DER-366: 550mA @ 39V Max, 190 ~ 265VAC in

This document is an engineering report describing an isolated power factor dimmable
LED driver (power supply) utilizing a LYT4314E from the LYTSwitch family of devices.

The DER-366 provides a single 20 W (36 VTYPICAL) dimmable constant 550 mA current output from an input voltage range of 190 to 265 VAC.

The key design goals were high efficiency to maximize efficacy and small size. This
allowed the driver to fit into PAR38 sized lamps and be as close to a production design
as possible.

LYTSwitch ICs allow the implementation of cost effective and low component count LED
drivers which both meet power factor and harmonics limits. The LYTSwitch driver IC,
combines the PFC function and secondary output constant current into a single switching
stage.

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 feedback components. No external current sensing is required on the primary side either as this is performed inside the IC, further reducing component costs and
switching losses. The internal controller adjusts the power MOSFET duty cycle to
maintain a sinusoidal input current and therefore high power factor and low harmonic
currents.

The LYT4314E also provides a sophisticated range of protection features including autorestart 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 and unit to unit consistency.
This design features compatibility with as wide a range of dimmers and as large of a
dimming range as possible.

The document contains the power supply specification, schematic, bill of materials,
transformer documentation, printed circuit layout, design spreadsheet and performance
data.