Hybrid structured buck converter with ripple cancellation and improved efficiency

Design of a ripple free switching mode power converter is a challenging task in power electronics industry. The conventional method for ripple reduction is to use passive filters, which makes the system bulky. Hybrid structured converters are introduced to reduce the ripple without using bulky output capacitors. In this type of converters, to cancel the ripple, opposite current / voltage of the ripple is injected to the output of converter. However the efficiency of the hybrid structure is poor due to the series resistor used for current sensing. This paper proposes a modified hybrid structure converter with improved efficiency as well as desirable ripple performance. The proposed circuit uses DCR current sensing method and reduces the losses. The modified structure gives 4.14 percent efficiency improvement at a load current of 2A compare to conventional hybrid converter. The ripple voltage is just 3mV even without output capacitor.