Onsemi NCP1361

Description

The NCP1361/66 offers a new solution targeting output powerlevels from a few watts up to 20 W in a universal−mains flybackapplication. Due to a novel method this new controller offers aprimary−side constant current control, saving secondary−sidecomponents to perform current regulation.The NCP1361/66 operates in valley−lockout quasi−resonant peakcurrent mode control mode at nominal load to provide high efficiency.When the secondary−side power starts diminishing, the switchingfrequency naturally increases until a voltage−controlled oscillator(VCO) takes the lead, synchronizing the MOSFET turn−on in adrain−source voltage valley. The frequency is thus reduced bystepping into successive valleys until the number 4 is reached. Beyondthis point, the frequency is linearly decreased in valley−switchingmode until a minimum is hit. Valley lockout during the first fourdrain−source valleys prevents erratic discrete jumps and providesgood efficiency in lighter load situations.

Features

±10% Current Regulation

• 560 V Startup Current Source
• No Frequency Clamp, 80 or 110 kHz Maximum SwitchingFrequency Options
• Quasi−Resonant Operation with Valley SwitchingOperation
• Fixed Peak Current & Deep Frequency Foldback @Light Load Operation.
• External Constant Voltage Feedback Adjustment
• Cycle by Cycle Peak Current Limit
• Built−In Soft−Start
• Over & Under Output Voltage Protection
• Wide Operation VCC Range (up to 28 V)
• Low Start−up Current (2.5 A typ.) with NCP1361
• Clamped Gate−drive Output for MOSFET
• CS & Vs/ZCD pin Short and Open Protection
• Internal Temperature Shutdown
• Less than 30 mW No−Load Performance at High Linewith NCP1366 Version
• These are Pb−Free Devices

Typical applications

• Ac−dc USB chargers for Cell Phones, Tablets and cameras
• Low power ac−dc Adapters for Chargers

More information

• Datasheet
• IC product information