Burst-mode operation and 250-µA operating current helps reduce standby-mode power consumption in Fairchild Semiconductor’s FSL306 and FSL336 650-V Green Mode ac buck switches. No-load power consumption is 25 mW at 230 V ac with external bias, and 120 mW at 230 V ac without external bias. In addition, power scalability from 0.5 to 3 W (FSL306) through the adjustable current-limit pin helps facilitate design. Thanks to vertical DMOS technology, higher avalanche energy is available at breakdown mode via a built-in avalanche rated 650-V SenseFET. Reliability is enhanced through various protection features, such as a safe auto restart mode—after a fault condition, the switch waits 650 ms before restarting. The switches combine a pulse-width-modulation (PWM) controller and a discrete MOSFET in one package. A high-voltage regulator eschews the need for auxiliary bias winding. To save space, a built-in amplifier provides direct feedback without a shunt regulator. Applications include home appliances, industrial motors, and smart meters.