| 摘要 |
PURPOSE:To construct a circuit and device in small sizes, preclude temperature rise of a switching element on the primary side of a converter transformer at the time of dimming, and avoid generation of noises. CONSTITUTION:A secondary winding n2 with an intermediate tap and a main winding n4 for a fluorescent lamp are furnished on the secondary side of a multi-output converter transformer T1, and the primary side is subjected to switching control using a switching element SW1 so that the output voltage of the main winding n4 becomes constant. Choke coils L2, L3 for limiting the lamp current are connected between one end of the secondary winding n2 and its intermediate tap and one end of the fluorescent lamp FL1. The dimming operation is performed by changing the on/off timings of bidirectional switch means DB3, SW3. According to this constitution, the impedance of the lamp current limiting choke coil viewed from the primary side can be made greater than conventional, and the current passing through the primary side switching element SW1 can be lessened, and it is feasible to construct the device in a small size. |
