Linear LT3799带PFC离线绝缘反激LED控制方案

    Linear 公司的LT3799是带有源PFC的离线绝缘反激LED控制器，TRIAC可调光，PFC大于0.97，不需要光耦合器，谐波含量低，LED电流稳定在±5%，LED开路和LED短路保护，主要用在离线4W-100W LED驱动和高DC VIN LED应用。本文介绍了LT3799主要特性，方框图，通用AC输入TRIAC调光20W 和4W LED驱动电路和像应的元器件值。

    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应用：

Offline 4W to 100W+ LED Applications

High DC VIN LED Applications

图1。LT3799方框图

图2。LT3799 90-150VAC输入TRIAC调光20W LED驱动器

图3。LT3799通用TRIAC调光20W LED驱动器
不同输入电压的元件值：


图4。LT3799通用TRIAC调光4W LED驱动器