law of sines meaning in English

正弦定理
正弦定律

" soft switching " is zero voltage switching or zero current switching , which the voltage ( or current ) of the switch varies by law of sine or quasi sine , the switch is on when its voltage reaches zero ( or switch is off when its current reaches zero ) by resonance . it makes switch loss is zero , so it can increase the operating frequency and raise power density , minimize the size of transformer and inductor
“软开关”是指零电压开关或零电流开关，它是利用谐振原理，使开关变换器的开关管电压(或电流)按正弦(或准正弦)规律变化，当电压过零时，使器件开通(或电流自然过零时，使器件关断) ，实现开关损耗为零，从而提高开关频率，减小变压器、电感的体积。