| 摘要 |
<p>[Object] To prevent a large current from flowing to an inductor L2 of a step-down chopper circuit 4 even when a high-pressure discharge lamp DL with unstable discharge is connected, in a lighting device for lighting the high-pressure discharge lamp DL by a polarity reversal step-down chopper circuit with a full-bridge configuration. [Means for Settlement] With a first output polarity, control to turn off a switching element Q2 performing a low-frequency operation after turning-off of a switching element Q5 performing a high frequency operation according to a current IL2 flowing to the inductor L2, and with a second output polarity, control to turn off a switching element Q3 after turning-off of a switching element Q4 performing the high frequency operation according to the current IL2 flowing to the inductor L2 are performed. For example, when the current IL2 flowing to the inductor L2 becomes equal to or larger than a predetermined value Ip2 or an inclination of the current IL2 flowing to the inductor L2 becomes equal to or larger than a predetermined value, a full bridge circuit 3 is put into a whole OFF state.</p> |
