NCP1308設計的50W四輸出STB電源技術

本文介紹了NCP1308主要特性, 內部電路架構圖, 典型應用電路圖以及50W四輸出機頂盒(STB)電源電路圖和材料清單(BOM).

NCP1308控制器把電流模式調制器和退磁檢測器集成在一起,可以在任何的負載/線路條件下保證有更寬的導通模式,過流保護自動恢復,內部軟起動時間1.0s,在AC/DC轉換器和離線電池充電器等有廣泛用途.

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典型應用:

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.)

圖1.NCP1308內部電路架構圖

圖2.NCP1308典型應用電路圖

50W四輸出機頂盒(STB)電源

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.

圖3.參考設計電路簡化框圖

圖4.50W四輸出機頂盒(STB)電源外形圖

圖5.機頂盒(STB)電源電路圖

50W四輸出機頂盒(STB)電源材料清單(BOM):