Modelling Lost Periodicity and Waveform Distortion of SMPS Devices with a-PFC Circuits

This paper analyses lost periodicity and to it related waveform distortion of switch-mode power supply (SMPS) devices with active power factor correction (a- PFC) circuits. The paper first presents results of the previous tests, demonstrating that modern SMPS' with a-PFC might lose operational stability and exhibit significant changes in performance when operating at low to medium powers. Using these results, the paper then introduces a component based time-domain model of one commercially available SMPS with a-PFC used in a standard desktop PC. The development of that model is discussed, with particular attention to assessing the impact of a-PFC SMPS circuit parameters on the operational instability and correlation between the lost periodicity and significant increase of waveform distortions (harmonics, interharmonics and de component). The paper also presents a brief analysis of the impact of a group of SMPS' devices operating together. The presented a-PFC SMPS model is validated under different operating power levels using the available measurement data.