Wide load range resonant converter supplying the SAE J-1773 inductive charging interface

The recommended practice for electric vehicle battery charging using inductive coupling (SAE J-1773), published in January 1995 by the Society of Automotive Engineers, Inc. (SAE), outlines values and tolerances for critical vehicle inlet parameters which must be considered when selecting a driving topology. The inductive coupling vehicle inlet contains a significant discrete capacitive component in addition to low magnetizing and high leakage inductances. Driving the topology with a variable-frequency, series-resonant converter results in a four-element topology with many desirable features: unity transformer turns ratio; buck-boost voltage gain; current source operation; monotonic power transfer characteristic over a wide load range; throttling capability down to no-load; high-frequency operation; narrow frequency range; use of zero-voltage-switched MOSFETs with slow integral diode; high efficiency; inherent short-circuit protection; secondary dv/dt control and current waveshaping for the cable, coupler and vehicle inlet resulting in enhanced electromagnetic compatibility