| 摘要 |
PURPOSE:To miniaturize an oscillation transformer so as to make a whole lighting device small and light by providing a switching circuit parallel to a discharge lamp. CONSTITUTION:A switch control circuit 23 is provided to turn off a switching circuit connected to a discharge lamp 12 in parallel, in the vicinity of the peak position of the output voltage waveform of a high frequency inverter circuit 2 and at the timing in which a discharge current through the lamp 12 is kept in the same phase to the output voltage waveform. Thus a current flows in a current limiting choke coil 11 until just before the turning off of the circuit 12 to stor electromagnetic energy in the coil 11, and this energy is superposed as an inverse electromotive force to the voltage waveform applied to the discharge lamp 12. As the timing of the turning off of the switching circuit 12 corresponds to the vicinity of the peak position of the voltage waveform, a voltage superposed with the inverse electromotive force is applied to the discharge lamp 12, hence the output voltage of an oscillation transformer 9 can be reduced. Thereby the oscillation transformer can be miniaturized to make the whole lighting device small. |
