LINEAR OFLFINE LED LIGHTING SIMPLIFIED HIGH POWER FACTOR, ISOLATED LED DRIVER NEEDS NO OPTO-ISOLATORS AND IS TRIAC DIMMER COMPATIBLE – DESIGN NOTE 490 WEI GU OWNER'S MANUAL
Summary
The LT3799 is a complete IC solution for isolated flyback converters, ideal for designing high-efficiency offline LED drivers ranging from 4W to over 100W. This manual details its simplified architecture, featuring integrated components that deliver high Power Factor Correction (PFC) and seamless TRIAC dimming compatibility. It provides reliable performance with built-in protections against open or shorted LEDs, making it perfect for professional lighting designers.
Page 1 Text Content
Offl ine LED Lighting Simplifi ed: High Power Factor, Isolated LED Driver Needs No Opto-Isolators and is TRIAC Dimmer Compatible – Design Note 490 Wei Gu Introduction opto-coupler. Its unique bleeder circuit makes the LED
As environmental concerns over traditional lighting in- driver compatible with TRIAC dimmers without additional crease and the price of LEDs decreases, high power LEDs components. Open- and shorted-LED protection ensures are fast becoming a popular lighting solution for offl ine long term reliability.
applications. In order to meet the requirements of offl ine
No-Opto Operation
lighting—such as high power factor, high effi ciency, isola-
Figure 1 shows a complete LED driver solution. The LT3799
tion and TRIAC dimmer compatibility—prior LED drivers
senses the output current from the primary side switch
used many external discrete components, resulting in
current waveform. For a fl yback converter operating in
cumbersome solutions. The LT®3799 solves complexity,
boundary mode, the equation for the output current is:
space and performance problems by integrating all the required functions for offl ine LED lighting. IOUT = 0.5 • IPK • N • (1 – D)
The LT3799 controls an isolated fl yback converter in IPK is the peak switch current, N is the primary to second- critical conduction (boundary) mode, suitable for LED ary turns ratio and D is the duty cycle. The IC regulates
applications requiring 4W to over 100W of LED power. Its
L, LT, LTC, LTM, Linear Technology, the Linear logo and μModule are registered novel current sensing scheme delivers a well-regulated trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
output current to the secondary side without using an
90V TO 270V
BR1L1
AC 33m H
4.7p FC5
VIN DCM D4
VIN_SENSE FB Z1
LT3799
VREF R16
CTRL3 GATE M1 LED
POWER
CTRL2 SENSE
CTRL1 VINTVCC RS
NTC 4.7μF
DN490 F01
FAULTFAULT COMP+CT COMP–
BR1: DIODES, INC. HD06
D1: CENTRAL SEMICONDUCTOR CMR1U-06M
D2, D3: DIODES INC. BAV20W D4: CENTRAL SEMICONDUCTOR CMR1U-02M Z1: FAIRCHILD SMBJ170A Z2: CENTRAL SEMICONDUCTOR CMZ5937B T1: COILCRAFT JA4429-AL M1: FAIRCHILD FDPF15N65
Figure 1. TRIAC Dimmable 20W Offl ine LED Driver Using the LT3799
Page Summary Contents For LINEAR OFLFINE LED LIGHTING SIMPLIFIED HIGH POWER FACTOR, ISOLATED LED DRIVER NEEDS NO OPTO-ISOLATORS AND IS TRIAC DIMMER COMPATIBLE – DESIGN NOTE 490 WEI GU OWNER'S MANUAL
Manual Details
| Brand | High Power |
|---|---|
| Pages | 2 |
| File Size | 121.95 KB |
| Published | May 21, 2026 |
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Frequently Asked Questions
Does the driver maintain performance when using TRIAC dimmers?
Yes, it uses a novel bleeder circuit and incorporates techniques to ensure compatibility with standard TRIAC dimming without an opto-coupler.
What kind of protection features are included?
Yes, the IC provides better output current regulation since its accuracy is barely affected by transformer turns ratio or LED cable voltage drop.
What are the key advantages of using the LT3799?
It greatly simplifies and shrinks offline LED driver solutions by integrating all required functions, eliminating bulky external components.