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Nexperia Case Study: Compact and Efficient E-Bike Motor Driver

CLIENT Startup Company
DATE 18.10.2019
TASK Compact and efficient e-bike motor driver operated by a 24 V battery

About the Company:

The Startup Company produces easy-to-install 250 to 500 W e-bike upgrade kits.

“Within minutes, you can turn your old dirt-bike into a brand new e-bike. Whether you are a casual cyclist who loves long trips across the countryside or you live in a busy city, and you need some light exercise while you navigate through the crowd with ease, the e-bike will allow you the freedom you always wanted”, says the CEO of the Startup Company

The Challenge:

While cities become overcrowded with cars, pollution levels steadily increase, year by year. In big cities, transportation becomes a real challenge. Therefore, electrically augmented bikes represent a perfect transportation solution: they are super-light, need a reasonably low amount of energy, and they are especially suitable for maneuvering through the city crowd. However, to allow as much range as possible with a 24 V battery, the hub motor driver has to be very efficient, and compact enough to fit inside a 24″ to 29″ bike wheel. In electronics, less voltage means more current, for the same power. More current also means thicker conductors, bulkier components, and more thermal losses. 24 V constraint became challenging for the designers.

The Solution:

By placing the driver circuitry inside the wheel, the length of wires, and thus their resistance, was reduced to a minimum. To overcome the second part of the problem (bulky switching components with a lot of heat dissipation), the designers used Nexperia’s MOSFET solution for motor driving. MOSFETs like the PSMNR70-40SSH feature low switching resistance (RDSON), low parasitic capacitance, and excellent thermal performance. By using clip bonding technology, these MOSFETs can achieve outstanding switching performances in a compact LFPAK88 package. Designers used these MOSFETs in the LFPAK88 package throughout the entire design, not only the motor driver (e.g., for battery management system), due to their outstanding performances.

Type number VDS max (V) RDSON max @ 10 V (mΩ) ID max @ 25 ˚C (A) Rth(j-mb) Typ. (K/W)
PSMNR70-40SSH 40 0.7 425 0.25
PSMNR90-40SSH 40 0.9 375 0.28
PSMN1R0-40SSH 40 1.0 325 0.32

About Nexperia

Nexperia is the expert in high-volume production of discrete and MOSFET components and analog & logic ICs that meet the stringent standards set by the automotive industry. We are the only company that focuses 100% of its efforts on making and supplying world-class discrete components, analog and logic ICs, and MOSFET devices. If you want to evaluate Nexperia’s industrial and automotive solutions for your own design, you can register for a free sample kit.