K. Rustom Wenkai Wu Weihong Qiu Issa Batarseh Asymmetry half bridge soft-switching PFC converter with direct energy transfer. 525-528 2002 ISCAS (5) http://doi.ieeecomputersociety.org/10.1109/ISCAS.2002.1010756 db/conf/iscas/iscas2002-5.html#RustomWQB02