Three-parameter Inductive Power Transfer Battery Charger With Configurable Constant Current Or Voltage Output

Compared with the traditional wired power transmission technology,inductive power transfer(IPT)technologies can deliver the energy from supply to load via the alternating electromagnetic field.Due to the electrical and mechanical isolation caused by transmission medium,IPT obtains the advantages of safety,convenience and strong environment adaptability.Therefore,IPT has been extensively used in the field of medical device,consumer electronics and transportation.The equipments in the above field are mainly powered by lithium-ion battery with high energy density and long cycle life.The charging process of lithium-ion battery involves an initial constant current(CC)mode and a subsequent constant voltage(CV)mode.Besides,the equivalent resistance of the battery increases during the whole process.To adapt the lithium-ion battery charging profile,a high-performance IPT battery charger should efficiently provide the required output as well as resistive input impedance to reduce device stresses and reactive power in a wide load.Current researches mainly focuse on the control strategy and compensation topology to realize the above requirements.The control strategy includes variable frequency control and phase shift control.The DC-DC converter is installed in the transmitter or receiver side to regulate the output at the expense of additional cost and volume.The phase shift control cannot realize soft switch for wide-range loads.Based on the four basic compensation networks which can’t provide the CC and CV output simultaneously,some researches combine various compensation topologies which has CC or CV output at the same frequency to form hybrid topology.The charging mode is altered by turning on/off corresponding ACS(AC Switch)which results in conduction loss in the system.Researches on high order compensation reveal that double-sided LCC compensation topology can realize CC and CV output at two ZPA operating frequencies.However,double-sided LCC compensation topology has six compensation parameters,and deviation of most compensation parameters affects input impedance and output gain.Focusing on the simplest compensation topology with CC and CV output,this paper lists all possible three-parameter compensation topologies.Firstly,three-parameter compensation topologies which has the characters of input ZPA and constant output are derivated according to resonant tank theory.Eight three-parameter compensation topologies which is suitable for square wave voltage source are also selected.Secondly,this paper systematically analyze the design freedom and relationship among compensation parameters and operating frequency of the above eight topologies on the basis of two-port network theory.Comparing the CC and CV output gain,the S-SP compensation topology with three capacitors is determined as the experimental topology.The sensitivities of compensation parameters to the input impedance and constant output are also analyzed to arrive at parameter configuration method that provides guidance for the design of soft switch.Finally,a single-stage IPT battery charger with rate of 48V/2A is built,and the experimental results verify the above theoretical analysis well.