Crossing the boundary: strategies for feedback across an isolation barrier

摘要

Designers often categorize power converters into two basic types: isolated and nonisolated, These categories refer to the relationship between the input power ground and the output power ground. Many applications require isolation between the two grounds. The isolation requirement often stems from various safety agencies, and the main purpose of isolation is to protect personnel from exposure to dangerous voltage levels. In some cases, the grounds must have sufficient isolation so that applying a potential of 1500V or more between them shows no indication of breakdown. The specification that quantifies this isolation requirement is a small leakage current. An isolated power-converter design imposes several extra design challenges on a power-supply designer. Transmitting power or feedback information from one ground reference to the other is often referred to as "crossing the boundary."