Research On High Frequency Power Conversion Of Small Power DC-DC Converter

The rapid computer industry development leads the power supplies to provide low output voltage(0.9～1.5V),high output current,High efficiency,high power density are all the requirements in the future application.To achieve these requirements,the power conversion must operate at higher switching frequency(above 1 MHz).In this dissertation,the state of the art of high frequency power conversion is reviewed firstly and some key issues are also presented.The topology selection and optimization are very important for the high frequency power conversion.The two-stage DC-DC converter is a suitable solution in applications with a wide input voltage range,low output voltage and high output current.A new ZVS-PWM Buck converter with an active clamping cell is proposed to be the optimal topology for the first stage,and the second stage uses a half bridge converter with D=0.5 as a step-down transformer.To reduce the high frequency gate drive losses,the class E resonant gate driver is investigated and a full-bridge type resonant gate drive circuit is proposed to drive a pair of switches.Compared with several high frequency resonant gate drivers,a new resonant gate drive circuit is proposed for driving a pair of switches.The single winding self-driven synchronous rectification is used in the second-stage half bridge converter.After a detailed research on high frequency magnetic components,the calculation scheme for planar transformer winding losses and core losses is proposed.The design and simulation procedure for planar transformer is also given.A hybrid modeling of planar transformer is proposed to help the design optimization.The integrated magnetic structure is investigated in a half bridge converter.Several high frequency conversion techniques are utilized in the design of the power module,such as high frequency loss analysis,resonant gate drive technology,self-driven synchronous rectification.Under the transformer winding design optimization,the multi-layer PCB Planar transformer is implemented in the prototype.The detailed experimental results for the two-stage DC-DC converter under two different control schemes are presented.The experimental results validate the theoretical analysis.