"More and more electrical products are used at home, especially after the popularity of open space design, the demand for appliances with lower noise and higher energy efficiency is growing", said Kannan Soundarapandian, general manager of Texas Instruments‘s motor drive business department.
From refrigerators to cooking machines, the noise can even range from 40dBA to 100dBA. Therefore, motor noise reduction is crucial. There are three common methods in motor noise reduction technology.
One is to prevent propagation, by blocking or absorbing sound along the propagation path to prevent the spread of noise; Second, change the noise, analyze the noise frequency and noise source through technical means, and use Psychoacoustics to change the sound; Thirdly, avoiding noise from the source is also the most highly recommended method by TI.
Data shows that nearly 45% of global energy is consumed by electric motors. Therefore, improving the energy efficiency of motors is very important, and there are relevant standards for energy efficiency worldwide. BLDC is an efficient motor, and transitioning from AC induction motors to BLDC motors can reduce power consumption, but it also poses three major challenges.
Firstly, the control of the BLDC system is very complex, and the development cycle will also be prolonged accordingly; Secondly, due to the complexity of the system, the number of hardware circuit boards and devices will also increase, and the overall circuit board size will also increase. For example, in designing BLDC motor drives, circuit boards similar to frequency converters are required, current sampling, switch device switching, etc; Thirdly, the extension of the design cycle has increased development costs, while the increase in circuit board size and devices has increased material costs.
Two distinctive motor drive chips
While BLDC has the magic of reducing noise and improving energy efficiency, it still faces the aforementioned challenges. The new generation BLDC motor drive in the market gradually does not need to be developed, but it is generally difficult to optimize performance or provide inconsistent performance. In addition, although the integration of BLDC motor drivers is increasing, there are still many areas that need to be improved urgently.
Kannan stated that TI‘s new products have addressed various challenges of BLDC drives one by one. First, the new product does not need programming. Empirical data shows that it takes weeks or months for a senior Electrical engineer to tune the motor, and the new product can reduce the tuning time to less than 10 minutes; Secondly, the product adopts real-time control to accelerate system response, assuming that when the product is installed on a vacuum cleaner, the suction force will not decrease when encountering large loads or obstacles; Thirdly, the new product has many advanced designs that can eliminate noise from the source.
The specific models of the new product are MCF8316A and MCT8316A, which are 70W BLDC motor drivers. The two adopt different technologies, with the former being field oriented control (FOC) and the latter being trapezoidal control. At the same time, both new products do not require sensors and can reduce the overall solution size by 70%.
Why can TI‘s chips reduce size so much? This is because generally speaking, the 70W BLDC motor drive fully discrete scheme includes three parts: MCU, MOSFET power device, and gate drive. In this case, the total number of components needs to be 28, with a size of nearly 7 square centimeters. If the solution is further integrated, fewer devices and smaller area can be obtained.
TI actually integrates all three major functions into one chip, reducing the total number of components to 10 and reducing the size to 2 square centimeters. MCF8316A and MCT8316A integrate six 40V, 50m Ω MOSFETs with gate drivers, current and voltage sensing, and controllers into a 7mm x 5mm QFN package, arranged in three - H bridges.
Kannan introduced that the two chips have a common function of preventing bus voltage pumping. When the BLDC motor runs at high speed and needs to be quickly reduced in speed, the motor will become a generator, and the energy of the motor itself will be poured back onto the bus of the driver. In this case, the bus voltage will rise, and some MOS transistors such as the bus capacitor and frequency converter will be burned out due to excessive voltage. So the two chips are equipped with this advanced function, which detects the bus voltage in real-time and dynamically adjusts the speed reduction ratio to always maintain the bus voltage is safe. In this way, both chips can reduce the speed while ensuring that the bus voltage does not exceed the standard, and the speed reduction time is 50% faster than traditional time.
The two products also have their own characteristics. As a sensorless field oriented control (FOC) motor driver, MCF8316A can automatically identify motor parameters during motor startup, solve concerns about parameter inconsistency, and automatically configure PI parameters without the need for engineers to correct them one by one; In addition, the chip can reduce the noise by up to 2 dbA through the automatic Dead time is not long.
In addition, MCF8316A also provides multiple functions, making sensorless field oriented control easier and motor operation more consistent. For example, the Motor Parameter Extraction Tool (MPET) provides a built-in, offline running utility to measure motor parameters and automatically load them into the device. TI has released a GUI that showcases each step of adjusting and optimizing the motor, which can be used in conjunction with our evaluation module. The closed-loop motor operation can be configured through register settings. Multiple startup methods and a wide range of custom options enable customers to start and stop motors safely and reliably.
As a sensorless trapezoidal control motor driver, MCT8316A can simplify the interface. Due to its built-in closed-loop control, there is no need to use an MCU. Five hardware interfaces can achieve speed closed-loop and torque control; Capable of providing motor speeds up to 3.5kHz; In addition, the chip has an optimized noise design, and engineers can easily reduce noise through internal advanced algorithms.
BLDC has significant lifecycle cost advantages
Why are brushless DC motors more favored? It is reported that the internal motors of electrical appliances may emit noise during operation, so electrical applications close to humans may become "troublesome". For example, ceiling fans must be completely silent, and air purifiers can make their operation more efficient by reducing noise, thereby creating more differentiated products. Brushless DC motors are usually the quietest type of motor, especially compared to brushless DC motors with mechanical commutation and noise generated by brushes. Controlling low noise motors is very difficult, and in many cases, it is necessary to use a very clean and smooth current that is close to a sine wave to drive the motor. If there is any distortion in the sine wave, it will generate audible noise. In addition, it is also necessary to measure the motor position very accurately in order to drive the motor correctly.
From the perspective of the entire lifecycle cost, the conversion from AC induction motors to BLDC is quite cost-effective. On the one hand, the overall energy efficiency of BLDC has been improved by 10% -15%, which can correspondingly reduce the cost of system design, including heat dissipation; On the other hand, BLDC motors have a longer overall life cycle and have cost advantages in terms of energy conservation, energy consumption, and life cycle.
Throughout the entire market, there are few products that can highly integrate functionality like MCx, without the need for programming. In addition, there are no other integrated controller solutions on the market that can achieve power transmission of 70 watts. According to Kannan‘s introduction, the two chips are widely used. Due to their ability to extract different motor parameters, they can be widely used in household appliances such as fans, water pumps, oil pumps, fans, vacuum cleaners, etc.
In addition to MCF8316A and MCT8316A, TI also provides MCUs such as C2000 that can be used with motor drivers such as DRV8316 to achieve a split layout. TI has a rich portfolio of control, driver, and sensing products, so customers can choose the appropriate architecture for their applications. We understand that market demand is constantly evolving, and TI provides more choices in this field by leveraging years of real-time control expertise.
We will continue to expand our BLDC product portfolio, including controllers, drivers, and gate drivers that meet automotive safety level certification. With a wide range of products that can provide ultra-high power density at any voltage, customers can quickly achieve smooth and accurate motor motion without affecting the robustness of systems and equipment, "said Kannan at the end of the press conference.
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