| Summary: | 碩士 === 國立交通大學 === 電機與控制工程系所 === 97 === The commercial possibilities of the LED are increasing gradually since the applications of light-emitting diode are more and more prevalent in large scanning boards, vehicle-used light-emitting systems and backlighting-used display systems. Considering the cost of light source in the panel of notebook computer, the cost of light-emitting diode is 2.5 times than that of the cold cathode fluorescent lamp (CCFL). That is, it costs more than 70% of the original design. However, there are some important advantages by means of LED as a backlight module. Especially, energy saving improves the battery lifetime longer than 40% of the original design by means of CFFL backlight module. The LED backlight module can reduce the thickness of panel module. Thus, the weight is light and the color saturation is better than before. The impeding of liquid crystal display technique expending to the liquid crystal television is the developing of the digital display technique. After scaling up the size of the liquid crystal television, it should lower the cost to compete with the conventional television and plasma television. Besides, the liquid crystal display is a non-self-luminous technique and thus it leans on the backlight source to display the image. In the applications of the LCD panel, the backlight source usually needs large amount of light-emitting diodes to provide enough brightness. Therefore, if the driver circuit has high efficiency and good driving capability, the cost of the LED system can be reduced.
This thesis proposes a LED driver with current Balance control circuit for the backlight of LCD display. This driver circuit design was simulated and fabricated in VIS 0.5�慆 embedded high voltage 5V/40V CMOS technology. The input voltage is 12V and the output voltage is 40V. The boost voltage regulator uses a pulse width modulation (PWM) and a reference tracking circuit according to the variation of forward voltage of LEDs. The advantage of the proposed method is to offer high reliability to the LED backlight system.
|
|---|
