Primary-side-control LED driver enables high power factor retrofit LED lamps

September 30, 2013 // By Graham Prophet
Diodes Inc. has announced the AP1684, a power factor-corrected AC-DC LED driver suiting a variety of offline LED lamp types, including E26, GU10, PAR and T8.

Using pulse-frequency modulation technology and operating in boundary-conduction mode, this device provides tight current regulation to an accuracy of ±2%, while achieving a power factor of .97 and THD of less than 20%. Helping to significantly reduce circuit BOM cost, this primary-side driver removes the need for opto-coupler, secondary-side control and loop-compensation circuitry. Driving an external bipolar junction transistor, the AP1684 requires only a small external component count and coupled with its SO8 packaging, enables lamp designers to reduce PCB footprint, increase power density and raise overall product reliability.

The driver keeps start-up and operating currents low and uses dynamic base driver control and valley-mode switching to minimise transition loss and achieve high efficiency, typically 93%. The AP1684’s circuit protection features include over-voltage, short-circuit and over-temperature facilities. They cost $0.18 (50k).

Diodes; www.diodes.com