描述 Description

The NCP1351 is a current mode controller targeting low power off line flyback Switched Mode Power Supplies (SMPS) where cost is of utmost importance. Based on a fixed peak current technique (quasi fixed TON), the controller decreases its switching frequency as the load becomes lighter. As a result, a power supply using the NCP1351 naturally offers excellent no load power consumption, while optimizing the efficiency in other loading conditions. When the frequency decreases, the peak current is gradually reduced down to approximately 30% of the maximum peak current to prevent transformer mechanical resonance. The risk of acoustic noise is thus greatly diminished while keeping good standby power performance.An externally adjustable timer permanently monitors the feedback activity and protects the supply in presence of a short circuit or an overload. Once the timer elapses, NCP1351 stops switching and stays latched for version A, and tries to restart for Version B.The internal structure features an optimized arrangement which allows one of the lowest available startup current, a fundamental parameter when designing low standby power supplies. The negative current sensing technique minimizes the impact of the switching noise on the controller operation and offers the user to select the maximum peak voltage across his current sense resistor. Its power dissipation can thus be application optimized.Finally, the bulk input ripple ensures a natural frequency smearing which smooths the EMI signature.

特性 Features

? Quasi fixed TON, Variable TOFF Current Mode Control
? Natural frequency foldback
? Frequency foldback with Peak Current Compression
? Noise free & improved efficiency in light load
? Short circuit protection (latchedA version or auto restart B version)
? Independent of the auxiliary Winding
? Primary or secondary side regulation
? Dedicated Latch Input for OTP, OVP
? Low start-up current
? Natural frequency jittering
? Negative current sensing with programmable current sense resistor

應(yīng)用 Application

? Auxiliary Power Supply
? Off-line battery chargers
? Printers
? Adapters

簡介

NCP1351屬于集成電路（IC）的ACDC轉(zhuǎn)換器離線開關(guān)。由制造生產(chǎn)的NCP1351AC DC 轉(zhuǎn)換器，離線開關(guān)該系列是元器件級控制產(chǎn)品，用于構(gòu)建將交流市電轉(zhuǎn)換為直流電（通常電壓大幅降低）的設(shè)備。集成和未集成系統(tǒng)主要開關(guān)元件的器件均包括在內(nèi)。由于高輸入輸出電壓比，以及此類系統(tǒng)中通常需要隔離，這些器件通常與外部變壓器配合使用。盡管通常使用定制變壓器來實現(xiàn)此用途，但也有許多專門用于此用途的庫存產(chǎn)品，請參見“開關(guān)轉(zhuǎn)換器，SMPS 變壓器”標題。