Fig. half-bridge inverter and protection circuit !" !产品与市场! !上接第53 页" The D sign of V rtical Scr w- eeder for Biom ss LIU Shi-fenga WANC Shu yanga JIANC Nian yonga BAI Xue Shuang (Northeast Forestry University, -arbin -eilongjiang 150040a China Abstr ct:The spiral con...