Patent ID: 8692480

Claim:
Power supply unit, comprising: an AC/DC conversion unit coupled with an input to an AC input voltage and with an output to a DC-bus voltage, for converting the AC input voltage to a DC voltage a DC bus capacitor coupled to the DC output of the AC/DC conversion unit, and at least one sub-power supply unit receiving the DC bus voltage as input for providing at least one power supply, wherein the power supply of the at least one sub-power supply unit is at least one of reduced and switched off if the DC-bus capacitor voltage falls below a predetermined threshold value, the power supply unit further comprising a first and a second sub-power supply unit, each coupled to the DC bus voltage, wherein at least some of the sub-power supply units are switched off if the DC bus voltage falls below an under-voltage lock-out level, wherein an under-voltage lock-out level of the first sub-power supply unit is selected lower than an under-voltage lock-out level of the second sub-power supply unit.