| 摘要 |
PURPOSE:To prevent cut-off and instability of an electric discharge lamp without giving stress to an element by lowering the frequency of a switching element periodically and for only a fixed term at the time of falling of a DC power supply voltage, and periodically generating a high voltage. CONSTITUTION:When a power supply voltage falls, output of a detection circuit 9 becomes L, a transistor Tr1 turns ON and a timer IC12 oscillates. When a third pin of IC12 is H and Tr2 is OFF, an oscillation circuit 7 oscillates with the frequency to be determined by the resistors R4, R5 and a capacitor C2 and when the third pin is L and Tr2 is ON, the circuit 7 oscillates with the frequency to be determined by the resistor R4 and the capacitor C2. Accordingly, high and low switching frequency is repeated periodically to generate a high voltage. The frequency and generated voltage can be set up by the resister and the capacitor. Thereby, cut-off and instability of the electric discharge lamp can be prevented without giving stress to an element. |
