High-frequency transformer is over IF frequency (10kHz) of the power transformer, mainly used for high-frequency switching power supply for high-frequency switching power supply transformer, but also for high-frequency and high frequency inverter for high frequency inverter welding machine in reverse change the power transformer. According to the level of the operating frequency can be divided into several grades: 10kHz-50kHz, 50kHz-100kHz, 100kHz ~ 500kHz, 500kHz ~ 1MHz, 1MHz or more. Transmission power is relatively large in the case, power devices generally use IGBT, because there IGBT turn-off current tailing phenomenon, so the frequency is relatively low; transmission power is relatively small, can be used MOSFET, the operating frequency is relatively high.