Illumination device including LEDs and a switching power control system

1. In an illumination device including light-emitting diodes, an alternating current input, a full-wave rectifier coupled to the alternating current input and configured to produce a rectified voltage output and a power converter, the power converter having a switching element electrically coupled to the rectified voltage output of the full-wave rectifier, an improvement comprising:

a feedback circuit configured to determine an average current across the light-emitting diodes and to invert a signal representing the average current to provide a switching signal to the switching element such that, for a range of operating points, increasing a current drawn into the power converter will decrease LED power and decreasing the current drawn into the power converter will increase LED power.

2. The device of claim 1 wherein the alternating current input comprises a ballast for a fluorescent bulb.

3. The device of claim 2 , further comprising:

protection circuitry electrically coupled between the ballast and the full-wave rectifier.

4. The device of claim 1 , wherein the light-emitting diodes are coupled to the rectified voltage output of the full-wave rectifier and the single switching element is a low-side switch electrically coupled between the light-emitting diodes and a sense resistor.

5. The device of claim 4 , further comprising:

an inductor in series with the light-emitting diodes and located between the light-emitting diodes and a connection point of the low-side switch and the light-emitting diodes.

6. The device of claim 5 , further comprising:

a diode in series with the inductor and the light-emitting diodes and electrically coupled to the rectified voltage output, a diode located between the connection point and the rectified voltage output.

7. The device of claim 4 wherein the current sensed by the sense resistor is a peak current occurring when the low-side switch is closed.

8. The device of claim 1 wherein the feedback circuit is configured to calculate the average current from the peak current obtained from at least one of a sense resistor and the emitted light output.

9. The device of claim 1 wherein the feedback circuit comprises a pulse width modulator and a control system for the pulse width modulator, the control system including an input coupled to the rectified voltage output and a second input coupled to a sense resistor.

10. The device of claim 1 wherein the single switching element is a high-side switch connected between the rectified output voltage and the light-emitting diodes.

11. The device of claim 10 , further comprising:

an inductor connected in series with the light-emitting diodes at a connection point between the light-emitting diodes and the high-side switch; and wherein a sense resistor is connected in series with the inductor and the light-emitting diodes and is coupled to ground.

12. The device of claim 11 , further comprising:

a diode connected to a connection point between the high-side switch and the inductor such that the recirculation diode is reverse-biased when the high-side switch is closed; and wherein the recirculation diode is in parallel with the light-emitting diodes.

13. The device of claim 11 wherein the feedback circuit comprises a pulse width modulator and a control system for the pulse width modulator, the control system including a first input coupled to the rectified voltage output and a second input coupled to a sense resistor.

14. The device of claim 1 , further comprising:

a remote signal receiver configured to receive a remote signal indicating a desired brightness level for the light-emitting diodes; and

a dimming circuit responsive to the remote signal receiver and configured to provide a control signal to the feedback circuit indicating the desired brightness level.

15. The device of claim 14 , wherein the remote signal receiver comprises one of an infrared receiver and a radio frequency antenna.

16. The device of claim 1 , wherein feedback circuit is configured to output a duty cycle with a value greater than the duty cycle used to achieve a maximum value of current through the light-emitting diodes.

17. A method of controlling a feedback circuit for an illumination device having at least one LED and a power converter with a switching element;

determining an average current across the at least one LED;

inverting a signal representing the average current such that, for a range of operating points, increasing a current drawn into the power converter will decrease LED power and decreasing the current drawn into the power converter will increase LED power; and

providing the switching signal to the switching element.