| Summary: | 碩士 === 國立中興大學 === 電機工程學系所 === 99 === In recent years, we have gradually accepted the concept of the energy conservation and reducing carbon dioxide emission, and the mainstream of the design and manufacturing idea for daily supplies will follow it. Therefore, it is very important for increasing the efficiency when we make use of energy. It is possible to conserve electricity energy by using some suitable components, LED especially. Long life of LED is its merit, and LED can be widely applied in many products, such as the lighting and lamps, large-scale electronic monitors, back lights, vehicles electronic parts, portable electronic devices and so on. In this thesis, it is mainly aimed at the LED driver to have a discussion about reducing the electricity energy loss and enhancing the accuracy of lower error driving current, and looking forward to more practical applications for automobile equipments that are necessary, for instance, the rear light, the turn signal, the head light, the brake light, the lighting, the indicator, the back light signal, the head light, the brake light, the lighting, the indicator, the back light panel, etc. When the battery power is unstable, or insufficient battery charge by the problems of charging circuit, engine or generator, it can assure the reliability of driving safety.
In addition to the system clock generator and the function control circuits, the circuit designed in this thesis makes use of a method of Automatic Pulse Frequency Modulation Control Output to design the boost converter circuits. It can supply a power source with preset and regulated voltage, offer a number of independent circuits for current balance which could preset different current in demand, and also control the lowest loading voltage automatically. In the experimental model, boost converter output voltage will rise to the preset value of 15.6V. The three current balance circuits provide the three LED strings with stable regulated current, respectively. Each LED string can serially connect from 1 up to 3 LEDs at will. The total loading current achieves approximately 150mA. Although the LED string has replaced the different number of LEDs, it can still maintain the same current, and the current error coefficient is just only 0.054%.
The circuit was designed by using TSMC 0.35μm 2P4M 3.3V/5V Mixed Signal CMOS fabrication process. The chip size is 1.328×1.328 mm2 .The chip was built in multi-function control circuit with pin out so that, it is so easy to be used for automobile electronic equipments.
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