Just like an ordinary switching power supply, it only combines the inductance with the primary of the transformer.

1 When the switch tube is turned on, the primary coil of the transformer is used to store energy.

When the switch tube is turned off, according to the principle of inductance, the primary coil generates a reverse polarity voltage near the power supply and transmits it to the secondary side to realize energy transfer.

The output voltage can be adjusted by adjusting the frequency and/or duty ratio of the switch tube and matching the appropriate transformer inductance.