基于iW3620的40W AC-DC LED驅動方案

iW3620是iWatt公司的高性能AC/DC離線LED驅動器，器件在高負載條件下工作在準諧振模式，以得到高的效率和各種內置的保護特性，降低EMI，工作頻率高達130kHz，通用輸入電壓85 Vac到 264 Vac，可驅動40W 的LED照明。本文介紹了iW3620主要特性以及典型應用電路。

iW3620：Digital PWM Constant Current Controller for AC/DC LED Driver

The iW3620 is a high performance AC/DC offline LED driver which uses digital control technology to build peak current mode PWM flyback power supplies. The device operates in quasi-resonant mode at heavy load to provide high efficiency along with a number of key built-in protection features while minimizing the external component count, simplifying EMI design and lowering the total bill of material cost. The iW3620 removes the need for secondary feedback circuitry while achieving excellent line and load regulation. It also eliminates the need for loop compensation components while maintaining stability over all operating conditions. Pulse-by-pulse waveform analysis allows for a loop response that is much faster than traditional solutions, resulting in improved dynamic load response. The built-in current limit function enables optimized transformer design in universal off-line applications over a wide input voltage range.

iW3620主要特性：

Primary-side feedback eliminates opto-isolators and simplifies design

Quasi-resonant operation for highest overall efficiency and low EMI

Up to 130 kHz switching frequency enables small size

Very tight LED constant current regulation

Built-in output constant-current control with primary-side feedback for LED driver.

Low start-up current (10 μA typical)

Built-in soft start

Built-in short circuit protection and output overvoltage protection

Current sense resistor short protection

Over-temperature Protection

Open circuit protection

Universal input range from 85 Vac to 264 Vac

Single-fault protection

Small input bulk capacitor

Long MTBF

High efficiency

iW3620應用：

Solid State LED lighting for incandescent, halogen, and fluorescent tube replacement


圖1 iW3620典型應用電路