High-frequency transformers are relative to audio and industrial frequency transformers. However, because the scale of high-frequency is so wide, it is very difficult to clearly divide them. Therefore, transformers with operating frequencies above audio can be collectively referred to as High frequency transformer.

High-frequency transformers are power transformers whose operating frequency exceeds intermediate frequency (10kHz). They are mainly used as high-frequency switching power supply transformers in high-frequency switching power supplies. They are also used in high-frequency inverter power supplies and high-frequency inverters. It is used as a high-frequency inverter power transformer in welding machines.

High-frequency transformers are divided into the following categories:

1. According to the working frequency band, they are divided into:

(1) Broadband transformer refers to a transformer that works in a very Transformers within a wide frequency range, such as impedance converter transformers, communication transformers, broadband power amplifier transformers, etc.

(2) Single-frequency or narrow-frequency high-frequency transformers refer to the operating frequency of a single frequency or a very narrow frequency band, such as converter transformers, oscillator transformers, etc.

2. Divided according to frequency range:

(1) MHz-level high-frequency transformers refer to high-frequency transformers with operating frequencies above 1MHz.

(2) kHz-level high-frequency transformers refer to high-frequency transformers with operating frequencies from 20 kHz to several hundred kHz.

1. Square wave transformer

The AC voltage waveform output by the square wave transformer is a square wave. The inverter circuits used in this type of transformers are not exactly the same, but the common feature is that the circuit is relatively simple and the number of power switch tubes used is small. The design power is generally between one hundred watts and one kilowatt. The advantages of square wave transformers are: simple wiring, cheap price, and easy maintenance. The disadvantage is that the square wave voltage contains a large number of high-order harmonics, which will produce additional losses in load appliances with iron core inductors or transformers, causing interference to radios and some communication equipment. In addition, this type of transformer has shortcomings such as insufficient voltage regulation range, incomplete protection function, and relatively high noise.

2. Step wave transformer

The AC voltage waveform output by this type of transformer is a step wave. There are many different lines for transformers to realize step wave output, and the number of steps in the output waveform varies greatly. . The advantage of the step wave transformer is that the output waveform is significantly improved compared to the square wave, and the high-order harmonic content is reduced. When the steps reach more than 17, the output waveform can achieve a quasi-sinusoidal wave. When using transformerless output, the overall efficiency is very high. The disadvantage is that the ladder wave superposition circuit uses a lot of power switch tubes, and some of the circuit forms require multiple sets of DC power inputs. This brings trouble to the grouping and wiring of solar cell arrays and the balanced charging of batteries. In addition, the staircase wave voltage still has some high-frequency interference to radios and some communication equipment.