by Salvatore Potestia, Business Development Manager & Ralf Hickl, Product Sales Manager in the Automotive Business Unit, Rutronik
Reference designs for 48V low-speed electric vehicles
Low-speed electric vehicles (LSEVs) are ideal for covering short distances in urban areas. Stricter environmental protection requirements such as restricted traffic zones in cities are likely to give these vehicles a considerable boost. Countries with large populations and many densely populated areas, such as China and India, will account for the largest share.
Diversity of micromobility
The term “micromobility” embraces any small, low- speed, electric-powered transportation device used as commercial vehicles or for passenger transportation. LSEVs include two-wheeled e-scooters, e-bikes, and pedelecs, along with two-, three-, and four-wheeled cargo bikes. The latter are particularly popular with service providers, such as couriers and delivery services, as well as families.
Three-wheeled vehicles include motorcycles with sidecars for private use and small passenger cars, such as the Piaggio Ape. They are suitable for passenger transport, for example in the tourism sector, and are also used by postal services.
Four-wheeled models range from e-quads to small e-cars, such as the Renault Twizy, and small e-vans. Depending on their actual size and design, they are used for a variety of commercial and personal transportation applications.
Performance, speed, and range
Depending on their vehicle class, LSEVs can achieve a range of speeds and power ratings. Smaller two-wheeled vehicles typically have a rated power of 1kW and can reach top speeds of 25km/h. Larger two- and three-wheeled types generally have a maximum power rating of 4kW and travel at up to 45km/h. Low-speed four-wheeled vehicles also travel at this maximum speed; their rated power, however, can be as high as 6kW. Heavy four-wheeled models, on the other hand, can reach top speeds of 90km/h with a rated power of 15kW. The range of low-speed electric vehicles varies depending on their power output; many can travel around 150km on a single battery charge.
Reference designs
Rutronik‘s Automotive Business Unit (ABU) sees great potential in low-speed electric vehicles. Following the successful reference design for a bidirectional HV switch for 800V DC and 50A, Rutronik is now working closely with Vishay to develop sample applications for LSEVs with a 48V electrical system. These are the on- board charger (OBC) and the traction inverter. Both applications focus on converter efficiency, compact design with low installation height, and automotive-grade quality.
On-board charger
The OBC provides a maximum charging power of 3.6kW. Its key components are the new VS-ENM040M60P power modules, optimized power factor correction (PFC) coils, and a pulse transformer developed specifically for this application. Passive components also play an important role since their properties are a key factor
in determining the efficiency of the circuitry. An integrated LLC transformer, such as the MTBB133971 from Vishay Custom Magnetics, is used as the pulse transformer (resonant inductors are already incorporated).
Traction inverter
The traction inverter has a rated power of 15kW with short-term peak power of 25kW. Vishay’s N-channel automotive trenchFETs in
the PowerPAK 8x8L Reverse Package are used as power semiconductors. Their top-side cooled package allows them to be thermally coupled directly to a heat sink rather than being cooled by the PCB.
Summary
LSEV reference designs provide hardware developers with design templates that can significantly reduce the time- to-market of their own circuit designs. By using the latest high-performance components, these circuits achieve high power density at low cost.