Design and Measurement of Integrated Converters for Belt-Driven Starter-Generator in 48 V Micro/Mild Hybrid Vehicles

With reference to a 48 V belt-driven starter-generator used in micro/mild hybrid vehicles, this paper shows the design and measurement of an integrated H-bridge and of a compact dc/dc converter, both fabricated in low-cost high voltage-metal oxide semiconductor (HV-MOS) technology. The H-bridge is in charge of rotor excitation and, thanks to a direct copper bonding of the HV-MOS devices on a ceramic substrate, it ensures a full-integrated solution with low on-resistance values. The compact dc/dc converter interfaces the 48 V power domain with the lower voltage domain of sensing and control electronics, such as 5 and 1.65 V in this case study, without using cumbersome inductors and transformers. The latter are difficult to integrate into silicon technology. The converter has a multistage architecture where each stage implements a switched capacitor regulation. Multiple voltage outputs are supported with a configurable regulation factor sustaining an input voltage variation from 6 V (in case of cranking) up to 60 V. Specific design techniques have been implemented to reduce electromagnetic interference (EMI), typical of switching converters. Experimental measurements on fabricated prototype chipsets confirm the suitability of the presented designs for low-EMI 48 V applications.