Cold-cathode tube drive device

Abstract

A cold-cathode tube drive device includes an inverter circuit (1) for generating a high-frequency voltage, a booster transformer (2) for boosting the high-frequency voltage generated by the inverter circuit (1), a cold-cathode tube (3) which is turned on by the high-frequency voltage after boosted by the booster transformer (2), a series circuit (6) having a reactance element (4) connected in parallel to the cold-cathode tube (3), a synthesis circuit (8) for combining the connected current value i2 of the series circuit (6) with the secondary side current value iL of the booster transformer (2) so as to indirectly detect the lamp current value iL of the cold-cathode tube (3), and a control circuit (9) for controlling the inverter circuit (1) according to the lamp current value iL indirectly detected by the synthesis circuit (8) and controlling the lamp current of the cold-cathode tube (3).

Description

technical field [0001] The invention relates to a driving device for a cold cathode tube. Background technique [0002] Under the prior art, in the back light (back light) of liquid crystal display panels such as liquid crystal television receivers (hereinafter referred to as "liquid crystal TV") and liquid crystal monitors, a plurality of cold cathode tubes (CCFL: Cold Cathode Fluorescent) are used. Lamp) (for example, refer to Patent Document 1). [0003] Fig. 4 is a circuit diagram showing a conventional cold-cathode tube driving device. In the device shown in Figure 4, the inverter circuit 101 generates a high-frequency voltage, and the step-up transformer 102 boosts the high-frequency voltage generated by the inverter circuit 101, and applies the boosted high-frequency voltage to the cold cathode tube 103. The resonant capacitor 104 is a capacitor that forms a resonant circuit together with the secondary winding of the step-up transformer 102 . [0004] The inverter...

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Problems solved by technology

[0007] On the other hand, in the wide-screen and large-scale liquid crystal display panels developed in recent years, the electric wires 106a and 106b become longer due to the use of the long cold-cathode tube 103, etc. , if one of the two wires 106a, 106b connected to the two poles of the cold cathode tube 103 is wound to the other, the parasitic capacitance will increase, the leakage current will increase, and the brightness will decrease. Reduced efficiency

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