type of course unit as specified in the article 7 of BUT Rules for Studies and Examinations.
Assesment methods and criteria linked to learning outcomes
Oral final exam - max. 70 points
Language of instruction
1. Ringing in the output power stage of the gate-driver loaded with the G-E capacity, specific properties.
2. Ringing appearing in the power circuit (collector circuit), Miller transfer to the gate, risk of positive feedback, ellimination with the construction of the power circuit and gate-driver.
3. Circuit examples of gate-drivers with respect to ellimination of both discussed ringing processes.
4. Specific requirements on gate-drivers for SiC MOS-FETs and GaN MOS-FETs.
5. Lossy and lossless (resonant) snubber circuits, specific circuitry for various converter types.
6. Concrete detailed description of a resonant converter (selected type).
7. Concrete detailed description of a quasi-resonant converter (selected type).
8. Problems regarding pulse transformenrs, choke-coils, core losses, skin-effect, proximity-effect, practical consequences.
9. Influence of parasitic capacitances in the power circuit (transistors, diodes, transformer, demagnetization problems in no-load state, correspondence with the gate-driver).
10. Practical influence of forward and reverse recovery effects of diodes in converter power circuits (on the primary side and also in the output rectifier) - current or voltage over-shoot, correspondence with the transformer leakage, di/dt and du/dt suppression, practical circuit realization.
11. Problems of a correct measurements in power circuits, influence of common-mode interference and other interference signals on the measured waveforms.
12. EMC-EMS problems - immunity of control circuits to own interference produced with the power circuit, PCB geometrical design, conception of control circuits with respect to the immunity to the interference.
13. EMC-EMI problems - suppresion of radiation of power circuits and interference propagation via input and output cables, EMC filters.
The goal of the course is to improve the knowledge in the field of power pulse converters, non-traditional power circuits, application of modern switching semiconductors and corresponding parasitic effects.
Specification of controlled education, way of implementation and compensation for absences
Study results are verified regularly during the semester based on a discussion over the degree of understanding the solved problems - max. 30 points.
Classification of course in study plans
- Programme DKC-KAM Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
- Programme DKC-EKT Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
- Programme DKC-MET Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
- Programme DKC-SEE Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
- Programme DKC-TLI Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
- Programme DKC-TEE Doctoral, any year of study, winter semester, 4 credits, compulsory-optional
Type of course unit
39 hours, optionally
Teacher / Lecturer