| In this paper, with the design of high-performance chips for the target, and combined with the current demand, a DC-DC converter XD1407 is designed On the basis of the project “Theoretical Research and Design of Key Technique for Power Management IC ”.Firstly, the switching power supply is introduced. Then combined with the current market situation, we analyze the core components of the switching power supply DC-DC converter, the importance and development trend of which are introduced; Then the basic structure and operational principle of DC-DC converter are detailedly described; Meanwhile the control mode and the efficiency of the Boost DC-DC converter are discussed. Combined with the chip features, we select the current-mode control, and propose solutions to improve efficiency; In addition, the system of XD1407 is researched and designed, and the system model is set up for the stability of the Boost DC-DC converter,we analyse the distribution of zeros and poles about the Boost DC-DC converter, and the stability of the chip is made simulation; Afterward, the design and simulation of key sub-circuits are presented; Finally, the simulation waves of the whole chip are given.The fixed switching frequency of the Boost DC-DC converter XD1407 is 500 k Hz, and the peak-current mode control is presented. The system with integrated power switch and synchronous rectifier makes its peripheral circuit simplified when it is applied and reduces the board space; The input voltage of the XD1407 is 2.5V-5V; the peak current is 8A;the maximum current is 5A. The XD1407 designs internal soft-start circuit, to prevent the damage caused by the output voltage overshoot or inductor current overshoot.The XD1407 works in both PWM mode and Light Load mode. When the load is small, by detecting the inductor current information the chip works at light load mode, in which the IC works a few cycles continuously, then enters a sleep mode, During sleep mode, the power switch and synchronous rectifier can not be turned on. the modules of the chip is turned off, and the chip’s quiescent current is reduced 55 u A.In this case conduction losses and switching losses can be almost zero and the output voltage begins to drop. In the circuit by detecting the feedback voltage FB to control the output voltage drop, using of the high-precision comparator output the pulsesignal.By the logic circuit control the chip to exit the sleep mode.The chip works like this.As the load increases, the chip can automatically switch to PWM mode. It can switch smoothly between the two modes of operation,which maintains high efficiency over the wide load range,while ensuring that the chip has a smaller output voltage ripple; By analysing the stability of the Boost DC-DC converter and setting up the mode with theoretical knowledgel, frequency compensation strategy is proposed in the IC. The system can work stably in the appropriate bandwidth and the phase margin by adjusting the parameters. At the same time XD1407 integrated a variety of protection circuits, make the chip in the low input voltage, high temperature and high voltage condition is not damaged.Based on the 0.35μm CMOS process, the design and simulation of XD1407 are completed by using Cadence software, which can ensure that the simulation results can meet the design requirements under different device models, different power and temperature.The simulation results show that the performance in application is excellent and can meet the design requirements. |
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