Kennith Kin Leong

A single stage 54V to 1.8V multi-phase cascaded buck voltage regulator module

This paper proposes a new design approach to the conventional two stages solution to convert the 48-60V low voltage bus to the 1-1.8V point of load (PoL) voltage for microprocessors in large telecoms server farms. The core idea is to stack or cascade the buck voltage regulator module (VRM) input voltage in series and connect their output in parallel. This single stage multi-phase cascaded buck (MCB) VRM has a large degree of design freedom depending on the load requirements. A 150W 6-phase MCB (two 3 phase modules in parallel) achieved a maximum efficiency of 91.3% in simulation. This paper also presents the results of a demonstrator of the same circuit which achieved a measured peak efficiency of 90.1%.

New control concept for soft-switching Flyback converters with very high switching frequency

A conventional Flyback converters synchronous rectification switch is controlled from the primary side via opto-isolators; introducing propagation delay. A new control concept is presented here that eliminates the need for opto-isolators, communicating instead through the coupled inductor to assist more precise soft-switching control at much higher frequencies. As a precursor to a 1-MHz GaN demonstrator, an initial 100-kHz prototype has been built to prove the feasibility of the concept.