OnSemiNCP127119V，3.0A通用AC－DC适配器设计方案

OnSemi公司的NCP1271是一款最新的固定频率电流模式PWM开关控制器，具有为低级声频噪声提供可调节的Soft-Skip待机操作模式，为节省待机功耗内部集成高压启动，过载故障检测定时器，内部锁保护功能特性。本文首先介绍NCP1271、基本特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。

The NCP1271 represents a new, pin to pin compatible, generation of the successful 7−pin current mode NCP12XX product series. The controller allows for excellent stand by power consumption by use of its adjustable Soft−Skip mode and integrated high voltage startup

FET. This proprietary Soft−Skip also dramatically reduces the risk of acoustic noise. This allows the use of inexpensive transformers and capacitors in the clamping network. Internal frequency jittering,ramp compensation, timer−based fault detection and a latch input make this controller an excellent candidate for converters where ruggedness and component cost are the key constraints.

NCP1271主要特性：

• Fixed−Frequency Current−Mode Operation with Ramp Compensation and Skip Cycle in Standby Condition

• Timer−Based Fault Protection for Improved Overload Detection

• “Soft−Skip Mode” Technique for Optimal Noise Control in Standby

• Internal High−Voltage Startup Current Source for Lossless Startup

• _5% Current Limit Accuracy over the Full Temperature Range

• Adjustable Skip Level

• Internal Latch for Easy Implementation of Overvoltage and Overtemperature Protection

• Frequency Jittering for Softened EMI Signature

• +500 mA/−800 mA Peak Current Drive Capability

• Sub−100 mW Standby Power can be Achieved

• Pin−to−Pin Compatible with the Existing NCP120X Series

• This is a Pb−Free Device

NCP1271应用领域：

• AC−DC Adapters for Notebooks, LCD Monitors

• Offline Battery Chargers

• Consumer Electronic Appliances STB, DVD, DVDR



图1. NCP1271内部方框图

NCP1271ADAPGEVB方案介绍：

This evaluation board user’s manual presents an example circuit using the NCP1271 (65 kHz version) in a flyback topology. The design steps and subsequent measurements are also included. An Excel based design worksheet is available at www.onsemi.com.

The measurements show that the 19 V, 3.0 A circuit delivers above 85% across a universal input (85 to 265 Vac).The no load standby consumption is 83 mW at 230 Vac and the light load operation is greater than 75% efficient.

NCP1271ADAPGEVB方案原理图：


图2. NCP1271ADAPGEVB方案原理图

NCP1271ADAPGEVB方案材料清单：




PCB元件布局图：




Top View