Patent ID: 7652437

Claim:
A drive circuit for driving a fluorescent tube lamp, the drive circuit comprising: a variable frequency oscillator for generating a lamp drive frequency, the variable frequency oscillator having a variable frequency oscillator input for setting the lamp drive frequency, a resonant drive circuit, connected to a variable frequency oscillator output of the variable frequency oscillator, for driving the lamp with the lamp drive frequency, and a control unit having a synchronization input for receiving a synchronization signal, the control unit for driving the variable frequency oscillator as to under control of the synchronization signal generate a preheating drive frequency for preheating the lamp, or generate an illumination drive frequency for operating the lamp in an illuminated state, characterized in that the control unit comprises a transition controller for, at a transition from the preheating drive frequency to the illumination drive frequency, limiting the drive frequency to an ultimate ignition frequency, and for only enabling transition from the ultimate ignition frequency to the illumination drive frequency after an ignition delay time.