| 摘要 |
PURPOSE:To stably light a lamp with a low-frequency rectangular wave current even for a choke coil of a small inductance in series with a discharge lamp by utilizing a current limiting function of a DC power supply. CONSTITUTION:A current limiting function is given to a DC power supply circuit 18 to light a discharge lamp 16 stationarily with low frequency rectangular waves. In a period during which all the witch elements of a full bridge inverter circuit 19 connected with an output terminal of the DC power supply circuit 18 get off, an output voltage of the DC power supply circuit 18 is increased up to a re-ignition voltage of the discharge lamp 16 or more using an energy accumulated at choke coils 6, 15 for lighting it stably. At the ime of starting, an output current limit value for the DC power supply circuit is increased, and a lighting frequency is set higher then that at a stationary time, so a large current is supplied to the discharge lamp 16 while the current is limited by the choke coil 15 to let stand-up of light speedy. |
