| 摘要 |
PURPOSE: To light a discharge lamp with a large power factor by carrying out a.c. input to a DC/AC transformer through a rectifying circuit and at the same time connecting connection points of a pair of diodes with one end of the discharge lamp through a capacitor, and connecting the other end with a switching transistor through an LC circuit. CONSTITUTION: After passing an EMI filter constituted of an inductane 6 and a capacitor 8 and an EMI filter constituted of an inductance 7 and a capacitor 10, a.c. voltage applied to the a.c. input terminals 1, 2 is rectified by diodes 11, 12. The resultant d.c. voltage is applied to d.c. input terminals 13, 14 of a half bridge DC/AC transformer 15 through a voltage doubler circuit 8. The voltage from the mutual connection points of the diodes 11, 12 is applied to one end electrode 27 of a discharge lamp 20 through a capacitor 21. The other end electrode 28 of the lamp 20 is connected with a mutual connection point 22 of switching transistors 18, 19 through an LC circuit constituted of inductances 24, 25 and the capacitor 26. When either one of Tr 18, 19 is turned on, the control circuit 34 controls as to turn off the other. |
