Design and Analysis of a Power Factor Corrected Quad Output Off-Line Isolated AC to DC Universal Power Supply with Improved Cross-Regulation

Multiple isolated DC voltage supplied from a single ac input is required for many applications, such as power supplies for medical and telecommunication applications. However, these offline power supplies usually have a severe issue with a low power factor (pf) and high total harmonic distortion. The cross-regulation problem is another significant concern that needs to be considered for these multiple-output power supplies. This paper chooses an RCD-clamped flyback topology operating in Continuous Conduction Mode (CCM) to achieve isolation and various outputs. Furthermore, a dual-stage active power factor correction circuit operating in continuous conduction mode and weighted voltage feedback mode control is proposed to improve the power factor and mitigate cross-regulation problems. This paper also presents a detailed procedure for designing a low-power multiple output offline isolated universal ac to dc power supply. Moreover, design considerations, including switch selection, the minimum value of primary inductance to ensure CCM, primary & secondary side peak & RMS current, choice of minimum wire size that can be used, and snubber design are discussed. A 124W universal quad-output offline power supply operating at 100 kHz is designed using the proposed procedure. The performance of the proposed offline power supply is evaluated for two different dual-stage active power factor correction techniques to analyse the pf & the total harmonic distortion (THD). Also, two different feedback control methods are used to analyse load regulation and line regulation with PSIM software.