| 摘要 |
PURPOSE: An inverter for a cold cathode fluorescent lamp is provided to enlarge the dimming range and to reduce a noise by implementing an analog type and a digital type dimming circuits. CONSTITUTION: The inverter for cold cathode fluorescent lamp comprises a battery(31), a transformer(32), a cold cathode fluorescent lamp(CCFL)(33), a controller(34), an analog dimming circuit(35), a digital dimming circuit(36), and a current sensing circuit(37). The output of the battery is converted into a high direct voltage through the transformer and supplied to the CCFL. The controller selectively controls the analog dimming circuit or the digital dimming circuit according to an external dimming signal. When the external dimming signal belongs to the range of 50 to 100 %, then the analog dimming circuit operates and the current sensing circuit detects the current flowing through the CCFL and the detected current is inputted into a step down circuit(38) through the analog dimming circuit. The step down circuit controls the supplying power according to the input signal. When the external dimming signal is under 50 %, then the digital dimming circuit operates and the step down circuit adjusts the output ON/OFF section ratio by using the predefined low frequency pulse width modulation to control the supplying power.
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