NCP1308设计的50W四输出STB电源技术

本文介绍了NCP1308主要特性, 内部电路架构图, 典型应用电路图以及50W四输出机顶盒(STB)电源电路图和材料清单(BOM).

NCP1308主要特性:

Free-Running Borderline/CriTIcal Mode Quasi-Resonant OperaTIon

Current-Mode with Adjustable Skip Cycle Capability

Dynamic Self-Supply Type of VCC

Auto-Recovery Overcurrent ProtecTIon

Improved UVLO for VCC below 10 V

Latching Overvoltage ProtecTIon on VCC

500 mA Peak Current Source/Sink Capability

Internal 1.0 ms Soft-Start

Internal 10us Minimum TOFF

Adjustable Skip Level

Internal Temperature Shutdown

Internal Leading Edge Blanking

Direct Optocoupler Connection

SPICE Models Available for TRANsient Analysis

This is a Pb-Free Device

NCP1308典型应用:

AC-DC Adapters for Notebooks, etc.

Offline Battery Chargers

Consumer Electronics (DVD Players, Set-Top Boxes, TVs, etc.)

Auxiliary Power Supplies (USB, Appliances, TVs, etc.)

图1.NCP1308内部电路架构图

图2.NCP1308典型应用电路图

50W四输出机顶盒(STB)电源

This reference document describes a built--and--tested, GreenPoint® solution for a 40 W (40 W nominal power, 50 W peak power) set--top box (STB) power supply. This document presents the results of various secondary rectification and regulation techniques thatwere used to find the highest practical efficiency scheme for a four--output, 40 watt set top box power supply.

The power supply design is built around ON Semiconductor’s NCP1308 Current--Mode controller, on the primary side, using free running quasi—resonance operation. The secondary side offers four outputs (+5 V, --5 V, 3.3 V and 12 V). The +5 V output is the main channel with the closed PWMloop while the 3.3 Voutput is derived by using the NCP1587 in a buck (step--down) DC—DC topology with synchronous rectification. The 12Voutput is derived from+5 V by stacking the 12 V secondary winding onto the 5 V winding.

图3.参考设计电路简化框图

图4.50W四输出机顶盒(STB)电源外形图

图5.机顶盒(STB)电源电路图

50W四输出机顶盒(STB)电源材料清单(BOM):