System design of a 3D integrated non-isolated Point Of Load converter

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Abstract
Thermal issues in the design of high-power and small-size non-isolated Point of Load (POL) converters have been significant and are becoming more so. If a heat sink is dispensed with, then a large area of multi-layer PCB material with significant amounts of copper is required for necessary cooling. A high-rate cooling fan is also necessary. So what at first seems like a small and elegant converter becomes bulky and challenging to position in the overall system when its thermal management is taken into account. This work finds a solution to these problems and investigates the use of Low- Temperature Co-fired Ceramic (LTCC) for integrating the inductor with the active stage. A buck POL is used to demonstrate these methodologies. The end result is a POL converter that can achieve full 20 A output current with no need for an external heat sink and no need for a cooling fan while providing a large step-down of 5 V to 1.2 V. High light- load efficiency of 92.2% is achieved and a high power density of 156 W/in3 including all the necessary thermal management, in natural convection condition, has been demonstrated.