Analyse and design of an automotive 48V to 12V DC/ DC converter (Dipl.-Ing. Andreas J. Hanschek)

Abstract
The European CommissionsCO2limits represent a challenge for the automotive indus-try that can no longer or hardly be achieved by conventional engines alone. This leadsto the need for alternative drive concepts that make it possible to drastically reduceCO2emissions during operation. One of these concepts is the hybrid technology which makesit possible to provide the energy from fuels and electrical energy for the drive. In order toreduce the ever increasing demands on theCO2emissions of combustion vehicles, hybridtechnology has established itself in vehicles. These vehicles use the energy from fossilfuels and electrical energy to power the vehicle. [23] To make better use of electricalenergy, the electrical system of the vehicles is therefore being extended by a additionalbus system. In the case of a mild hybrid vehicle this is a 12 V bus and a 48 V bus. The 48V batteries of the hybrid vehicle are charged by a 48 V generator. For reasons of space,cost and efficiency, the entire power supply must be provided by the 48 V generatorwhile driving. Since it is not possible to connect the 12 V bus with its storage directly tothis generator, a connecting link must be established between the two bus systems. Thisinterface is provided by a 48 V/12 V bidirectional dc/dc converter. This is to stabilizethe voltage level of the 12 V bus and provide the required voltage to charge the 12 Vbattery if necessary. Under certain conditions, such as acceleration or starting, energymay be transferred from the 12 V bus to the 48 V bus. This is one of the reasons why theconverter is bidirectional

Development and Design of an Interface Energy Storage Power Converter for Robotic Applications (Jesacher Erwin)

This work focuses on the design of a DC-DC converter used in an automated guided vehicles (AGVs) application, to filter high peak power stress during operation by the use of a super-capacitor module. This ensures a filtered and constant battery power, which should reduce the battery stress and increase the battery lifetime. In addition, partial power processing is implemented to increase the efficiency, as only a part of the power is processed by the converter.Initially, different hybrid energy storage systems (HESS) will be analyzed and compared in detail. HESS in this application consist of a battery and a super-capacitor. The aim of this work is to understand and analyze how the recuperated energy due to the braking of an AGV can be fed into a super-capacitor with the lowest possible losses. The battery and the interface converter are out of the scope of the thesis and will not be considered.The braking process will be analyzed in detail to determine the worst-case condition and design the parameters of the converter in this worst-case. Based on the defined parameters, various design options are considered to improve the design, such as the parallelization of switching cells, the use of interleaving or multi-cell converters. Interleaving reduces the stress and size of filter inductors and filter capacitors, which will be explained in more detail in the following chapters.In addition, the design of the super-capacitor is described, based on the current and voltage load capability. A voltage balancer circuit is designed to keep the split DC bus voltage constant and equal to the half of the full DC bus voltage.In continuation, the Altium PCB design will be described in detail. The schematic and the layout are created, followed by a list of components that will be placed on the PCB.And finally, the results of a real-time simulation implemented in the RT box and measurements during the testing of PCB are presented. The final chapters of the thesis summarize the conclusions and the outlook of the work.