原标题：OnSemi NCL30081 3.6W反激式阶梯可调光LED设计方案

　　OnSemi公司的NCL30081是一款定位在隔离反激式拓扑和非隔离恒流拓扑的PWM电流模式控制器。该控制器采用准谐振模式提供高效率，这种新颖的控制方法可以从原边精确控制输出恒定LED电流，该控制输出通过副边反馈电路系统、偏置电路和一个光耦合器实现。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。

　　The NCL30081 is a PWM current mode controller targeting isolated flyback and non−isolated constant current topologies. The controller operates in a quasi−resonant mode to provide high efficiency. Thanks to a novel control method, the device is able to precisely regulate a constant LED current from the primary side. This removes the need for secondary side feedback circuitry, biasing and an optocoupler.

　　The device is highly integrated with a minimum number of external components. A robust suite of safety protection is built in to simplify the design. This device is specifically intended for very compact space efficient designs. It supports step dimming by monitoring the AC line and detecting when the line has been toggled on−off−on by the user to

　　reduce the light intensity in 5 steps down to 5% dimming.

　　NCL30081主要特性：

　　• Quasi−resonant Peak Current−mode Control Operation

　　• Primary Side Sensing (no optocoupler needed)

　　• Wide VCC Range

　　• Precise LED Constant Current Regulation ±1% Typical

　　• Line Feed−forward for Enhanced Regulation Accuracy

　　• Low LED Current Ripple

　　• 250 mV ±2% Guaranteed Voltage Reference for Current Regulation

　　• ~ 0.9 Power Factor with Valley Fill Input Stage

　　• Low Start−up Current (10 _A typ.)

　　• Small Space Saving Low Profile Package

　　• 5 State Quasi−log Dimmable

　　• Wide Temperature Range of −40 to +125°C

　　• Pb−free, Halide−free MSL1 Product

　　• Robust Protection Features

　　♦ Over Voltage / LED Open Circuit Protection

　　♦ Secondary Diode Short Protection

　　♦ Output Short Circuit Protection

　　♦ Shorted Current Sense Pin Fault Detection

　　♦ Latched and Auto−recoverable Versions

　　♦ Brown−out

　　♦ VCC Under Voltage Lockout

　　♦ Thermal Shutdown

　　NCL30081应用：

　　• Integral LED Bulbs

　　• LED Power Driver Supplies

　　• LED Light Engines

　　图1. NCL30081内部方框图

　　NCL30081方案介绍：

　　This documentation package covers an NCL30081 LED driver for use in a GU10 based LED lamp. The output is mains isolated by double insulation. Maximum input power is 5 W. The ECA (Electronic Circuit Assembly) supports 2 versions; one step dimming and one non-dimming version. The version is controlled through minor bill-of-material changes. The LED current dims in 5 discrete levels sequentially by detecting the interruption of the AC mains briefly (about 1 s) to step the LED current down one level until it cycles back to full current.

　　NCL30081方案原理图：

　　图2. NCL30081方案原理图

　　NCL30081方案材料清单：

　　PCB元件布局图：