The Design Of The Single-chip DC/DC Converter Based On Peak Current-Mode

With the development of IC industry,Various types of electronic equipment and systems Request switching power supply put forward higher equirements including Switching power supply smaller,Higher power density,Higher conversion efficiency and Better reliability. Switch-model DC/DC converter is a kind of direct current to direct current power converter with high efficiency,stable output power,less ripple and high integration, which can be widly used in various portable electric device. This thesis Achieve a Current on-chip sampling peak current mode step-down DC / DC converter which can meet the required of switching power supply in portable equipment application through the principles of analysis,system sesign,circuit cesign and performance simulation.This thesis choose a peak current mode PWM control scheme and design a DC / DC converter chip at the basis of depthly analyzing the basic principlesof DC / DC converters working mode and summing up the principal strengths and weaknesses ofthe modern DC / DC conversion technology. For current-mode DC / DC converter in the current sampling of the key technical problems, it proposes a current sampling program which achieves a low-power precision current sampling and improvesthe response and conversion efficiency when the supply voltage and load are changing. After analyzing the peak current-mode converter loop model open-loop unstable and slope compensation, it gives a compensation network program and detailed circuit design. it specially designes a DAC with on-chip soft-start circuit which effectively eliminates surge current and output voltage overshoot for the application environment needs.And it designe a chip with a low on-resistance of the power switching circuit which reduces the power consumption at the same time increase the reliability of the circuit.Functional and performance parameters similation is done for each sub-circuit module and the overall circuit using 0.35μm CMOS process and HSPICE simulation software.the results show that with voltage input between 2.6V～4.2V, when adapting 10μF capacitor and 4.7μH inductor for off-chip filtering network, the trasformer can provide up to 500mA load output, all performance indicators meet the design requirements.