Given their capability to improve car safety, convenience and fuel efficiency, semiconductor magnetic sensors used in automotive motors will enjoy fast market growth with revenue expanding by nearly 40 percent in 2012, according to IHS iSuppli. Revenue derived from the use of magnetic sensors in automotive motors will reach $160.3 million in 2012, up a solid 38.2 percent from $116.0 million this year, extending the steady rise of the market over the last three years. And although revenue growth after 2012 will moderate to the single digits, the five-year compound annual growth rate from 2010 to 2015 still will equate to a robust 16 percent. By 2015, magnetic sensor revenue in automotive motors will amount to $193.6 million.
"While the average motorist isn't aware of this, each time he drives a car, he can make use of as many as 100 small motors, performing tasks ranging from enabling the power steering, to actuating the fans in the heating, ventilation and air conditioning (HVAC) system," said Richard Dixon, Senior Analyst for MEMS and sensors at IHS. "These motors often employ magnetic sensors to ensure their safe and efficient operation. Because of this, magnetic sensors have attained widespread and fast-growing usage in the automotive segment." At present, the automotive industry accounts for half of semiconductor magnetic sensor market revenue.
Each low-end to midrange car, for instance, incorporates more than 10 electric motors on average, used for purposes such as fan cooling, the alternator and front and rear wipers. Luxury cars have almost 100 motors -- a long list including sensors for HVAC blowers, electronic steering and throttle control, and transmission sensors for automatics and new double-clutch systems. Other uses include seat positioning, sunroof, tachometer, headlight positioning, headrests and even control of air input flaps based on air quality information.
An important driver for efficient motors is energy consumption, where fractions of a liter in fuel savings can be critical -- and each gram of carbon dioxide produced as emissions is counted. Here, the trend is toward the electrification of pulley-driven motors and replacement by brushless DC motors. These efficient motors allow on-demand operation of the main powertrain components, such as water-cooling pumps, oil pumps and other auxiliary pumps, and to reduce overall energy needs.
Another application of magnetic sensors to motors is in shaft position encoding -- this is found, for instance, in power windows for cars, in which the sensors determine how many complete turns a shaft has made in order to control the length of travel of the window lifter. Unusual loading conditions due to the presence of a hand also can be detected by the sensor to provide a so-called anti-pinch functionality, which results in the motor turning backward if an obstruction is encountered.
Electronic power steering is likewise a fast-growing direct motor application, replacing electro-hydraulic alternatives that use a pump to build pressure in order to provide for greater fuel efficiency. The sensor requirement is in commutation of the motor and also in sensors that detect current.
In hybrid electric vehicles, magnetic sensors come into play in the monitoring of auxiliary motor inverters, where the battery direct current needs to be changed to the motor alternating current. Such a conversion requires the use of three current sensors—one for each phase of the motor.
Use of Hall IC and AMR sensors needed for advanced auto applications
In general, automotive motors use Hall integrated circuit (IC) sensors in a three-phase motor for commutation. A three-phase motor typically has six states, measured by three digital Hall ICs for closed-loop regulation. In some cases, magnetic sensors may not be required, and Hall ICs may be replaced by simple current measurement in the circuit. For example, DC motors that operate in an environment with constant speed and no load changes -- such as a fan that constantly rotates -- can infer the required knowledge of speed without the need for sensors.
However, in advanced motors where load changes and knowledge of torque is needed, the use of Hall ICs or anisotropic magnetoresistive (AMR) sensors is required in order to measure the motor position of the shaft.
In particular, the use of AMR will increase in the next five years. An example of its use is for the tachometer motors used to indicate speed and RPM instruments, for reasons of motor quietness.
NXP Semiconductors of the Netherlands is a major provider of AMR sensors, while Hall sensor IC alternatives are supplied by Micronas of Switzerland, Infineon Technologies of Germany, U.S. based Allegro Microsystems, Melexis N.V. of Belgium and Japan's Asahi Kasei Microsystems.