| 摘要 |
PURPOSE:To reduce the damage or wear of filaments at the time of lighting by generating two kinds of frequencies with an oscillator driving a driving transformer, holding the discharge lamps lighting by the generation of serial resonance for a fixed period after a power source is turned on until preheating is thoroughly performed. CONSTITUTION:A frequency switching circuit 13 is made nonoperational until the time set by a timer circuit 14 after a power source is turned on, and the first frequency signal is outputted from an oscillator 3. This frequency is set not to generate the serial resonance by capacitors 7 and 8, inductance elements 9 and 10, and capacitance elements 11 and 12, discharge lamps La1 and La2 are not lighted, and filaments are thoroughly preheated in a short time. When a switching signal is outputted from the circuit 14 to operate the circuit 13, the second frequency is outputted from the oscillator 3, a serial resonant circuit is resonated, and the high voltage is generated across filaments of discharge lamps La1 and La2 by the serial resonance current to light them. |
