Research On Asymmetrical Half Bridge DC/DC Converter

The effect of power supply efficiency on the environment has been paid more and more attention to the worldwide scale. Committed to the protection of natural resources for global governments and standardized institutions have launched the measures and popularized actively efficient energy. These guidelines drove the designer adopting the new topology such as resonant converter and soft switching converter.The asymmetrical half-bridge(AHB) topology discussed in the paper is one of the complementary driven pulse-width modulated converter topology, which presents an inherent zero-voltage switching(ZVS) capability. This type of converter utilizes the resonance between the leakage inductance of the transformer and the parasitic capacitance of the switch to achieve zero-voltage switching during the transition between two switches. Without additional component, it can achieve ZVS and increase the system efficiency. Firstly, the analysis of ZVS operation and operation principle for asymmetrical half-bridge converter are introduced. Each state of the total switching period has been studied in detail, then the condition of zero voltage switching is attained. Moreover, the influence on the ZVS due to the duty cycle, load current and so on is discussed. Secondly, through comparing the load current ZVS with magnetizing current ZVS, then advantage and disadvantage, the condition of zero voltage switching and application for two ZVS mode are attained. By using synchronous rectifier, the efficiency of DC/DC converter can be further improved. In this paper, self-driven synchronous rectifier is realized by using the auxiliary winding of the transformer, which simplified the driven circuit and make the converter economical. Finally, the simulation performed by PSPICE software confirm the correctness of theoretical analysis and the feasibility of zero voltage switching. Based on the theory study and simulation analysis, a prototype of asymmetrical half bridge was build. The experimental results based on the 12V/16.7A output load and the L6591 controller are presented to verify the system performance. From the experiment, the converter can operate on ZVS along a wide load range and high efficiency in this paper.