A power supply device comprising: at least a first and second power supply means (14A, 14B), each adapted to supply power to a same load at an output of the power supply means (14A, 14B), the power supply device being configured so that power is supplied to the load by the first power supply means (14A, 14B), while any other power supply means is in a standby state not supplying power to the load, the power supply device being further configured so that, when abnormality in the first power supply means (14A, 14B) is detected by an abnormality detection unit, supplying power to the load is switched to the second power supply means (14A, 14B), wherein each of the power supply means (14A, 14B) includes pulse generating means for generating a pulse width modulation signal, the width of the pulses of the pulse width modulation signal being generated so as to correspond to a voltage and current to be output at the output of the power supply means (14A, 14B), wherein each power supply means (14A, 14B) is adapted to receive a first signal indicating that abnormality occurs in the other power supply means, the power supply device being characterized in that each of the power supply means (14A, 14B) includes feedback control means configured to perform cyclically, according to a cycle, a feedback control on the pulse generating means, by determining a first value of a width of a pulse from an estimation of a current flowing at the output of the power supply means (14A, 14B), and providing the first value to the pulse generating means; each of the pulse generating means being adapted to modify, according to the first value, the generation of the pulse width modulation signal, so as to more accurately correspond to the first voltage and current to be output at the output of the power supply means (14A, 14B); and the feedback control means is configured, when the respective power supply means (14A, 14B) receives the first signal, to change the cycle at which the feedback control means performs the feedback control of a pulse voltage, from the first cycle to a second cycle shorter than the first cycle. at least a first and second power supply means (14A, 14B), each adapted to supply power to a same load at an output of the power supply means (14A, 14B), the power supply device being configured so that power is supplied to the load by the first power supply means (14A, 14B), while any other power supply means is in a standby state not supplying power to the load, the power supply device being further configured so that, when abnormality in the first power supply means (14A, 14B) is detected by an abnormality detection unit, supplying power to the load is switched to the second power supply means (14A, 14B), wherein each of the power supply means (14A, 14B) includes pulse generating means for generating a pulse width modulation signal, the width of the pulses of the pulse width modulation signal being generated so as to correspond to a voltage and current to be output at the output of the power supply means (14A, 14B), wherein each power supply means (14A, 14B) is adapted to receive a first signal indicating that abnormality occurs in the other power supply means, the power supply device being characterized in that each of the power supply means (14A, 14B) includes feedback control means configured to perform cyclically, according to a cycle, a feedback control on the pulse generating means, by determining a first value of a width of a pulse from an estimation of a current flowing at the output of the power supply means (14A, 14B), and providing the first value to the pulse generating means; each of the pulse generating means being adapted to modify, according to the first value, the generation of the pulse width modulation signal, so as to more accurately correspond to the first voltage and current to be output at the output of the power supply means (14A, 14B); and the feedback control means is configured, when the respective power supply means (14A, 14B) receives the first signal, to change the cycle at which the feedback control means performs the feedback control of a pulse voltage, from the first cycle to a second cycle shorter than the first cycle.