High-efficiency tightly-coupled LLC resonance transformer

Abstract

The invention discloses a high-efficiency tightly-coupled LLC resonance transformer. The high-efficiency tightly-coupled LLC resonance transformer comprises an annular main transformer which is provided with a magnetic core having no air gaps; one end of a primary coil of the main transformer is connected with an input auxiliary inductor; the two ends of a second secondary coil of the main transformer are respectively connected with the two ends of an output auxiliary inductor; the primary coil is uniformly intertwined on the innermost layer of the magnetic core of the main transformed after being coated with an insulating layer which is bound by a plurality of varnished wires or flat copper; a first secondary coil of the main transformer is uniformly intertwined a second layer of the magnetic core of the main transformed after being coated with an insulating layer which is bound by a plurality of varnished wires or flat copper; the second secondary coil is uniformly intertwined on the outermost layer of the magnetic core of the main transformed after being coated with an insulating layer which is bound by a plurality of varnished wires or flat copper. The high-efficiency tightly-coupled LLC resonance transformer disclosed by the invention guarantees tight coupling of the transformer, nearly prevents magnetic leakage, can also satisfy the requirements on parameters of a magnetic inductor, and is greatly improved in energy transmission efficiency in comparison with a traditional LLC transformer.

Description

technical field [0001] The invention relates to an LLC resonant transformer used in an electric vehicle charging pile, in particular to a transformer used in a high-power half-bridge or full-bridge LLC resonant converter. Background technique [0002] LLC resonant topology is one of the most commonly used circuit topologies in high-power switching power supplies at present. Because of its good soft switching characteristics, the secondary rectifier diode can achieve zero-current shutdown (ZCS), and no output filter inductor is needed. The working current waveform is close to the sine wave and other characteristics, so that it has the advantages that other topological structures hope but are difficult to achieve: small electromagnetic interference and high efficiency (can exceed 96%). As a key device in the LLC resonant topology, the transformer plays a key role in the reliability and efficiency of the circuit. [0003] At present, most of the winding methods of LLC resonant...

AI Technical Summary

Problems solved by technology

Due to the consistency of the process, the deviation of the magnetic core permeability, etc., it is difficult to ensure the consistency of the leakage inductance, which will affect the efficiency and reliability of the power supply

Due to the addition of the air gap, the magnetic flux leakage of the transformer increases during the working process, and the temperature rise at the air gap is relatively high, and the magnetic flux leakage will cause the ferromagnetic materials and copper materials of the transformer to generate eddy currents, which greatly reduces the energy transmission efficiency of the transformer. The air gap of magnetic core grinding also increases the complexity and difficulty of transformer processing

Since the primary and secondary are loosely coupled, when the transformer secondary adopts a structure with a center tap, the inconsistency of the positive and negative half-cycle leakage inductance will cause the inconsistency of the positive and negative currents of the LLC resonant circuit, reducing the efficiency and reliability of the power supply

[0004] Invention patent "Winding method of resonant transformer coil for high-efficiency LLC constant current power supply" (application number 201210554330.6) proposes that the secondary coil adopts a double-wire parallel winding method to reduce the positive and negative half-cycle leakage inductance of the transformer with a center-tapped structure. Inconsistency leads to inconsistencies in the positive and negative currents of the LLC resonant circuit, but the loose coupling method with isolation walls and air gaps is still used to obtain the inductance parameters required for LLC resonance

The document "Design Methodology for Transformers Including Integrated and Center-tapped Structures for LLC Resonant Converters" shows that transformers with air gaps cause relatively serious eddy current losses inside the transformer due to magnetic flux leakage (including eddy current iron losses and eddy current copper losses, mainly concentrated in the air gap accessories), because of these losses reduce the efficiency of the transformer to transfer energy

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