原标题：Powerint LNK403-409EG带TRIAC调光LED驱动方案

　　powerint 公司的LinkSwitch-PH 系列LNK403-409EG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。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。

　　The LinkSwitch-PH dramatically simplifies implementation of LED drivers requiring PF >0.9, TRIAC dimmer capability and high efficiency. The single-stage PF and constant current controller eliminates passive circuitry required for power factor correction and electrolytic bulk capacitor. The advanced primary-side control techniques used by the LinkSwitch-PH device provide accurate constant current control while eliminating the need for an optocoupler and secondary-side current control circuitry.

　　LinkSwitch-PH incorporates a 725 V power MOSFET, a continuous-mode PWM controller, a high voltage switched current source for self biasing, frequency jittering, cycle-by-cycle current limit and hysteretic thermal shutdown circuitry, all in a monolithic IC.

　　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