Electronic ballast with high power factor

1. An electronic ballast circuit for a fluorescent lamp, comprising:

a power circuit that outputs power to the lamp; the power circuit having:

a rectifier for converting an alternating current input voltage into a direct current output voltage, and

a circuit including a combined power factor correction (PFC) stage and an inverter; and

an integrated power supply for a controller circuit; the integrated power supply providing start-up power to the controller circuit; and also providing steady state power to the controller circuit when the lamp is at full power and when the lamp is dimmed; and

wherein a steady state power circuit of the integrated power supply provides the steady state power to the controller circuit; the steady state power circuit including an auxiliary winding associated with an inductor of the inverter;

wherein the power circuit operates with only one switch; and

wherein the integrated power supply receives a portion of output power from the power circuit and delivers the portion of the output power to the controller circuit.

2. The electronic ballast circuit of claim 1 , wherein the PFC stage includes a single ended primary inductor converter (SEPIC).

3. The electronic ballast circuit of claim 1 , comprising a start-up circuit of the integrated power supply for providing the start-up power, the start-up circuit including a series resistor and capacitor connected across the rectifier.

4. The electronic ballast circuit of claim 1 , wherein the inverter is selected from any one of a resonant inverter and a current fed inverter.

5. The electronic ballast circuit of claim 1 , wherein the inverter is a current fed inverter including a C-L-L resonant circuit.

6. The electronic ballast circuit of claim 1 , wherein the fluorescent lamp is a compact fluorescent lamp (CFL).

7. The electronic ballast circuit of claim 1 , wherein the PFC stage and the inverter share the one switch.

8. A method of providing power to a fluorescent lamp, comprising:

rectifying an alternating current input voltage to produce a direct current voltage;

providing the direct current voltage to a power circuit that operates using only one switch to produce output power for the lamp;

combining a power factor correction (PFC) stage and an inverter for the power circuit;

sharing the one switch between the PFC stage and the inverter;

using a portion of the output power to provide power to a controller for the power circuit;

associating an auxiliary winding with an inductor of the inverter, wherein a steady state power circuit of an integrated power supply for the controller provides the steady state power to the controller, wherein the steady state power circuit includes the auxiliary winding associated with the inductor of the inventor; and

providing start-up power to the controller, and providing the steady state power to the controller when the lamp is at full power and when the lamp is dimmed.

9. The method of claim 8 , including operating the shared switch at a selected duty ratio.

10. The method of claim 8 , including operating the shared switch with a variable duty ratio.

11. The method of claim 8 , further comprising:

using a dimmer to adjust the alternating current input voltage;

wherein adjusting the alternating current input voltage adjusts brightness of the fluorescent lamp.

12. The method of claim 11 , wherein the dimmer is a leading edge dimmer.

13. The method of claim 11 , wherein the dimmer is a trailing edge dimmer.

14. The method of claim 8 , wherein the fluorescent lamp is a compact fluorescent lamp (CFL).