Linear 公司的LT3799是帶有源PFC的離線(xiàn)絕緣反激LED控制器，TRIAC可調光，PFC大于0.97，不需要光耦合器，諧波含量低，LED電流穩定在±5%，LED開(kāi)路和LED短路保護，主要用在離線(xiàn)4W-100W LED驅動(dòng)和高DC VIN LED應用。本文介紹了LT3799主要特性，方框圖，通用AC輸入TRIAC調光20W 和4W LED驅動(dòng)電路和像應的元器件值。
The LT®3799 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 typically achieves power factors of 0.97. The FAULT pin provides notification of open and short LED conditions.
The LT3799 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.

LT3799主要特性：
Isolated PFC LED Driver with Minimum Number of External Components
TRIAC Dimmable
VIN and VOUT Limited Only by External Components
Active Power Factor Correction (Typical PFC > 0.97)
Low Harmonic Content
No Opto-Coupler Required
Accurate Regulated LED Current (±5% Typical)
Open LED and Shorted LED Protection
Thermally Enhanced 16-lead MSOP Package

LT3799應用：
Offline 4W to 100W+ LED Applications
High DC VIN LED Applications

圖1。LT3799方框圖

圖2。LT3799 90-150VAC輸入TRIAC調光20W LED驅動(dòng)器

圖3。LT3799通用TRIAC調光20W LED驅動(dòng)器
不同輸入電壓的元件值：


圖4。LT3799通用TRIAC調光4W LED驅動(dòng)器