This application note presents design considerations for LED lamp systems employing Fairchild Semiconductor components. It includes designing the transformer and output filter, selecting the components, and implementing constant-frequency control.
This document presents a design guideline for LED lamp systems utilizing the Primary-Side Regulation (PSR) topology. It focuses on the Fairchild Semiconductor PWM PSR controller FAN103 and the Fairchild Power Switch (FPS) FSEZ1317 to simplify meeting efficiency requirements with fewer external components. The note explains how PSR controls output voltage and current precisely using information from the primary side only, eliminating secondary-feedback circuitry and sensing loss.
The guide details a step-by-step design procedure, including estimating efficiencies, determining the DC link capacitor, and calculating the transformer turns ratio. It covers operation principles of the Discontinuous Conduction Mode (DCM) flyback converter and provides equations for designing the transformer and output filter, as well as implementing constant-current control.
It is typical to select a DC link capacitor as 2-3uF per watt of input power.
The frequency is reduced to 33kHz to prevent CCM operation.