Starting Mechanism of Inductively Coupled Electrodeless Lamp Operating at 135 kHz

Abstract

The present electrodeless lamp system operates at 135 kHz and has a higher efficiency and output than the high pressure mercury lamp system, which is currently very popular in the market. However, in terms of the starting performance, the 135 kHz electrodeless lamp system needs a much higher voltage than its 13.56 MHz predecessor. With regard to the ignition for inductively coupled electrodeless lamps, it has been reported that there are theoretically two types of ignition: E-discharge and H-discharge. E-discharge uses capacitively coupled plasma and is utilized for plasma processing as the dielectric barrier discharge lamp (DBD lamp) or for back lighting as the external electrode fluorescent lamp (EEFL). This lamp plasma is sustained by the electric field passing through the glass wall from the power source. H-discharge uses inductively coupled plasma and is utilized for lighting. This lamp plasma is sustained by the electromotive force generated by the alternating magnetic field. The ignition of this lamp is defined as the time when the H-discharge occurs, as this is an inductively coupled electrodeless lamp. The starting voltage of the 135 kHz electrodeless lamp system is higher than 1 kV, so it is expected to reduce the starting voltage because of the insulation. Observation of the starting state of the 135 kHz electrodeless lamp system showed that discharge occurred at a relative low coil voltage. It was also shown that the starting voltage could be decreased when the turns of the coil wire are decreased under the condition that the product of the wire turns and the frequency and current are both kept constant.