As a synchronous motor, BLDC is very suitable for mobile products because of its high torque density. Especially in recent years, there are many applications of BLDC in such rapidly developing industries as UAV, robot and electric vehicle. The components exhibition focuses on the comprehensive display of various electronic components and materials required for the design and production of electronic products. This article introduces the BLDC special driver chip under the development trend of high integration and non-inductive FOC.
Because BLDC can make the back EMF waveform trapezoidal, it can use DC voltage with rectangular waveform to generate a rotating magnetic field with low torque ripple, and rectangular voltage is easy to generate. So any MCU, C2000 series DSP or even 51 single chip computer can produce this kind of P
At present, the terminal market has put forward higher requirements for motor control performance, which not only requires electric WM wave, but also why BLDC control and drive can be very simple. BLDC is almost the choice for low cost and high efficiency applications. The machine can achieve high efficiency and multi-function control. It also needs to achieve the control effect of low noise and low vibration while pursuing high speed. These high standard performance requirements put forward more stringent requirements for the control chip. More and more high-performance motor drive control chips are emerging under the two opportunities of high market demand and high performance standards.
Complete full integration with single chip
In fact, it is not only the special chip for motor drive and control, but also the goal of higher integration for the integrated circuit design industry. For the special chip for motor drive and control, if a single chip has higher device or function integration, it can greatly simplify the peripheral devices and circuits in application. This is also critical to the overall reliability of BLDC.
Recently, Texas Instruments (TI) released two BLDC drives, MCF8316A and MCT8316A. Although it hasn‘t officially launched yet, we can see its powerful performance from the information disclosed so far.
MCF8316A and MCT8316A integrate real-time control function and up to 18 discrete components including MOSFET. MCF8316A is a sensorless field-oriented control motor driver, which intelligently extracts motor parameters; The MCT8316A is a sensorless trapezoidal control motor driver, which does not require a microcontroller interface and has high integration, so it can simplify the system.
It is reported that MCF8316A contains a patented precision automatic dead time compensation technology. This technology can compensate the current distortion and greatly optimize the acoustic performance of the motor. MCT8316A reduces BLDC noise through different trapezoidal control technologies.
These two new products integrate three drivers and six high-side and low-side MOSFETs, each with a 50 m Ω on-resistance. The advantages of single-core high integration can be seen from the advanced BLDC motor drive performance of Texas Instruments. The two products can provide up to 70W power and 8A peak current in 12V and 24V systems. These are not the only manifestations of high integration. Low voltage drop (LDO) regulator, DC/DC step-down regulator and current detection amplifier are all integrated in a single core, saving up to 18 discrete components. For low-voltage energy-saving systems, these two products should be ideal choices.
When the motor driver integrated with sensorless control function is used for real-time control, no Hall effect sensor is needed in the motor, so the system reliability can be improved and the total cost of the system can be reduced. The cost reduction brought by full integration of single chip is also a key point for downstream customers.
Sensorless FOC
The BLDC motor control algorithm is also updated from generation to generation. With the improvement of motor control performance requirements year by year, BLDC control algorithm has also been transformed from square wave control to inductive SVPWM, and then to FOC. The sensorless FOC control algorithm has now established a leading position in major manufacturers, mainly because FOC can achieve the motor control objectives of high efficiency, low vibration, low noise and high response speed to a large extent.
These two TI products are based on Field Oriented Control. Here we look back to China. From the domestic BLDC control chips and solutions, we can see that basically all domestic manufacturers have chosen FOC to push.
FU6832 launched by Fenglin Technology is a high-performance BLDC dedicated drive MCU with insensitive FOC embedded. In fact, this model also has a single core full integration, which integrates high-speed motor control engine, Predriver, LDO, operational amplifier, comparator, high-speed ADC and high-speed multiplier and divider, and can automatically complete the FOC/BLDC operation control of the motor by hardware.
The motor commutation performance under FOC control is excellent, and the forward and reverse switching can be very smooth at high speed. At the same time, FOC can carry out three closed-loop control of current (torque), speed and position. Through clock speed regulation and PWM speed regulation, BLDC under FOC control has lower vibration, lower noise and faster response speed.
In the sensorless FOC algorithm, due to the integration of advanced control technology, it can significantly speed up the motor tuning, for example, by measuring the motor parameters or automatically performing the tuning of the control loop.
Chipon KF32 series also optimizes FOC for BLDC motor applications.
The powerful core of KF32 series can achieve an electrical speed of>240000 RPM under non-inductive FOC without any hardware algorithm acceleration.
At the same time, KF32 enhanced ECCP is used to output 6-way PWM. The sampling resistance converts the current signal into a voltage signal. Then the differential operational amplifier integrated in KF32 is used to sample the size of the signal with the ADC module of KF32. The sampling value is adjusted to control the duty cycle of the PWM output through the FOC algorithm, so that the operating speed of the motor can reach the given speed.
Many chip manufacturers in China have launched special chips based on BLDC applications, which will not be listed here.
Summary
The trend of BLDC motor drive chip industry technology to single-core high-integration and non-inductive FOC control has become clear. How BLDC drive chip manufacturers make breakthroughs in efficiency, low energy consumption and stability under the opportunity of market expansion will be the key to win the market.
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