| 摘要 |
<p>PURPOSE:To prevent excessive peak in the output of a discharge lamp when lighting is started and preclude temp. rise, deterioration, etc., of a power semiconductor element. CONSTITUTION:A DC booster circuit 2 makes PWM control of a power NMOS transistor 7 and supplies a DC power to a discharge lamp 3. A timer circuit 17 controls the DC output power so that the booster circuit 2 emits a DC power larger than the DC constant power to be fed to the discharge lamp 3 at the time of lighting from the time when a DC power supply 1 is turned on, till the time a certain period T1 has elapsed predetermined according to the point of time with overshoot generated in the output of the discharge lamp 3. The DC output power of the DC booster circuit 2 is controlled so that the DC booster circuit 2 outputs a DC smaller than DC large power and presenting a decremental tendency secularly when the specified period T1 has elapsed.</p> |
