For energy efficiency purposes, Switching Mode Power Supplies (SMPS) are the most common for power conversions of over 250W. Typically, SMPS supplies need to meet certain efficiency requirements either governed by a government agency requirement or end customer specifications. The block diagram on the bottom left illustrates a simplified AC/DC SMPS. It consists of three main function blocks, the first being the rectification stage which converts AC voltage from the power line into quasi-dc.