| 摘要 |
PURPOSE:To drive the system and to heat and light a discharge lamp securely even in the condition of a deep dimming by placing and connecting a resistance between bases of the first and the second transistors in series to the feedback winding of an oscillatory transformer. CONSTITUTION:Between bases of the first and the second transistors Q3 and Q4, the fourth resistance R5 is placed and connected in series to the feedback winding N3 of an oscillatory transformer OT1. As a result, the current from the emitter of the third transistor Q2 is prevented from flowing into the winding N3 of the oscillatory transformer OT1 through the second and the third resistances R3 and R4, and all the currents I1 and I2 flowing from the emitter of the transistor Q2 through the resistances R3 and R4 can be made flow in to the bases of the transistors Q3 and Q4. As a result, when the output of a rectifying circuit II is set off by a preceding preheating divided voltage resistance R1 in a preceding preheating time, for example, and even though the power supply is turned on in the condition of a deep dimming, a sufficient base current can be fed to the transistors Q3 and Q4, and the discharge lamp can be started and lighted securely. |
