| Summary: | 碩士 === 清雲科技大學 === 電機工程所 === 99 === Along with the trend the high power white LED is taking position ad the mainstream in the automobile headlight market, this dissertation aims to develop an SEPIC converter with innovative topology for LED headlight driving. The proposed headlight system consists of automobile power-set, SEPIC power converter, digital control circuit, dimming circuit, and LED load module. The innovated SEPIC converter is designed with dual coupled inductors. While the primary coupled inductor is used to convert energy, the current-sharing coupled inductor is applied for current balancing between the right and the left LED headlight. A third winding is included as well in the inductor for de-magnetization and energy recovery. Dimming to half output of the LED headlights while automobile is running at zero speed is
Incorporated in SEPIC drivers in order to reduce unnecessary power consumptions.
Except analysis, design and simulation, prototype SEPIC converter is
Implemented for theoretical verification. The prototype comprises two sets of SEPIC converter with rating 40W/18.5V/2200mA and 40W/18.5V/1400mA, which are used respectively to drive high beam and low beam LED module. Converter voltage
regulation is realized by analog IC TL494 and digital signal processor
TMS320F28035. The zero speed dimming is accomplished by PWM current control.
In terms of LED load, the low beam Bridgelux 7W/700mA LED module is
connected with 3 LEDs in series and 2 LEDs in parallel. The high beam Citizen
20W/1100mA LED module is connected with 2 LEDs in parallel. As a result, the
measured converter waveformss confirm the theoretical design, and consistency of
load currents in different headlight is obtained as well. The measured converter
efficiency at full load is 90%, and is 93%at half load. The low beam flux at full load
is metered at 2400 lm, and 3000 lm for high beam flux, which satisfies the
internations LED headlight code requirement.
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