The NCP1343 is a highly integrated quasi−resonant flyback

controller suitable for designing high−performance off−line power

converters.

The NCP1343 features a proprietary valley−lockout circuitry,

ensuring stable valley switching. This system works down to the 6th

valley and transitions to frequency foldback mode to reduce switching

losses. As the load decreases further, the NCP1343 enters quiet−skip

mode to manage the power delivery while minimizing acoustic noise.

Additionally, the NCP1343 integrates power excursion mode

(PEM) to minimize transformer size in designs requiring high

transient load capability. If transient load capability is not desired, the

NCP1342 offers the same performance and features without PEM.

To ensure light load performance with high frequency designs, the

NCP1343 incorporates Rapid Frequency Foldback with Minimum

Peak Current Modulation to reduce the switching frequency quickly.

To help ensure converter ruggedness, the NCP1343 implements

several key protective features such as internal brownout detection, a

non−dissipative Over Power Protection (OPP) for constant maximum

output power regardless of input voltage, and a latched overvoltage

and NTC−ready overtemperature protection through a dedicated pin.

Features

• Integrated High−Voltage Startup Circuit with Brownout Detection

• Wide VCC Range from 9 V to 28 V

• 28 V VCC Overvoltage Protection

• Abnormal Overcurrent Fault Protection for Winding Short Circuit or

Saturation Detection

• Internal Temperature Shutdown

• Valley Switching Operation with Valley−Lockout for Noise−Free

Operation

• Frequency Foldback with 25 kHz Minimum Frequency Clamp for

Increased Efficiency at Light Loads

• Rapid Frequency Foldback for Fast Reduction of Switching

Frequency at Light Loads

• Skip Mode with Quiet−Skip Technology for Highest Performance

During Light Loads

• Minimized Current Consumption for No Load Power Below 30 mW

• Frequency Jittering for Reduced EMI Signature

• Latching or Auto−Recovery Timer−Based Overload Protection

• Adjustable Overpower Protection (OPP)

• Adjustable Maximum Frequency Clamp

• CCM Operation During Power Excursion Mode (PEM)

• Fault Pin for Severe Fault Conditions, NTC Compatible for OTP