Power adapter market is an important trend is the customer needs to have a higher output power, smaller size of the adapter, which involves the use of a new topology. Power Adapter mainly reflects some important trends. First, the work efficiency and standby (no-load) energy demanding. For example, the U.S. Environmental Protection Agency (EPA) "Energy Star" project was launched in April 2008 for an external power supply specification version 2.0, which for the external power supply EPA 2.0 version of the specification will be held November 1, 2008 came into effect. Power adapter includes two categories, one is the internal AC / DC (AC / DC) power converter, built-in electronic products internally and may possess multiple output voltages, such as a desktop computer's internal power supply, etc.; the other is the external one-way Output AC / DC or AC / AC (AC / AC) power adapter with single output voltage, typically referred to as an external power supply (EPS), widely used in printers, laptops, LCD monitors and gaming applications. In addition to the "Energy Star" kind of industry energy efficiency specifications, some large OEM customers may also have their own unique work of energy efficiency and energy requirements. For example, for computer power EPA 4.0 specification for the use of an external power supply laptop and tablet PC requirements are primarily reflected in the standby power consumption (≤ 1.0 W), sleep power consumption (≤ 1.7 W), etc.; comparison, Dell against such power requirements mainly in the particular load conditions of different energy efficiency, that is 0.7 W (input power Pin <1 W), 1.5 W (Pin <2 W), 10.7 W (Pin <12.6 W) and 17 W (Pin <20 W) load conditions, can be respectively more than 70% efficiency, 75%, 85% and 85%. It is worth mentioning is that the future will continue to regulate the energy efficiency requirements continuously improve and evolve. With laptop AC-DC power adapter, for example, the industry in no-load mode, a high level of energy consumption is about 300 mW or more, while the next 150 mW no-load mode power consumption could become targets. Moreover, the requirement for multi-output adapter may also be included among the criteria. ON Semiconductor's NCP1605 power factor correction (PFC) controller and NCP1396 resonant mode controller can be used to design 200 W or 300 W Adapter Desktop Adapter. From the notebook adapter, its power requirements has grown from 50 W to 70 W range up to more than 100 W rating. In addition, such as the Apple MacBook Air and the Lenovo ThinkPad X300, and other new ultra-portable notebook power adapter is also smaller and lighter.