Performance comparison of three main SMPS types under sinusoidal and distorted supply voltage

This paper presents detailed results of experimental evaluation of performance of switch-mode power supplies (SMPS') used in standard desktop PCs. The results provide comparison of changes in efficiencies, power factors and waveform distortion of SMPS' operating at different powers and under both ideally sinusoidal and distorted supply voltage conditions. Although a small sample of six SMPS' was tested, they are selected as typical representatives of the three main types of PC-SMPS' regarding used power factor control (PFC) circuits: without PFC (no-PFC), with passive PFC (p-PFC) and with active PFC (a-PFC). The comparison shows that in the high-power operating range (i.e. above 50% of rated power) SMPS' with a-PFC have better performance, i.e. higher efficiencies and power factors, with lower waveform distortions, than no-PFC and p-PFC SMPS'. In the low and very low power ranges, however, the performance of a-PFC SMPS' deteriorates, becoming similar to no-PFC and p-PFC SMPS'.