| The switch power possesses the advantages of high efficiency, high reliability and compact size compared with conventional linear power which becomes a pop research object home and abroad. Due to its characteristics of fast response, good stability, inherent current limiting, current-mode controller has been widely applied in power management circuits. In this background, DC-DC switching converter that adopts a novel dual slope compensation technology is studied in this dissertation. The allowable input voltage ranges from 2.7V to 5.5V and its output voltage can be programmed between 2.7V and 13V, and its operation frequency is 250 kHz, additionally, the output current is in a 200mA range in typical application. It can take place of the primary boosted converter of thin-film transistor liquid-crystal displays of a triple-output. The dessertation primarily studies the slope compensation theory in PCM converter.The oscillations both input voltage variation and inductor current perturbation resulted in are analyzed. A middle method presented can reject the two instabilities. The thesis presents an idea of dual slope compensation beyond of conventional single slope compensation. The corresponding design of dual slope compensation circuit is finished, the dual slope compensation signals as difference mode ones are put in circuit through a sum comparator, disturbing signals in the dual slope compensation signals are rejected in effect, which strengthens the accuracy of slope compensation and improves the control accuracy of converter. The sum comparator architecture in place of error amplifier and PWM comparator can parallel process both slope compensation signals and feedback variable of conventional serial process, which minishes delayed time of both slope compensation and PWM, and increases the transient state response speed of the system. The overheat protection and under voltage protection modules are integrated in the die to allow the reliable operation of the system.The design and analysis of sub-block circuits are provide in the thesis where sweep -generation circuit, the generator circuit the dual slope compensation signals, current sampling transition circuit and sum-comparator are detailed discussed, and reference and current limit is analyzed too, and other sub circuits are briefly analyzed. Through the whole simulation, the system output stability is good for 3.3 voltage input. Its output ripples is within 1%. After adding the couple slope compensation into the system, the system exhibits a good load transient response performance when load current abruptly varies. The system can also exhibit excellent power rejection capability. Its efficiency can go up to 91% under PWM. |
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