OnSemiNCP1014能源之星离线8WLED驱动方案.docx

On Semi NCP1014能源之星离线8W LED驱动方案 关键词：电源管理,LED驱动器, SMPS On Semi 公司的NCP101x系列自供电单片开关电路,主要用于低待机功耗的离线开关电源(SMPS),集成了固定频率电流模式控制器和700V MOSFET,提供实现可靠低成本电源所需要功能,包括软起动,频率抖动,短路保护,跳频,最大峰值电流设定和动态自供电(不需要辅助线圈).主要用在小功率充电器适配器,USB,家用电器,TV等辅助电源.本文介绍NCP101x系列主要特性,方框图, 6.5W反激转换器和通用火线电压输入的7.0W转换器以及能源之星离线8W LED驱动器参考设计NCP1014LEDGTGEVB电路图和材料清单(BOM).NCP1014: Self-Supplied Monolithic Switcher for Low Standby-Power Offline SMPSThe NCP101X series integrates a fixed?frequency current?mode controller and a 700 V MOSFET. Housed in a PDIP?7, PDIP?7 Gull Wing, or SOT?223 package, the NCP101X offers everything needed to build a rugged and low?cost power supply, including soft?start, frequency jittering, short?circuit protection, skip?cycle, a maximum peak current setpoint and a Dynamic Self?Supply (no need for an auxiliary winding).Unlike other monolithic solutions, the NCP101X is quiet by nature: during nominal load operation, the part switches at one of the available frequencies (65 ? 100 ? 130 kHz). When the current setpoint falls below a given value, e.g. the output power demand diminishes, the IC automatically enters the so?called skip?cycle mode and provides excellent efficiency at light loads. Because this occurs at typically 1/4 of the maximum peak value, no acoustic noise takes place. As a result, standby power is reduced to the minimum without acoustic noise generation.Short?circuit detection takes place when the feedback signal fades away, e.g. in true short?circuit conditions or in broken Optocoupler cases. External disabling is easily done either simply by pulling the feedback pin down or latching it to ground through an inexpensive SCR for complete latched?off. Finally soft?start and frequency jittering further ease the designer task to quickly develop low?cost and robust offline power supplies.For improved standby performance, the connection of an auxiliary winding stops the DSS operation and helps to consume less than 100 mW at high line. In this mode, a built?in latched over