| Switching regulators have been widely used over the world for the virtues of high integration level, more cost effective, lower component count switcher solution, high efficiency. With the development of the battery-operated portable systems, it is becoming an essential common building block since the linear voltage regulator cannot be used because of its low power efficiency, especially for the development of battery-operated portable systems.For the portable electronic products powered from batteries, the implementation technique of PWM current mode in DC/DC converter is studied in this thesis and a boost DC-DC converter using 0.6um BCD technology is designed. This regulator can generate output voltage as high as 12V with wide input voltage range of 2.6V to 5.5V. It has the advantages of high-precision, simple circuit, low power consumption, wide temperature range of -25℃to 85℃and 90% high convert efficiency. At the same time, the IC has two switching frequencies (640kHz or 1.2MHz selectable), under-voltage protection and programmable soft-start. Cooperating with simple periphery component, a full DC/DC converter is formed. It can be used in LCD displays, PCMCIA cards, portable applications.In the thesis, the basic operation principle and topologies of DC/DC converters are given first. The PWM current mode is mainly discussed. Then, according to the function application and characteristics, the whole chip structure is given and analyzed. Some sub-block circuits (error amplifier, soft-start, enable comparator and under-voltage protection circuit) are designed and several electrical characteristics are simulated using HSPICE. Finally, the whole chip performance is simulated. And the results show the satisfaction to both function targets and characteristics. It is a worthwhile and valuable experience. |
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