An emergency power supply unit configured to operate an emergency lighting means,the emergency power supply unit comprising: an energy storage unit configured to provide a battery supply voltage being a first voltage (V Bat) with a first voltage value in case of a mains voltage loss; a monitoring unit configured to monitor the battery supply voltage (V Bat); a driving unit configured to drive the emergency lighting means; a controlling unit configured to control an operation of the emergency power supply unit based on the actually monitored battery supply voltage (V Bat); a voltage converting unit which is configured to convert the first voltage (V Bat) into a voltage with a value higher than the first voltage value, wherein the voltage converting unit is configured to convert the first voltage (V Bat) in dependence of a control signal of the control unit to the voltage with a voltage value higher than a second voltage value or equal to a third voltage value, wherein the voltage converting unit comprises a voltage regulator configured to reduce the voltage into a second voltage with the second voltage value; and switching means provided in series with the energy storage unit; wherein the emergency power supply unit is configured to operate in a plurality of operating modes including a first operating mode, a second operating mode and a third operating mode; wherein the first operating mode of the emergency power supply unit is a mode wherein the voltage converting unit converts the first voltage into a third voltage (V CC) with the third voltage value, the controlling unit is supplied with the second voltage (V DD) with the second voltage value such that the control unit is powered to be operative to control the drive unit, wherein the driving unit is supplied by the third voltage (Vcc) with the third voltage value such that the driving unit is powered to be operative, wherein the second voltage value is lower than the third voltage value, and wherein the emergency lighting means is switched-on by the driving unit; wherein the second operating mode of the emergency power supply unit is a mode wherein the voltage converting unit converts the first voltage into a voltage having a voltage value in between the second voltage value and the third voltage value, the controlling unit is supplied with the second voltage such that the control unit is powered to be operative, and wherein the driving unit is supplied by the voltage having the voltage value lower than the third voltage value such that the driving unit does not operate and switches off the emergency lighting means; and wherein the third operating mode of the emergency power supply unit is a mode wherein the battery supply voltage (V Bat) is galvanically isolated from the controlling unit by the switching means provided in series with the energy storage unit. an energy storage unit configured to provide a battery supply voltage being a first voltage (V Bat) with a first voltage value in case of a mains voltage loss; a monitoring unit configured to monitor the battery supply voltage (V Bat); a driving unit configured to drive the emergency lighting means; a controlling unit configured to control an operation of the emergency power supply unit based on the actually monitored battery supply voltage (V Bat); a voltage converting unit which is configured to convert the first voltage (V Bat) into a voltage with a value higher than the first voltage value, wherein the voltage converting unit is configured to convert the first voltage (V Bat) in dependence of a control signal of the control unit to the voltage with a voltage value higher than a second voltage value or equal to a third voltage value, wherein the voltage converting unit comprises a voltage regulator configured to reduce the voltage into a second voltage with the second voltage value; and switching means provided in series with the energy storage unit; wherein the emergency power supply unit is configured to operate in a plurality of operating modes including a first operating mode, a second operating mode and a third operating mode; wherein the first operating mode of the emergency power supply unit is a mode wherein the voltage converting unit converts the first voltage into a third voltage (V CC) with the third voltage value, the controlling unit is supplied with the second voltage (V DD) with the second voltage value such that the control unit is powered to be operative to control the drive unit, wherein the driving unit is supplied by the third voltage (Vcc) with the third voltage value such that the driving unit is powered to be operative, wherein the second voltage value is lower than the third voltage value, and wherein the emergency lighting means is switched-on by the driving unit; wherein the second operating mode of the emergency power supply unit is a mode wherein the voltage converting unit converts the first voltage into a voltage having a voltage value in between the second voltage value and the third voltage value, the controlling unit is supplied with the second voltage such that the control unit is powered to be operative, and wherein the driving unit is supplied by the voltage having the voltage value lower than the third voltage value such that the driving unit does not operate and switches off the emergency lighting means; and wherein the third operating mode of the emergency power supply unit is a mode wherein the battery supply voltage (V Bat) is galvanically isolated from the controlling unit by the switching means provided in series with the energy storage unit.