NCP1351 Datasheet | onsemi

Variable Off Time PWM Controller 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 bees 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. An externally adjustable timer permanently monitors the feedback activity and protects the supply in presence of a short-circuit or an overload. Once the timer elapses, NCP1351 stops switching and stays latched for version A, and tries to...