LNK403-409EG设计的带TRIAC调光LED驱动技术

本文首先介绍了LNK403-409EG主要特性，功能方框图，以及TRIAC调光和无调光的LED驱动电路图。接着介绍了采用LNK403-409EG的15W TRIAC调光单级PFC LED驱动器参考设计技术指标，电路图和材料清单与变压器电路图。

LinkSwitch-PH 系列LNK403-409EG是Powerint 公司的集成了725V功率MOSFET，连续模式PWM控制器，用于自偏压的高压开关电流源，频率抖动，逐个周期的电流限制和延迟热关断电路，主要用在离线LED驱动器。

LNK403-409EG产品亮点：
DramaTIcally Simplifies Off-line LED Drivers
• Flicker-free phase-controlled TRIAC dimming
• Single stage power factor corrected and accurate constant current (CC) output
• Eliminates optocoupler and all secondary current control circuitry
• Eliminates all control loop compensaTIon circuitry
• Simple primary-side PWM dimming interface
• Universal input voltage range
• Enables designs that are electrolyTIc-free
Accurate and Consistent Performance
• Compensates for transformer inductance tolerances
• Compensates for line input voltage variaTIons
• Frequency jittering greatly reduces EMI filter size and costs
Advanced Protection and Safety Features
• Auto-restart for short-circuit protection
• Open circuit fault detection mode
• Automatic thermal shutdown restart with hysteresis
• Meets high voltage creepage requirement between DRAIN and all other signal pins both on PCB and at package
EcoSmart® – Energy Efficient
• Low standby power remote ON/OFF feature (<50 mW at 230 VAC)
• No current sense resistors – maximizes efficiency
• High efficiency operation, >85% achievable
Green Package
• Halogen free and ROHS compliant package
LNK403-409EG应用：
• Off-line LED driver

图1。LNK403-409EG功能方框图

图2。隔离TRIAC调光通用输入14W LED驱动器电路图

图3。隔离不调光通用输入7W LED驱动器电路图
采用LNK403-409EG的TRIAC调光单级PFC LED驱动器参考设计
The document describes a power factor corrected LED driver designed to drive a nominal LED string voltage of 50 V at 0.3 A from an input voltage range of 90 VAC to 265 VAC. The LED driver uses the LNK406EG from the LinkSwitch-PH family by Power Integrations.
LinkSwitch-PH ICs allow the implementation of cost effective and low component count LED drivers which meet both power factor and harmonics limits; and also offer an enhanced end user experience. This includes ultra-wide dimming range (not used in this demo), flicker free operation (even with low cost AC line TRIAC dimmers) and fast, clean turn on.
The topology used is an isolated flyback operating in continuous conduction mode. Output current regulation is sensed entirely from the primary side eliminating the need for secondary side feedback components. No external current sensing is required on the primary side either as this is performed inside the IC further reducing components and losses. The internal controller adjusts the MOSFET duty cycle to maintain a sinusoidal input current and therefore high power factor and low harmonic currents.
The LNK406EG also provides a sophisticated range of protection features including autorestart for open control loop and output short-circuit conditions. Line overvoltage provides extended line fault and surge withstand, output overvoltage protects the supply should the load be disconnect and accurate hysteretic thermal shutdown ensures safe average PCB temperatures under all conditions.
The key goals of this design were low profile and high efficiency. This was to allow the driver board to fit into the space behind the LED load board inside a T8 tube and operate with an acceptable temperature rise. This necessitated careful selection of components and mounting methods but was simpler than alternate solutions due to the low component count required for a primary side regulated LinkSwitch-PH design.
This document contains the LED driver specification, schematic, PCB diagram, bill ofmaterials, transformer documentation and typical performance characteristics.

图4。LED驱动器参考设计外形图
LED驱动器参考设计主要特性：

Low profile design, <10 mm component height
Allows driver board to sit behind LEDs giving uniform illumination in a T8 replacement
tube application

Superior performance and end user experience
Clean monotonic start-up – no output blinking
Fast start-up (<200 ms) – no perceptible delay

Highly energy efficient
≥86% at 115 VAC and ≥87% at 230 VAC

Low cost, low component count and small printed circuit board footprint solution
No current sensing required
Frequency jitter for smaller, lower cost EMI filter components

Integrated protection and reliability features
Output open circuit / output short-circuit protection with auto-recovery
Line input overvoltage shutdown extends voltage withstand during line faults
Auto-recovering thermal shutdown with large hysteresis protects both components
and printed circuit board
No damage during brown-out or brown-in conditions

Meets IEC 61000-3-2 Class C harmonics and EN55015 B conducted EMI
LED驱动器参考设计主要指标：


图5。15W LED驱动器参考设计电路图
LED驱动器参考设计材料清单（BOM）：



图6。LED驱动器参考设计变压器电路图