A power converter for an LED assembly, the power converter comprising: • a control unit (130, 930, 1440, 1510) arranged to receive an input signal representing a required load voltage for powering the LED assembly, • an AC/DC converter arranged to provide a variable DC supply voltage, wherein the control unit is arranged to control the AC/DC converter in accordance with the required load voltage; • a switched mode power supply arranged to power the LED assembly, • wherein the AC/DC converter is arranged to provide the variable DC supply voltage to the switched mode power supply, • characterised in that: the AC/DC converter comprises: • a transformer arranged to provide a variable AC output voltage based on a control signal from the control unit and • a first rectifier for converting the variable AC output voltage to said variable DC supply voltage, • wherein: • the transformer comprises a plurality of transformer modules and a switching element for enabling a series and/or parallel connection of a subset or all of the plurality of transformer modules to thereby, in use, providing the variable AC output voltage, the switching element being controlled by the control signal of the control unit based on the input signal, and • each of the plurality of the transformer modules comprises a primary winding connectable to an AC power source (170, 910) and a secondary winding connectable to the first rectifier. • a control unit (130, 930, 1440, 1510) arranged to receive an input signal representing a required load voltage for powering the LED assembly, • an AC/DC converter arranged to provide a variable DC supply voltage, wherein the control unit is arranged to control the AC/DC converter in accordance with the required load voltage; • a switched mode power supply arranged to power the LED assembly, • wherein the AC/DC converter is arranged to provide the variable DC supply voltage to the switched mode power supply, • characterised in that: the AC/DC converter comprises: • a transformer arranged to provide a variable AC output voltage based on a control signal from the control unit and • a first rectifier for converting the variable AC output voltage to said variable DC supply voltage, • wherein: • the transformer comprises a plurality of transformer modules and a switching element for enabling a series and/or parallel connection of a subset or all of the plurality of transformer modules to thereby, in use, providing the variable AC output voltage, the switching element being controlled by the control signal of the control unit based on the input signal, and • each of the plurality of the transformer modules comprises a primary winding connectable to an AC power source (170, 910) and a secondary winding connectable to the first rectifier. • a transformer arranged to provide a variable AC output voltage based on a control signal from the control unit and • a first rectifier for converting the variable AC output voltage to said variable DC supply voltage, • wherein: • the transformer comprises a plurality of transformer modules and a switching element for enabling a series and/or parallel connection of a subset or all of the plurality of transformer modules to thereby, in use, providing the variable AC output voltage, the switching element being controlled by the control signal of the control unit based on the input signal, and • each of the plurality of the transformer modules comprises a primary winding connectable to an AC power source (170, 910) and a secondary winding connectable to the first rectifier. • the transformer comprises a plurality of transformer modules and a switching element for enabling a series and/or parallel connection of a subset or all of the plurality of transformer modules to thereby, in use, providing the variable AC output voltage, the switching element being controlled by the control signal of the control unit based on the input signal, and • each of the plurality of the transformer modules comprises a primary winding connectable to an AC power source (170, 910) and a secondary winding connectable to the first rectifier.