ONSEMI NCP1255 25W离线电流模式PWM控制器参考设计方案

ONSEMI公司的NCP1255是一款soic-8封装的坚固高性能离线高集成PWM控制器，输入电压范围最高可达35V。该控制器具有过功率保护、掉电保护、轻载变频、斜率补偿、内建软启动、过载及短路自动定时恢复等功能。本文首先介绍芯片的简介、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 NCP1255 is a highly integrated PWM controller capable of delivering a rugged and high performance offline power supply in a SOIC−8 package. With a supply range up to 35 V, the controller hosts a jittered 65−kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while freezing the peak current setpoint.

To help build rugged converters, the controller features several key protective features: a brown−out, a non−dissipative Over Power Protection for a constant maximum output current regardless of the input voltage, two latched over voltage protection inputs – either through a dedicated pin or via the Vcc input − and finally, the possibility to externally adjust an auto−recovery timer duration.
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