Design of a 5.4 kJ/s three-phase resonant converter based on a lithium polymer battery

This paper describes the design and manufacture of a 5.4 kJ/s three-phase resonant converter based on a 22 and 44 V lithium polymer (LiPo) battery as a high density power supply. Using the low LiPo battery input voltage generates a relatively high current that causes problems such as a large current burden on the used components and high peak-to-peak noise when the switch is turned off. To resolve such problems, the three-phase resonant converter in this work is used to handle the high input current. In the three-phase inverter structure, the amount of current flowing in a single switch is smaller than that of a single-phase current. In addition, the delta-star structure is intentionally introduced to reduce the turns ratio which helps to decrease the current on the transformer's primary side when the same output power is required. Furthermore, components such as series and parallel resonant capacitors are placed on the secondary side of the transformer, which have a high voltage and low current. These voltage and current conditions of the secondary side are more appropriate for commercialized film capacitors, which normally use series and parallel resonant capacitors because the film capacitors have been manufactured with high voltage and low current rated capacity. In terms of the design procedure, the used delta-star three-phase resonant circuit is redrawn on the secondary side of the transformer as a single-phase resonant equivalent circuit for the three-phase resonant converter design. Based on the simplified design, the operating mode and simulation of the 22 and 44 V LiPo battery-based chargers were analyzed, and the comparison of the resistor and capacitor load test results for the two chargers verifies both the aforementioned features and the performance of the proposed chargers using 300 and 150 A of the LiPo battery. The advantages are confirmed, and the capacitor bank is charged to 600 V for 80 ms, achieving power efficiencies of 82 and 92.5% for the 22 and 44 V based capacitor chargers, respectively.