DEVICE FOR CONTROLLING TO A DESIRED VALUE THE LIGHT OUTPUT OF A HIGH OR LOW PRESSURE GAS DISCHARGE LAMP

摘要

To hold constant the desired light output of a high or low pressure gas discharge lamp in cold operation, the current through the gas discharge lamp is measured and the difference with a desired reference value is determined. On the basis of the measured difference the frequency is controlled of a high frequency alternating voltage which is generated by a continuously variable oscillator. When current flow through the lamp is too low the frequency is lowered, whereby the resistance in the branch in which the lamp is arranged is decreased and the current flow is increased until the desired value is reached.