POWER SUPPLY UNIT

PROBLEM TO BE SOLVED: To give simultaneously to a power supply unit the respective monitor functions of its output voltage and its cooling fan even when its space is restricted, by outputting the respective monitoring results of its cooling-fan monitoring means and its output-voltage monitoring means from an external terminal common to them. SOLUTION: A power supply unit 1 has output terminals +Vo, -Vo for outputting from a power supply circuit 2 a predetermined output voltage, i.e., a DC output voltage, and a cooling fan 22 for cooling a switching element 6 of a heat generating part configuring the power supply circuit 2. Also, there are provided a cooling-fan monitoring means 23 for the operating state of the cooling fan 22, an output-voltage monitoring means 12 for the state of the DC output voltage, and a common external terminal (M) for outputting therefrom the respective monitoring results of both monitoring means 23, 12. Therefore, since the respective results of the cooling-fan monitoring means 23 and the output-voltage monitoring means 12 are outputted from the external terminal M common to both means 23, 12, the number of the external terminals M can be reduced by that portion. Therefore, both monitoring functions of the DC output voltage and the cooling fan 22 can be given simultaneously to the power supply unit 1.