The DiodesZetex AP31251 is a current mode PWM controller which is optimized for high performance, low standby power and cost effective offline fly back converters. The PWM switching frequency at normal operation is internally fixed (about 65kHz). In middle load, the IC will enter green mode to improve system efficiency with the help of frequency fold back. A minimum switching frequency (about 20kHz) is set to avoid the audible noise. In no load or light load, the IC will enter the burst mode to minimize standby power. Furthermore, the frequency dithering function is built-in to reduce EMI emission. It is available in SOT26 package.

Very low start-up current Non-audible-noise green-mode control Internal slope compensation Soft start during start-up process Frequency fold back for high average efficiency with many other features