Learn more about the wide variety of available motor control drivers from Toshiba America Electronics Corporation (TAEC).
Toshiba’s MCD line-up meets wide application range
As you read this article at your workplace, at your favorite table in a café, or in your living room, chances are that you are in close proximity to at least one motor that helps spin your computer’s hard drive, print this article, grind coffee beans, pump hot water for your espresso, circulate cool air or vibrate your phone. And that is just a minuscule fraction of what motors do for us today.
In a wide variety of areas like consumer electronics, home appliances, computers and peripherals, medical devices, and automotive segments, motors find a home wherever there is a need for continuous movement or precise positioning.
Depending on your project requirements and cost considerations, if it’s for low power designs, you are most likely to choose from among three types of motors — brushed DC (BDC), brushless DC (BLDC) or stepping motors. And depending on the motor, you will need suitable motor control drivers (MCDs) for turning the motor on and off, regulating speed and torque, and achieving high efficiency.
Brushed DC motors
Brushed DC motors are the simplest of the three types of motors and ones that we first read about in school. With windings on the rotor or armature and either permanent magnets or field windings on the stator, these motors need commutators and brushes to change the polarity of the winding during spin so that torque develops continuously in one direction. Since these motors are relatively simple to manufacture and control, they are generally cheaper and, while they are often used in toys and other cost-sensitive applications, they also find their way into home appliances, like electric blinds and locks.
Controlling BDCs is relatively simple — varying the average voltage applied to the motor varies its speed — and can be achieved with an H-bridge and a microcontroller; however, selection of driver ICs may require some thought.
That is simplified by the wide operating voltage range of the TB67H450FNG,EL from Toshiba Electronic Devices & Storage Corporation (TDSC). Its operating voltage ranges from 4.5 V all the way to 44 V for large-current (less than 3.5 A) devices, such as office automation (OA) equipment, banking terminals, home appliances, including battery-powered products like robotic vacuum cleaners, electronic locks, and small robots, and devices using 5 V USB power supplies. The driver draws just 1 μA on standby and comes in the small 8-pin HSOP8 surface-mount package.
If you need a lower operating voltage but a larger current, the TC78H653FTG,EL is a dual-H-bridge driver IC that offers the 1.8 V-to-7.0 V operating voltage range and two current modes — the small current mode with 2.0 A DC and a 2.5 A DC peak (less than 10 ms) in two channels and the large current mode with 4.0 A DC and a 5.0 A DC peak in a combined channel. Its low on resistance means more current flows through the motor for higher torque. If your project involves mobile devices like cameras and portable devices that use 3.7 V lithium-ion batteries, or home appliances like gas stove actuators, smart meters, electronic locks, or other applications using two 1.5 V dry batteries, this driver’s combination of characteristics make it well suited for design-in.
TDSC offers more devices for BDC motors, with several of them pin-compatible to common brushed motor drivers so that engineers can swap parts with minimal or no change to the design in response to changing market requirements.
Brushless DC (BLDC) motors
BLDC motors are mechanically simpler than the brushed ones, with typically the permanent magnets on the rotor and the windings on the stator. BLDCs eliminate the noisy, spark-prone, torque-limiting mechanical commutation, while delivering higher torque and speed. However, they require accurate control to achieve the higher efficiency they promise for applications ranging from computer fans to servo mechanisms in industrial equipment.
Control over the polarity and magnitude of the current flowing through the coils and its synchronization with the rotor is achieved by measuring the position of the magnets with Hall Effect sensors or by detecting the back-electromotive force (Back-EMF) zero-crossing in sensor-less BLDCs, and feeding this information back through motor drivers. But repeated adjustments of phase differences between motor voltage and motor current are required in the rotation speed range to achieve optimal efficiency characteristics. Yet, current tends to lag in high-speed drives because of inductance at high frequencies.
A proprietary Intelligent Phase Control (InPAC) technology from TDSC makes BLDC motor control simpler and more accurate. It compares the phase of the motor current and the phase of motor voltage from the Hall signal, and feeds back the result to the motor current control. The adjustment of phase difference between motor voltage and motor current is accomplished automatically over a wide range of motor speeds with merely an initial setting. This considerably reduces the development burden on engineers.
TDSC has four new three-phase BLDC motor control solutions that use this technology, the controller parts TC78B041FNG,EL, housed in an SSOP30 package and the TC78B042FTG in a VQFN32 package, the fully integrated driver, TC78B016FTG, and the controller with integrated gate driver, TC78B027FTG. The MCDs use a sine-wave drive system for a smooth current waveform to reduce noise and vibration in high-speed motors for applications like air conditioners, fans, air purifiers, pumps, as well as industrial equipment.
TDSC also offers MCDs for sensor-less operation, if your project allows sensor-less BLDCs to reduce the motor costs. The TB67B001FTG,EL is such a three-phase pulse-width modulation (PWM) chopper driver that controls motor speed by changing the PWM duty cycle. Rated at 3 A max for output current and 25 V max for power supply, it offers overlapping commutation at 120°, 135° and 150°, selectable soft switching, adjustable startup settings, overcurrent protection, thermal shutdown, and under-voltage lockout. A new controller with integrated gate-driver part, the TC78B009FTG offers designers the flexibility of sizing proper power-stage MOSFETs for the applications. TC78B009FTG is sampling now and scheduled to be in production by Q1 2020.
Stepping motors
The third type of motor you may also encounter is the stepping motor. It finds use in designs that require high-precision angular motion, such as desktop printers, 3D printers, security cameras, camera lenses, medical scanners, intelligent lighting, and CNC milling machines.
Stepping motors are managed by controlling pulse width, duty cycle or period of input pulses. The challenge for stepping motor control lies in avoiding stalls, as the motors or the electronics can be burnt — if synchronization is lost during overload or a rapid speed change, the motor stalls while the driver is still conducting in full strength. This requires you to provide enough current margin to prevent sudden heavy torque changes. However, the trade-off in this setup is reduction in efficiency and increase in heat generation.
The additional current may be reduced to avoid that trade-off by implementing current adjustment through real-time monitoring of torque and current feedback with the addition of sensors and microcontrollers; however, this adds design complexity and cost.
TDSC’s Active Gain Control (AGC) technology targets this problem by automatically optimizing the motor current depending on the torque needed. This prevents the motor from stalling and provides optimum control to deliver the best efficiency and lowest heat generation possible.
The company’s TB67S128FTG,EL part, a bipolar stepping motor driver offering an ultra-smooth 128 micro-steps (per quarter cycle) driving against 32 conventional steps, utilizes the AGC technology. Its 50 V / 5 A rating offers a high-power drive to applications, including 3D printers, surveillance cameras, ATMs, and OA equipment.
Additionally, the TB67S128FTG uses the company’s Advanced Dynamic Mixed Decay (ADMD) technology, which discharges the inductive motor current more effectively and quickly than the conventional mixed-decay mode. ADMD can stretch a generally slow speed stepper motor to its limit without missing steps. The part also takes advantage of TDSC’s Advanced Current Detect System (ACDS) technology to detect current limit without external current-sensing resistors which, in turn, reduces space, part count and bill-of-materials (BOM) cost.
A drive for all motor control needs
TDSC makes the MCD selection easier by addressing all motor types and a wide range of voltage and power requirements. Its broad range of motor drivers covers an equally broad range of applications, including home appliances, industrial equipment, office machines, and computer peripherals. What’s more, it is available in a wide range of packages, such as HSIP, HZIP, WQFN EP, HSOP, and VQFN EP, many of which are pin compatible.
Visit Arrow.com today to select a TDSC MCD that best matches your design requirements.
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