Pentacentra Transformer for Multiphase LLC Converter in High-Current Data Center Application

The role of data centers has become significant in the era of information technology, and their operation consumes a substantial amount of energy. Therefore, the point-of-load converter or voltage regulation module used in data centers must have high efficiency and power density to deliver a large current to specific servers. A common bus voltage 48 V at the rack stage needs to be stepped down to intermediate bus voltage, which is 6-5 V in this case. To achieve this, a new pentacentra transformer was developed for a four-phase LLC converter. A centra bar serving as the fifth leg of the core is added to the conventional four-leg matrix transformer. The interleaving and integration of windings in the proposed pentacentra transformer enabled balanced current sharing and reduced conduction loss by 45% compared to the traditional winding layout. The experimental prototype of the converter was designed to achieve 800 W power output at a switching frequency of 500 kHz and 48 V-40 V/6 V-5 V voltage conversion. The peak efficiency achieves 98.1% along with the power density of 240 W/in 3 with the experimental result. Without the heatsink, the whole converter is operating at rated power within a safe temperature lower than 86°. The excellent thermal performance ensures the reliable operation of the converter and promises a larger power delivery capability.