New PCB Winding ”Snake-Core” Matrix Transformer for Ultra-Compact Wide DC Input Voltage Range Hybrid B+DCM Resonant Server Power Supply

Given the demand for higher power density, higher efficiency and lower realization cost solutions in data centers, dc-dc converters using PCB winding magnetics and resonant operation have been intensively studied in literature. In this paper, a new approach for 300V-430V dc input and 12V dc output server power supplies is proposed, which is based on a series resonant converter topology using a synergy between boundary and discontinuous conduction mode operation, whereby low peak-to-average ratio transformer current waveforms, soft-switching throughout the full power range and tight regulation of the output voltage for a wide input voltage range are achieved. Furthermore, a PCB winding ”snake-core” matrix transformer is introduced, which provides only a single path for the magnetic flux and therefore ensures an equal flux linkage and/or induced voltage of the parallel-connected secondary windings despite possible geometric PCB layout asymmetries. This approach avoids the emergence of circulating currents between parallel-connected secondary windings and guarantees at the same time equal secondary-side voltages in power supplies with multiple isolated outputs. Thus, a higher degree of freedom in the design of the primary windings of PCB winding-integrated transformers is achieved, whereby the design of these transformers is considerably simplified.