DER-427 - 33W dimmable LED driver for T8 tubes

The engineering report describes a wide output voltage range isolated flyback LED driver using the LYT4325E from the LYTSwitch-4 family of devices. The DER-427 provides a constant output current of 350 mA over an output voltage range of 45 V to 95 V and supports an input range of 170 VAC to 300 VAC. This power supply complies with JEL 801 requirements and provides 0 V to 10 V analog dimming for T8 tube applications. The LYTSwitch-4 driver IC combines PFC functionality (to meet power factor and harmonic requirements) and constant current driver into a single conversion stage. The topology used is an isolated flyback topology operating in continuous conduction mode. Constant current and dimming adjustments are achieved through a secondary feedback control circuit utilizing a quad operational amplifier. The LYTSwitch-4 controller adjusts the power MOSFET duty cycle to maintain sinusoidal input current, providing high power factor and low harmonic current. The LYT4325E also provides comprehensive protection features, including auto-restart to protect against open control loop and output short-circuit fault conditions, as well as line overvoltage and overtemperature protection. Line overvoltage provides longer line fault and surge tolerance. Output overvoltage protects the power supply if the load is disconnected, while accurate hysteretic thermal shutdown ensures safe PCB temperatures are maintained under all conditions. This document contains power supply specifications, schematics, bill of materials, transformer documentation, printed circuit layout, design spreadsheet, and performance data