The CPU of the CNV controller 13 functions as means for controlling the electric power converter 11 by executing the control program of the switching elements S1 to S4, the program of the phase shift, or the like, stored in the storage unit of the computer. Specifically, the CNV controller 13 generates a first PWM signal PWM1 and a second PWM signal PWM2 and outputs the first PWM signal PWM1 and the second PWM signal PWM2 to the switching elements S1 to S4. The first PWM signal PWM1 corresponds to a duty ratio that sets electric charge storage/discharge periods of the first reactor L1 of the first step-up/step-down circuit CNV1. The second PWM signal PWM2 corresponds to a duty ratio that sets electric charge storage/discharge periods of the second reactor L2 of the second step-up/step-down circuit CNV2. That is, the CNV controller 13 controls the on/off operations of the switching elements S1 to S4 via the PWM signals PWM1, PWM2. In addition, the CNV controller 13 controls the first step-up/step-down circuit CNV1 and the second step-up/step-down circuit CNV2 through control over the switching elements S1 to S4.

Operation of Electric Power Converter

The detailed operation of the electric power converter 11 is already known from the above-described JP 2013-013234 A, or the like, so only a parallel step-up/step-down mode associated with a phase shift (described later) will be described. In addition, as for the parallel step-up/step-down mode, because of duality between a step-up mode and a step-down mode, only a parallel step-up mode will be described, and the description of a parallel step-down mode is omitted.