Design Of Current-mode PWM Buck Converter

With the portable electronic products has been becoming more popurlar in the market, the requirement of power management is increaseingly. So, the new types of PWM controller are the most important. There are two circle controlling systems in PWM controller. The current mode controlling mode improve the system of line regulation and load regulation, heighten the transient responding velocity and strength the system stability. These advantages make the current mode PWM controller used more widely.In this thesis, kinds of DC-DC converter and modulates are introduced first. Then the control techniques of DC-DC converters are completely described, and illustrate the principle of voltage mode and current mode in detail. The advantages and disadvantages of each method is analyzed and compared. And also the thesis analyzed the synchronous rectifier and system stability. Then the methods of how to compensate the error amplifier is introduced, a double-zero, double-pole construction is analyzed individually.By the research of the basic theory of DC-DC converter, a current mode PWM buck DC-DC converter that converting 3.3V-1.8V is designed in the thesis. Each sub-circuit is designed reasonably according to the principle and character of PWM switching converter, such as: bandgap reference, error amplifier, current-sensing, PWM comparator, OSC, slope compensation, PWM control, dead time control module and so on, and protection module including over-temperature module and under voltage module is designed to make the system normal.The design is based on SMIC 0.18μm mix signal CMOS process, and each module and whole system are simulated with Spectre. And the results indicate that all modules have met the requirements. The output voltage stabilizes at 1.8V when the input voltage changes from 2.8V to 4.5V and the ripple voltage is less than 20mV. The output current rating is 360mA. The system exhibits a good load transient response performance when load step from 180mA to 360mA. And in rated load situation, the efficiency achieves 90%. The simulation result shows that a majority of the parameters satisfy design target, and namely proleptic aim is accomplished...