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Power electronics plays a critical role in modern vehicle systems. The voltage rating of vehicle power electronics is predominantly determined by the transient immunity requirement, which considerably exceeds the maximum operating voltages of the 14 V and 28 V vehicle power systems, and imposes a large cost penalty. In contrast, the emerging 42 V systems require a much improved bus voltage regulation to maintain system affordability. We discuss the feasibility of reducing the DC breakdown voltage requirement and subsequently the cost of various vehicle power systems by employing a new class of semiconductor transient voltage suppressors, termed MOSTVS. The MOSTVS, combining power MOSFET and polysilicon thin-film technologies, provides a much more accurately controlled clamping voltage than conventional Zener diodes and MOVs over a wide range of current and temperature. The MOSTVS can be used in the conventional alternator/rectifier/regulator configuration or the more advanced drivetrain motor/generator configuration. It is estimated that the cost of power semiconductor transistors and filter capacitors can be reduced by up to 70% if the voltage rating of the 14 V automotive system is reduced from 50 to 30 V. Similar benefits can also be achieved in the 28 V and 42 V systems.