The efficiency of internal combustion engines in trucks and passenger cars are low (<40%). Much work has been done to make the engines more efficient internally, by improving the mechanical and electrical components. However, there is still a large amount of fuel power, which gets converted into heat and escapes through exhaust gases as waste heat. Taking advantages of thermoelectricity, part of that heat power can be converted into electrical power. In this paper, the most suitable DC/DC converter for Thermoelectric Generator in Heavy Duty Vehicles is proposed and based on the simulation results, different aspects of designing high-efficient DC/DC converters are discussed.

Today's combustion engines have low efficiency and a large amount of useful energy converts to heat as waste in different type of vehicles. Improving the dynamics of the car body, injection system, the shape of the internal engine components and manipulating the fuel compositions have had influence on fuel economy, but still less than 50% of energy in the fuel is converted to useful mechanical power. Since the lost energy escapes through the exhaust system as heat, taking advantage of thermoelectricity, part of that energy can be converted to useful electrical energy, improving the overall efficiency. However, the output voltage from a thermoelectric generator is a function of hot and cold side temperature and since, the electrical system of the vehicle operates with constant voltage, the use of a power converter is necessary. In this paper, simulation and experimental results of such a high-efficiency converter(94-96%), designed for thermoelectric generators on heavy duty vehicles is presented and discussed.

The European Union’s 2020 target aims to be producing 20 % of its energy from renewable sources by 2020, to achieve a 20 % reductionin greenhouse gas emissions and a 20 % improvement in energy efficiency compared to 1990 levels. To reach these goals, the energyconsumption has to decrease which results in reduction of the emissions. The transport sector is the second largest energy consumer in theEU, responsible for 25 % of the emissions of greenhouse gases caused by the low efficiency (<40 %) of combustion engines. Much workhas been done to improve that efficiency but there is still a large amount of fuel energy that converts to heat and escapes to the ambientatmosphere through the exhaust system. Taking advantage of thermoelectricity, the heat can be recovered, improving the fuel economy. Athermoelectric generator (TEG) consists of a number of thermoelectric elements, which advantageously can be built into modules,arranged thermally and electrically, in a way such that the highest possible thermal power can be converted into electrical power. In aunique waste heat recovery (WHR) project, five international companies and research institutes cooperated and equipped a fully drivableScania prototype truck with two TEGs. The entire system, from the heat transfer in the exchangers to the electrical power system, wassimulated, built and evaluated. The primary experimental results showed that approximately 1 kW electrical power could be generatedfrom the heat energy. In this paper the entire system from design to experimental results is presented.

A considerable part of the fuel energy in vehicles never reaches the wheels and entirely converts to waste heat. In a heavy duty vehicle (HDV) the heat power that escapes from the exhaust system may reach 170 kW. The waste heat can be converted into useful electrical power using thermoelectric generator (TEG). During the last decades, many studies on the electrical power conditioning system of TEGs have been conducted. However, there is a lack of studies evaluating the electrical instrumentation, the impact of the converter-efficiency, and the TEG arrangement on a real large-scale TEG on-boarda drivable vehicle. In this study, the most important parameters for designing electrical power conditioning systems for two TEGs, developed for a real-scale HDV as well as experimental results demonstrating the recovered electrical power, are presented. Eight synchronous inter-leaved step-down converters with 98 % efficiency with perturb and observe maximum power point tracker was developed and tested for this purpose. The power conditioning system was communicating with the on-board computers through the controller area network and reported the status of the TEGs and the recovered electrical power. The maximum recovered electrical power from the TEGs reached 1 kW which was transmitted to the electrical system of the vehicle, relieving the internal combustion engine.

The demand for high-efficiency power converters is increasing continuously. The switching losses are typically significant in power converters. During the switching time, the component is exposed to a considerable voltage and current causing power loss. The switching time is limited by parasitic inductance produced by traces and interconnections inside and outside the package of a device. Moreover, the parasitic inductances at the input-terminal together with the Miller capacitance generate oscillations causing instability and additional losses. In order to eliminate the package parasitic inductance, four 1.2kV SiC-MOSFET bare dies, two in parallel in each position, were directly attached to a PCB sandwich designed as a half bridge. The obtained structure forms a planar power module. From ANSYS Q3D simulations it was found that the parasitic inductance between drain and source for each transistor in the proposed planar module could be reduced 92 % compared to a TO247 package. The planar module was also tested as a dc-dc converter. Switching waveforms from these experiments are also presented.

Silicon Carbide (SiC) MOSFETs offer excellent properties as switches in power converters. However, the package of the device is an issue that prevents utilizing the advantages of SiC, as for instance fast switching speed. The packages of currently available SiC devices are the same as those previously used for silicon devices with moderate electrical and thermal characteristics resulting in accelerated aging and reliability issues. Moreover, the parasitic inductance caused by the package, limits the switching time and operating frequency. By excluding the package, the parasitic inductances will be eliminated to a large extent. In this study, the procedure of manufacturing a half-bridge planar power module, using four SiC MOSFET bare dies and PCB, is described. According to simulations, the parasitic inductance Lstray of the structure is approximately 96 % lower than most commercial half-bridge modules. It is also shown that double-side cooling can be employed for the proposed module if substrates with low thermal resistance are employed.

Parasitic inductances caused by the package of semiconductor devices in power converters, are limiting the switching speed and giving rise to higher switching losses than necessary. In this study a half-bridge planar power module with Silicon Carbide (SiC) MOSFET bare dies was designed and manufactured for ultra-low parasitic inductance. The circuit structure was simulated and the parasitic inductances were extracted from ANSYS-Q3D. The values were then fed into LT-Spice to simulate the electrical behavior of the half-bridge. The experimental and simulation results were compared to each other and were used to adjust and easily extend the simulation model with additional MOSFETs for higher current capability. It was shown that the proposed planar module, with four parallel SiC MOSFETs at each position, is able to switch 600V and 400A during 40 and 17ns with E-ON and E-OFF equal to 3.1 and 1.3mJ, respectively. Moreover, unlike the commercial modules, this design allows double-sided cooling to extract the generated heat from the device, resulting in lower operating temperature.