What are the differences in EMC performance between a PAC (Power Actuator) under full load and no load?

The EMC performance of a power supply controller (PAC) differs under full load and no-load conditions. Under full load, power supply noise increases, and switching devices heat up, potentially leading to increased radiated emissions, especially at switching frequency harmonics. Under no-load conditions, some power supplies may operate in intermittent mode, generating low-frequency noise.

Testing requires measuring conducted and radiated emissions, as well as immunity, under both full load (rated load) and no-load conditions. Typically, emissions are higher under full load, and immunity may decrease. Worst-case scenarios must be considered in the design, ensuring that limits are met even under full load. For example, power supply filtering should be designed for full load with a margin. Understanding these differences helps optimize the design and ensures that the PAC complies with EMC standards under various operating conditions.