A Compact Vertically Stacked Converter Module with Thermal Balancing and High-Power Dissipation Capability

A compact vertically stacked buck converter is designed with improved thermal performance. Three copper core PCBs and two vertical double-diffused MOSFETs (VDMOS), in TO-Leaded Topside-Cooled (TOLT) package, are stacked together to form the half-bridge output stage. The inductor, the input and output capacitors, and the gate driver ICs are also assembled in this module. For comparison purposes, a horizontally laid out buck converter with the same components using a conventional FR4 PCB is also built. Under forced air cooling, the proposed vertically stacked 48 to 12 V buck converter, switching at 355 kHz, can achieve an output power of more than 160 W with a peak temperature of 81 degree Celsius. The same buck converter in horizontal configuration can only achieve a maximum output power of 60 W with a peak temperature of 90 degree Celsius. At 60 W output, the hottest point for the proposed vertically stacked converter is 23 degree Celsius lower than that of the conventional PCB layout. Moreover, the power conversion efficiency of the proposed vertically stacked converter is improved at the same 60 W power level. Switching at 244 kHz with optimized deadtimes, the maximum output power of the vertically stacked converter is measured to be 291 W. Benefited from the high-power dissipation capability, the converter can maintain a nearly constant efficiency across a wide range of output power from 194 to 291 W.