Fully-Integrated Solid Shunt Planar Transformer for LLC Resonant Converters

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.

Fully-Integrated Transformer With Asymmetric Primary and Secondary Leakage Inductances for a Bidirectional Resonant Converter

“…The magnetising inductance, primary and secondary leakage inductances and turns ratio of the designed transformer are chosen to suit the CLLLC resonant converter (Table II). The thickness and air-gap length of the primary and secondary shunts (ℓ GP , ℓ GS , 𝑏𝑏 SHP and 𝑏𝑏 SHS ) are estimated in order to provide the required primary and secondary leakage inductances, using ( 29) and (30), and considering the dimensions of the selected core. Similary, the transformer airgap length (ℓ G ) is estimated to provide the required magnetising inductance, using (17).…”

“…The energy stored in the inserted shunts and their corresponding air gaps can be obtained from the reluctance model using the method outlined by Ansari, et al, [8,22,30]. According to the reluctance model presented in Fig.…”

“…Finally, from ( 18), ( 22)-( 24), ( 27) and ( 28), the primary and secondary leakage inductances of the proposed inserted-shunt integrated transformer may be obtained as shown in ( 29) and (30)…”

“…In a design process for the proposed transformer, the required primary and secondary leakage inductances and magnetising inductance can be obtained by ( 17), ( 29) and (30). Particular values can be selected for a particular design by regulating the air gaps ℓ G , ℓ GP and ℓ GS , and the shunt thicknesses 𝑏𝑏 SHP and 𝑏𝑏 SHS .…”

Fully-integrated transformer with asymmetric leakage inductances for a bidirectional resonant converter

“…Many methods have been introduced for the integration of magnetic components in an LLC resonant converter [15]. Amongst these methods, inserted-shunt integrated planar transformer has gained popularity since this method benefits from many advantages such as precise estimation of leakage inductance, achieving high leakage inductance and simple manufacturing [16][17][18][19][20][21][22]. In this method, the leakage inductance can be increased in both primary and secondary sides by inserting different types of magnetic shunts.…”