本文首先介紹了LNK403-409EG主要特性，功能方框圖，以及TRIAC調光和無調光的LED驅動電路圖。接著介紹了采用LNK403-409EG的15W TRIAC調光單級PFC LED驅動器參考設計技術指標，電路圖和材料清單與變壓器電路圖。

LinkSwitch-PH 系列LNK403-409EG是Powerint 公司的集成了725V功率MOSFET，連續模式PWM控制器，用于自偏壓的高壓開關電流源，頻率抖動，逐個周期的電流限制和延遲熱關斷電路，主要用在離線LED驅動器。

LNK403-409EG產品亮點：

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應用：

? Off-line LED driver

圖1。LNK403-409EG功能方框圖

圖2。隔離TRIAC調光通用輸入14W LED驅動器電路圖

圖3。隔離不調光通用輸入7W LED驅動器電路圖

采用LNK403-409EG的TRIAC調光單級PFC LED驅動器參考設計

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.


圖4。LED驅動器參考設計外形圖

LED驅動器參考設計主要特性：
?
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驅動器參考設計主要指標：



圖5。15W LED驅動器參考設計電路圖
LED驅動器參考設計材料清單（BOM）：



圖6。LED驅動器參考設計變壓器電路圖