48 V low-speed electric vehicle reference design accelerates development of micromobility technology
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48 V low-speed electric vehicle reference design accelerates development of micromobility technology

Posted Date: 2024-01-24

Many countries are committed to meeting climate goals and making urban transport emission-free. In addition to the electrification of passenger cars, low-speed electric vehicles can also make an important contribution.

Salvatore Potestia, Business Development Manager, Rutronik Automotive Business Unit (ABU) and Ralf Hickl, Product Sales Manager


To meet growing demand, China's production of low-speed electric vehicles will increase significantly in the coming years
Image credit: Scharfsinn/Shutterstock

Low-speed electric vehicles (LSEVs) are ideal for driving short distances in urban areas. In addition, an increasing number of cities are imposing stricter requirements on environmental protection, for example in the form of restricted traffic zones, which may significantly facilitate the development of these vehicles. P&S Intelligence predicts that the global LSEV market will grow from US$35.2 billion in 2017 to US$68 billion in 2025. Populous and densely populated countries such as China and India will account for the largest share. As a result, the production of low-speed electric vehicles is also increasing, for example in China, where Research In China predicts that the production of low-speed electric vehicles in China will increase by 15 million units between 2021 and 2025.

Diversity of micro travel

Low-speed electric vehicles also belong to the category of "micromobility", including a variety of vehicles. They can be used both as commercial vehicles and for urban passenger transport. Since they are a lower class than passenger cars, the requirements regarding vehicle type approval are significantly different from traditional passenger cars.

For example, LSEV includes two-wheeled vehicles (e-scooters, e-bikes and bicycles), as well as two-, three- and four-wheel cargo bikes. The latter are particularly popular with service providers, such as couriers and delivery services, as well as households, as they can move quickly in densely populated city center areas and offer some storage space.

Three-wheeled vehicles include personal motorcycles with sidecars and small passenger cars, such as the Piaggio Ape. They are suitable for passenger transport, such as tourism, and are also used in postal services.

Four-wheel models include electric four-wheelers, small electric cars (such as the Renault Twizy) and small electric vans. Depending on actual size and design, they can be used in a variety of commercial and personal transportation applications.

Small LSEV performance, speed and range

Depending on the vehicle class, low-speed electric vehicles can achieve different speeds and power ratings. Microcars and low-speed two-wheelers have a maximum speed of 25 km/h and their power rating is usually 1 kilowatt. Larger two-wheelers and three-wheelers typically have a maximum power rating of 4 kilowatts and a top speed of 45 km/h. Low-speed four-wheelers are also capable of this top speed, but their power ratings can be as high as 6 kilowatts. The heavy-duty four-wheeler has a top speed of 90 km/h and a rated power of 15 kilowatts. The driving range of low-speed electric vehicles varies depending on their power output, with many electric vehicles capable of traveling approximately 150 kilometers on a single charge.


Electronic power applications in LSEV (Image source: Rutronik)

Reference design for low-speed electric vehicle applications

For these reasons, Rutronik's Automotive Business Unit (ABU) sees great potential in low-speed electric vehicles. Following the successful development of the 800 VDC and 50 A bidirectional HV switch reference design, Rutronik is now working closely with Vishay to develop sample applications for low-speed electric vehicles equipped with 48 V electrical systems. These applications include on-board chargers (OBCs) and traction inverters for 48V battery systems. The design focus is on converter efficiency, compact design with low mounting height, and automotive grade quality.

car charger

The on-board charger has a maximum charging power of 3.6 kW and its key components are the new VS-ENM040M60P power module, an optimized power factor correction (PFC) coil, and a pulse transformer developed specifically for this application. The power module integrates a half-controlled input rectifier, a diode and a MOSFET for power factor correction, as well as a half-bridge for the pulse transformer. The package used is Vishay's EMIPAK-1B, which enables higher power densities compared to structures using discrete semiconductors, and its press-fit contacts ensure quick assembly and a secure connection to the printed circuit board.


Components in the Vishay VS-ENM040M60P power module (Image source: Vishay)

Passive components also play an important role, as their characteristics are a key factor in determining the efficiency of the circuit. Integrated LLC transformers such as Vishay Custom Magnetics' MTBB133971 are used as pulse transformers and have an integrated resonant inductor.

Traction inverter

The traction inverter is rated at 15 kW with a short-term peak power of 25 kW. The power semiconductor uses Vishay's N-channel automotive TrenchFET (PowerPAK 8x8L reverse package). This top-cooled package enables direct thermal coupling to the heat sink rather than cooling via the PCB. This reduces thermal resistance and improves heat dissipation.

Summarize

The new low-speed electric vehicle reference design provides 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, customers can implement high power density circuits at low cost.

Advantages of low-speed electric vehicles at a glance

For developers/vendors

• Safety regulations are more relaxed
• Lower cost of motors and electronics compared to 400V and 800V vehicles
• Higher component reliability compared to 400V and 800V vehicles
• No risk of high voltage

For users

• Easily recharge via standard socket
• Convenient for short trips in the city
• Requires smaller parking space
• Less impact on climate and environment
• Can drive in certain environmental protection areas


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