High power-factor buck LED driver meets worldwide retrofit lamp requirements

Introduced by Diodes Incorporated and designed to meet or exceed worldwide power-factor regulations for non-dimmable retrofit LED bulbs and tube lighting, the AL1676 universal AC-input LED driver provides a design that also delivers high efficiency and a low BOM cost. Options for the integrated MOSFET allow for 300V to 650V drain voltages and 1A to 4A drain currents in order to suit most 3W to 18W bulb requirements. High power-factor operation is achieved with a single-stage buck converter topology, which uses constant on-time control and a simple closed loop to ensure the driver delivers an accurate constant LED output current with good line and load regulation. Operating in boundary conduction mode eases EMI/EMC design requirements while the ability to detect off-time helps eliminates the need for an auxiliary winding, contributing to the device’s very low BOM count and cost. It includes multiple protection features such as under- and over-voltage, over-temperature and thermal fold-back that all help to increase system reliability within the high ambient temperatures encountered in an LED bulb. The high level of integration coupled with a small 5mm x 6mm SO-7 package also enable a very compact solution size, reusing the same design footprint for different wattage bulbs by virtue of the MOSFET options.