A Current-mode Control Research And Design Of The Pwm Switching Power Supply Circuit

Switching power supply is paid much attention for its high efficiency and low power consumption. Now it is popular used in general switching power supply, special-purpose switching power supply, special switching power supply. Core unit - control circuit integration of the switching power supply has been one of switching power supply development for many years. A smaller volume, the less EMI, over current and over voltage protection circuit technology has been developing in this process.The switching power supply unifies all kinds of advanced technology. It is suitable for high power AC-DC Adapters for Notebooks, Offline Battery Chargers, Set-Top Boxes Power Supplies, TV, Monitors, etc. Therefore the project is worth studying. A current-mode PWM switching power supply circuit is designed in this thesis. It is based on UMC 0.6μm BCD process. The system is controlled by current mode feedback loop on the basis of fly-back topology. With input voltage 200V and 400V, an output voltage up to 19.3V can be stably generated. It works at 100KHz frequency and maximum duty is 80 percent. Slope compensation maintains stability at duty more than 50 percent. Soft-start can eliminate the inrush current when the power switch starts. The chip itself goes into cycle skipping at light loads. Inter frequency jitter function is used for improved EMI. Over current and over voltage protection are provided. This circuit can operate in the temperature rage of -25℃to 85℃.The whole chip architecture was proposed according to basic operation of fly-back topology and basic principles of current mode control. Then, with different loads the whole chip operational principle was analyzed on the basis of the application circuit. Based on the whole chip function requirements, sub-block design and simulation were completed, including frequency jitter circuit, oscillator, slope compensation, over voltage protection circuit, leading edge blanking, over temperature protection circuit, logic drive control circuit, timer, RS trigger and accessory power supply circuit. At last, the whole circuit was simulated with regulation loads, light loads and heavy loads. In the conclusion of this thesis, the author summarized own work. Based on the whole circuit principle analysis and sub-block design, the author simulated the sub-block circuits and the whole circuit by applying the EDA tool HSPICE. The simulation results indicate that the switching power supply circuit has achieved expectation of the function target and the electrical characteristics. Moreover, the circuit principle analysis and design has been verified. Although there are unavoidable disadvantages of this thesis, it is a worthwhile and valuable experience.