Electrothermal Circuit Design With Heat Flow Control—Synchronous Buck Converter Case Study

Abstract

Electrothermal design of a synchronous buck converter with heat flow control is presented. A commercial reference circuit design for a synchronous buck converter is selected for the study. A functional printed circuit board (PCB) of the converter is fabricated and tested to establish baseline performance. The baseline PCB layout is modified by incorporating a design of electrothermal traces from a heat flow control optimization study. Electrical plus thermal characteristics of each design are experimentally evaluated. It is found that the modified design manipulates the heat flow across the PCB. At low output current (<5 A) and under free convection, the circuit with electrothermal traces produces slightly lower switch and inductor temperatures, 1 °C–3 °C, and higher circuit efficiency (up to 7.4%). At higher power levels with free convection, the modified circuit exhibits slightly higher device temperatures and the same circuit efficiency as the baseline circuit. Adding a thermoelectric cooler to the system for active temperature control in combination with the electrothermal traces yields a 3 °C–5 °C device temperature reduction at 20-A output current. The unpopulated PCB inductance and populated board electrical impedance are measured separately for the modified circuit design. Higher inductance, modified electrical impedance, and reduced input current amplitude is observed due to a low-pass filter effect from the electrothermal traces. A discussion is provided regarding a range of future electrical and thermal research directions for circuit applications. The need for further integration of multiphysics codesign methodologies with the state-of-the-art analysis tools is explained.