原标题：PowerInt LYT2004E 8.6W LED驱动电源参考设计(DER424)

　　powerint公司的LYTSwitch-2系列产品是不需要光耦和次级控制电路的低功率恒流(CC) LED驱动器,包括了750V高压开关MOSFET,创新的ON/OFF控制状态机,用于自偏压的高压开关电流源,降低EMI的频率抖动器,逐个周期的限流和滞后的热关断等功能,无负载功耗低于30mW.主要用于LED灯,顶灯, 照明器具,镇流器和T8管灯.本文介绍了LYTSwitch-2系列产品亮点,功能框图,典型应用电路,以及采用LYT2004E的通用输入22V- 48V/180mA绝缘的反激LED驱动器参考设计424主要特性和技术指标,电路图,材料清单和PCB元件布局图.

　　The LYTSwitch-2 family of ICs dramatically simplifies low power CC LED drivers by eliminating the optocoupler and secondary control circuitry. The family introduces a revolutionary control technique to provide accurate output current regulation, compensating for transformer and external component variations, and device parameter tolerances as well as input voltage variations.

　　The device incorporates a high-voltage switching MOSFET, a novel ON/OFF control state machine, a high-voltage switched current source for self-biasing, frequency jitter to reduce EMI, cycle-by-cycle current limit and hysteretic thermal shutdown circuitry into a monolithic IC. This high level of integration enables highly cost-effective designs with very few external components, reducing solution cost and driver size.

　　LYTSwitch-2 parts use very little energy when the output is unloaded. Practical designs can easily achieve less than 30 mW no-load consumption.

　　The 725 V power MOSFET used in LYTSwitch-2 devices increases the circuits’ ability to withstand input surge. Each package is designed to maximize the creepage distance between high-voltage pins and logic level inputs. This increased pin spacing increases driver lifetime and reliability in polluted environments. The inbuilt protection features also protect the entire circuit from excess temperature operation, greatly increasing lifetime in thermally challenging environments.

　　LYTSwitch-2系列产品亮点:

　　Accurate CC Regulation, Meets ±3% in a Typical Design

　　Controller Automatically Compensates For:

　　Transformer inductance variation

　　External component changes with temperature

　　Input line voltage variations

　　This ensures accurate regulation in production

　　Cost-Effective, Small Size Designs

　　Eliminates the optocoupler and secondary CC control circuitry

　　Eliminates control loop compensation circuitry

　　Frequency jittering greatly reduces EMI filter cost

　　Programmable switching frequency reduces transformer size

　　725 V switching power MOSFET enables clampless flyback designs

　　Advanced Protection/Safety Features

　　Auto-restart protection reduces power delivered by >90% for output short-circuit and control loop faults (open and short-circuit components)

　　Hysteretic thermal shutdown – with automatic recovery Reduced field returns

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

　　EcoSmart™– Energy Efficient

　　No-load consumption <30 mW1

　　No current sense resistors – maximizes efficiency

　　Green Package

　　Halogen free and RoHS compliant package

　　LYTSwitch-2系列应用:

　　LED bulbs, down lights, luminaires, ballasts and T8 tubes

　　图1. LYTSwitch-2系列功能框图

　　图2. LYTSwitch-2系列8.6W LED电源(平均效率>86%,无负载输入功率<30mW)

　　图3. LYTSwitch-2系列无偏压电源的反激电源电路图

　　采用LYT2004E的通用输入22V-48V/180mA绝缘的反激LED驱动器参考设计424

　　This engineering report describes the design for a universal input, 22 V to 48 V, 180 mA LED driver. This power supply utilizes the LYT2004E device from the Power Integrations LYTSwitch-2 family.

　　This document contains the power supply and transformer specifications, schematics, bill of materials, and typical performance characteristics pertaining to this power supply.

　　反激LED驱动器参考设计424主要特性:

　　• Accurate (primary-side control) constant current (CC)

　　• Accurate CC, less than ±5% variation over load and line

　　• Provides ±5% constant voltage (CV)

　　• Wide LED load operating range (22 V to 48 V)

　　• Efficiency >86% at 230 VAC

　　• Low-cost, low component count (21), small size PCB

　　• Fast start-up time (<100 ms) – no perceptible delay

　　• No-load consumption <35 mW at 230 VAC

　　• Integrated protection and reliability features

　　• Output short-circuit protected with auto-recovery

　　• Auto-recovering thermal shutdown with large hysteresis

　　• No damage during brown-out conditions

　　• Easily meets EN55015 and CISPR-22 Class B EMI standards

　　反激LED驱动器参考设计424技术指标:

　　图4. 反激LED驱动器参考设计424外形图

　　图5. 反激LED驱动器参考设计424 PCB外形图:顶层

　　图6. 反激LED驱动器参考设计424 PCB外形图:底层

　　反激LED驱动器参考设计424材料清单: