This presentation addresses the design challenges and solutions for UBS-PD AC/DC adapters to achieve high efficiency, high power density, and low cost. The USB-PD adapters are used for many applications, including mobile phones, tablets, and notebook computers. The large market size makes the solution more interesting and valuable to the power supply industry. In this presentation, based on reviewing the traditional USB-PD adapter solutions, the design challenges associated with the USB-PD adapters are discussed. The challenges include the controller biasing issue caused by the variable output voltage, the increased cost and design complexity due to the transformer auxiliary winding, as well as the efficiency and EMI impacts. A new Flyback solution is introduced using a self-biasing technique to address the IC biasing issue. Additionally, the auxless sensing technique is discussed to completely eliminate the need for auxiliary winding. The EVM demonstration shows an 80% control portion BoM and PCB size reduction. High efficiency and high power-density are demonstrated through a USB-PD adapter reference design. Target audience: This topic could be suitable for the sessions of AC-DC converters, especially the external AC-DC adapters. The content should target the beginner and intermediate engineers.
