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Why Semi-Shielded Inductors Are Ideal Solutions for Automotive Applications

There is a growing interest in using semi-shielded power inductors in several automotive applications. One targeted application is in response to current mandates that car manufacturers install “Black Boxes” that record vehicle operation information such as vehicle speed, airbag deployment, brake usage, if seatbelts were worn, steering angles, and even GPS location in the event of a crash. In the U.S., the National Highway Traffic Safety Administration (NHTSA) requires that as of September 1, 2014, every new vehicle must have one installed. Similarly, the European Union (EU) passed a law that all new cars from 2018 must have an emergency call black box device. For automotive black box data recorders, designers have found that semi-shielded power inductors provide the integrated, smaller form factor solution to reliably support high current with low DC resistance (DCR).

LED headlamps and other automotive lighting represent another application example. The standardization and optimization of LED modules has led to improved performance, lower power consumption and decreasing costs resulting in more vehicles being equipped with LED lighting. Because of their flexibility and high efficiency, these LED designs are increasing the use of semi-shielded power inductors.

In addition, other applications such as car control boards for exterior mirrors or cameras can realize the benefits from semi-shielded power inductors that deliver higher current in smaller form factors that meet space-constrained and performance requirements.

Automotive-grade Solutions

A prime example of an optimized power inductor solution for vehicle data recorders is with the latest inductors in Bourns’ SRN series. They are offered in an extremely low 0.8mm (max) profile, with a desired inductance range of 0.47 to 10μH. This series is also completely tested and qualified to the AEC-Q200 specification featuring extended temperature range (-40 to +125 °C) operation, and is manufactured in facilities that are fully certified to TS 16949.

Helping to advance LED lighting installations is the “metal epoxy” shielding of power inductors that has contributed to resolving Electromagnetic interference (EMI) prevalent in most electronic devices with a power supply. While a fully shielded inductor with higher inductance might be considered an ideal solution here, it does present current handling issues. Using a semi-shielded inductor of the same size offers the capability of handling much higher current providing a very acceptable solution.

Doing a comparison between two similarly sized Bourns power inductors illustrates the optimal part for an automotive LED application. Bourns’ shielded Model SRR0745A-470M versus its semi-shielded Model SRN6045TA-470M provided the following results: Model SRR0745A-470M has a current of 1.05A Irms, whereas, Model SRN6045TA-470M features a current 1.6A Irms and, in addition, has a lower DCR demonstrating that it is the ideal solution for this application.

Bourns continues to expand its semi-shielded power inductor portfolio with the goal to meet the requirements of demanding applications such as those in the automotive market. Automotive designers can select from Bourns’ nine semi-shielded power inductor model series that provide low-profile sizes from 2mm to 8mm, with more models in its roadmap planned to be introduced this year. Furthermore, Bourns has an ongoing commitment to automated production process improvements that result in increased yields to help its automotive customers meet cost constraints.

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