PURPOSE: To improve form factor of second EC output by controlling the conducting state of a control rectifying element such that the output from a first power converter (EC) can be varied according to the output voltage from a second EC at the time of starting or brake final speed operation control of an electric vehicle.

CONSTITUTION: A controller 10A comprises a chopper controller 11 for delivering gate signals GON1A, GON2A, respectively, to a step-down chopper 5a and a step-up chopper 5b and varying output voltages therefrom depending on the output from a pulse width modulation inverter (PI) 8. In other words, at the time of starting or brake final speed operation control of an electric vehicle where the rotational speed of an induction motor 9 is low, conduction time of a control rectifying element constituting the PI 8 is determined by the ratio between an input voltage and a target output voltage thus setting a target output voltage. Consequently, magnitude of sine wave can be improved such that the pulse width extends over minimum ON time in the vicinity of 0° and 180° by lowering output voltages from the step-down chopper 5a and the step-up chopper 5b.