Latest motor control technologies that enhance a motor’s performance considerablyLatest trends in the motor control technologies recommended
by Toshiba and their applications
Motors essential as a source of mechanical power for various electric and electronic systems.
It is generally considered that motors consume lots of power and generate considerable noise.
The fact is that a motor driver IC significantly affects the power consumption and noise of a motor.Toshiba Electronic Devices & Storage Corporation (“Toshiba”) has more than 40 years of experience in motor drivers.
At present, Toshiba’s product portfolio contains roughly 170 motor drivers.
The following describes Toshiba’s latest motor control technologies while providing answers to frequently asked questions and examples of Toshiba’s motor driver ICs.
Motors are used in a myriad of applications to provide mechanical power.
Because of their principle of operation, motors consume lots of power and generate much heat, vibration, and noise, and often account for a large percentage of a system’s power consumption.
Although the principle of operation of motors is straightforward, sophisticated control technologies are necessary to reduce their power consumption and noise.
The following describes the latest motor control technologies and how they should be used to derive the maximum benefits.
Latest motor control and drive technologies that provide stable motor rotation and a reduction in power consumption
CASE : 01
―― We are planning to redesign circuits related to motors.
As we are going to create new designs, we would like to use the latest motor drive technology.
What technologies are available?
In recent years, various motor control drivers (MCDs) incorporating new technologies have appeared.
Having cultivated its power electronics expertise over many years, Toshiba has also leveraged its proprietary technologies to develop MCDs.
Functional and electrical performance enhancement are not the only highlights of these MCDs; adjustment-free control and self-detection are key attributes of our MCDs.
Having shifted its focus in MCD development, Toshiba has developed four major technologies to date and begun incorporating them into new MCDs.
Two of the four technologies are for brushless DC (BLDC) motors, and the other two are for stepping motors.
Specifically, those for BLDC motors are:
· Intelligent Phase Control (InPAC), a high-efficiency drive technology
· Closed Loop for Speed Control, a motor rotation stabilization technology
The technologies for stepping motors are:
· Active Gain Control (AGC), a drive current optimization technology
· Ultra-Fine Microstepping, a vibration and noise reduction technology
These technologies are detailed later. The MCDs incorporating these technologies help reduce your workload for system design and production while stabilizing motor rotation and reducing power consumption.
How does InPAC provide
high-efficiency motor drive?
CASE : 02
―― I heard that adjustment is necessary to drive a BLDC motor with high efficiency.
Does adjustment take a lot of time?
Does inadequate adjustment result in lower efficiency or louder noise?
In the case of BLDC motors, there is a slight phase difference between drive voltage and current because of the effects of circuit impedance and other factors.
When voltage and current are not in phase, electric power is wasted since it is not used to perform work.
A phase difference also causes the motor noise to increase because of fluctuating drive strength.
Lead angle adjustment, a technology for reducing the phase difference, is effective in reducing the power consumption and acoustic noise of a motor.
The lead angle has conventionally been adjusted manually.
However, the phase difference varies with rotation speed,(rpm:rotation per minutes).
For applications in which a motor runs at variable rpm, it is necessary to perform lead angle adjustment at multiple rpm points in order to obtain sufficient benefits.
With InPAC, you need to adjust a lead angle at only one rpm point within the rated rpm range.
Then, an MCD performs optimum lead angle control automatically.
MCDs with InPAC detect the phase of the current that actually flows through a motor and automatically align it with that of a voltage phase signal from the motor through feedback control.
Therefore, InPAC considerably reduces the time required for lead angle adjustment while reducing a motor’s power consumption over a wide rpm range.
MCDs with InPAC not only minimize the phase difference but also provide quiet motor operation through three-phase sine-wave commutation.
How does AGC optimize motor drive current?
CASE : 03
―― We have been having difficulty reducing system power consumption.
A stepping motor constitutes a large percentage of system power consumption.
Since out-of-step operation must be avoided, it is difficult to reduce motor drive current. Are there any effective solutions for this problem?
A stepping motor must be driven with sufficient torque because a lack of torque causes motor stall.
Basically, it is necessary to estimate the maximum torque requirement and allow an adequate margin for motor drive current so that stall mode will not occur.
This means that plenty of electric power is wasted because of the additional current margin.
Extra power consumption causes an increase in heat dissipation.
In many cases, component placement must be carefully considered so as to improve heat dissipation.
To reduce the waste of power consumption, it is effective to control motor drive current according to the required torque.
Indeed, it is true that this is possible simply by adding a torque sensor and providing feedback control using a microcontroller (MCU).
However, this solution might incur a substantial increase in cost because of the need for a torque sensor, an MCU with real-time control performance, and control software.
So, you face a difficult decision of whether to prioritize system cost or power consumption.
Here comes Toshiba’s MCD incorporating AGC, which has the ability to constantly optimize motor drive current on its own.
More specifically, the MCD with AGC performs feedback control by monitoring the voltage at the last output stage.
It detects load variations and optimizes motor drive current accordingly.
Since the feedback loop exists within the MCD, AGC simplifies system design, compared to the case of using an additional sensor and MCU, and helps reduce power consumption and heat dissipation at considerably lower cost.
Without AGC, extra power is wasted particularly at low torque.
In contrast, AGC constantly supplies drive current with a minimal margin and therefore helps reduce both power consumption and heat dissipation.
How does Closed Loop for
Speed Control stabilize motor rotation?
CASE : 04
―― Is it possible to reduce rpm variations caused by load and supply voltage variations without using a microcontroller?
The rpm of a BLDC motor is affected by load and supply voltage variations.
In addition, the rpm might have variations because of motor-to-motor variations or part-to-part variations of load components. Although conventional MCDs can bring voltage and current into phase based on the rpm signal from a motor, it was necessary to add a feedback control loop to control the motor rpm.
These MCDs need an MCU with sufficient performance and control software as well as the accompanying circuit design, which obviously incur an increase in cost.
This extra cost could be prohibitive for relatively simple and cost-sensitive applications such as fans and pumps.
Toshiba’s Closed Loop for Speed Control provides feedback control on its own.
MCDs with Closed Loop for Speed Control support flexible speed curves.
These MCDs help reduce your design workloads and product costs considerably while stabilizing motor rotation speed and product quality.
Without Closed Loop for Speed Control, extra power is wasted particularly at low torque.
This technology provides feedback to the MCD to control the motor rpm.
An MCU and accompanying control software have conventionally been necessary for motor rpm control whereas the MCD with Closed Loop for Speed Control provides this capability on its own and therefore helps reduce your design workloads and product costs.
How does Ultra-Fine Microstepping reduce the vibration and noise of a motor?
CASE : 05
―― We want to minimize the vibration and noise of a stepping motor.
Are there any good solutions?
We need a 5-A motor to obtain the necessary torque.
Since stepping motors move and hold the rotor position at each step of a full rotation, they tend to generate lots of vibration and noise.
Acoustic noise can be a problem with a high-current, high-torque motor.
In recent years, some home appliances with high-current stepping motors have been designed for use where people live.
Therefore, quiet operation is required for these stepping motors.
In fact, one more factor contributes to the vibration and noise of the motor: the waveform of motor drive current.
With sinusoidal drive current, the rotor moves more smoothly and therefore generates less vibration and noise.
However, the output current from MCDs is a stair-stepped digital approximation of a sine wave, not completely sinusoidal.
To date, each quarter of a sine-wave cycle (90°) has generally been divided into four steps.
Such a coarse-stepped drive current causes unwanted vibration and noise.
To address this problem, Toshiba has developed Ultra-Fine Microstepping technology to divide each quarter of a sine-wave cycle into up to 128 steps.
This technology allows the motor rotor to move smoothly and therefore helps reduce vibration and noise.
However, a waveform close to a sine wave results in a reduction in the average drive current and might cause a lack of motor torque.
Conversely, motors with large torque tend to cause a noise problem, as described above.
To address this problem, Toshiba has released Ultra-Fine Microstepping MCDs with a rated output current of 5 A first.
Conventionally, a full rotation of a stepper motor has generally been divided into coarse steps.
To reduce the vibration and noise of the motor, Toshiba has developed Ultra-Fine Microstepping technology.
Reducing power consumption for low-voltage applications with power supply constraints
CASE : 06
―― At present, we are planning to develop a motor application that operates with two batteries.
Are there any recommended MCDs to maximize the battery life?
Stepping motors are also entering widespread use in low-voltage, low-power-consumption applications.
For example, stepping motors are best suited for small robots.
Motors are widely used in digital cameras, security cameras, and many smart home appliances.
Various types of motors are used according to their applications.
Many of these motor applications operate with small rechargeable or non-rechargeable batteries and therefore impose a severe constraint on power consumption.
Obviously, the manufacturers of motor applications pay attention to the selection of MCDs so as to minimize their power consumption.
In response, Toshiba is expanding the lineup of its MCDs to satisfy the requirements of motor applications that operate with battery or USB power. Specifically, Toshiba has released a low-voltage (2.7-V) MCD and an ultra-low-voltage (1.8-V) MCD for brushed DC motors.
In addition, Toshiba will shortly release a 2.7-V Ultra-Fine Microstepping MCD for stepping motors and is planning MCDs with even lower drive voltage.
MCDs from another company are widely used for low-voltage and ultra-low-voltage applications.
However, their drawback is low power efficiency because of the control circuitry composed of bipolar devices.
In addition, bipolar ICs exhibit considerable power loss and cause a decrease in motor torque. In contrast, Toshiba’s MCDs are composed of FET devices. Because of their high efficiency, Toshiba’s MCDs consume less power and help extend battery life.
Moreover, the low power loss of Toshiba’s MCDs helps reduce a decrease in motor torque.
Our product lineup extends to 2.7 V and lower.
CASE : 07
―― Where can I obtain evaluation and other tools for MCDs incorporating leading-edge technologies such as InPAC and AGC?z
Detailed information about InPAC and AGC is available on Toshiba’s website,which provides videos and illustrated guides on each technology as well as free design packages comprising all the data necessary to create an evaluation board, such as a bill of materials (BOM) list, a schematic, and Gerber data for an application circuit.
The webpages describing each technology have the Download button.
All the tools and design packages become available for download following user registration.
If you want to perform an evaluation more promptly, you can use third-party evaluation boards. At present, 40 evaluation boards are available from Marutsuelec, and 16 from Digi-Key.
In addition, PSpice simulation models for MCDs and other devices are available for download from Toshiba’s website. Click Design / Support from the top bar of our website and then select Simulation Model.
Our website also provides land pattern data in dxf format, which can be imported into design CAD systems.