Offline Isolated Flyback LED Controller with Active PFC

The LT3799-1 is an isolated flyback controller with power factor correction specifically designed for driving LEDs. The controller operates using critical conduction mode allowing the use of a small transformer. Using a novel current sensing scheme, the controller is able to deliver a well regulated current to the secondary side without using an opto-coupler. A strong gate driver is included to drive an external high voltage MOSFET. Utilizing an onboard multiplier, the LT3799-1 typically achieves power factors of 0.97. The FAULT pin provides notification of open and short LED conditions. The LT3799-1 offers improved line regulation over the LT3799, but is not designed for use with a TRIAC dimmer.

The LT3799-1 uses a micropower hysteretic start-up to efficiently operate at offline input voltages, with a third winding to provide power to the part. An internal LDO provides a well regulated supply for the part’s internal circuitry and gate driver.

Triac Dimmable

LED Current Regulator

LT3799

Yes

± 10%

LT3799-1

No

± 5%

Applications

* Offline 4W to 100W+ LED Applications

* High DC VIN LED Applications

* Isolated PFC LED Driver with Minimum Number of External Components* VIN and VOUT Limited Only by External Components* Active Power Factor Correction (Typical PFC > 0.97)* Low Harmonic Content