【摘要】 在全桥变换器中引入谐振电感和钳位二极管,可以使开关管在较宽的负载范围内实现零电压开关,并且消除输出整流二极管上的电压尖峰。在重载情况下,当钳位二极管导通时,谐振电感被短路,其电流保持不变,在开关管和钳位二极管中产生较大的导通损耗;而当负载减轻至一定程度时,钳位二极管工作在硬关断状态,不但产生较大的反向恢复损耗,甚至会损坏钳位二极管。本文首先详细分析该变换器在轻载情况下的工作原理,提出三种钳位二极管电流的复位方式,相应分析现有的几种钳位二极管电流复位方法的优缺点,并提出加辅助变压器的ZVS PWM全桥变换器。利用引入的辅助变压器,在任意负载下均可以使钳位二极管电流快速复位到零,不但可以减小变换器原边的导通损耗,提高变换效率,同时还可避免钳位二极管的硬关断,提高变换器的可靠性。本文详细分析了加辅助变压器的ZVS PWM全桥变换器的工作原理,并讨论辅助变压器的设计,最后进行实验验证,并给出实验结果。更多还原

【Abstract】 Introducing a resonant inductor and two clamping diodes into the full bridge converter can widen the load range of zero-voltage-switching(ZVS) and eliminate the voltage spike across the rectifier diodes.The resonant inductor is short-circuited and its current keeps constant when the clamping diode conducts under heavy-load condition,resulting in larger conduction losses in the power switches and clamping diodes.Furthermore,the clamping diodes are turned off hard when the load current is reduced to a certain degree,leading to serious reverse recovery loss or even failure of the clamping diodes.In this paper,the operation principle of the full bridge converter with clamping diodes under light-load condition is analyzed in detail and three kinds of clamping diode current resetting schemes are presented,in the meanwhile,the pros and cons of several existing clamping diode current resetting circuits are compared and a novel ZVS PWM full bridge converter employing auxiliary transformer to reset clamping diode current is proposed.With the introduced auxiliary transformer,the clamping diode current can be decayed rapidly over the whole load range,thus not only the conduction losses can be reduced and the conversion efficiency can be increased,but also the hard turn-off of the clamping diodes can be avoided.The operation principle of the novel ZVS PWM full bridge converter with auxiliary transformer is analyzed and the design of the auxiliary transformer is discussed in this paper,and experimental results verify the effectiveness of the proposed full bridge converter.更多还原