1. What is a high frequency transformer?
High-frequency transformer is the most important component of switching power supply. High-frequency transformer is a power transformer whose operating frequency exceeds intermediate frequency (10kHz). It is mainly used as high-frequency switching power supply transformer in high-frequency switching power supply and also used in high-frequency inverter. It is used as a high-frequency inverter power transformer in power supplies and high-frequency inverter welding machines.
According to the working frequency, high-frequency transformers can be divided into several grades: 10kHz-50kHz, 50kHz-100kHz, 100kHz~500kHz, 500kHz~1MHz, and above 10MHz. When the transmission power is relatively large, the power device generally uses IGBT (Insulated Gate Bipolar Transistor). Since IGBT has the off-current tailing phenomenon, the operating frequency is relatively low; when the transmission power is relatively small, MOSFET (Semiconductor Field Transistor) is used. effective transistor), the operating frequency is relatively high.
2. Working principle of high frequency transformer
High-frequency transformer is a device that uses the principle of electromagnetic induction to transform AC voltage, current and impedance. Its main components include primary coil, secondary coil and iron core.
When AC current flows through the primary coil, AC magnetic flux is generated in the iron core (or magnetic core), causing the secondary coil to induce voltage (or current), which is used as a boost, step-down, or isolation in the power supply.
3. Advantages of high frequency transformers:
For high-frequency transformers used with DC step-up and step-down technology, the switching frequency is generally at least greater than 10KHz, and the maximum switching frequency is limited by the heat resistance of the switching power components (BJT, MOSFET, IGBT) and the iron core material. The size of the iron loss, in other words, is limited by the temperature that the material can endure. The core material of this type of transformer used in power supplies is mainly made of ferrite power materials, commonly known as "high frequency". transformer".
In the case of higher power consumption and longer transmission distance, the AC power system far outperforms the DC system.
Generally speaking, AC power systems are either 50Hz or 60Hz. As long as the transformer is designed for use with a power frequency of 50Hz/60Hz, it is commonly known as a 'low-frequency transformer'. It is generally used in conjunction with the power system and is also called a power transformer. The core materials are mainly silicon steel sheets.
The frequency is determined by the number of switching times per second of the switching component, so it is also called the switching frequency fs. When the input voltage of the transformer is the same, increasing the switching frequency can reduce the number of turns N and reduce the size of the iron core. How much power is transmitted depends on the conductor. Wire diameter, so usually the purpose of increasing the switching frequency is to reduce the number of turns or reduce the core volume, so the volume of the high-frequency transformer will be much smaller than that of the low-frequency transformer.