Patent ID: 7902764

Claim:
Driving device for a discharge lamp having two cathodes, comprising first means having a supply input voltage, for providing an alternating voltage at the terminals of said cathodes, second means for monitoring a condition of each of said cathodes and measuring a first direct voltage signal of the waveform of a voltage of the lamp that develops when said lamp approaches an ageing condition, third means coupled to said second means for deactivating said first means when a predetermined variation of said first direct voltage signal occurs, fourth means for supplying to said third means a second direct voltage signal proportional in value to said supply voltage, said third means being further operable for deactivating said first means when a predetermined variation of said first direct voltage signal occurs in relation to said second direct voltage signal, wherein said second direct voltage signal comprises a first component and a second component, said first and said second component forming respectively a higher threshold voltage and a lower threshold voltage for said first direct voltage signal.