Martin Honsberg-Riedl

Thermal characterisation of power devices during transient operation

An experimental infrared method for the thermal characterisation of semiconductor devices during fast transient operation, in the range from a few microseconds and up to some milliseconds, is presented. The features which make it suitable and convenient, particularly for use with power electronics applications are pointed out; its time and space resolution are illustrated by means of properly chosen examples. The considered solution qualifies as a very versatile and powerful tool in many diverse lines of investigation.

On-chip reliability investigations on power modules actually working in inverter systems

The paper contains the results of temperature measurements for reliability investigations on IGBT modules actually working in inverters for industrial and traction applications. For this, the chip temperature and its transient behaviour have been monitored under different driving conditions of the inverters. Specially prepared IGBT-modules have been used to investigate the industrial and the traction inverters in their electrical and thermal behaviour. The measurement techniques were suitably adapted to the different configurations of the two inverters.

Inaudible cooling: A novel approach to thermal management for power electronics based on acoustic streaming

A new approach for forced convection cooling based on “Reynolds streaming” is presented, which allows for additional heat dissipation in situations where conventional active cooling devices (e.g. fans) are not suitable. The system operates inaudible, has no moving parts and is therefore durable and immune to dust. Its operation is dependent on numerous influences that have been identified and analyzed through experiment and simulation. It employs a new kind of acoustic driver delivering high intensity fields within air, while maintaining a small build volume. This transducer was designed and optimized using FEM-Simulation and verified with real-world prototypes at each major simulation milestone. All of the taken measures improved the performance by a factor of nearly 2 while reducing the system size by a factor of over 6 at the same time when compared to the first working system. This last generation device delivers comparable cooling performance.

A piezoelectric actuator concept for LED cooling by ultrasonic streaming

The thermal management of high power LED bears the potential of achieving higher efficiencies as well as an increased lifetime. Yet so far none of the conventional cooling techniques are suitable for use with general illumination: The devices emit audible noise, have a short life time, or are sensitive against dust and debris. The goal behind this work was to develop a solution that has none of these drawbacks. The effect of acoustic streaming was chosen for a closer look and delivered very good results during first experiments. Within this paper a device will be presented that is able to cool a 5000 lm LED light engine without emitting any audible sound. To achieve this all aspects of the device were examined and optimized.