| 摘要 |
To operate a high pressure discharge lamp, and more particularly a low-power high-pressure discharge lamp, only in quiet or stable lamp operation, a microprocessor (MC) is provided which establishes a test phase of limited time duration during which the frequency of operation of the lamp is varied by frequency modulation within a predetermined range. Lamp operation is monitored, for example by deriving a test voltage across a coupling capacitor (C6) receiving lamp current. If the monitored voltage, which is representative of lamp operation, shows that the lamp operates quietly and stably, the then pertaining frequency is stored by the microprocessor and, after the test phase is finished, the lamp is operated within a frequency window formed by the largest number of contiguous modulation frequencies which are suitable for, or result in, stable lamp operation. The test phase is carried out repetitively, at least upon each energization of the lamp, so that different operating characteristics of the lamp (e.g. due to changes in temperature, aging, or the like) are compensated. |
