Reliability & Robustness

Simulation, design, implementation and measurement of temperature and degradation phenomena as well as thermal behaviour and EMI of power modules

Open student thesis

Temperature is an important parameter for robust power electronics, as its variation has a direct impact on the end-of-life (EoL) of the device.

Measurement is possible through temperature sensitive electrical parameters (TSEPs), but these parameters can change their value during the lifetime of a power device and affect temperature sensing. In this thesis, temperature measurement is implemented using the VSD method. The specific features for its use in a back-to-back converter are also considered.

Tasks & Goals

  • familiarization & literature search (10 %)
  • Implementation of power switch to disconnect AC side (20%).
  • Implementation of a disconnectable cur-rent source (20 %)
  • Adaptation of the control (20 %)
  • Verification of the design (15 %)
  • written thesis & presentation (15 %)

Previous Knowledge

  • Power Electronics I/II lecture or similar
  • Knowledge from RPSS1 helpful
  • Knowledge of OPV-based circuits helpful

Start: immediately

Contact: Kevin Muñoz Barón

 

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Most failures in power semiconductors are caused by thermal stress. Temperature changes lead to mechanical fatigue of the device components and thus to a reduced lifetime. Conventional active power cycling tests (PCT) are based on a constant current supplied to the DUT and thus do not reflect the heating that occurs in typical switched operation due to switching and conduction losses.

Based on the existing inverter, the proper procedure of the PCT will be implemented in this work.

Tasks & Goals

  • familiarization & literature search (10 %)
  • design and component selection (35 %)
  • assembly and test (40 %)
  • written thesis & presentation (15 %)

Previous Knowledge

  • Power Electronics I/II lecture or similar
  • Experience in practical lab work

Start: immediately

Contact: Kevin Muñoz Barón

 

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State-of-Health (SoH) monitoring is becoming more and more important, to enable power electronics with highest reliability. One of the parameters that is of interest is the on-state voltage (V_(DS,on)) of power MOSFETs. Due to the high dynamic range of the V_(DS,on) in on- and off-state, specialized measurement circuits are needed. These are called „clipper circuits“.

In this work a cascaded clipper circuit based on depletion mode MOSFETs is to be analyzed. Of particular interest is the effect of the cascading on the performance of the clipper.

Tasks & Goals

  • Familiarization & literature search (10 %)
  • Design and Simulation (25 %)
  • Cascading of the clipper circuit in simulation
  • PCB Design (10 %)
  • Design of a measuring circuit for verification
  • Setup and Measurements (40 %)
  • Initial operation of the designed measuring circuit
  • Evaluation of the measurement results
  • Written thesis & presentation (15 %)

Previous knowledge

  • Knowledge from RPSS1 helpful

Start: immediately

Contact: Kevin Muñoz Barón

 

PDF

Combining two half-bridges into an H-bridge is typically done for motor inverter applications, but can also be used in lifetime testing applications as so-called back-to-back converters. Here both half-bridges are joined on the DC and AC side to allow for high currents to flow through the transistors without needing excessive energy from the supply.

In this work a back-to-back converter is to be developed and tested based on SiC-half-bridge modules from Infineon. The base for this converter is an already available converter based on modules from Rohm (see figures).

Tasks & Goals

  • familiarization & literature search (10 %)
  • design and component selection (35 %)
  • assembly and test (40 %)
  • written thesis & presentation (15 %)

Previous Knowledge

  • Power Electronics I/II lecture or similar
  • Experience in practical lab work

Start: immediately

Contact: Kevin Muñoz Barón

 

PDF

Task

As in many technological areas, the aim in power electronics is to make components smaller, lighter and at the same time more powerful. 3-dimensional circuit carriers such as MID's (Molded Interconnect Devices) have many advantages in this respect. On the one hand they have the potential for further system miniaturization and function integration. On the other hand, the variety of parts in a system can be reduced and heat dissipation can be individually optimized. In addition to thermoplastic-based MIDs, thermoset and ceramic substrate materials have recently been developed and are of interest for power electronics. With smaller power modules and higher power density, however, the demands on packaging and interconnection technology (AVT) are also increasing. Thermal performance is an important criterion for material selection and AVT. The calculation of the transient temperature behavior of the semiconductors for a given power loss profile can be determined e.g. by Zth-curves.

In the context of this work, WBG power semiconductors on novel three-dimensional substrates are to be measured transiently thermally. A part of the work is the conception, design, construction and assembly of test samples with modern AVT-technologies like soldering, silver-sintering or semi-sintering.

The student work is supervised in cooperation between Hahn-Schickard and the ILH.

Individual activities

  • Structure of test specimens
  • Implementation of Zth-examinations
  • Evaluation and summary of the results
  • Documentation of the work

Start: immediately

Contact ILH: Dominik Koch

Contact Hahn-Schickard: Kai Werum

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In power electronics the temperature plays a major role. For example the junction-temperature is a crucial parameter and mandatory for a safe operation. In addition a boundary value for example the heating sink temperature has to be taken into account. To measure these temperatures different measurement methods are used, which all have different advantages and disadvantages.

In this work different sensors should be compared qualitative regarding accuracy, dynamic and complexity. In addition the different sensors should be controlled and read out by a SPI interface and compared at different operations. For this an adapter PCB should be designed, where different sensors can be connected and read out centrally.

Timetable:

  • Familiarization & literature search(10 %)
  • Design and simulation of adapter PCB (20 %)
  • Programming of SPI-interface (20 %)
  • Messung und Evaluierung der einzelnen Sensoren (30 %)
  • Written thesis & presentation (20 %)

Previous knowledge:

  • Circuit/layout design in Altium
  • Experience in practical lab work
  • Ability to work on your own

 

Contact: Kevin Muñoz Barón

Contact: Dominik Koch

PDF

For the operation of power electronic circuits the knowledge of the temperature of the components is an important parameter to control the performance of the cooling system, to detect asymmetric load cases and to detect failures with different time constants.

In many conventional power modules, diodes or resistive temperature sensors are positioned as discrete components next to the power transistor, so that the reaction time of the sensor to a temperature change in the power semiconductor is relatively large (ms…s).

The lateral structure of GaN transistors allows the monolithic integration of sensor and logic circuit parts directly next to the power transistor, which has already led to a significant reduction of the reaction time for temperature measurements in first experiments.

In this thesis a measurement circuit has to be developed, which further reduces the reaction time of the monolithic integrated temperature sensor and thus improves the general failure detection for the power electronic components.

Topics:

  • Temperature protection circuits:
    • Types of protection circuits
    • Simulation possibilities of temperature measurement
    • Possibilities of measured value processing
  • Circuit design of an evaluation circuit
  • Validation of the developed concept

Contact: Jan Hückelheim

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This image shows Benjamin Schoch

Benjamin Schoch

M.Sc.

Research Assistant

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