High frequency transformer principle

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Guide: Transformers believe that everyone is familiar with, then how high is the frequency of high-frequency transformers ? Let us learn about high-frequency transformers and their principles.

1. Principle of high frequency transformer - introduction

The high-frequency transformer is the most important component of the switching power supply. The ratio of the turns of each winding of the high-frequency transformer determines the output voltage. It is a power transformer with a working frequency exceeding the intermediate frequency, and is mainly used as a high-frequency switching power supply transformer in a high-frequency switching power supply. The transmission power is relatively large, the operating frequency is relatively low; the transmission power is relatively small, and the operating frequency is relatively high. In this way, there are differences in operating frequency and transmission power. The design method of the power transformer with different operating frequencies is different, and it should be self-evident.

2. Principle of high frequency transformer - working principle

The high frequency transformer is the most important part of the switching power supply. The switching power supply generally adopts a half-bridge power conversion circuit. When working, two switching transistors are turned on to generate a high-frequency pulse wave of 100 kHz, and then stepped down by a high-frequency transformer to output a low-voltage alternating current, and each winding coil of the high-frequency transformer. The ratio of turns determines the amount of output voltage.

The main cause of electromagnetic interference in high-frequency power transformers is the suction between the cores and the repulsive force between the winding wires. The frequency of these forces varies with the operating frequency of the high frequency power transformer. Therefore, a high-frequency power transformer with a working frequency of about 100khz has no special reason for not generating audio noise below 20khz.

3. Principle of high frequency transformer - design principle

In the design of high-frequency transformers, the leakage inductance and distributed capacitance of the transformer must be minimized because the high-frequency transformer in the switching power supply transmits a high-frequency pulse square wave signal. During transmission transients, leakage inductance and distributed capacitance can cause inrush currents and spikes, as well as top oscillations, resulting in increased losses. Usually, the leakage inductance of the transformer is controlled to be 1% to 3% of the primary inductance.

Leakage inductance of the primary coil—the leakage inductance of the transformer is caused by the fact that the magnetic flux between the primary and secondary coils is not fully coupled between the layers and between the layers.

Distributed Capacitor----Between the windings of the transformer windings, between the upper and lower layers of the same winding, between the different windings, the capacitance formed between the winding and the shielding layer is called the distributed capacitance.

The primary winding----the primary winding should be placed in the innermost layer, so that the length of the primary winding of the transformer can be minimized, so that the entire winding is minimized, which effectively reduces the distribution of the primary winding itself. capacitance.

The secondary winding----the primary winding is wound, and the (3~5) layer of insulating pad is added to rewind the secondary winding. This reduces the capacitance of the distributed capacitance between the primary winding and the secondary winding, and also increases the dielectric strength between the primary and secondary, in accordance with the insulation withstand voltage requirements.

The bias winding—the bias winding is wound between the primary and secondary, or the outermost layer, and the switching power supply is adjusted based on the secondary voltage or the primary voltage.

Expand reading:

1. High-frequency electronic transformer knowledge in switching power supply

2. Graphic winding method of high frequency transformer

3. High frequency electronic transformer and its development direction

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