| Summary: | 碩士 === 國立交通大學 === 電機與控制工程系所 === 96 === In the past, the backlight module for liquid crystal displays (LCD) consisted mainly of cold cathode fluorescent lamp (CCFL). However, with the greatly improving technology of light emitting diode (LED) process, the benefit for LED backlight is more and more obviously such as high color saturation, longer product life and none hydrargyrum. Thus, people are trying to replace CCFL to RGB LED to reach the high quality images in displays targeted for market.
Two most popular approaches for LED driver implementation are an inductor-less charge pump converter and an inductor-based converter. Although the cost and EMI problem of a charge pump is low, the load ability and efficiency is poor compared to those of a switching regulator. In the application of high brightness LED driver, the high power characteristics are needed, since the number of LEDs for backlight implementation is above hundreds. The highly efficient voltage regulators are needed for energy transform, because of low power consumption in converters. Moreover, owing to driving a large number of LEDs in one controller, the cost of the system is reduced.
This thesis presents a current domain DC-DC boost converter for LED application with 12V input voltage and 48V output voltage. The boost voltage regulator utilizes a pulse width modulation (PWM) current programmed control method, which transfers the control signal in current domain to improve the transient response. The disadvantage of this method is big static error. The supply voltage of the controller is in the range from 2.5V to 3.6V. The best efficiency of the converter is 92% at 300mA load current. This converter design is simulated and fabricated in UMC 0.35�慆 embedded high voltage 3.3V/18V CMOS technology.
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