1. Introduction to Transformer Principle

As the name implies, a transformer is an electronic power instrument that changes voltage. It is a device that uses the principle of Faraday electromagnetic induction to change the AC voltage, and is mainly composed of a primary coil, an iron core, and a secondary coil. It can realize the matching conversion of input and output current, voltage and impedance, and can also realize the physical isolation of primary and secondary. According to different primary and secondary voltages, it can be divided into step-down transformer, step-up transformer, isolation transformer, etc.

2. According to different working frequencies, it is divided into low frequency transformer and high frequency transformer.

The frequency of electricity production in our daily life is 50 Hz, and we call this alternating current low-frequency alternating current. If the transformer works at this frequency, we call this transformer a low-frequency transformer, also called a power frequency transformer. This kind of transformer is large in size and low in efficiency. The iron core is stacked with mutually insulated silicon steel sheets. The primary and secondary coils are wound with enameled wire. The primary and secondary voltages are proportional to the number of turns.

In addition, some transformers work in dozens of settings and hundreds of kilohertz, which become high-frequency transformers. High-frequency transformers generally use magnetic cores instead of iron cores. The high-frequency transformer has a small volume, few turns of the primary and secondary coils, and high efficiency.

3. The difference and connection between high and low frequency transformers.

The working frequency of high-frequency transformer is generally from tens of kilohertz to hundreds of kilohertz. The transformer uses a magnetic core. The main component of the magnetic core is manganese-zinc ferrite. This material has low eddy current, low loss and efficiency at high frequencies. high. The operating frequency of low-frequency transformers is 50 Hz in China. The core of the transformer is made of soft magnetic metal material. The thin silicon steel sheet can greatly reduce the eddy current loss, but it is still larger than the core loss of the high-frequency transformer.

For transformers with the same output power, high-frequency transformers are much smaller than low-frequency transformers and have low heat generation. Therefore, many power adapters for consumer electronics and network products are switching power supplies, and the internal high-frequency transformer is the most important part of the switching power supply. The basic principle is to convert the input AC power to DC first, then turn it into a high frequency through a high-frequency transformer through a transistor or field effect tube, and then rectify the output again, plus other control parts to stabilize the output DC voltage.