Texas Instruments (TI) has claimed the industry’s first 70-W brushless DC (BLDC) motor drivers with code-free, sensorless trapezoidal and field-oriented control (FOC), reducing design time while making motor systems quieter and smaller. The devices enable engineers to spin a BLDC motor in less than 10 minutes, said TI, eliminating months of design time for engineers developing industrial systems such as home appliances and medical applications such as ventilators and continuous positive airway pressure (CPAP) machines.
The motor drivers speed system response time while reducing board space by as much as 70%, thanks to its integrated real-time control and high integration level.
A large portion of all energy generated in the world is used by motors today, so getting the motor quieter is a growing need, and also given the fact that much of the power consumption is just motors, energy efficiency is also key, said Kannan Soundarapandian, vice president and general manager, motor drivers, Texas Instruments.
But there are challenges when transitioning from older technology like AC induction motors to fairly newer technology like BLDC motors, and meeting the needs to achieve the energy efficiency, the acoustic performance, and the designers’ need to get product out in the market quickly, he added.
What’s happening today is that the move to open-concept floor plans have increased the demand for quieter motors, said Soundarapandian. With open-concept floor plans that natural sound blocking that you would have before doesn’t exist anymore, he said.
Every appliance in your house has possibly more than one or even two motors, said Soundarapandian. “There are ways to effectively combat noise created by motors, which generally falls into three buckets – blocking it by embedding some sort of sound absorption system in the appliance, shaping it by applying psychoacoustic insights, like harmonic modification, and personally my favorite is avoiding it by not creating noise in the first place.”
For example, the vacuum cleaner is arguably one of the highest noise sources along with the food processor with average noise levels anywhere from 85 to 100 dBA so they make a lot of noise, and it’s not just acoustics, there is an ongoing need for greater energy efficiency, he added.
One of the major ways in which energy efficiency is achieved these days is by moving away from older technology like AC induction motors to brushless DC motors, he said. “But BLDC motors are more difficult to drive. They’re more complex; they need better commutation and control from the outside, and that basically increases design cycle time, increases the board size because it has more electronic components, and as a whole the system cost itself is increased, so these are the three major challenges to gain that efficiency increase.”
Soundarapandian said motor drivers are evolving to meet market needs and the new TI BLDC motor drivers address the three challenges of BLDC motor design – increased design cycle time, increased board space, and increased system cost.
These two devices – one of them is based on a commutation scheme called FOC, or field oriented control, and the other one is based on an older version of commutations called trapezoidal control, said Soundarapandian.
Click for a larger image. (Source: Texas Instruments)
One of the biggest benefits of the new portfolio is that it reduces tuning time from weeks to less than 10 minutes through real-time control and dynamic capability, translating into a faster system speed response. Also contributing to the accelerated design time are the capabilities to self-extract motor parameters and autotune the current control loop.
“From an acoustic performance standpoint, we have a lot of features built into this. I’m talking about a couple of things like automatic dead-time compensation and just fundamentally FOC itself,” he said. “The way we commutate this motor and the way we control it has shown us in the lab that we can actually reduce noise by a large percentage. In this particular example we’re talking about 2 dBA in one of the quietest laptops out there. Even in the lab environment without excessive tuning these motors are already running at, in this case, about 16 to 20 percent lower but we’ve got IP in the lab that can take that down to 50 percent or even more.”
At the same time, the total solution size can be implemented up to 70% smaller, he added.
“The level of integration that we’ve got in the MCF8316, the intelligence built in, the diagnostics, and the robustness capabilities, this level of integration is what allows us to get this kind of size improvement.”
Click for a larger image. (Source: Texas Instruments)
The MCF8316A and MCT8316A motor drivers
The MCF8316A sensorless trapezoidal control motor driver and MCT8316A sensorless FOC motor driver integrate three gate drivers and six high- and low-side mosfets with 50 mΩ of on-state resistance (RDS(on)) each, making them the first BLDC motor drivers to enable up to 70 W of power with 8 A of peak current for 12- and 24-V systems, according to TI. Other integrated components include a low-dropout regulator, DC/DC step-down regulator, and current-sense amplifiers, eliminating as many as 18 discrete integrated circuits.
The MCT8316A motor driver can reach a maximum motor electric speed of 3.5 kHz, which is faster than any other code-free, sensorless motor driver, making it suitable for applications such as robotic vacuums that require fast and precise motor control, said TI.
Click for a larger image. (Source: Texas Instruments)
TI also claims both devices are the industry’s first to provide a quick and controlled way to actively decelerate a motor, enabling engineers to stop a motor 50 percent faster than traditional motor-control techniques. They also can stop a motor without pumping energy back into the rail, which protects the system from damage.
“We have some quite sophisticated techniques built in to do very controlled deceleration that is generally about 50 percent faster than traditional control techniques and we believe this is something that is going to be very useful for designers going forward,” said Soundarapandian.
The MCF8316A and MCT8316A BLDC motor drivers include a unique set of commutation control algorithms that eliminate the need to develop and qualify motor-control software, which eliminates months of design time, according to Soundarapandian. The algorithms, in combination with high integration, enable these motor drivers to manage critical functions such as motor fault detection and implement protection mechanisms to increase system reliability.
In addition, the motor drivers use sensorless technology to determine the rotor position, which eliminates the need for external Hall sensors, ultimately reducing system cost and further increasing reliability.
As noted by Soundarapandian, the MCF8316A motor driver intelligently or self-extracts motor parameters, enabling designers to quickly tune a motor. It also helps deliver consistent system performance regardless of motor manufacturing variations. In addition, designers can tune a motor using only five hardware pins, simplifying systems by eliminating the need for a microcontroller interface.
Both BLDC motor drivers provide advanced real-time control capabilities for increased acoustic performance in applications such as air purifiers, refrigerators, washing machines and fans. The MCF8316A includes a precise automatic dead-time compensation technique that compensates for current distortion to enable engineers to optimize motor acoustic performance, and a variable trapezoidal control techniques that designers can use to reduce motor noise.
Pre-production versions of the MCF8316A and MCT8316A are available exclusively on TI.com in a 40-pin, 5 × mm quad flat no-lead package. Pricing starts at $1.75 in quantities of 1,000. TI will demonstrate the MCF8316A and MCT8316A during the company’s TI Live! Tech Exchange virtual event, Sept. 27-29, 2021.
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