The NCP1611 is active power factor corrected (PFC) controller specifically designed for use as a boost preconverter in ac-dc adapters, flat TVs, lighting ballasts and other medium powered offline applications.The controller is based on an innovative Current Controlled Frequency Foldback(CCFF) method. In this mode, the circuit classically operates in Critical conduction Mode (CrM) when the inductor current exceeds a programmable value. When the current is below this preset level, the NCP1611 linearly reduces the frequency down to about 20 kHz when the current is at a null. CCFF maximizes the efficiency at both nominal and light load. In particular, the standby losses are reduced to a minimum.The controller features a robust suite of protection features to properly handle an array of power supply operating and fault conditions.

• Critical Conduction mode with current controlled frequency foldback
• Dynamic Response Enhancer
• Soft Overvoltage Protection (S-OVP)
• -500 mA/+800 mA Drive Capability
• Valley Turn On
• Wide Vcc Range of 9.5-35V
• Two Vcc Startup Versions: 10.5V (A) and 17V (B)
• AC Line Brownout Detection
• Saturated Inductor and shorted boost or bypass protection
• Open Pin Protection including Ground
• Undervoltage and Fast Over voltage protection
• Near Unity Power Factor
• Cycle-by-cycle current protection