Patent ID: 8541960

Claim:
A method comprising: (a) stopping an illuminating current from flowing through a gas of a lamp by closing a switch; (b) determining a first magnitude of a waveform at a first time; (c) determining a second magnitude of the waveform at a second time that occurs after the first time; (d) determining a third magnitude of the waveform at a third time that occurs after the second time; (e) determining a first difference between the third magnitude and the second magnitude; (f) determining a threshold difference for the waveform between the second time and the third time; (g) comparing the third magnitude to the first magnitude if the first difference is smaller than the threshold difference; (h) after the comparing in (g), determining that a local minimum of the waveform has been reached if the third magnitude exceeds the first magnitude; and (i) opening the switch at a predetermined time interval after the third time.