The NCP1351 is a current−mode controller targeting low power off−line flyback Switched Mode Power Supplies (SMPS) where cost is of utmost importance. Based on a fixed peak current technique (quasi−fixed TON), the controller decreases its switching frequency as the load becomes lighter. As a result, a power supply using the NCP1351 naturally offers excellent no−load power consumption, while optimizing the efficiency in other loading conditions. When the frequency decreases, the peak current is gradually reduced down to approximately 30% of the maximum peak current to prevent transformer mechanical resonance. The risk of acoustic noise is thus
greatly diminished while keeping good standby power performance.

FEATUREs
•Quasi−fixed TON, Variable TOFF Current Mode Control
•Extremely Low Current Consumption at Startup
•Peak Current Compression Reduces Transformer Noise
•Primary or Secondary Side Regulation
•Dedicated Latch Input for OTP, OVP
•Programmable Current Sense Resistor Peak Voltage
•Natural Frequency Dithering for Improved EMI Signature
•Easy External Over Power Protection (OPP)
•Undervoltage Lockout
•Very Low Standby Power via Off−time Expansion
•Internal Temperature Shutdown
•SOIC−8 Package