Thermal management for multi-phase current mode buck converters

Abstract

This paper deals with thermal management and power sharing in multi-phase buck converters. In conventional designs, each phase is regulated to share the load current equally. However, due to variations in PCB layout, parasitic resistances, airflow, and transistor on-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ), it is common to observe significant temperature variations between the converter phases, leading to reliability issues and suboptimal device utilization. Several past research efforts have demonstrated closed-loop analog and digital techniques to achieve a uniform temperature in all phases. In this work, a thermal management unit (TMU) with four independent linear controllers is proposed to regulate the phase temperatures in a four-phase mixed-signal peak-current mode converter. The digital TMU is designed based on a lumped thermal model of the system and dynamically adjusts the peak current in each phase to match the moving average temperature. Experimental results from a digitally controlled 12 V to 1 V, 50 A, 250 kHz four-phase peak current mode buck converter demonstrate the effectiveness of the proposed thermal management technique in the presence of uneven air flow and dynamic load currents.