The states of power electronic devices in PWM converters which operated in current continuous mode ( CCM ) are most severe . It requests that the PSS technology makes the power electronic devices turned-on or turned-off in soft-switching condition .

在电感电流连续模式（CCM）的PWM变换器中工作的电力电子器件的开关状态最恶劣，要求PSS技术能使电力电子器件的 开通与关断都处于软开关状态。

In order to realize soft-switching the diagonal pairs of switches of the bridge legs should stagger their turn-on instance the early turned-on switches are called the leading switches and the later turned-on switches are called the lagging switches as well .

分析表明，要实现开关管的软开关，必须 使全桥 逆变桥中斜对角的两只开关管错开开通， 先 开通的开关 管称为超前管，后开通的开关管称为滞后管。