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Research Of High Power Density DC-DC Converters And Passive Components Integration Within Them

Posted on:2009-04-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y J ZhangFull Text:PDF
GTID:1102360272477841Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
With the rapid development of the information technology, a great market is brought to the power electronics industry. And it also brings some challenges to the power electronics converters: higher efficiency and higher power density. To increase the conversion efficiency of the power converters, the researchers have conducted a lot of work towards the following directions: 1. Designing better circuit topologies, 2. Developing better power devices, 3. Utilizing better passive components. To increase the power density, generally there are two different ways: 1. Increasing the switching frequency, 2. Using the passive components integration technology. Nowadays the switching frequency of the dc power converters has been pushed higher and higher. After the switching frequency is pushed higher, the impact of some parasitic circuit parameters can't be neglected any more. We can also utilize the passive integration technology to integrate the parasitic parameters through proper selection of material and proper design of structure, and thus utilize them as part of the circuit parameter to relieve their impact on the circuit performance.The resonant converters can realize the soft switching of the switches, thus it is suitable for high frequency operation. It can also utilize some parasitic circuit parameters-such as the transformer leakage inductor-as part of circuit components. LLC resonant converter has received wide attention in the recent years. In this dissertation we propose a kind of circuit parameter design method for LLC resonant converter. Firstly through the selection of the desired operation region and the desired operation switching frequency range we can decide the transformer turn ratio n and the series resonant frequency f_o. Then we define two parameters k and Q which is related to the circuit parameters. Through studying the influence of parameter k and Q on the converter voltage gain, the switching frequency range and the efficiency we can determine their selection principle. After the parameter n, f_o, k and Q is decided the circuit parameters can be calculated out.After designing the circuit parameters, in this dissertation we propose a method utilizing the multiple layer foil to realize passive integration in LLC resonant converter. There are altogether four passive components in the resonant tank: the series resonant inductor, the resonant capacitor, the parallel inductor and the transformer. The parallel inductor can be integrated with the transformer by using transformer magnetizing inductor. The series resonant inductor can be integrated with the transformer through two different methods: utilizing transformer leakage inductor and using the "common magnetic path" method. For the resonant capacitor, we can use the proposed multiple layer foil to realize its integration with transformer. In our application, the fully integrated structure can reduce the total size of the passive components in resonant tank by 36% compared to the discrete structure.A new accurately regulated multiple output ZVS dc-dc converter is proposed. Two outputs are regulated through the duty cycles of two asymmetrical half bridge converters, and the third output is regulated through the phase shift between them. All the outputs are accurately regulated, so that the resolution of the three output voltages is very good. All the main switches can realize ZVS ON, therefore the converter can work at higher switching frequency with higher efficiency.
Keywords/Search Tags:magnetic integration, passive integration, LLC resonant converter, soft switching, multiple output dc-dc converter
PDF Full Text Request
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