The NCP1361 offers a new solution targeting output power levels from a few watts up to 20 W in a universal-mains flyback application. Thanks to a novel method this new controller saves the secondary feedback circuitry for constant current regulation while achieving excellent line and load regulation with traditional opto coupler and TL431 voltage reference. The NCP1361 operates in valley lockout quasi-resonant peak current mode control mode at high load to provide high efficiency. When the power on the secondary side starts to diminish, the controller automatically adjusts the duty-cycle then at lower load the controller enters in pulse frequency modulation at fixed peak current with a valley switching detection. This technique allows keeping the output regulation with tiny dummy load. Valley lockout at the first 4 valleys prevent valley jumping operation and then a valley switching at lower load provides high efficiency.

• No frequency clamp, 80 or 110 kHz Maximum Switching Frequency
• Quasi-Resonant with Valley Switching Operation
• Fixed Peak Current & Deep frequency foldback @ light load operation
• Wide Operation VCC range (up to 28 V)
• Cycle by Cycle peak current limit
• CS & Vs/ZCD pin Short and Open Protection
• Internal Temperature Shutdown
• Constant Current Primary-side feedback eliminates secondary controller
• ±10% Current Regulation
• Clamped Gate-drive Output for Mosfet
• Built-in soft-start
• Low Start-up current ( 2 μA typ.)
• Less than 30 mW No-Load Performance at High Line
• These are Pb-Free Devices