基于LinkSwitch-PH設計的14W TRIAC調光LED驅動方案
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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.
LinkSwitch-PH系列主要特性:
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® C Energy Efficient
Low standby power remote ON/OFF feature (50 mW at 230 VAC)
No current sense resistors C maximizes efficiency
High efficiency operation, >85% achievable
Green Package
Halogen free and ROHS compliant package
LinkSwitch-PH系列應用:
Off-line LED driver
圖1.LinkSwitch-PH系列功能方框圖
圖2.LinkSwitch-PH系列TRIAC調光14W LED驅動器電路圖
圖3.LinkSwitch-PH系列TRIAC調光7W LED驅動器電路圖
TRIAC調光14W LED驅動器參考設計
Reference Design Report for a High Efficiency (≥85%), High Power Factor (>0.9) TRIAC Dimmable 14 WTYP LED Driver Using LinkSwitch®-PH LNK406EG
參考設計主要特性和指標:
Superior performance and end user experience
TRIAC dimmer compatible (including low cost leading edge type)
No output flicker
>1000:1 dimming range
Clean monotonic start-up C no output blinking
Fast start-up (300 ms) C no perceptible delay
Consistent dimming performance unit to unit
Highly energy efficient
≥85% at 115 VAC, ≥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 protected 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 61000-4-5 ringwave, IEC 61000-3-2 Class C harmonics and EN55015 B conducted EMI
The document describes a high power-factor TRIAC dimmable LED driver designed to drive a nominal LED string voltage of 28 V at 0.5 A from an input voltage range of 90 VAC to 265 VAC. The LED driver utilizes the LNK406EG from the LinkSwitch-PH family of ICs.
LinkSwitch-PH ICs allow the implementation of cost effective and low component count LED drivers which both meet power factor and harmonics limits but also offer enhanced end user experience. This includes ultra-wide dimming range, flicker free operation (even with low cost with 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.
In any LED luminaire the driver determines many of the performance attributes experienced by the end customer (user) including startup time, dimming, flicker and unit to unit consistency. For this design a focus was given to compatibility with as wider range of dimmers and as large of a dimming range as possible, at both 115 VAC and 230 VAC. However simplification of the design is possible for both single input voltage operation, no dimming or operation with a limited range of (higher quality) dimmers.
This document contains the LED driver specification, schematic, PCB diagram, bill of materials, transformer documentation and typical performance characteristics.
圖4.TRIAC調光14W LED驅動器參考設計外形圖
參考設計電源指標:
圖5.TRIAC調光14W LED驅動器參考設計電路圖
參考設計材料清單(BOM):
圖6.變壓器電連接圖
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