| As the rapid development of technology, a variety of electronic devices continue to be invented and put on the market. Switching power management chip is a important part of the electronic equipment. With the electronic devices quickly updating, a high performance switching power supply chip can significantly improve the market competitiveness of electronic products. High-accuracy output voltage, high efficiency, small size is the goal that the switching power supply chip pursues.This paper presents a step-down DC-DC converter based on bipolar process, it uses PWM modulation, peak current mode to regulate the entire system. With integrated power switch inside the chip, the maximum load current can reach 4.5A. The input voltage ranges from 6 to 25 V, the output voltage is 5V and the switching frequency is 500 KHz.After the briefly introduction of switching power supply development and future trend, we analyze and discuss the various topologies, modulation methods and control modes of DC-DC converter. After comparing their advantages and disadvantages, we ultimately opt PWM modulation and peak current mode for the chip. To solve the sub-harmonic oscillation problem, a detailed analysis of the necessity of the slope compensation circuit is present. Then, we design the peripheral chip topology and deduce the requirements of peripheral devices. We design the overall architecture of the whole chip, describe the function of each module. Then several major modules specific analysis and design, and simulation capabilities are provided. In particular, we focus on the reference circuit design, and propose a high and low temperature high-order curvature compensated reference.Based on CSMC 2μm Bipolar technology, we carry on the overall simulation for the chip. Simulation results show that the chip can well achieve the intended function. The linear transient response and the load transient response is excellent. The chip has high conversion efficiency and the output voltage is stable. |
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