DER-277: 21V @ 380mA, 90 ~ 265VAC in

The document describes a power-factor corrected dimmable LED driver designed to drive an LED string of 18 V at a current of 0.38 A (both nominal) from an input voltage range of 90 VAC to 265 VAC. The LED driver utilizes the LNK403EG from Power Integrations.The design specifically eliminates electrolytic capacitors which limit operating life, especially when operated at high temperature.

LinkSwitch-PH ICs allow the implementation of cost effective and low component count LED drivers which both meet power factor and harmonics limits but also offer enhanced end user experience. This includes ultra-wide dimming range, flicker-free operation (even with low cost with AC line TRIAC dimmers) and fast, clean turn on.

The topology used is an isolated flyback operating in continuous conduction mode. Output current regulation is sensed entirely from the primary side eliminating the need for secondary side feedback components. No external current sensing is required on the primary side either as this is performed inside the IC further reducing components and losses. The internal controller adjusts the MOSFET duty cycle to maintain a sinusoidal input current and therefore high power factor and low harmonic currents.

The LNK403EG also provides a sophisticated range of protection features including auto-restart for open control loop and output short-circuit conditions. Line overvoltage provides extended line fault and surge withstand, output overvoltage protects the supply should the load be disconnect 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 customer (user) including start-up time, dimming, flicker and unit to unit consistency. For this design a focus was given to compatibility with as wider range of dimmers and as large of a dimming range as possible, at both 115 VAC and 230 VAC. However simplification of the design is possible for single input voltage operations, non-dimming or operation with a limited range of (higher quality) dimmers.

This document contains the LED driver specification, schematic, PCB diagram, bill of materials, transformer documentation and typical performance characteristics.