Resonant circuit for halogen lighting

1. An apparatus for driving a halogen lamp, the apparatus comprising:

a series-resonant driving circuit operable near a series resonance frequency, the series-resonant driving circuit coupled to the halogen lamp in a series configuration; and

a controller coupled to the series-resonant driving circuit, the controller operable to control a frequency of operation of the series-resonant driving circuit.

2. The apparatus of claim 1 , wherein the series-resonant driving circuit is operated in an alternating current (AC) mode.

3. The apparatus of claim 2 , wherein the controller controls a brightness of the halogen lamp by skipping pulses in the AC drive current.

4. The apparatus of claim 1 , wherein upon lighting of the halogen lamp, the controller controls an inrush current to the lamp by operating the series-resonant driving circuit at a frequency above the series resonance frequency.

5. The apparatus of claim 4 , wherein after lighting of the halogen lamp, the controller operates the series-resonant driving circuit substantially at the series resonance frequency.

6. The apparatus of claim 1 , wherein the controller controls the frequency of operation of the series-resonant driving circuit to regulate an output current to the halogen lamp.

7. An apparatus for driving a halogen lamp, the apparatus comprising:

an alternating current (AC) series-resonant driving circuit operable near a series resonance frequency, the series-resonant driving circuit coupled to the halogen lamp in a series configuration; and

a controller coupled to the series-resonant driving circuit, the controller operable to control a frequency of operation of the series-resonant driving circuit to regulate an output current, wherein

upon lighting of the halogen lamp, the controller controls an inrush current to the lamp by operating the series-resonant driving circuit at a frequency above the series resonance frequency, and

after lighting of the halogen lamp, the controller operates the series-resonant driving circuit substantially at the series resonance frequency.

8. The apparatus of claim 7 , wherein the controller controls a brightness of the halogen lamp by skipping pulses in the AC drive current.

9. The apparatus of claim 8 , wherein an amplitude of the current is reduced before and after pulse skipping.

10. The apparatus of claim 7 , wherein the controller operates the series-resonant driving circuit substantially at the series resonance frequency when a resistance of the halogen lamp has substantially stabilized.

11. A method for driving a halogen lamp, the method comprising the steps of:

providing (i) a series-resonant driving circuit for the halogen lamp, wherein the series-resonant driving circuit is operable near a series resonance frequency and (ii) a controller operable to control a frequency of operation of the series-resonant driving circuit;

operating the series-resonant driving circuit above the series resonance frequency during startup of the halogen lamp; and

operating the series-resonant driving circuit substantially at the series resonance frequency after startup of the halogen lamp.

12. The method of claim 11 , wherein the operating steps include operating the series-resonant driving circuit in an alternating current (AC) mode.

13. The method of claim 12 , further comprising the step of controlling a brightness of the halogen lamp by skipping pulses in the AC drive current.

14. The method of claim 13 , wherein an amplitude of the current is reduced before and after pulse skipping.

15. The method of claim 11 , wherein the operating after startup step occurs after a resistance of the halogen lamp has substantially stabilized.

16. The method of claim 11 , wherein the operating after startup step includes frequency controlling the series-resonant driving circuit with PWM signals to regulate an output current to the halogen lamp.