High-performance Chips Pave the Way for Electric Bikes

Electrical drives are not new in transport: trams and trains have been running on electricity for a long time. Electrically driven vehicles have been around since the 1830s and more than 100 years have now passed since the invention of the electric bicycle. In 1895, Ogden Bolton Jr. applied for the first patent for a battery-operated bicycle with a six-pole brush motor built into the rear wheel. Development and commercialization of the electric bicycle have come a long way in those 110 years. From a technological point of view, the breakthrough undoubtedly came with the availability of long-lived accumulators—such as the lithium polymer battery—and with the increase in the power and efficiency of electric motors brought about by the use of electronics.

Electric bikes are part of a wide range of Light Electric Vehicles (LEVs). Generally designed for one person and small cargo capacity, electric bike range, speed, and costs are moderate, providing clean, quiet, convenient and efficient local transportation. What is that market? Worldwide, bicycles and scooters are the number one mode of transportation. An estimated one billion bicycles are in daily use, and more than 100 million new bicycles enter the world market each year. China, for example, has 34 bicycles per 100 inhabitants and has a market for more than 30 million bicycles annually. So it is no surprise, that the commercialization of the electric bicycle has been driven mainly by its introduction and subsidization in China. The production figure of only 40,000 electric bicycles in China in 1998 rose to 10 million within seven years. By 2008 this figure had almost doubled. What caused this breakthrough for the electric bicycle in China?

These conveyances became the favorite means of transport for the Chinese populace because they offer a cheap, convenient form of personal mobility as an attractive alternative to public transport and the push-bike. In China, electric bicycles are subsidized by national and many local governments, thanks to their low energy consumption and freedom from emission.

In Europe, the electric bicycle suffered from a negative image for many years. It was heavy, and was regarded as un-sportsmanlike, and found a place more as an aid than as a means of transport in its own right. In view of the stream of announcements of new, so-called “Pedelecs” (Pedal Electric Cycles), these times seem to be over at last. Cities in Europe are also beginning to invest in this means of transport. In Switzerland, too, the Elektrovelo is booming, thanks to the NewRide subsidization programme; in Austria, the Klima:aktiv-Programme subsidizes the purchase of a Pedelec to the tune of up to €400, and in numerous German cities, such as Stuttgart and Kaiserslautern, new mobility concepts involving electric bicycles are being launched.

New business concepts are emerging. Personal mobility is becoming a service, analogous to mobile communications. Companies such as Movelo rent out Pedelecs, and also offer battery exchange in interesting holiday resorts and urban areas. This way, users pay for mobility as required, and do not have to worry about servicing, such as battery maintenance. Electric bicycles have also been in service in a commercial environment for years; in many countries, mail is already being delivered by Pedelec.

The technical breakthrough for electric bicycles came with the use of electronics. These control electric motors efficiently, thus optimizing performance and battery life. The most frequently used topography in series production of electric bicycles today is a brushless DC motor (BLDC) with Hall sensors. A basic electric bicycle runs on a BLDC motor, is powered by batteries and controlled from an ECU (Embedded Control Unit). The BLDC motor for the electric bicycle is of the standard three-phase trapezoidal type, typically rated at a few hundred watts and the battery voltage is usually 36V or 48V. Almost all the electronics in the electric bicycle are found in the ECU, it contains the inverter circuit for the motor; temperature sensor; fault detection; SMPS; analog and digital I/Os; and finally the controller itself. Some ECUs have advanced features such as remote controlled alarm and electric horn as well. All of these as well as the wiring are usually packed into a robust and very compact metal box.

Infineon is the leading company in the area of semiconductors for electric bicycles. In about every second electric bicycle worldwide, the motor is controlled by an 8-bit microcontroller from Infineon’s XC800 family. One reason for this is that the product characteristics are tailor-made for this application at low cost. The special functions in the microcontroller (fast ADC, Capture/Compare unit, etc.) make for particularly fast signal recognition and signal generation to switch the individual phase currents of the motor. The cyclist notices this by the excellent performance of the electric bicycle in every load state. Another reason is high quality and reliability as products are built on automotive proven technologies. Further essential elements of the motor electronics are the robust, intelligent power semiconductors.

The e-bike is one example of the broad range of applications which benefits from the unique features of the OptiMOS2 or OptiMOS3 power MOSFETs, offering a combination of the lowest available on-state resistance in comparable packages and lowest gate drive requirements. These MOSFETs feature excellent switching performance, help to increase power density in the application, and consequently save energy. In addition these MOSFETs provide the highest immunity to dynamic turn-on.

Electric drives for bicycles know no limits. The next generation in the upper performance range is going into mass production: the so called E-Scooter. The electric motor has also found its way into the motor-cycling world.

New business models, like the renting of electric bicycles in urban areas and holiday resorts, will certainly remove any obstacles in the run-up to Pedelec mobility with regard to the charging and maintenance of batteries. It will be exciting to see what interesting kinds of electric-powered bicycle will come on the market in the coming months and years, and what concepts cities and towns will offer consumers with regard to personal mobility with Pedelecs.

Infineon Technologies
www.infineon.com