Abstract
A new topology for achieving high leakage inductance in inserted-shunt integrated magnetic planar transformers is proposed. In the proposed topology, two one-segment shunts are placed across the planar E-core air gap and between the primary and secondary windings. The proposed topology benefits using solid inexpensive ferrite shunts, making manufacturing easier. A detailed mathematical model is derived from which a design methodology is developed, providing accurate estimation for the leakage and magnetising inductances. The theoretical analysis has been verified using finite-element analysis and experimental implementation. AC resistance analysis and efficiency comparison are also presented for the proposed topology and a recent topology with inserted-segmental-shunt, which shows the proposed topology provides higher efficiency because of lower AC resistance. In addition, an isolated LLC resonant converter is designed and built to investigate the performance of the proposed topology in practice. The three magnetic components needed for the designed LLC resonant converter is integrated in a single planar transformer using the proposed topology and the converter operates properly.
Highlights
HARD-SWITCHED pulse-width-modulated (PWM) converters such as the buck and boost converters cannot be operated at high frequency under continuous conduction mode (CCM) since they suffer from high switching losses under high-frequency operation
Resonant converters are displacing traditional hard-switched converters because they benefit from soft-switching capability inherently and can provide high efficiency at high frequency operation [9]
The leakage inductance can be regulated by changing the thickness of the shunt, tsh, and the shunt air gap length, ls, and the magnetising inductance can be regulated by air gap length, lg, separation between the E-cores
Summary
HARD-SWITCHED pulse-width-modulated (PWM) converters such as the buck and boost converters cannot be operated at high frequency under continuous conduction mode (CCM) since they suffer from high switching losses under high-frequency operation. Inserting a low-permeability magnetic shunt in the centre of a planar transformer while its primary and secondary windings are separated (by being located above and below the magnetic shunt) can provide a high leakage inductance and provides greater and more precise control of its value [29,30,31] This topology benefits from the advantages of planar transformers, viz high power density, improved cooling capability, modularity and manufacturing simplicity. All three magnetic components of an isolated LLC converter can be integrated in a single planar transformer Even though this structure enhances the leakage inductance and allows for its value to be estimated precisely, the inserted shunt must have a specific and unusually low permeability, leading the design and manufacturing to difficulty and higher cost.
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