AN4105

www.DataSheet4U.com www.fairchildsemi.com Application Note AN4105 Design Considerations for Switched Mode Power Supplies Using A Fairchild Power Switch (FPS) in a Flyback Converter Introduction Flyback switched mode power supplies (SMPS) are among the most frequently used power circuits in household and consumer electronics. The basic function of an SMPS is to supply regulated power to the load on the secondary, or output side. An SMPS typically incorporates a power transformer, secondary-side rectifier diodes, a switching semiconductor device with control IC, and peripheral circuitry. If the level of integration of the switching and control circuitry is not high enough, then additional, separate circuits will be required to accommodate all functions. Such additional components raise the overall SMPS cost and not uncommonly reduce reliability. Fairchild Power Switches are highly-integrated ICs for power supply applications. They combine a high-voltage power MOSFET (SenseFET) and pulse width modulation (PWM) based control IC in one package. Moreover, they provide enhanced IC functionality, thereby minimizing the number of additional components needed in an SMPS. Fairchild Power Switch (SPS) ICs are widely used in the power circuits of a variety of equipment, such as color TVs, printers, PCs, monitors, battery chargers and ac adapters. They typically incorporate a variety of enhanced protection functions and they permit a much reduced power consumption in standby modes. This...