DER-637 - 35 W High Power Factor, Isolated Flyback Switched Valley-Fill PFC LED Driver

This engineering report describes a constant voltage (CV) output 35 W isolated flyback power supply with a single-stage power factor correction circuit for LED lighting applications. This power supply is designed to provide a constant 12 V voltage on a 0 A to 2.92 A output current load. It is also capable of providing a 2.98 A constant current output for LED lighting applications. The board is optimized to operate over an input voltage range of 140 VAC to 320 VAC. The LYTSwitch-6 IC combines primary, secondary and feedback circuits in a single surface mount offline flyback switch IC. It contains the primary FET, primary side controller and secondary side synchronous rectification controller. The device also features innovative FluxLink™ technology that safely bridges the isolation barrier and eliminates the need for an optocoupler. A Switched Valley-Fill PFC circuit has been added to meet high PF requirements in lighting applications. The energy stored on the PFC inductor is transferred to the load via direct energy transfer, thereby reducing power losses. The DER-637 uses a LYTSwitch-6 IC, which provides accurate and fast transient response, constant voltage power supply, and high power factor over the entire input range. The key design goals are to achieve high efficiency and high power factor over the entire input voltage range. This document contains power supply specifications, schematics, bill of materials, transformer documentation, printed circuit board layout, and performance data.