High frequency transformer is a power transformer with working frequency exceeding intermediate frequency (10kHz). It is mainly used as high frequency switching power transformer in high frequency switchmode power supply, as well as in high frequency inverter power supply and high frequency inverter welding machine. According to the working frequency, it can be divided into several grades: 10kHz-50kHz, 50kHz ≤ 100kHz, 100kHz ≤ 500kHz, 500kHz ≤ 1MHz, more than 10MHz.