| 摘要 |
<p>If a dimming ratio of a light source unit (9) is higher than a first ratio, an ON width of a first switching device (Q1) is increased with a second switching device (Q2) kept off when the dimming ratio is increased, and also the ON width of the first switching device (Q1) is decreased with the second switching device (Q2) kept off when the dimming ratio is decreased. If a dimming ratio of the light source unit (9) is lower than the first ratio, the ON width of the second switching device (Q2) is regulated with the ON width of the first switching device (Q1) held at a lower limit.</p> |
