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Driving brushless DC motors at higher efficiencies

How semiconductor advances can drive improved motor control

The move from brushed to brushless DC motors (BLDC) has of itself resulted in a marked improvement in power consumption. The electronic commutation of the rotor, coupled with precise feedback on rotor position, has led to a wide range of BLDC control solutions. But with electric drives consuming around 40% of the world’s electricity worldwide, developers are continuously looking for simple approaches to further reduce power consumption.

BLDC motors are implemented in a wide range of home appliances and industrial applications, especially for pumps and fans. Conventional motor drivers utilize the signals from a Hall sensor to determine rotor position and apply the correct electrical commutation. However, as the rotational speed increases, the phase difference between the voltage applied and the current drawn also gradually increases. This is caused by the impedance of the motor windings. This phase difference results in a reduction in drive efficiency.

To compensate for this, designers must usually measure these losses at varying rotational speeds and apply adjustments in software algorithms, often in a microcontroller’s application code. Compensating for just one rotational speed results in poor efficiency outside of the point of compensation.

In order to simplify the development of high-efficiency BLDC drives, Toshiba has developed Intelligent Phase Control (InPAC) technology. By monitoring the phase of the motor current and comparing it with the rotor angle as supplied by the Hall sensors, the lead angle is automatically adjusted within the control loop. Motor drivers featuring this technology are capable of achieving higher efficiencies than conventional BLDC motor controllers, without the need to manually determine and implement phase corrections.

Devices such as the TC78B016FTG provide 3-phase sine-wave PWM drive output for BLDC control applications. Supporting input voltages of up to 40 V, and drive currents of up to 3 A, it is a fully integrated solution. Rotation speed is determined by either an analog or PWM input signal. Provision is also made for electronic phase difference correction in the case of mechanical shift of the hall sensor.

Toshiba also provide a comprehensive reference design to speed up development with this BLDC motor controller. The package includes an application note, bill-of-materials (BOM), schematic, and gerber files. To download your free InPAC design package, please click here:

Click here to find out more about next generation BLDC motor control

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·Before creating and producing designs and using, customers must also refer to and comply with the latest versions of all relevant TOSHIBA information and the instructions for the application that Product will be used with or for.