| 摘要 |
PURPOSE:To improve efficiency at a low cost by controlling the drive pulse width of a switching element without using a feedback circuit and a constant- voltage circuit. CONSTITUTION:A switching element 12 is connected to the primary side of an inverter transformer 10 connected with a DC power voltage on the primary side and a fluorescent lamp 13 on the secondary side, and the fluctuation of the DC power voltage is detected by a drive pulse generating circuit 15. The width of the drive pulse PD synchronous with the external synchronization signal S1 is changed in response to the fluctuation, the on/off period of the switching element 12 is controlled by the drive pulse PD, and the electric power fed to the fluorescent lamp 13 is made constant. |
