What is the design principle of high-frequency transformers?

In the design of high-frequency transformers, it is essential to minimize leakage inductance and distributed capacitance because high-frequency transformers in switch-mode power supplies transmit high-frequency pulse square wave signals. During the transient transmission process, leakage inductance and distributed capacitance can cause surge currents, voltage spikes, and ringing, leading to increased losses. Typically, the leakage inductance of transformers is controlled to be 1% to 3% of the primary inductance.

Leakage Inductance of Primary Coil: The leakage inductance of a transformer occurs because the magnetic flux between primary and secondary coils, layers, and turns is not entirely coupled.

Distributed Capacitance: The capacitance formed between turns of the winding, between upper and lower layers of the same winding, between different windings, and between windings and shielding layers is called distributed capacitance.

Primary Winding: The primary winding should be placed on the innermost layer to minimize the length of wire used for each turn of the primary winding, effectively reducing the distributed capacitance of the entire winding.

Secondary Winding: After winding the primary winding, (3-5) layers of insulation padding are added before winding the secondary winding. This reduces the capacitance of the distributed capacitance between the primary and secondary windings and increases the insulation strength between the primary and secondary windings, meeting the insulation withstand voltage requirements.

Bias Winding: The bias winding is wound between the primary and secondary windings or on the outermost layer, and its adjustment in switch-mode power supplies depends on whether it is related to the secondary voltage or the primary voltage.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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