Frequency modulation method and device for high intensity discharge lamp

1. An electronic control gear (ECG) for a high intensity discharge (HID) lamp, comprising:

a function generator that receives an input signal, wherein the input signal operates the lamp, wherein the function generator frequency modulates the input signal, generating a frequency modulated output signal that drives an arc of the lamp, wherein the frequency modulation of the input signal by the function generator sweeps continuously between a low frequency modulation and a high frequency modulation, the low frequency modulation being a frequency f 1 in a range of about 125 kHz to 150 kHz and the high frequency modulation being a frequency f 2 in a range of about 230 kHz to 300 kHz, where f 2 minus f 1 is at least 0.4 times f 1 ; and

a variable gain transformer that adjusts a voltage of the frequency modulated output signal during starting of the lamp.

2. The ECG of claim 1 , wherein a frequency of the frequency modulation changes substantially linearly between the low frequency modulation and the high frequency modulation.

3. The ECG of claim 1 , wherein a sweep time from the low frequency modulation to the high frequency modulation and back to the low frequency modulation is about 2-20 ms.

4. The ECG of claim 1 , further comprising a power amplifier that receives the frequency modulated output signal from said function generator and changes an amplitude of the frequency modulated output signal during the low frequency modulations so that a current amplitude of the frequency modulated output signal is substantially constant.

5. A method of operating a high intensity discharge (HID) lamp, the method comprising:

frequency modulating an input signal, wherein the input signal operates the lamp, to generate a frequency modulated output signal, wherein the frequency modulation of the input signal sweeps continuously between a low frequency modulation and a high frequency modulation, the low frequency modulation being a frequency f 1 in a range of about 125 kHz to 150 kHz and the high frequency modulation being a frequency f 2 in a range of about 230 kHz to 300 kHz, where f 2 minus f 1 is at least 0.4 times f 1 ;

driving an arc of the lamp with the frequency modulated output signal; and

adjusting a voltage of the frequency modulated output signal during starting of the lamp.

6. The method of claim 5 , further comprising changing an amplitude of the frequency modulated output signal during at least one of the high and low frequency modulations so that a current amplitude of the frequency modulated output signal is substantially constant.

7. The method of claim 5 , wherein a sweep time from the low frequency modulation to the high frequency modulation and back to the low frequency modulation is about 2-20 ms.

8. The method of claim 5 , wherein a frequency of the frequency modulation changes substantially linearly between the low frequency modulation and the high frequency modulation so that the frequency of the frequency modulation has a generally triangular pattern.

9. The method of claim 5 , wherein the triangular pattern is symmetric.

10. The method of claim 5 , wherein the triangular pattern is asymmetric.