An Integrated High Power Self-Equalized Battery Charger Using a Voltage Multiplier and Phase-Shifted Full-Bridge DC-DC Converter for Lithium-Ion Batteries

Conventional energy storage systems (ESSs) such as super-capacitors and lithium-ion batteries require voltage equalization systems to eliminate voltage imbalances, and bidirectional dc-dc converters to complete the charging process. These separated systems require some sensors, inductors, switches, and transformers. Consequently, the ESSs volumes, prices, and their complexity are dramatically increased by increasing the required series connected batteries count. Here, a self-equalized battery charger is proposed for lithium-ion batteries by combining a voltage multiplier (VM) and a phase-shifted full-bridge (PSFB) dc-dc converter. In the proposed self-equalized battery charger, the voltage multiplier eliminates the voltage imbalances and the PSFB dc-dc converter carries out the charging process. By combining the voltage equalizing and the charging systems into a single system, an integrated converter is obtained which leads to simultaneous charging and equalization operations, power and control sections simplicity, as well as low volume and price. By utilizing the phase-shift control method, zero-voltage-switching (ZVS) operation of power MOSFETs is obtained which leads to high efficiency and low EMI noise. The experimental results for 8 batteries including 48 lithium-ion cells, are in good agreement with the given mathematical analyses and simulation and clearly show the simultaneous charging and voltage equalizing operations, as well.