In an apparatus, a predicting unit uses, as an initial value of a controlled variable, at least one of a first measured value of the controlled variable and a second measured value of a physical variable expressed as a function of the controlled variable. The predicting unit predicts, based on the initial value of the controlled variable, a value of the controlled variable when a driving mode of a switching element of a power converter is set. A driving unit has an integral element and determines, based on an output of the integral element to which a deviation between the predicted value of the controlled variable and a command value of the controlled variable is inputted, an actual driving mode of the switching element to thereby drive the switching element in the determined driving mode.