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SG1540/SG2540/SG3540
OFF-LINE START-UP CONTROLLER
DESCRIPTION
The SG1540 is an integrated circuit designed to efficiently provide start-up power from a high-voltage DC bus to a PWM control circuit in a switching power supply. When used on the primary side, it reduces start-up current to less than 1mA and allows any standard PWM control circuit to be used as a primary-side controller. When used to power a controller on the secondary side, it efficiently eliminates the need for a heavy 50/60Hz line transformer with its associated low frequency magnetic fields.
The circuit consists of three sections: a micropower bandgap comparator/power switch referenced to 2.
SG1540 Datasheet
