| 摘要 |
PURPOSE:To enhance luminous efficiency by interposing a DC-DC converter between a full wave rectifier and an inverter to gradually adjust light dependently on addition of the output of the DC-DC converter into the output of the full wave rectifier. CONSTITUTION:A DC-DC converter 20 is inoperative in a light adjustment mode when a switch 2 is in a position (j), and only an output of a full wave rectifier 4 is applied to an inverter 6. Accordingly, a lamp 7 is extinguished when the output voltage of the inverter 6 is decreased lower than a specific voltage while the lamp 7 is lit with an increase of the voltage, and as a result, the luminous efficiency of the lamp 10 is low due to the repetitive switching operation. The DC-DC converter 20 is operative in a full lighting mode when the switch is in a position (k). A dc voltage of the output of the full wave rectifier 4 added into the output of the DC-DC converter 20 is supplied into the inverter 6 so that the input voltage of the inverter 6 is smoothed, thereby preventing the output voltage of the inverter 6 from being decreased lower than the specific voltage. Therefore, the re-lighting of the lamp can be prevented so as to enhance the luminous efficiency. |
