原标题：Powerint LNK454DG RDR268超小型LED驱动方案

　　powerint 公司的RD-268是采用LinkSwitchTM-PL系列LNK454DG的1.1W PFC LED驱动器(非绝缘)参考设计,单路恒流输出366mA,LED电压3.0V,通用85 VAC到265 VAC, 47 Hz 到63 Hz输入,功率系数大于0.85,THD小于25%,具有很小的尺寸,可以装入枝状大烛台的有限空间.本文介绍了LinkSwitch-PL系列产品的亮点, 功能方框图, 典型应用电路图, 替代A19白炽灯的5W 15V LED驱动电路以及采用LinkSwitchTM-PL系列 LNK454DG的1.1W PFC LED驱动器(非绝缘)参考设计RD-268电路图和材料清单(BOM).

　　The LinkSwitch-PL family enables a very small and low cost single-stage power factor corrected constant current driver for solid state lighting. Optimized for direct LED current sensing, the LinkSwitch-PL operates over a wide input voltage range delivering an output power of up to 16 W. The LinkSwitch-PL control algorithm provides flicker-free TRIAC dimming with minimal external components.

　　Each device incorporates a 725 V rated power MOSFET, a novel discontinuous mode variable frequency variable on-time controller, frequency jitter, cycle by cycle current limit and hysteretic thermal shutdown in a monolithic 4-pin IC, available in SO-8C, eSOP-12, and eDIP-12 packages.

　　LinkSwitch-PL系列产品亮点:

　　Dramatically Simplifies Off-line LED Drivers

　　• Flicker-free phase-controlled TRIAC dimming

　　• Single stage power factor correction and accurate constant current (CC) output

　　• Very low component count with small non-electrolytic bulk capacitor for compact replacement lamp designs

　　• Compact SO8, eSOP, and eDIP packages

　　• Completely eliminates control loop compensation

　　Advanced Performance Features

　　• Optimized for non-isolated flyback designs

　　• Frequency jitter greatly reduces EMI filter size and costs

　　• Low dissipation direct sensing of LED current

　　Advanced Protection and Safety Features

　　• Cycle skipping regulation for abnormally low output power to clamp peak output current delivered

　　• 725 V integrated power MOSFET allows small bulk capacitance and maximizes power capability

　　• Short-circuit, overload, open feedback and output overvoltage protection

　　• Hysteretic thermal shutdown

　　• Meets high-voltage creepage between DRAIN and all other pins both on PCB and at package

　　EcoSmart™ - Energy Efficient

　　• High power factor optimizes system lumen per input VA

　　• Control algorithm balances switching and conduction losses over line and load to maintain optimum efficiency

　　图1.LinkSwitch-PL系列功能方框图

　　图2.LinkSwitch-PL系列典型应用电路图

　　图3.替代A19白炽灯的5W 15V LED驱动电路

　　采用LinkSwitchTM-PL LNK454DG的1.1W PFC LED驱动器(非绝缘)参考设计

　　Reference Design Report for a 1.1 W Power Factor Corrected LED Driver (Non-Isolated) Using LinkSwitchTM-PL LNK454DG

　　This document is an engineering report describing a non-isolated LED driver (power supply) utilizing a LNK454DG from the LinkSwitchTM-PL family of devices. It contains the power supply specification, schematic, bill of materials, transformer documentation,printed circuit layout, and performance data.

　　The RD-268 provides a single constant current output of 366 mA with a nominal LED voltage of 3 V.

　　The board was optimized to operate over a universal AC input voltage range (85 VAC to 265 VAC, 47 Hz to 63 Hz) but suffers no damage over an input range of 0 VAC to 300 VAC. This increases field reliability and lifetime during line sags and swells.Key benefits of this design are the very high power factor (>0.85), low THD (<25%) and low harmonic content (a significant challenge due to the low output power) and the ability to fit inside the limited space of a candelabra size lamp base.

　　High PF is a requirement or desire in many commercial applications, for example large chandeliers in hotel foyers. Here a large number of lamps (25 to >200) are connected in parallel however by using individual lamps that have PFC allows the overall fixture to meet PFC and THD requirements with the large energy savings that come from using LEDs vs. incandescent lamps.

　　The form factor of the board was chosen to meet the requirements for standard candelabra shaped LED replacement lamps. The output is non-isolated and requires the mechanical design of the enclosure to isolate the output of the supply and the LED load from the user.

　　1.1W PFC LED驱动器(非绝缘)参考设计主要特性:

　　Single stage power factor correction and accurate constant current (CC) output

　　Low cost, low component count and small PCB footprint solution

　　Superior performance and end user experience

　　Clean monotonic start-up – no output blinking

　　Fast start-up (<300 ms) – no perceptible delay

　　Universal input

　　Integrated protection and reliability features

　　Output open-circuit protected /output short-circuit protected with auto-recovery

　　Auto-recovering thermal shutdown with large hysteresis protects both components and printed circuit board

　　No damage during brown out conditions

　　Extended pin creepage distance between device DRAIN pin and other pins for reliable operation in high pollution and humid environments

　　Surge protected for high reliability

　　Meets IEC ringwave and differential mode surge

　　Meets EN55015 conducted EMI

　　PF >0.9 at 115 VAC and PF>0.85 at 230 VAC

　　%ATHD <15% at 115 VAC and <25% at 230 VAC

　　Meets EN61000-3-2 harmonic current requirements

　　电源指标:

　　图4.参考设计RD-268外形图

　　图5.装在枝状大烛台基座的RD-268驱动器板外形图(金属部分是LED散热器)

　　图6.RD-268参考设计电路图

　　RD-268参考设计材料清单(BOM):