Application Note AN4339
November 2013
Harjeet Singh
Due to recent directives by the "Bureau of Energy Efficiency" (BEE) to reduce power consumption of consumer loads, it is necessary to analyze energy consumption by each of the house hold loads and implement how the energy can be saved in running such equipment. Some of the major loads that fall under this category are like lighting loads, refrigerators, air-conditioners, fans, televisions, audio equipment and so on. There are developments going on in different segments meet the desired energy saving norms. The fan is one of the major contribution in house hold as well as industrial usages. Currently fans build up with an AC induction motor which is approximately 60 - 70 W power rated. These motors are heavier and less efficient, not more than 50% of overall efficiency.
In the near future these motors will be phased out and instead a BLDC (brushless DC motor) is going to be introduced in fan application. In a practical scenario it is seen that a 40 - 50% lesser power rated motor can provide the same amount of air flow output. That means that the approximately 30 W BLDC based fan system will replace existing 60 - 70 W power consumption with the AC induction motor. This is a huge power saving. Moreover the BLDC motor are much lighter as compared to the heavy AC induction motor.
In this application note the proposed scheme to drive a BLDC fan motor is described. Usually the low voltage DC motor is well suited for this application, mainly a 24 V BLDC motor. The system requires mainly 2 sections: a front-end AC/DC power supply for the universal range followed by a 3-phase bridge inverter to drive a motor. The power supply has to be galvanic isolated having high efficiency, high PF and low THD. For the same the design of single stage high power factor flyback topology using the STMicroelectronics® innovative PFC L6564 controller is considered. The L6564 device is a current mode PFC controller operating in transition mode (TM). The highly linear multiplier, along with a special correction circuit that reduces crossover distortion of the mains current, allows wide range mains operation with an extremely low THD even over a large load range. ...
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BLDC fan solution block diagram scheme
