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® – 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
LinkSwitch-PH系列应用:
• Off-line LED driver
图1.LinkSwitch-PH系列功能方框图
图2.LinkSwitch-PH系列TRIAC调光14W LED驱动器电路图
图3.LinkSwitch-PH系列TRIAC调光7W LED驱动器电路图
TRIAC调光14W LED驱动器参考设计
Reference Design Report for a High Efficiency (≥85%), High Power Factor (>0.9) TRIAC Dimmable 14 WTYP LED Driver Using LinkSwitch®-PH LNK406EG
参考设计主要特性和指标:
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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 – no output blinking
Fast start-up (300 ms) – 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
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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.
图4.TRIAC调光14W LED驱动器参考设计外形图
参考设计电源指标:
图5.TRIAC调光14W LED驱动器参考设计电路图
参考设计材料清单(BOM):
图6.变压器电连接图
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