NCP1681

The NCP1681 is a high-efficiency, current-mode PWM controller designed for offline applications such as power supplies in consumer electronics, industrial equipment, and lighting systems. It features an integrated high-voltage startup circuit and operates over a wide input voltage range from 8 V to 27 V, making it suitable for both low- and high-voltage applications. The device supports continuous conduction mode (CCM) and discontinuous conduction mode (DCM), enabling flexible design options for various power levels. Key features include built-in slope compensation, which improves stability and reduces sub-harmonic oscillations, especially at duty cycles above 50%. The NCP1681 also incorporates a precision reference voltage of 2.5 V with ±1% accuracy, ensuring consistent performance across temperature and load variations. Its internal oscillator allows frequency adjustment via an external resistor, supporting operation from 20 kHz to 1 MHz—ideal for optimizing efficiency and minimizing component size. The controller includes comprehensive protection mechanisms such as over-current protection (OCP), over-voltage protection (OVP), and thermal shutdown. These features enhance system reliability and prevent damage under fault conditions. Additionally, the NCP1681 offers a programmable soft-start function that limits inrush current during startup, reducing stress on components and improving overall system longevity. Designed for flyback converter topologies, the NCP1681 enables efficient power conversion with minimal external components. It integrates a high-side driver capable of driving external MOSFETs up to 300 V, allowing for compact and cost-effective designs. The device also supports burst mode operation at light loads, significantly reducing quiescent current and improving standby efficiency—critical for meeting modern energy standards like Energy Star and EU CoC. This IC is commonly used in applications such as LED drivers, battery chargers, small power adapters, and AC/DC converters where high efficiency, compact footprint, and robust protection are essential. Its flexibility in operating modes and extensive protection suite make it well-suited for both isolated and non-isolated power supply designs. The NCP1681 is packaged in a 8-pin DIP or SOIC format, offering ease of integration into existing PCB layouts.