Two-port Noise Source Equivalent Circuit Model for DC/DC Buck Converter with Consideration of Load Effect

As the conducted disturbance of a power converter changes with its load value, the relationship between the electromagnetic interference of the power converter and its load needs to be investigated. This work examines a 2-port equivalent circuit model for a DC/DC buck converter with consideration of the load effect. Factors that influence the model accuracy are also discussed. We used a synchronous buck converter operating under a continuous conduction mode condition to determine the load effect and evaluate the model. Results showed that the input port of the fixed-load model and load-variable model had good accuracy up to 70 MHz. We also predicted the load effect on input port noise and found that the input port noise of an 8.2-Ω load could be predicted from the other two load values (6.6 Ω and 11.6 Ω).