At present, an LCD screen of desktop and notebook computers, personal digital assistants (PDAs) and webpads utilizes a driver device to drive a high-voltage driven cold cathode fluorescent lamp (CCFL) and project a light on a backlit panel, so that users can view the display on screen clearly. Further, some of the present CCFL driver device manufacturers are solving the problems on how to equalize and stabilize the brightness of the CCFL.
Some of the circuit designs related to the way of equalizing the brightness of the CCFL were disclosed in the R.O.C. Patent Publication No. 383122; the Japan Patent Publication Nos. 09-102397, 2000-150191, 2000-292775, 2004-69907, 2004-39336, 2000-243586, 2000-340388 and 2004-220810; and the U.S. Pat. No. 6,188,177. The common technical characteristic of these patents resides on providing a temperature compensation device, which is used to detect the temperature of the illuminant region of the CCFL and then output a temperature signal to a control unit, such that the control unit outputs different drive signals corresponding to the impedance at different temperatures of every cold cathode fluorescent lamp to maintain the luminosity of each CCFL. In other words, the aforementioned patents focus on changing the magnitude of the drive signal by the ambient temperature as to equalize the brightness of the CCFL. However, a very difficult problem exists in the screen industry that the CCFL luminous area is a closed space and the heat produced cannot be dispersed effectively by the existing technology as to equalize the brightness of the CCFL, and it usually requires a higher drive voltage and current to overcome the problem, but on the other hand, the heat produced is increased (for example, the brightness should be adjusted for outdoors). Besides this, if the screen is placed at a position with a high ambient temperature such as the living room illuminated by sunlight will give rise to an overloading ambient temperature to the overall screen, and thus affecting the service life of all electronic components and the liquid crystal display panel. As a result, the CCFL will be damaged easily, and the resin equalizer will be deteriorated to produce the yellow phenomenon due to the high temperature. Since the CCFL and equalizer are important components of a screen and it is difficult to replace the components once they are damaged, therefore most consumers are forced to replace the whole set of screen, which does not comply with the service life and economic benefits of the existing screens.