Design And Research On Current-mode PWM Switching Power Supply Chip

Integrated PWM switching power supplies have been widely used in communication systems, computers, etc. Motivated by portable applications that demand high performance, switching power supplies are developed mainly aiming to high efficiency, high precision and small sizes.The switching power supply unifies all kinds of advanced technology. It is suitable switching AC/DC Adapter, Batty Charger, Open Frame Switching Power Supply and TV Power. Therefore the project is worth studying. A current-mode PWM switching power supply circuit is designed in this thesis. It is based on CSMC 0.5μm BCD process. The system is controlled by current mode feedback loop on the basis of fly-back topology to realize system stability. It uses Internal High-Voltage Startup Circuit to realize power saving. It uses the green-mode to avoid generation of noise. It normally works at 65 KHz frequency and green mode frequency is 22 KHz. This circuit can operate in the temperature rage of -20℃to 140℃.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 Internal High-Voltage Startup Circuit , oscillator, slope compensation, over voltage protection circuit, over OLP protection circuit, logic drive control circuit, timer, RS trigger, 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.