As can be seen from the figure, the

As can be seen from the figure, the so-called hard switch refers to a sudden forced switching process when the voltage and current on the switch are not zero, that is, the forced switching device is turned on when the voltage is not zero or turned off when the current is not zero. Compared with hard switches, the ideal opening waveform of soft switches is that the voltage first drops to zero, and then the current slowly rises to the on-state value, so there will be no loss and noise during the opening. Soft-opening switches are called zero-voltage switches. softThe ideal turn-off waveform of the switch is that the current first drops to zero, and then the voltage slowly rises to the on-state value, so there will be no loss and noise when the switch is turned off. The soft switch is called zero current switch. At the same time, du/ DT and DI/DT are also greatly reduced, so the corresponding electromagnetic interference (EMI) and radio frequency interference (RFI) will also be reduced, improving the stability of the converter. Soft switch reduces switching loss and switching noise, which is beneficial to the further increase of switching frequency of power devices.