Implementation of a Resonant Converter with Input Series Connection and Output Parallel Connection

Series resonant converters with variable frequency modulation have been widely used for high efficiency consumer power supplies such as power units of LCD monitor and all-in-one computer. The advantages of LLC resonant converters are higher voltage gain, zero voltage switching (ZVS) turn-on for power switch with wide load range, zero current switching (ZCS) turn-off for rectifier diodes, and output voltage regulation at no-load condition. In the proposed converter, the output sides of LLC converters are connected in parallel to reduce the current stresses on output diodes. Thus the current stress of rectifier diodes is reduced and output diodes have no reverse recovery loss. The root mean square currents on transformer secondary windings, transformer copper losses, and thermal losses can be further reduced. The input sides of two LLC converters are connected in series thus the voltage stresses of each power switches are clamped to half of dc input voltage. Thus low conduction resistance of MOSFETs can be used to reduce the conduction losses. The principle of operation, steady state analysis and design example of the proposed converter are provided and discussed in detail. The proposed converter can be used for high efficiency consumer products such as LCD-TV, PDP-TV and server power supply unit. The laboratory experiments are provided to verify the effectiveness of the proposed converter. Copyright (C) 2010 Praise Worthy Prize S.r.l. - All rights reserved.