原标题：On Semi NCP4303高效开关电源解决方案

　　On Semi 公司的NCP4303是次级同步整流驱动器，是高效开关电源(SMPS)解决方案。NCP4303具有阈值可调的精密的次级零电流检测，工作模式包括CCM，DCM和QR反激拓扑。工作电压高达30V，具有5A/2.5A峰值沉/源驱动能力，典型应用包括笔记本电脑适配器，大功率密度的AC/DC电源，游戏机和所有高效开关电源。本文介绍了NCP4303主要特性，方框图，ZCD检测电路框图以及LLC转换器，DCM或QR反激转换器与在宽频LLC应用的电路。

　　Secondary Side Synchronous Rectification Driver for High Efficiency SMPS Topologies

　　The NCP4303A/B is a full featured controller and driver tailored to control synchronous rectification circuitry in switch mode power supplies. Thanks to its versatility, it can be used in various topologies such as flyback, forward and Half Bridge Resonant LLC.

　　The combination of externally adjustable minimum on and off times helps to fight the ringing induced by the PCB layout and other parasitic elements. Therefore, a reliable and noise less operation of the SR system is insured.

　　The extremely low turn off delay time, high sink current capability of the driver and automatic package parasitic inductance compensation system allow to maximize synchronous rectification MOSFET conduction time that enables further increase of SMPS efficiency.

　　Finally, a wide operating VCC range combined with two versions of driver voltage clamp eases implementation of the SR system in 24 V output applications.

　　NCP4303主要特性：

　　Self−Contained Control of Synchronous Rectifier in CCM, DCM, and QR Flyback Applications

　　Precise True Secondary Zero Current Detection with Adjustable Threshold

　　Automatic Parasitic Inductance Compensation Input

　　Typically 40 ns Turn off Delay from Current Sense Input to Driver

　　Zero Current Detection Pin Capability up to 200 V

　　Ultrafast Trigger Interface to External Signal for CCM operation

　　Disable Input to Enter Standby or Low Consumption Mode

　　Adjustable Minimum On Time Independent of VCC Level

　　Adjustable Minimum Off Time Independent of VCC Level

　　5 A / 2.5 A Peak Current Sink / Source Drive Capability

　　Operating Voltage Range up to 30 V

　　Gate Drive Clamp of Either 12 V (NCP4303A) or 6 V (NCP4303B)

　　Low Startup and Standby Current Consumption

　　Maximum Frequency of Operation up to 500 kHz

　　SOIC−8 Package

　　These are Pb−Free Devices

　　NCP4303典型应用：

　　Notebook Adapters

　　High Power Density AC/DC Power Supplies

　　Gaming Consoles

　　All SMPS with High Efficiency Requirements

　　图1。NCP4303方框图

　　图2。NCP4303 ZCD检测电路框图

　　图3。NCP4303典型应用案例：LLC转换器

　　图4。NCP4303典型应用案例：DCM或QR反激转换器

　　图5。NCP4303在CCM反激转换器的应用电路图

　　图6。NCP4303在宽频LLC应用的电路图