Switched Voltage Regulator ICâ€s Part 1

The 6-pin PFC controller NCP1602 is designed to drive PFC boost stages. It is based on an innovative Valley Synchronized Frequency Fold-back (VSFF) method. In this mode, the circuit classically operates in Critical conduction Mode (CrM) when Vcontrol voltage exceeds a programmable value Vctrl,FF. When Vcontrol is below this preset level Vctrl,FF, the NCP1602 linearly decays the frequency down to about 30 kHz until Vcontrol reaches the SKIP mode threshold. VSFF maximizes the efficiency at both nominal and light load. In particular, the stand-by losses are reduced to a minimum. Like in FCCrM controllers, internal circuitry allows near-unity power factor even when the switching frequency is reduced. Housed in a TSOP6 package, the circuit also incorporates the features necessary for robust and compact PFC stages, with few external components.

• Near-Unity Power Factor
• Critical Conduction Mode (CrM)
• Valley Synchronized Frequency Fold-back (VSFF): Low Frequency Operation is Forced at Low Current Levels
• Works With or Without a Transformer w/ ZCD Winding (simple inductor)
• On-time Modulation to Maintain a Proper Current Shaping in VSFF Mode
• Skip Mode at Very Low Load Current
• Fast Line / Load Transient Compensation (Dynamic Response Enhancer)
• Valley Turn-on
• High Drive Capability: -500 mA / +800 mA
• VCC Range: from 9.5 V to 30 V
• Line Range Detection for Reduced Crossover Frequency Spread
• This is a Pb-Free Device

Safety Features

• Thermal Shutdown
• Non-latching, Over-Voltage Protection
• Second Over-Voltage Protection
• Brown-Out Detection
• Over Current Limitation
• Disable Protection if the Feedback Pin is Not Connected
• Low Duty-Cycle Operation if the Bypass Diode is Shorted
• Open Ground Pin Fault Monitoring