LED lighting arrangement

1. An LED lighting arrangement comprising:

an LED load comprising a number of LEDs;

input terminals for connection to a power supply realised to provide an input voltage at a primary input voltage level;

a voltage boost module realised to boost the input voltage to a level above the primary input voltage level on the basis of a dim level input signal; and

a dimming module realised to decrease the LED current through the LED load when the boosted voltage exceeds the primary input voltage level.

2. The LED lighting arrangement according to claim 1 , wherein the voltage boost module is realised to boost the input voltage in direct proportion to an increase in dim level.

3. The LED lighting arrangement according to claim 1 , wherein the voltage boost module is realised to boost the input voltage to a maximum boost level for a dim level input signal corresponding to a maximum dim level.

4. The LED lighting arrangement according to claim 1 , wherein the dimming module is realised to decrease the LED current to zero as the boosted input voltage approaches a maximum boost level.

5. The LED lighting arrangement according to claim 1 , realised as a retrofit LED light bulb, with connectors for insertion into a socket of a lighting fixture powered by a DC power supply.

6. The LED lighting arrangement according to claim 1 , wherein the voltage boost module is realised to boost the input voltage by up to 3 V.

7. The LED lighting arrangement according to claim 1 , wherein the voltage boost module comprises a boost converter.

8. The LED lighting arrangement according to claim 1 , comprising an interface circuit for converting the dim level input signal to a switch control signal for controlling a switch of the boost converter.

9. The LED lighting arrangement according to claim 1 , wherein the LED load is arranged in series with a first semiconductor switch and a current sense resistor; and wherein the dimming module comprises

a current control circuit comprising a reference input and a variable input, which current control circuit is realized to regulate LED current through the first semiconductor switch according to a difference between the reference input and the variable input; and

a voltage monitor circuit realized to generate the variable input to the current control circuit on the basis of the boosted input voltage.

10. The LED lighting arrangement according to claim 9 , wherein the voltage monitor circuit comprises a programmable shunt regulator.

11. The LED lighting arrangement according to claim 9 , wherein the current control circuit comprises a comparator realised to compare the variable input with the reference input, and wherein the gain of the comparator is controlled by the boosted input voltage.

12. The LED lighting arrangement according to claim 11 , wherein the comparator is connected to decrease the current through the first semiconductor switch when the boosted input voltage exceeds the primary input voltage level.

13. A method of driving an LED lighting arrangement that has an LED load comprising a number of LEDs, which method comprises the steps of:

connecting the LED lighting arrangement to a power supply realised to provide an input voltage at a primary input voltage level;

connecting a dim level input signal to the LED lighting arrangement to indicate a desired dim level;

boosting the input voltage to a level above the primary input voltage level on the basis of the dim level input signal; and

decreasing the LED current when the boosted input voltage exceeds the primary input voltage level.

14. The method according to claim 13 , comprising the step of maintaining the LED current at a maximum drive level when the boosted input voltage does not exceed the primary input voltage level.

15. The method according to claim 13 , comprising the step of reducing the LED current linearly as the boosted input voltage increases above the primary input voltage level.