A study on the ignition characteristics of magnetic coupled electrodeless lamp

Summary form only given: Almost twenty years have passed since the first electrode-less lamp operated at 13.56 MHz was put on the market. Since then, it has come to be expected that the lumen output and the efficiency of these lamp systems would be improved, and as a result research to reduce the operating frequency has been done. This is because if the operating frequency were decreased, many semiconductor devices for higher lumen output could be used and the switching loss could be reduced for higher efficiency. The present electrode-less lamp system operated at 135 kHz has higher efficiency and output than the high pressure mercury lamp system which is very popular in the market. Thus the characteristics of this lamp when it is turned on have been researched and developed. However, the ignition mechanism of the electrode-less lamp has not yet been completely worked out. To grasp the ignition voltage and time is very important for designing this lamp system, because these influence the cost of the system. The authors investigated how to reduce the ignition time. Generally it is explained that the discharge ignites when equation (1) is fulfilled. gamma(exp(alphad)-1) = 1 (1) Where a is the coefficient of ionization by collision, gamma is the number of the second electrons emitted from the cathode which one ion collides with, and d is the distance between electrodes. As the electrode-less lamp has no electrode, this definition is not applicable. With regard to the ignition for magnetic coupled electrode-less lamp, it was reported that there are theoretically two types of ignition, which are E-discharge mode and H- discharge mode. However, the definition of the ignition actually is regarded as the time when the H discharge occurs. Thus in order to reduce the ignition time it is very useful to understand the mechanism about how E-discharge changes to H-mode. The authors observed the starting state of the electrode-less lamp and found out that something to produce the- initial electron inside the lamp bulb before starting should be set in.