Abstract:

The subject of designing power converters is crucial for electrical engineering students to comprehend. Learning the fundamentals of switching mode power supplies from a topological perspective is straightforward with ample literature available. However, the real challenge lies in understanding and measuring the performance of a switching mode power supply.

There are various experimental training kits for teaching power supplies, but the feedback from the undergraduate students, is that these experimental training kits are too specific, to the producer of that specific kit. A more general experimental test bench would benefit to the students understanding and therefore a new educational experimental test bench has been developed. This new educational test bench has been tested in a series of experimental laboratory courses on power supplies, where undergraduate students were performing measurements on 15 different power supply topologies with dedicated learning objectives. The structure of the experiments and the requirements from the learning objectives were evaluated and applied to a second prototype. This prototype was then again used in a series of laboratory experiments and evaluated. The general approach of the new prototype, was conceived by the students as contributing to improve their knowledge on the subject of power supplies.

This paper presents the concept of Universal Two Leg (U2L), an educational power converter capable of being configured into 15 different switch mode power supply topologies. The U2L can be set into open-loop and closed-loop configurations, with two modes –voltage control and current control. The U2L's educational silkscreen and numerous test points make it easy to learn and use its various modes, while the built-in over voltage and over current protection ensure it is safe for students to use. With the use of online simulation and tooling, the students prepare the laboratory hands-on tutorials in details. The expected wave forms to be measured in the laboratory are first explained using the online simulations and tooling. Next, the students perform the experiments on the Universal Two Leg and compare the measured waveforms withe waveforms obtained through simulation. The influence of various important design issues and parameters is then practiced on the U2L test bench. The student can change parameters by selecting various options on the U2L test bench and can exchange control methods by interchanging small controller boards on the U2L test bench.
By varying parameters of several components inside the U2L test bench, the students get a better understanding on their influence on a switched mode power supply. The U2L test bench is build around industry standard components and the application and power rating is equal to commonly used switched mode power supplies, like, for example, laptop power supplies, led drivers or USB phone chargers. Students get a deeper understanding on the design and functioning of a switched mode power supply, compared to only following theoretical classes and mathematical exercises.

Since the U2L test bench is configurable into the most commonly switched mode power supplies, a single U2L test bench can be used during different lectures within the course. Open loop experiments are generally performed in undergraduate courses, while the closed loop experiments are for the graduate courses.

Keywords:

Power Electronics, Laboratory, test bench, experiment, simulation.