The NCP1361/66 offers a new solution targeting output power

levels from a few watts up to 20 W in a universal−mains flyback

application. Due to a novel method this new controller offers a

primary−side constant current control, saving secondary−side

components to perform current regulation.

The NCP1361/66 operates in valley−lockout quasi−resonant peak

current mode control mode at nominal load to provide high efficiency.

When the secondary−side power starts diminishing, the switching

frequency naturally increases until a voltage−controlled oscillator

(VCO) takes the lead, synchronizing the MOSFET turn−on in a

drain−source voltage valley. The frequency is thus reduced by

stepping into successive valleys until the number 4 is reached. Beyond

this point, the frequency is linearly decreased in valley−switching

mode until a minimum is hit. Valley lockout during the first four

drain−source valleys prevents erratic discrete jumps and provides

good efficiency in lighter load situations.

Features

• ±10 Current Regulation

• 560 V Startup Current Source

• No Frequency Clamp, 80 or 110 kHz Maximum Switching

Frequency Options

• Quasi−Resonant Operation with Valley Switching

Operation

• 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 Line

with NCP1366 Version

• These are Pb−Free Devices

Typical Applications

• Low power ac−dc Adapters for Chargers

• Ac−dc USB chargers for Cell Phones, Tablets and Cameras