RDK-195: 500mA @ 32Vmax, TRIAC Dimmable, 90 ~ 265VAC

This design features a high power factor (PF) TRIAC dimmable LED driver designed to drive a nominal LED string voltage of 28 V at 0.5 A from an input voltage range of 90 VAC to 265 VAC. The LED driver utilizes the LNK406EG from the LinkSwitch-PH family of ICs.

LinkSwitch-PH ICs allow the implementation of cost effective and low component count LED drivers which both meet power factor and harmonics limits and 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 LNK406EG 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 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 startup time, dimming, flicker and unit to unit consistency. For this design a focus was given to compatibility with as wide a 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 both single input voltage operation, no dimming or operation with a limited range of (higher quality) dimmers.