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Speed-Control Techniques in AC-DC Operated BLDC Applications

Speed-Control Techniques in AC-DC Operated BLDC Applications

To achieve energy efficiency, ceiling fans and ventilation fans are moving from simple alternate-current (AC) induction motors to brushless direct-current (DC) motors (BLDC). An AC-operated BLDC motor requires two sections to run the BLDC motor: the AC-DC power conversion section and the DC to 3-phase AC conversion section. The Texas Instruments reference design, TIDA-00652, helps to meet these challenges of higher efficiency and power factor in a simpler way by using a single-stage power supply to convert the AC mains input into a low-voltage DC output. This reference design also combines a fully integrated and well protected single-chip, DRV10983, sensor-less sinusoidal brushless motor controller for low-noise operation.

For the DRV10983 device, the motor can be controlled directly through PWM, analog, or I 2C inputs. Withthe physical arrangement of ceiling fans, the speed control of an AC-operated BLDC motor can be possible with an infrared (IR) remote or any high-end wireless control. The speed can also be varied with a change in the supply voltage of the DRV10983 device, but with the variation of AC over universal range, the output of AC-DC is regulated to 24 VDC. Therefore the speed of the fan is controlled by providing a fixed DC or PWM signal at the SPEED pin of the DRV10983 device. The speed of the fan can also be controlled using the I 2C input of theDRV10983 device, as demonstrated in the TIDA-00652 reference design.

This application report presents two different ways to control the AC-operated BLDC ceiling fan with existing infrastructure. The first solution is to vary the speed by only toggling the AC mains switch. The second solution is to vary the speed using the TRIAC component similar to an existing AC-operated ceiling fan.

 




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