POWER CONTROL AND ENERGY SAVING METHOD AND APPARATUS FOR HIGH-INTENSITY GAS DISCHARGE (HID) LAMPS USED IN ILLUMINATION SYSTEMS

摘要

A method and an apparatus for controllably operating a gas discharge lamp in an electrical circuit containing an electromagnetic ballast and at least one electrical device selected from the group which includes a variable-impedance electrical circuit, a selector device and a variable inductive element, measuring at least one physical or electrical variable of the electrical circuit using measurement means connected to a controller, generating at least one control signal from the resulting measurement, and using the control signal to operate said electrical device in such a way that the physical or electrical variable remains within a predetermined range. The invention is useful, e.g., for operating a gas discharge lamp at a constant power level, a constant brightness level and/or at reduced power at certain times.