| 摘要 |
PURPOSE:To prevent decrease in light output caused by decrease of circumferential temperature by forming a heat control means such that it supplies a current to a heater for a discharge part when high frequency power source output is not applied to a coil while it supplies a current to a heater for a lowermost part when circumferen tial temperature is below a specified level. CONSTITUTION:A high frequency power source 3 supplies a current to a coil 2 by amplifying a high frequency signal generated by a high frequency generation part 3a by means of a power amplifying part 3b. When the part 3b is in operation, a current supply signal Vo is output and both beaters 4, 5 are controlled by means of a heat control means 7 on the basis of the output of a temperature sensor 6a for the signal Vo and a circumferential temperature detecting means 6. When the signal Vo is not output and the output of the power source 3 is not applied to the coil 2, a heater for a discharge part is energized so that the discharge part of a glass bulb 1a is heated, and on the other hand when circumferential temperature is below a specified level, a heater 5 for a lowermost temperature part 1b is energized so that the part 1b is heated. It is thus possible to prevent light output decrease caused by circumferential temperature decrease and to give a stable light output immediately after starting operation. |
