EVL6563S-200ZRC

AN3180 Application note A 200 W ripple-free input current PFC pre-regulator with the L6563S Introduction A major limitation of transition-mode-operated PFC pre-regulators is their considerable input ripple current, which requires a large differential mode (DM) line filter to meet EMI requirements. The ripple-steering technique, with its ability to reduce an inductor ripple current, theoretically to zero, can be very helpful in reducing the need for DM filtering in any offline switching converter and in PFC pre-regulators in particular, where DM noise is an issue as there is no electrolytic capacitor just after the bridge. This application note illustrates the use of this technique, providing both the theoretical base and practical considerations to enable successful implementation. Furthermore, it shows the bench results of the EVL6563S-ZRC200 demonstration board, a 200 W ripple-free PFC pre- regulator based on an L6563S controller, designed according to the criterion proposed in this application note. Figure 1. EVL6563S-200ZRC 200W PFC demonstration board September 2010 Doc ID 17273 Rev 1 1/39 www.st.com Contents AN3180 Contents 1 Basic topologies with zero-ripple current 4 2 Zero-ripple current phenomenon: theory 6 3 Sensitivity of zero-ripple current condition . 10 4 Zero-ripple current phenomenon: practice 13 5 Capacitor selection . 18 6 A 200 W ripple-free input current PFC pre-regulator 19 7 Conclusions . 27 8 References 28 Appendix A Electrical equivalent circuit models of coupled inductors and transformers 29 Appendix B Measuring transformer and coupled inductor parameters 36 Revision history 38 2/39 Doc ID 17273 Rev 1