| 摘要 |
PURPOSE:To prevent an inverter from being deteriorated, by controlling the feedback quantity of a positive feedback circuit according to temperature. CONSTITUTION:A single-transistor self-excitation inverter 30 is provided with a current transformer 31, and through the primary winding 311 of the current transformer 31, the collector of a transistor 7 is connected to the primary winding 101 of a current transformer 10, and through the secondary winding 312 of the current transformer 31, a capacitor 11 is connected to the secondary winding 102 of the current transformer 10. In the current transformer 31, for its magnetic core, a temperature sensitive ferrite which changes its property from ferromagnetic to paramagnetic at a specified temperature is used. A positive feedback circuit is composed of the current transformer 31 and the capacitor 11, and a negative feedback circuit is composed of the current transformer 10 and the capacitor 11. Then, at a specified temperature or lower, the positive feedback quantity of the current transformer 31 gets larger than the negative feedback quantity, and selfexcitation oscillation is caused, and a discharge lamp 4 is lit. However, at a temperature higher than a specified one, the positive feedback quantity gets smaller and the inverter 30 stops the self-excitation oscillation, and the discharge lamp 4 is extinguished, and the temperature rise is prevented. |
