负半周 meaning in English

negative half period

The second , at the high frequency primary coil , when switch turn on with control signal ( the spwm pulse is modulated ) , in the positive or negative semi - period of low frequency modulation signal , transformer coil with same direction voltage . the magnetic flux of transformer core will increase step by step . at the end , it leads to magnetic flux saturation
二、在高频变压器原边，当开关管接收控制信号脉冲列(经调制的spwm波列)导通时，在低频调制信号的正半周或负半周内，施加在变压器绕组上的是同一方向的电压，变压器磁芯中的磁通可能将级进地逐渐增加，导致磁芯饱和，造成磁偏或单向磁化，导致低频电信号放大失真或由于很大的磁化电流而无法正常工作。