| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 92 === Using the LED Print Head for exposure structure inside the Photographic Printer has three benefits: First, it can make the volume of the printer smaller; second, it can make the printer more reliable; last, it can decrease the capital of the printer. But this kind of skill is always controlled by Japanese. To adapt the demand in internal market, this thesis designed a driver IC for LED Print Head. The driver IC adopts a skill of Pulse Width Modulation (PWM) which uses 4-bits digital signal to produce 16 kinds of pulse width under a fixed current. The thesis also designs a Dynamic Pulse Width circuit to make pulse width more variable. In CMOS process, the process will make each IC different. In order to solve this problem, the thesis provides two compensation circuits to compensate the difference between ICs. One is the Pulse Start-Limited circuit which is used to limit the start time of the pulse; the other is the Reference Current Control circuit which is used to adjust the reference current of the current mirror. The range of each adjustable reference current step is 0.1mA. As for the difference between each LED in the LED array itself, the thesis brings up a way to solve this problem. The way is adopting an Output Current Control circuit which can make some adjust in each LED drive current. The range of each adjustable output current step is 0.05mA. As to the problem of power consumption, the thesis also provides two solutions: One is Multi-Chip Segment Exposure, the other is Single-Chip Segment Exposure, both two can decrease the transient large current and the transient power consumption. The whole chip was completed by 0.5um 2M1P CMOS process. After testing, the drive chip can really work well.
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