The rapid advancement of artificial intelligence (AI) has continuously boosted the computing power of data centers, imposing stringent requirements on the efficiency and power density of low-voltage high-current power modules. The capacity expansion of planar transformers mainly includes vertical and horizontal expansion. Vertical expansion tends to cause unbalanced current among windings, accompanied by a diminishing marginal effect in loss reduction, while horizontal expansion increases the module footprint, making it difficult to achieve a high-power-density design. This paper proposes a side-connected rectified planar transformer scheme. By optimizing the winding layout and arranging the secondary-side rectifier devices on the side of windings, a balanced winding current and linear capacity expansion gain are realized, which effectively improves winding utilization and reduces power loss. Based on the proposed scheme, the PCB design and prototype development are completed, and its effectiveness is verified through numerical simulation and experiments. The full-load test results at 6 V/140 A show that the module delivers a full-load efficiency of 97.5%, a power density of 3066 W/in3, and a current density of 0.33 A/mm2. Meanwhile, a peak efficiency of 98.8% is achieved at an operating condition of 4.8 V/50 A. The loss breakdown results are highly consistent with theoretical analysis and simulation data.
Cao et al. (Thu,) studied this question.