Search

The surge in electric vehicle technology has brought attention to the manufacturing and design of 22-kW on-board chargers using printed circuit boards (PCBs), owing to their manufacturability and compact nature. However, designing transformers for these applications is challenging due to the demands of higher power and a smaller profile. The challenges include achieving optimal current distribution in parallel windings and easier transformer structure with better thermal performance. In addition, the integration of resonant inductance is crucial for regulatory functions and higher power densities. The integration with parallel windings also impacts the overall transformer performance, which needs to be analyzed. This article presents a detailed analysis and design approach for a 22-kW PCB-based transformer with good current sharing, controllable leakage inductance, and a simplified core structure. The study also includes an in-depth analysis of the transformer's flux distribution to minimize core loss. A 22-kW CLLC resonant converter is developed to validate the proposed transformer using PCB-packaged devices. With its modified flux distribution and good current sharing, the integrated transformer enables the converter to achieve a power density of 11.6 kW/L and a peak efficiency of 98.5%.

This article proposed a printed-circuit-board (PCB) based integrated magnetics with a winding cancellation technique to reduce common-mode (CM) noise for an 11-kW single-phase CLLC (1PCLLC) resonant converter. Shielding design is effective in reducing CM noise; however, its benefits come along with increased cost with more layers of PCB and increased winding loss due to increased eddy effect in the shielding layers. More shielding layers are required for multiple-turn applications, which makes the idle shielding design unattractive. Implementing windings as active shielding for noise cancellation is a good solution. A symmetrical 1PCLLC converter with symmetrical resonant tanks and symmetrical integrated magnetics is required to achieve the winding cancellation technique. The proposed integrated magnetics consists of three elemental transformers (ETs) with two identical ETs with built-in leakage inductance and one pure transformer. The physical middle points in the primary and secondary windings of the pure transformer become the static-electrical-potential points that can adopted as the starting point to achieve winding cancellation with proper winding arrangements. The effectiveness of the proposed concept was demonstrated through a high-efficiency, high-power density 1PCLLC dc/dc converter for an 800-V 11-kW onboard charger. The designed converter can achieve a power density of 420 W/in3 and a peak efficiency of 98.5%. Compared with the existing solution, the proposed integrated transformer with winding cancellation techniques shows 17-dB CM noise reduction at switching frequency.