An electric-power conversion apparatus comprising: a chopper circuit comprising an upper stage power semiconductor device connected between a first electric potential and an intermediate node and a lower stage power semiconductor device connected between the intermediate node and a reference electric potential, whereby a terminal of the upper stage power semiconductor device is connected to a terminal of the lower stage power semiconductor device; a current sense resistor arranged to detect the output current of the chopper circuit, wherein a terminal of the current sense resistor is connected to said intermediate node; a differential detection circuit arranged to output, as a differential detection signal, a voltage across the current sense resistor; and a calculation means (13; 13a; 13b) arranged to correct the differential detection signal from the differential detection circuit by use of a desired pulse width signal for the chopper circuit so as to calculate the output current of the chopper circuit, the calculation means (13; 13a; 13b) comprising: means (21; 21 to 24) for generating a switching signal (S1, G1, G2) for turning on or off the chopper circuit based on a comparison of a level of the desired pulse width signal with a level of a triangular-shaped carrier-wave signal; a low-pass filter arranged to generate a filtered differential detection signal (vof) by low-pass filtering the differential detection signal; a gain calculator arranged to calculate a corrected signal (voc) by multiplying the desired pulse width signal by a gain factor (Koff); and means for calculating the output current of the chopper circuit by subtracting the corrected signal (voc) from the filtered differential detection signal (vof). a chopper circuit comprising an upper stage power semiconductor device connected between a first electric potential and an intermediate node and a lower stage power semiconductor device connected between the intermediate node and a reference electric potential, whereby a terminal of the upper stage power semiconductor device is connected to a terminal of the lower stage power semiconductor device; a current sense resistor arranged to detect the output current of the chopper circuit, wherein a terminal of the current sense resistor is connected to said intermediate node; a differential detection circuit arranged to output, as a differential detection signal, a voltage across the current sense resistor; and a calculation means (13; 13a; 13b) arranged to correct the differential detection signal from the differential detection circuit by use of a desired pulse width signal for the chopper circuit so as to calculate the output current of the chopper circuit, the calculation means (13; 13a; 13b) comprising: means (21; 21 to 24) for generating a switching signal (S1, G1, G2) for turning on or off the chopper circuit based on a comparison of a level of the desired pulse width signal with a level of a triangular-shaped carrier-wave signal; a low-pass filter arranged to generate a filtered differential detection signal (vof) by low-pass filtering the differential detection signal; a gain calculator arranged to calculate a corrected signal (voc) by multiplying the desired pulse width signal by a gain factor (Koff); and means for calculating the output current of the chopper circuit by subtracting the corrected signal (voc) from the filtered differential detection signal (vof). means (21; 21 to 24) for generating a switching signal (S1, G1, G2) for turning on or off the chopper circuit based on a comparison of a level of the desired pulse width signal with a level of a triangular-shaped carrier-wave signal; a low-pass filter arranged to generate a filtered differential detection signal (vof) by low-pass filtering the differential detection signal; a gain calculator arranged to calculate a corrected signal (voc) by multiplying the desired pulse width signal by a gain factor (Koff); and means for calculating the output current of the chopper circuit by subtracting the corrected signal (voc) from the filtered differential detection signal (vof).