| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 88 === The thesis is to study and realize a zero-voltage-switching pulse width modulation half-bridge converter (ZVS-PWM HB), adopting constant-off time mode with variable frequency control, to perform zero-voltage switching and to obtain high efficiency. The state-space averaging method is used to analyze the resonant behavior. Matlab is adopted to simulate the linear charge/discharge performance of the resonant stage. In respect of small-signal model analysis, state-space averaging method is also applied to obtain the open-loop transfer function, with K factor of Venable’s criterion for compensation to make system stable. In order to increase the efficiency, MOSFETs are used with low RDS(ON) at the output end to achieve synchronous rectifier, and the usage of wiring transformer secondary side to drive MOSFET, so as to decrease the complexity of the driver circuit. Finally, a detailed description for design process of the converter is conducted. A 100W ZVS-PWM half-bridge DC/DC converter is designed and realized with 48V dc input to verify the theoretical estimation. For practical measurement, the efficiency is above 85% when input is 48V dc and more than 90% when input is 40V dc. For all-range control, the load regulation and the line regulation are always kept within ±0.7% and ±0.02% , respectively.
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