ℋ<sup>2</sup>-optimal thermal management for multi-phase current mode buck converters

Abstract

This paper demonstrates a new digital controller for thermal management in multi-phase current mode buck converters. While the majority of today's multi-phase designs emphasize equal load current sharing between all phases, variations in PCB layout, parasitic resistances, transistor on-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ), and airflow, cause significant temperature variations between the converter phases. In this work, a digital multi-variable thermal management unit (TMU) based on ℋ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -optimization theory is demonstrated to rapidly achieve a uniform temperature distribution by adjusting the phase currents. Experimental results from a digitally controlled 12 V to 1 V, 50 A, 250 kHz four-phase peak current mode buck converter demonstrate a 5.1°C reduction in peak phase temperature and a 10.6°C reduction in phase temperature differences. This illustrates the effectiveness of the proposed thermal management technique in the presence of uneven air flow and multiple load steps. Infrared scans of the converter confirm that the peak and average temperatures are reduced, leading to improved long-term reliability. The TMU also exhibits stable transient response during load steps.