| 摘要 |
PURPOSE:To improve the safety of a circuit economically and reasonably by suppressing an overvoltage generated in a switching element for a period, during which a voltage vibration system has a transient apex, in an inverter apparatus equipped with said voltage vibration system including an inductor an a capacitor. CONSTITUTION:Because an oscillation frequency is high directly after power closing, the ON period of a transistor Q1 is short and the energy stored in a resonance inductor L1 is reduced so that the peak value of a resonance voltage for the OFF period falls. After that, with the lapse of time, the reference voltage Vk of a comparator CP1 becomes gradually higher and the oscillation frequency of an inverter circuit 1 lowers gradually from a preheating frequency to shift to a lighting-up time frequency. Said change of frequency is smoothly conducted according to the time constant of a capacitor C5 and a resistance R10. Thus, said reference voltage Vk is set arbitrarily so that the ON period of said transistor Q1 can be changed over a wide range and a starting frequency and said preheating and lighting-up time frequencies can be set arbitrarily. |
