Analog-digital switching mixed mode low ripple-high efficiency Li-ion battery charger

This paper describes a low noise and high efficiency analog-digital switching mixed mode battery charger for production facilities of Li-ion batteries. The requirements for battery chargers for production facilities are very strict. The accuracy of output voltage and output current should be below 0.1% with very low ripple current. Therefore analog type linear regulators are widely used for a battery charger in spite of their inefficiency and bulkiness. We combined a linear regulator as a voltage source with digital switching converter as a dependent current source. Low current ripple and high accuracy are obtained by a linear regulator while high efficiency is achieved by digital switching converter. Experimental results show that the proposed method has 0.1% ripple and 90% efficiency at an output current of 1 A for a battery voltage of 4 V.