Comparative Topology and Power Loss Analysis on 48V-to-1V Direct Step-Down Non-Isolated DC-DC Switched-Mode Power Converters
Jin Woong Kwak, D. Brian
Abstract
Along with the exponential growth of datacenter business, power delivery systems for datacenters act quickly to adopt 48V power architecture in order to achieve less distribution (I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> R) loss, higher power density, and reduced cost. However, 48V power architecture faces major challenge in its efficiency of direct power conversion from 48V down to 1V. This paper presents a comparative power loss analysis between half-bridge buck converter, multi-level buck converters, and hybrid Dickson converters. The performance of each converter was verified in a high voltage 0.18μm BCD process, with major power switches implemented with power LDMOS FETs. The switch sizes of each converter were optimized at load current of 10A and effective output switching frequency (f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SW,EFF</inf> ) of 1MHz. Inductor sizes were selected to keep current ripples at 1.5A, while flying capacitor sizes were selected to keep voltage ripples within 5% of respective capacitor voltages. Output capacitors were selected to keep the output ripples below 10mV. In the load range from 1A to 30A, multi-level buck converters achieve at least 12% higher efficiency than half-bridge buck converter but with at least 92% silicon area overhead. Hybrid Dickson converters achieve at least 19.2% higher efficiency than half-bridge buck converter, and a double series-capacitor buck converter achieves a peak efficiency of 91.95% at 7A while keeping silicon area overhead within 38%.