Intelligent Phase Control technology optimizes brushless motor performance by capitalizing the brushless motors' efficiency to the maximum.
Brushless motors are used in many applications, powering a wide range of high-speed equipment ranging from home vacuum cleaners to industrial machinery to data center server cooling fans.
A major challenge facing designers is ensuring that the motors they select operate reliably and efficiently. To help achieve these goals, Toshiba has developed its new Intelligent Phase Control motor controller series.
Intelligent phase control
To meet a growing demand for improved energy efficiency and lower noise, equipment designers are increasingly turning to inverters to control brushless motors. With conventional technology, in order to obtain high-level efficiency, it's necessary to adjust the phase, or lead angle, of the motor voltage and motor current for individual motors.
Figure 1. Lead Angle Illustration
A lead angle is the angle of timing at which voltage is advanced to apply to the coil.
It takes some time to apply voltage to the coil until current increases to the maximum value. In a high-speed rotation, a rotor may pass through the next turn-on point before the magnetic drive reaches maximum power. In this case, the rotor power will not be the maximum. To avoid this situation and improve the drive efficiency, a rotor is advanced to a certain angle from the calculated angle. This advanced angle is called a lead angle. A lead angle varies depending on characteristics, rotational speeds, and load conditions of the brushless motors.
Achieving optimal efficiency over a wide range of rotational speeds—from almost zero rotations per minute (rpm) at start-up to high speeds of thousands rpm—requires many characterizations for phase adjustment and can usually optimize at a limited range. Intelligent Phase Control's advantage lies in intelligent phase control, a technology that allows brushless motors to rotate efficiently at high speeds with uniform accuracy.
Toshiba's approach marks a distinct departure from conventional motor controllers. With previous-generation technologies, it was necessary to adjust a phase difference between the voltage and current of a motor at several points in its operating rpm range. Toshiba's Intelligent Phase Control technology eliminates this need, and speeds development, by automatically adjusting the phases of a motor's voltage and current, thereby achieving the highest possible efficiency across the entire operating rpm range only through initialization. Also, Toshiba’s solution achieves flexible rotation speed control by hard logic without the microcontroller, thereby saving additional development efforts.
How it works
When a brushless motor is driven with a sine wave, changes in its rpm resulting from its impedance create a phase difference between its voltage and current, decreasing drive efficiency. To provide the phase adjustment necessary to improve efficiency, Intelligent Phase Control compares the relationship between the current phase (current information) and the voltage phase (Hall-effect signal) and provides feedback to the motor current control signal in order to adjust their phase relationship automatically, leading to higher efficiency.
Intelligent Phase Control instantly detects the motor current phase and feeds back information for auto lead angle control. In sensor-based motor applications, the Hall signal phase is automatically adjusted to match that of the motor drive current. High efficiency is achieved regardless of the motor's rpm, load torque or power supply voltage. Intelligent Phase Control also helps reduce the number of external parts required for lead angle adjustment.
To achieve the highest possible efficiency with conventional motor control technology, it's necessary to adjust a phase difference between the voltage and current of a motor at several points in its operating rpm range. Intelligent Phase Control does away with this requirement, enabling designers to automatically adjust motor voltage and current phases to achieve the highest possible efficiency across the entire operating rpm range only through initialization, reducing the development workload.
For example, at 3,000 rpm, Intelligent Phase Control reduces supply current by approximately 10%, compared with conventional fixed lead angle control.
Optimization and efficiency
To achieve optimal motor efficiency, the lead angle must be adjusted with real-world equipment, although it is controlled based on the information on rotor positions provided by Hall sensors. The lead angle must also be adjusted according to the motor's constants, including rpm and several other factors, even when a motor controller/driver has an auto lead angle control function. Given these critical limitations, a need has emerged over the past several years for an improved control method that reduces designer burden.
Intelligent Phase Control addresses this issue by rapidly detecting the motor current phase and instantly feeding the information back for automatic lead angle control. When a motor application is equipped with a sensor, the phase of the Hall signal is automatically adjusted to match that of the motor drive current. High efficiency is achieved regardless of a motor's rpm, load torque or power supply voltage. Intelligent Phase Control also helps reduce the number of external parts necessary for lead angle adjustment and eliminates the need for any programming related to a motor's changing operating states.
The use of a sine wave drive system with a smooth current waveform also offers the benefit of generating less noise and vibration than motors with a rectangular wave drive system.
Requirements versions and specifications
Intelligent Phase Control devices are available in several versions, each developed to meet a specific design need. The TC78B016FTG is a fully integrated motor control driver rated 40V/3A maximum. This IC requires a power supply operating anywhere in the range of 6 to 36 volts and provides a sine wave drive. Designers can also take advantage of the low ON resistance of 0.24 ohms (total of high and low sides) typical, which reduces the device's self-heating during operation, thereby allowing the IC to generally support 1.0-1.5A applications. Speed is controlled by a simple pulse width modulation (PWM) signal or an analog voltage input. Built-in protections include thermal shutdown, over-current protection and motor lock detection. The part is offered in a compact VQFN32 5x5mm2 package.
The TC78B041FNG and TC78B042FTG are flexible controller products that allow users to tailor the application power requirement and use the proper gate driver and MOSFET for the designs. The TC78B041FNG adopts a SSOP30 type package and the TC78B042FTG adopts a VQFN32 5x5mm2 package.
The TC78B027FTG is a controller with a gate driver where users can select the right MOSFETs for the applications. It also incorporates a one-Hall drive system that allows users to employ a less costly one-sensor brushless motor. The device is housed in a VQFN24 4x4mm2 package.
For more information
Toshiba has over 35 years of experience in the fabrication of motor drivers and offers an extensive portfolio of brushless motor drive controllers with Intelligent Phase Control technology, suitable for various needs. To evaluate your product plan for using a brushless motor incorporating Intelligent Phase Control, reference designs are available to download.
See related product
