Fairchild’s 650V green-mode buck switches offer high efficiency and design scalability

Home appliance, industrial motor and smart meter applications require solutions that provide low standby power in order to achieve energy efficiency for the end user. At the same time, designers need power scalability to increase the power rating of a device for additional system functionality while simplifying designs. To meet this challenge, Fairchild Semiconductor developed the FSL306 and FSL336 650V Green Mode AC buck switches.

These devices offer burst-mode operation with the low available operating current (250 µA) that helps to reduce standby mode power consumption for increased energy efficiency. Power scalability from 0.5 W to 3 W (FSL306) through the adjustable current limit pin helps simplify designs and reduce design time.

The FSL306 and FSL336 provide higher reliability through rich protection features, such as a Safe Auto Restart Mode. After a fault condition, the switch waits 650 ms before restarting. This feature reduces the stress on the system during a long-term fault, improving system reliability.

These devices combine a PWM controller and a discrete MOSFET in a single package. A high-voltage regulator enables operation without the need for an auxiliary bias winding. Using a built-in error amplifier, the FSL306 and FSL336 provide direct feedback without a shunt regulator. This helps to reduce the overall bill of material cost while saving board space.

“Our customers are searching for higher power for their designs because of the added smart functionality and relay functions in their systems,” JaeKuk Ryu, Fairchild’s Home Appliance and Industrial Power Product Line Marketing Manager, said. “To address this, we developed a higher power buck switch that has the lowest RDS(ON) available. The FSL336 features an industry-leading RDS(ON) of 4 ? , which in turn enables our customers to provide the most energy efficient solutions to their end-users.”

Features and Benefits:
•    Built-in avalanche rated 650 V SenseFET; higher avalanche energy at breakdown mode due to vertical DMOS technology
•    Power scalability from 0.5 W to 3 W (FSL306) by using I limit adjustable function pin
•    No-load power consumption: 25 mW at 230 VAC with external bias; 120 mW at 230 VAC without external bias
•    No need for auxiliary bias winding
•    Ultra-low operating current – 250 µA – reduces standby power consumption
•    Fixed 650 ms restart time for safe auto-restart mode of all protection features

The development of these 650 V Green Mode AC Buck Switches leverages Fairchild’s expertise in power semiconductor solutions, offering higher efficiency and increased system reliability. These devices help designers meet the engineering challenges faced when designing low power AC-input power supplies.

Fairchild Semiconductor