| 摘要 |
PROBLEM TO BE SOLVED: To suppress stress placed on a constitutive element of a lighting circuit during unloaded and to remove actuating failure by providing a protection network for detecting irregularities of a load comprised of a high frequency power supply coil and an electrodeless discharge lamp, being connected to the output end of a high frequency power source, for blocking-oscillating the high frequency power source when the load is irregular, and for maintaining the oscillation in a suspended state. SOLUTION: When an electrodeless discharge lamp turns its state from the lighting to the unloaded, voltage of both ends of a detection resistor rises, a transistor Q5 is turned on to stop a high frequency output, and the transistor Q5 is turned off to actuate oscillation. During this period, the output of a comparator IC 2 becomes a high level with repeating this blocking oscillation and a capacitor C5 is continuously charged so that the transistor Q5 is kept on and the oscillation halt is maintained. After detecting the unloaded state, the desired number of blocking oscillation is performed and the oscillation halt is maintained so that stress placed on a constituent elements of a lighting circuit can be suppressed, this device can be easily actuated when the electrodeless discharge lamp is at low temperature or the first starting, and the generation of harmonic noise when starting can also be suppressed. |
