DER-366 - 20 W high efficiency >86% TRIAC dimmable LED driver for PAR38 lamps

This document is an engineering report describing an isolated power factor dimmable LED driver (power supply) using the LYT4314E from the LYTSwitch family of devices. The DER-366 provides a single 20W (36 VTYPICAL) dimmable constant 550 mA current output over an input voltage range of 190 to 265 VAC. Key design goals are high efficiency to maximize efficacy and small size. This allows the driver to be installed into a PAR38 sized lamp as close as possible to the production design. LYTSwitch ICs enable cost-effective, low component count LED drivers while meeting power factor and harmonic constraints. LYTSwitch driver IC, combines PFC functionality with secondary output constant current into a single switching stage. The topology used is an isolated flyback topology operating in continuous conduction mode. Output current regulation is sensed entirely from the primary side, eliminating the need for secondary feedback components. There is also no need for external current sensing on the primary side as this is performed internally within the IC, further reducing component cost and switching losses. An internal controller adjusts the power MOSFET duty cycle to maintain a sinusoidal input current, thereby maintaining high power factor and low harmonic currents. The LNK4314E also offers a range of sophisticated protection features, including automatic restart for open control loop and output short-circuit conditions. Line overvoltage provides longer line fault and surge tolerance, output overvoltage protects the power supply when the load is disconnected, and accurate hysteretic thermal shutdown ensures safe average PCB temperatures under all conditions. In any LED luminaire, the driver determines many of the performance attributes experienced by the end user, including start-up time, dimming and unit-to-unit consistency. The design is designed to be compatible with the widest possible range of dimmers and the largest possible dimming range. This document contains power supply specifications, schematics, bill of materials, transformer documentation, printed circuit layout, design spreadsheet, and performance data.