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Hello and welcome to Texas Instruments Precision Labs. My name is Dalton Ortega, product marketing engineer from the brushed-DC and stepper motor drivers group here at TI. In this video, we will discuss the differences between brushed-DC, brushless-DC, and stepper motors, and common applications for each motor type.

The first motor type we will look at is the brushed-DC motor. Using a brushed-DC motor is one of the simplest ways to move a load. For the purposes of this video, we will consider a bidirectional permanent magnet and brushed-DC motor, which can be controlled using an H bridge. By turning on a high side and low side MOSFETs, we create a current path through the out one and out two terminals.

Current is then pass through the commutator and motor windings of the rotor, creating a magnetic field around the rotor. The stator magnets are permanently fixed in this brushed-DC motor, which causes a static magnetic field. These static magnetic fields push against the magnetic fields of the energized coils resulting in motor rotation, in this case, clockwise or forward rotation. To stop the motor, the same MOSFETs are put in the off state until current is decayed.

To run the brushed-DC motor in two directions, the voltage polarity on the out one and out two terminals needs to be reversed. And we can do that by turning on the opposite side MOSFETs, which will result in clockwise or reverse rotation. Brushed-DC motors are a simple and low cost solution for load actuation in many different applications. On top of being generally cheaper than other motor types, brushed-DC motors are very easy to control and do not require current control in most applications.

Some disadvantages of brushed-DC motors include limited lifetime of the motor brushes, noise, sparking, and possible EMI concerns. Brushed motors may not be suitable for some environments where sparks or brush dust is a concern. The simplicity of brushed-DC motors also has another downside. If position or speed control are required in the system, then additional circuitry or sensors must be used. Some common applications using brushed-DC motors are smart meters, automotive lift gates and windows, vacuum robot wheels and brushes, smart locks, electronic and robotic toys, currency counters, and many, many more. Check out our brushed-DC applications page to discover more uses for brushed-DC motors and our key TI products design to drive these systems.

Now let's look at the brushless-DC motor or, in short, BLDC motor. Typically, there are two types of brushless-DC motors. As the name indicates, inner rotor BLDC motors have the rotor inside the stator. This is a more conventional BLDC type used by many motor manufacturers. For outer rotor BLDC motors, the rotor is on the outside of the stator, which is also called outrunner design.

The inner rotor design typically benefits from smaller construction, better heat dissipation, and higher torque and speed. The outer rotor design typically benefits from low cogging torque. It being easier to wind the electric magnetic coils on the stator and not needing high performance magnets.

Now let's look into the three phases of BLDC motor windings. BLDC motor construction can vary in winding connection of its three motor phases. Shown on the left is a Wye winding or star connection, which is the most common winding use for a BLDC motor. On the right is the delta winding connection.

The Wye winding naturally is more efficient, has less resistive losses, is more immune to parasitic current, and has higher torque at lower speeds. Whereas the delta winding's main advantage, on the other hand, is higher top speed. A very important thing to note is that, regardless of the motor connection, both motors are driven the exact same way.

Brushless-DC motors are highly efficient thanks to its mechanical construction as there is no direct contact with the stator and rotor. It provides high speed with ultra low noise and is more reliable over the lifetime of the motor as there are no brushes to wear down as in the brushed-DC motor. On the other hand, brushless-DC motors are more expensive and they require more design complexity and control compared to a brushed-DC and stepper motor.

Some common applications for BLDC motors in automotive systems are power steering, traction inverter, pumps, fans, and power seats. BLDC motors are also used in industrial applications such as home appliances, power tools, industrial robots, and factory automation. Personal electronic systems, like drones, desktop, and laptop fans, and gaming, can also use BLDC motors. Check out our BLDC applications page to learn about other use cases for BLDC motor drivers from Texas Instruments.

The final motor type we will discuss today is the bipolar stepper motor. Compared to a brushed-DC or brushless-DC motor, stepper motors can drive loads in an open loop system without the need for a position and speed sensors or complex computation algorithms. Typical stepper motors have two pair windings on the stator requiring two H bridges to control the current through the winding pairs.

By energizing the windings in the stepper motor, the rotor is repelled by the stator's magnets causing the rotor to rotate and align with said magnetic fields. Integrated stepper drivers control rotor position by energizing the stepper windings in a particular sequence. In this example, the microcontroller sends a pulse to the stepper driver to indicate that the stepper rotor should be move to the next position. When the driver receives this step pulse, it energizes one of the motor phases in the sequence. When it receives the next pulse, it energizes the next phase so the rotor can continue moving.

The H bridges integrated in the separate driver can control the current in the phase windings in both directions to change the polarity of the windings and continue moving the rotor. If the microcontroller stops sending these pulses, the rotor will remain stationary and aligned with the magnetic field in the energized phase. Stepper motors have a basic angle of movement that corresponds to each input pulse also called a step angle. And this is provided by the motor manufacturer. Using this known step angle, angular position and speed can be inferred by controlling the input signal frequency.

Stepper motors provide an easy way to accurately control a load's position and speed without needing surrounding sensing circuitry. They can also hold motor position for a long period of time without complicated algorithms and are typically lower cost versus brushless-DC motors. There are some drawbacks, however. If a stepper motor loses current regulation, this can often lead to audible noise. And resonance can cause vibration in the system. To avoid this, current control and regulation must be implemented. Some common applications using stepper motors are ATMs, HVAC expansion valves, automotive headlights, printers, projectors, and many more. Check out our stepper motor applications page to discover more uses for stepper motors and our key products designed for these systems.

To conclude, the three motor types we discussed today are brushed-DC, brushless-DC, and stepper motors. There are high level trade offs for each motor type. Brushed-DC motors are less expensive. They're easier to use. And they have simpler designs. But their mechanical brushes can wear out over the lifetime of the motor. They're also highly inefficient compared to other motor types.

On the other hand, brushless-DC motors do not have brushes that wear out or cause EMI radiation. This makes BLDC motors highly efficient and extends the life of the motor while providing smooth motion and better performance. But these benefits come with a higher cost for the motor and a more complex design to commutate the motor compared to brushed-DC and stepper motors.

Stepper motors are what we consider a poor man's brushless-DC motor. Stepper motors are used to recreate a smooth wave form and motor movements similar to a BLDC motor by using current, controlled rising and falling steps. With stepper motors, we can use open loop architecture for speed and position control with no sensors needed. This makes designing with stepper motors easier when compared to the brushless-DC systems. However, since the current stepper motors needs to be controlled in order to avoid noise, vibration, and resonance with the motor, current regulation is often needed.

We recommend taking a look at TI's application reference designs listed here for each motor type. These tools provide a quick and easy way to see how our motor application can be implemented with our motor drives and supporting ICs. Thanks for taking time to learn about the motor basics.

This video is part of a series