Power supply designers grapple with diverse efficiency standards - Standby power has become a hot topic, and every country seems to mandate a different solution

摘要

Low-voltage, transformer-based wall-warts - those little external power supplies used to power mobile phones, digital cameras, printers, scanners, and PDAs - have quickly become a pervasive part of our lives. The Environmental Protection Agency (EPA) estimates more than 3 billion are in use in the United States alone and about 10 billion worldwide. Individually these little black boxes don't consume large amounts of power. But since many are based on low-cost linear transformers, their efficiency generally runs less than 50%. Accordingly, a 3-W adapter, even when it's in no-load mode, is wasting half its rated power 365 days a year.