According to the magnetic sensor special report of IHS iSuppli Corporation, the application of silicon magnetic sensors in automotive motors will grow rapidly due to the improvement of vehicle safety, convenience, and fuel efficiency, and sales in this market will increase by nearly 40% in 2012.

In 2012, sales of magnetic sensors in the automotive and electrical sector will reach US$160.3 million, a surge of 38.2% from the US$116 million this year, which will continue the steady growth momentum in the past three years. Although the sales growth rate will slow down to single digit after 2012, the compound annual growth rate for 2010-2015 will still reach 16%. By 2015, sales of magnetic sensors in the automotive motor sector will increase to US$193.6 million, as shown in Figure 1.

Magnetic sensors are widely used in various motors in industrial automation processes, and are particularly popular in the automotive industry, accounting for 50% of their market value. For example, there are more than 10 types of motors in mid-range and low-end cars, such as fan cooling, alternators, and windshield wipers. The limousine has nearly 100 motors, including sensors for air conditioning blowers, electronic steering and throttle control, and transmission sensors for automation and new dual clutch systems; and for seat position adjustment, sunroof, tachometer, headlights Position adjustment, pillow sensors, and even used to control the intake damper based on air quality information.

An important factor that motivates people to increase motor efficiency is energy consumption. Saving every drop of fuel is critical, and every gram of CO2 generated must be taken into account. The trend here is to electrify belt-driven motors and replace them with brushless DC motors. These more efficient motors allow the main power transmission components to be operated on demand, such as water-cooled pumps, oil pumps, and other auxiliary pumps, and can reduce overall energy requirements.

Another application of the magnetic sensor in the motor is shaft position coding - for example, in a power window, the sensor can determine how many turns the shaft has to control the lift of the window regulator. The sensor can also detect the abnormal load caused by a human hand and provide a so-called "anti-clamping" function. When the object is touched, the motor can be reversed.

Electric power steering is also a fast-growing DC motor application that replaces electro-hydraulic systems that use pumps to generate pressure to improve fuel efficiency. Sensors are used for motor commutation and current detection.

In hybrid electric vehicles, magnetic sensors are used to monitor auxiliary motor inverters. The inverter is used to convert the direct current of the battery into the alternating current of the motor. This conversion requires the use of three current sensors, one for each phase of the motor.

Advanced Automotive Applications Need to Use Hall ICs and AMR Sensors Typically, automotive motors use Hall ICs for commutation in three-phase motors. Three-phase motors usually have six states measured by three digital Hall ICs to achieve closed-loop regulation. In some cases, magnetic sensors may not be required and the Hall IC may be replaced by a simple current measurement method in the circuit. For example, a DC motor that operates in a constant speed and no-load change environment (such as a fan that transfers at a constant speed) can infer the required speed information without using a sensor.

However, for advanced motors that need to understand load changes and torque information, Hall ICs and certain anisotropic magnetoresistive (AMR) sensors are needed to measure the position of the motor on the shaft.

In particular, the use of AMR will increase over the next five years. The largest application will be tachometer motors in speed and speed meters, which can quiet motors.

NXP Semiconductors of the Netherlands is the main supplier of AMR sensors, while Switzerland Micronas, Germany's Infineon, the United States Allegro Microsystems, Belgium Melexis N. V. Hall sensor ICs are also available from Japan and Asahi Kasei Microsystems.

Richard Dixonj Senior analyst of MEMS and sensors at IHS.