Matching Circuit Design Minimized Coil Change Affects for an Inductively Coupled Discharge Lamp System
Akihiro Inouye, Keiichi Shimizu, Ichiro Yokozeki · JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN · 1999
The effects of a change in the inductively coupled coil inductance on an electrodeless discharge lamp are investigated theoretically. The lamp power curve has a single peak as a function of the coil inductance. The power of the lamp changes considerably if a matching circuit is not designed suitably. High-frequency generator output current also changes considerably if the generator current curve has a sharp peak as a function of the coil inductance. This sometimes causes the generator switching device to fail, but if the current curve has a dull peak, the peak point almost coincides with the peak of the lamp power curve and the current change is not so rapid. If the matching circuit is designed to match the point near this peak, the lamp power and the generator output current not increase but onlydecrease slowly by the coil inductance changing.This paper clarifies the design rules of the matching circuit to minimize the lamp power and the high-frequency generator output current changes. Tests are conducted to check that the designed circuits satisfy the rules.