Novel current limitation technique without current feedback for digital-controlled battery charger in UPS applications

The objective of this paper is to present a new current limitation technique without current feedback for digital-controlled battery charger in UPS applications. A control method is proposed to achieve constant current and constant voltage charging without current feedback. The basic idea is to keep constant charging current by limiting the duty of charger. As the battery voltage is increased after charge, constant voltage mode is achieved by voltage mode control. A digital-controlled charger is designed and implemented for UPS applications. A low cost MCU is used to realize the proposed control method in software. Experimental results demonstrate that the effectiveness of the design and implementation.