Analysis of 3 methods to accelerate the design cycle of brushless DC motor

The global effort to reduce power consumption is gaining momentum. Many countries require home appliances (see Figure 1) to meet efficiency standards set by organizations such as the China National Institute of Standardization (CNIS), Energy Star in the United States, and Blue Angel in Germany. To meet these standards, more and more system designers are moving away from the simple and easy-to-use single-phase AC induction motor in their designs and turning to more energy-efficient low-voltage brushless DC (BLDC) motors. Designers of small appliances such as robot vacuum cleaners are also turning to more advanced BLDC motors in many of their systems to achieve longer life and quieter operation. At the same time, advances in permanent magnet technology are simplifying the manufacture of BLDC motors, reducing system size while providing the same torque (load), while also improving efficiency and reducing system noise.

Designing systems using BLDC motors is challenging because complex hardware and optimized software design are often required to provide reliable real-time control. One option to speed up the design cycle is to use BLDC motor modules from specialized suppliers, but these modules are not optimized for the needs of a specific system. Therefore, in order to build an optimized, high-performance system to meet specific application needs, a deep understanding of motor design and control is still required, even when using modules. In this article, I will introduce three methods that can speed up BLDC motor system design while providing smarter, smaller, and energy-saving solutions.

Method 1: Sensorless control without programming

Programmable motor drivers include built-in control commutation algorithms, eliminating the need for motor control software development, maintenance, and certification. These motor drivers typically take feedback from the motor (such as Hall signals or motor phase voltage and current signals), calculate complex control equations in real time to determine the next motor drive state, and provide pulse-width modulated signals to analog front-end components such as gate drivers or metal-oxide semiconductor field-effect transistors (MOSFETs) (as shown in Figure 2).

Figure 2: Typical sensorless BLDC motor system

When using motor drivers with integrated sensorless control functions (such as the MCF8316A motor driver with field-oriented control (FOC) function) for real-time control, the Hall effect sensor is not required in the motor, thereby improving system reliability and reducing the overall system cost. The motor driver without programming can also manage important functions (such as motor fault detection) and implement protection mechanisms, making the entire system design more reliable. These devices can come with pre-certified control algorithms implemented by certification agencies such as Underwriters Laboratories, enabling OEMs to shorten the design time of their home appliances.

Method 2: Easily tune the motor using intelligent motor control

System performance parameter requirements such as speed, efficiency, and noise are difficult to address by tuning the BLDC motor. This problem can be addressed by developing a sensorless trapezoidal control algorithm where the commutation is determined by the motor's back-EMF voltage, making the tuning operation independent of the motor parameters. Integrated motor drivers such as the MCT8316A with integrated sensorless trapezoidal control can provide optimized system performance without the need for complex interfaces to the microcontroller. Also, note that during the motor tuning process, the integrated motor driver provides feedback signals such as motor phase voltage, current, and motor speed displayed on an oscilloscope.

In the sensorless FOC algorithm, motor tuning can be significantly accelerated due to the integration of advanced control techniques, for example, by measuring motor parameters on its own or automating the tuning of the control loop. The guided tuning graphical user interface (GUI) provides default motor start options (as shown in Figure 3) to help smooth the tuning process and get the motor spinning as quickly as possible. Programming-free motor drivers (such as the MCF8316A for FOC and the MCT8316A for trapezoidal control) include multiple configurable options for motor start as well as closed-loop and motor stop operation. With these options, motor performance can be optimized in just a few minutes, significantly shortening the design cycle.

Figure 3: Guided Tuning GUI

Method 3: Reduce the size

Building the BLDC system hardware is daunting for many system designers. A typical system requires gate drivers, MOSFETs, current sensing amplifiers, voltage sensing comparators, and analog-to-digital converters. Most systems require a dedicated power architecture (including devices such as low-dropout regulators or DC/DC buck regulators) to power all the components on the board. An integrated BLDC driver combines all of these components to provide a compact but easy-to-use solution, as shown in Figure 4.

Figure 4: Fully integrated BLDC motor solution

Motor drivers with integrated control functions include protection features such as overcurrent and overvoltage protection for MOSFETs and temperature monitoring, allowing designers to easily provide a robust solution. For motor applications with power consumption less than 70W, such as vacuum robots, home ceiling fans, or pumps used in washing machines, devices with integrated MOSFETs can be selected to further reduce board space. The MCF8316A and MCT8316A devices support up to 8A peak current in 24V applications. For high-power applications, the power MOSFET can be placed on the board, allowing the gate driver and motor control functions to be integrated into a single chip.

The concepts discussed in this article help speed up system design cycles while providing smaller, smarter BLDC motor systems. With sensorless BLDC motor drivers such as the MCF8316A and MCT8316A, which do not require programming, you can quickly design optimized, high-performance, real-time control systems. These devices can provide up to 70W of power for 24V applications. With integrated intelligent control technology, both motor drivers are easy to tune and can be used to achieve high-performance and reliable system solutions, making them ideal for building the next low-voltage, energy-saving BLDC-based system.