Battery charging circuit and charging method

A charging circuit is provided that charges a battery for supplying power to a motor drive system that includes a three-phase motor and a three-phase inverter for controlling the three-phase motor. The three-phase inverter includes first to third sets of switching elements. Each set corresponds to one of the three phases. The charging circuit includes a single-phase output transformer, a rectifier circuit, a line, and a controller. The single-phase output transformer includes a secondary side output section having a first terminal and a second terminal. The rectifier circuit is connected in parallel with the three-phase inverter and the battery. The rectifier circuit is also connected to the first terminal of the secondary side output section. The line connects a connecting point between the first set of the switching elements in the three-phase inverter with the second terminal of the secondary side output section. The controller performs on-off control of the first to third sets of the switching elements. D