| 摘要 |
PROBLEM TO BE SOLVED: To make adjustments of the intensity of lamp output by a user possible during operation by arranging a clamp circuit having a control circuit for controlling the voltage across a control winding wire according to an error signal, representing the difference between a set point signal selectable by the user and a feedback signal showing the time average value of a lamp operation parameter. SOLUTION: In a clamp circuit 62, lamp voltage is raised so that the cathode of a lamp reaches the desired temperature during preheating period with a preheating switch 82 and a control circuit 84. Lamp voltage is raised to a level capable of lighting the lamp by using a voltage clamp 80, together with diode/ bridges 74a, 74b. By controlling a switch 72 according to a feedback signal of a node 66 and a set point selectable by a user, obtained by a user input 68, lamp voltage reaches the level of a stationary state. The user can change the brightness of the lamp for example. |
