In an apparatus, a norm setter sets, based on a request torque for a rotary machine and a rotational velocity of a rotor, a norm of a vector of an a output voltage in a two-phase rotating coordinate system defined in the rotor. A phase setter sets, based on a deviation between a generated torque and the request torque, a phase of the vector of the output voltage of the power converter in the two-phase rotating coordinate system. A drive signal determiner determines, based on the norm set by the norm setter and the phase set by the phase setter, a drive signal, and applies the drive signal to a switching member to thereby drive the switching member such that the generated torque is adjusted to the request torque.