HIGH-PERFORMANCE RIPPLE FEEDBACK FOR THE BUCK UNITY-POWER-FACTOR RECTIFIER

The buck unity-power-factor rectifier has harmonic-free input current with complete load regulation down to zero output voltage. A new ''non linear ripple feedback'' is proposed which exactly cancels the spoilin g effect of dc-side current ripple on the low-distortion ac line curre nt waveforms, even for large amounts of ripple. This cancellation is i ndependent of operating point and readily implemented with analog hard ware, thereby permitting economies in the design of the dc filter whil e maintaining harmonic-free operation. Both large-single and increment al analyses of the rectifier are given. Confirming experimental result s from a 1-kW 48-V isolated battery charger operating with current-rip ple levels ranging from 50% to discontinuous-conduction-mode operation are given.