This combination IC integrates power factor correction (PFC) and

quasiïresonant flyback functionality necessary to implement a

compact and highly efficient Switched Mode Power Supply for an

adapter application.

The PFC stage exhibits nearïunity power factor while operating in a

Critical Conduction Mode (CrM) with a maximum frequency clamp.

The circuit incorporates all the features necessary for building a robust

and compact PFC stage while minimizing the number of external

components.

The quasiïresonant currentïmode flyback stage features a

proprietary valleyïlockout circuitry, ensuring stable valley switching.

This system works down to the 4th valley and toggles to a frequency

foldback mode with a minimum frequency clamp beyond the 4th

valley to eliminate audible noise. Skip mode operation allows

excellent efficiency in light load conditions while consuming very low

standby power consumption.

Common General Features

• Wide VCC Range from 9 V to 30 V with Builtïin Overvoltage

Protection

• HighïVoltage Startup Circuit and Active Input Filter Capacitor

Discharge Circuitry for Reduced Standby Power

• Integrated HighïVoltage BrownïOut Detector

• Integrated HighïVoltage Switch Disconnects PFC Feedback Resistor

Divider to Reduce Standby Power

• Fault Input for Severe Fault Conditions, NTC Compatible (Latch and

AutoïRecovery Options)

• 0.5 A / 0.8 A Source / Sink Gate Drivers

• Internal Temperature Shutdown

• Power Savings Mode Reduces Supply Current Consumption to

70 A Enabling Very Low Input Power Applications

PFC Controller Features

• Critical Conduction Mode with Constant On Time Control (Voltage

Mode) and Maximum Frequency Clamp

• Accurate Overvoltage Protection

• BiïLevel LineïDependent Output Voltage

• Fast Line / Load Transient Compensation

• Boost Diode ShortïCircuit Protection

• FeedïForward for Improved Operation across Line and Load

• Adjustable PFC Disable Threshold Based on Output Power

QR Flyback Controller Features

• Valley Switching Operation with Valleyï

Lockout for NoiseïFree Operation

• Frequency Foldback with Minimum Frequency

Clamp for Highest Performance in

Standby Mode

• Minimum Frequency Clamp Eliminates

Audible Noise

• TimerïBased Overload Protection

(Latched or AutoïRecovery options)

• Adjustable Overpower Protection

• Winding and Output Diode ShortïCircuit

Protection

• 4 ms SoftïStart Timer

NCP1937属于集成电路（IC） > PFC（功率因数校正）。安森美半导体公司制造生产的NCP1937PFC（功率因数校正）功率因数校正 (PFC) 是用于调整交流电路中的电压和电流之间的相位角，使之趋近于零的半导体器件。不同模式包括平均电流、边界导通、连续导通、临界导通、电流控制式频率折返、不连续和不连续导通，开关频率从 6 kHz 至 1.7 MHz 可调。