Currently, the trend towards electronic functionality in automobiles is intensifying to address increasingly stringent fuel efficiency regulations and meet consumers' higher demands for energy conservation, safety, comfort, and convenience. Automobiles have transformed from purely mechanical products into complex mechatronic devices, with the number of motors installed in vehicles continuously increasing. It is predicted that by 2020, each luxury car will contain as many as 120 motors. Due to their numerous advantages, brushless direct current (BLDC) motors are increasingly being integrated into components such as water pumps, oil pumps, fuel pumps, radiator fans, HVAC systems, hybrid systems, and seat fans to achieve higher energy efficiency and performance.
Figure 1: Application of brushless DC motors in automobiles
Advantages of DC brushless motors
Brushless DC motors eliminate the need for brushes and commutators, solving space-constrained system designs and eliminating concerns about common wear, sparks, and noise. They offer excellent control and provide variable speed control for specific automotive applications. More importantly, brushless DC motors improve fuel efficiency, saving approximately 60%–70% of energy consumption. When brushless motors are used in electric power steering (EPS), driving range increases by 3–5%; in electric water pumps (EWP) and electric oil pumps (EOP), efficiency is improved by approximately 3%; and in fuel pumps, efficiency is improved by approximately 1%. For example, water pumps and fuel pumps typically operate using engine power. If the engine stops, the engine start-stop system has no power. However, if motors are used in water pumps and fuel pumps, these functions can operate independently whether the engine is running or stopped, thus improving fuel economy.
Design considerations for using a brushless DC motor
If brushless DC motors replace brushed motors, the work that previously had to be done mechanically by the commutator can now be accomplished electrically by a three-phase inverter. The inverter requires a gate driver, which is typically controlled by a microcontroller implementing complex software algorithms. This increases system complexity and poses a significant technical challenge for engineers. ON Semiconductor's LV8907 intelligent brushless DC motor control and drive chip solves this challenge. This solution eliminates the need for external motor position sensors or system microcontrollers, reducing PCB footprint. It features built-in embedded control algorithms, eliminating the need for custom motor control algorithms, thus reducing system complexity, shortening development cycles, and accelerating time-to-market.
Figure 2: The LV8907 eliminates the need for microcontrollers and sensors found in traditional solutions.
Overview of the LV8907 Intelligent DC Brushless Motor Solution
The LV8907 utilizes sensorless drive logic to achieve sensorless 120° or 150° commutation control, employing near-sine wave operation to meet silent drive requirements. Configurable parameters are suitable for a range of motor and load combinations. One-time programmable (OTP) memory provides parameter storage, enabling customized solutions and eliminating the need for external components to execute various settings, allowing for independent operation. An integrated gate driver drives external N-MOSFETs, and a charge pump driver provides 100% duty cycle and extended low-voltage operation. The chip interacts with the outside world via a LIN interface, and an SPI interface provides configuration, real-time control, and diagnostics. In automotive applications, operation at an ambient temperature (Ta) of 150°C and a junction temperature (Tj) of 170°C is required. The LV8907 withstands a junction temperature of up to 175°C, ensuring reliability in harsh automotive environments and fully complying with AEC-Q100 standards.
Figure 3: Block diagram of LV8907
Because the LV8907 highly integrates MOSFET gate drivers, LIN transceivers, and low-dropout regulators (LDOs), it minimizes footprint; it requires no position sensors, has no software defects, and offers comprehensive fault monitoring and diagnostic functions. It integrates a series of protection features, including cycle-by-cycle current limiting, overcurrent protection, overvoltage/undervoltage protection, overtemperature protection, and stall protection. The state machine-based solution uses OTP for parameterization, eliminating data corruption caused by EMI/EMC issues and achieving maximum system reliability. The LV8907 requires no software and is easy to customize, reducing development time by up to 80% compared to microcontroller-based solutions, accelerating time-to-market, and saving on bill of materials costs.
More integrated intelligent power modules (IPMs)
As the demands for reduced costs, smaller size and weight, and higher reliability in automotive electronics continue to grow, intelligent power modules are better positioned to meet these trends. For example, ON Semiconductor's STK984 series integrates a BLDCLV8907 and multiple independent power MOSFETs, eliminating the need for circuit boards, sensors, and external microcontrollers. This saves space, reduces weight, and lowers costs, making it ideal for driving automotive sliding doors, EPS units, pumps, wipers, HVAC systems, and cooling fans while providing greater reliability.
Figure 4: Independent sensorless motor control IPM
The STK984 series employs a unique Insulated Metal Substrate Technology (IMST) to integrate semiconductor components, passive devices, and other parts of different structures into a single module. The IMST structure uses an insulating layer to cover an aluminum sheet, placing copper foil on top and etching it, allowing for free customization of the single-layer wiring pattern. Based on IMST, the IPM minimizes temperature detection errors and achieves high-precision temperature monitoring because power transistors, temperature sensing control circuitry, and protection circuitry can be mounted on the same board. A distributed capacitance between the aluminum sheet and copper foil on the metal substrate, passing through insulating resin, effectively reduces noise. Furthermore, the IMST structure provides excellent heat dissipation performance.
For example, the 3-phase brushless motor driver IPMSTK984-090A-E/091A-E integrates a pre-driver IC, shunt resistor, and charge pump circuit, and features overcurrent, overtemperature, overvoltage/undervoltage protection. It can be used in automotive blower fans, cooling fans, water pumps, and sliding doors, etc.
For example, the STK984-190-E integrates seven MOSFETs into a single small package using a direct-bonded copper (DBC) substrate, eliminating the need for insulating pads. This results in low thermal resistance, excellent heat dissipation and design flexibility, built-in reverse-connection battery protection for enhanced reliability, and full compliance with AEC-Q100 requirements. It can handle motor power up to 300W in 12V systems. Compared to discrete solutions, the STK984-190-E reduces footprint, weight, component count, and thermal resistance by 48.7%, 36.2%, 53.8%, and 21.1%, respectively, making it an ideal device for applications such as automotive wipers, fans, and pumps.
Summarize
To address the trend of automotive functional electrification, automotive motors are becoming increasingly prevalent, evolving from brushed DC to brushless DC. With growing demands for smaller size and weight, lower system costs, and higher reliability, there is a need for continuously increasing integration. ON Semiconductor offers a comprehensive range of brushless motor solutions, including discrete and integrated solutions such as the sensorless BLDCLV8907 and the more integrated IPMSTK984 series, addressing challenges related to software development, space, cost, and design time. These solutions provide higher energy efficiency, power density, and system reliability, making them ideal for automotive applications such as water pumps, oil pumps, fuel pumps, cooling fans, HVAC systems, windshield wipers, and sliding doors.
