Simplifying Automotive Electrification

September 05, 2013 // By Roy Davis, Fairchild Semiconductor
The drive to reduce fuel consumption and CO2 emissions by automobile manufacturers worldwide is clearly aided by the electrification of accessories and powertrains alike. Such developments become more practical, efficient, and cost-effective as suppliers develop high performance standard products to support system suppliers in their quest to deliver solutions to automotive OEMs. Fairchild has recently released the FTCO3V455A1 full three-phase bridge MOSFET automotive power module (APM), shown in Figure 1, as a standard product suitable for applications requiring up to about 2kW, providing designers another option for their system designs.

With the release of this product, Fairchild brings to market a highly reliable, durable, efficient, and automotive qualified MOSFET inverter power stage in a compact and easily integrated package that is suitable for 12V accessories up to 150A or more depending on thermal conditions. Also under development are modules capable of handling even higher current for 12V applications, and a version populated with 80V MOSFETs suitable for 48V applications. These modules employ Fairchild's PowerTrench® MOSFET technology and shielded gate PowerTrench® MOSFET technologies.

In this article, we discuss the features and benefits of the power module, and describe how it can be used to improve the system design for electrified automotive accessories.

Designers of power electronic systems must overcome many challenges to produce a durable, reliable, and efficient electric motor drive, especially for automotive applications where the environment and application conditions are severe and cost pressures are high. Rack mounted electric power steering systems, for example, may experience ambient temperatures in excess of 100˚C, high shock and vibration loads, exposure to petroleum products and salt water spray, while being required to deliver motor phase currents of 150A or more with a minimum of losses.

Key challenges arise at the interfaces between electrical, mechanical, and thermal domains. These include high current interconnections from the vehicle 12V battery to the inverter, high current interconnections from the inverter to the motor, stable mechanical interconnection of the inverter to its support, and an efficient thermal interconnection from the inverter power devices to the coolant, which in many instances is hot air or hot metal! The Fairchild APM addresses these challenges as described below.

Electrical Performance

The primary function of the inverter is to produce variable voltage, variable frequency ac power to drive an electric motor and, as such, must exhibit excellent electrical performance. The six MOSFETs comprising the inverter are of Fairchild’s 40V PowerTrench family, achieving typical die Rds(on) of 1.15 mW for high current,

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