Power converter for an LED assembly and lighting application

1. A power converter for an LED assembly, the power converter comprising:

a switched mode power supply arranged to power the LED assembly;

an AC/DC converter arranged to provide a variable DC supply voltage to the switched mode power supply; and

powering the LED assembly, the control unit being arranged to control the AC/DC converter, in accordance with the required load voltage;

wherein the control unit is arranged to control the AC/DC converter to provide the variable DC supply voltage at a level substantially matching or proportional to the required load voltage;

wherein 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 voltage to the variable DC supply voltage; and

wherein the transformer comprises a primary winding having multiple terminals connectable to an AC power source via a selector element, said selector element being controlled by the control signal of the control unit, and a secondary winding connected to the first rectifier.

2. The power converter according to claim 1 wherein the secondary winding comprises multiple terminals connectable to the first rectifier via a selector element, said selector element being controlled by the control signal of the control unit.

3. A power converter for an LED assembly, the power converter comprising:

a switched mode power supply arranged to power the LED assembly;

an AC/DC converter arranged to provide a variable DC supply voltage to the switched mode power supply; and

powering the LED assembly, the control unit being arranged to control the AC/DC converter, in accordance with the required load voltage;

wherein the AC/DC converter comprises a transformer arranged to provide a variable AC output voltage based on a control signal from the control unit, the transformer comprising

a primary winding having multiple terminals connectable to an AC power source via a selector element, said selector element being controlled by the control unit; and

a plurality of secondary windings, each secondary winding being provided with a first rectifier for, in use, converting the variable AC voltage over the secondary winding to the variable DC supply voltage.

4. The power converter according to claim 3 wherein the AC/DC converter comprises a second rectifier for rectifying the AC power source having a comparatively low frequency and a frequency converter for converting the rectified AC power source to the AC power source having a comparatively high frequency, the second rectifier and frequency converter being controlled by the control unit, based on the input signal.

5. The power converter according to claim 4 wherein the AC power source having a comparatively low frequency is an AC mains supply at 50 Hz or 60 Hz.

6. The power converter according to claim 4 wherein the comparatively high frequency is more than 500 Hz.

7. The power converter according to claim 1 wherein the input signal is based on a forward voltage measurement of the LED assembly or based on a set point obtained from a user interface.

8. A Lighting application comprising a power converter according to claim 1 and an LED assembly arranged to, in use, being powered by the switched mode power supply of the power converter.

9. The lighting application according to claim 8 wherein the control unit is further arranged to control a current, in use, provided by the switched mode power supply to the LED assembly.

10. The lighting application according to claim 8 wherein the LED assembly comprises a chain of multiple LED units in series, each LED unit being provided with a parallel switching element that is controlled by the control unit.

11. The power converter according to claim 3 wherein the input signal is based on a forward voltage measurement of the LED assembly or based on a set point obtained from a user interface.

12. A Lighting application comprising a power converter according to claim 3 and an LED assembly arranged to, in use, being powered by the switched mode power supply of the power converter.

13. The lighting application according to claim 12 wherein the control unit is further arranged to control a current, in use, provided by the switched mode power supply to the LED assembly.

14. The lighting application according to claim 12 wherein the LED assembly comprises a chain of multiple LED units in series, each LED unit being provided with a parallel switching element that is controlled by the control unit.