| As a type of switching power supply, DC-DC converters have the merits such as flexibilityof topologies, high conversion efficiency, wide application range and high integration etc., whichare widely used in the power management units (PMU) of many kinds of portable electronicproducts. With the rapid development of the white LED lighting, mobile power supply and theintelligent lithium battery charger, Boost-type DC-DC converter chips, a nessesary part of theseproducts, have become a hotspot of research in recent years.Aimed at the chargers for single lithium battery, a peak current mode Boost converter chiphas been designed with SMIC0.18μm process in this thesis. The input voltage range of theproposed Boost converter is1.8V to3.3V, the output voltage is stabilized in4V, and the rangeof the load current is200mA to600mA, the switching frequency is1MHz. A novel currentsensing circuit is proposed to acheive high accuracy, low mismatching error and low powerconsumption. Meanwhile, a slope compensation circuit with gilbert cell is proposed toeffectively eliminate the subharmonic oscillation phenomenon which usually occurs in currentmode control. The simulation results show that the efficiency of the Boost converter chip is up to92%and it has the features such as fast transient response and low ripple coefficient etc., theaverage recovery time is48.7μs and the maximal output voltage ripple is72mV.This thesis firstly introduces the common topologies, modulation modes and feedbackmechanisms of DC-DC converter. Then the common formulas of the Boost topology in thecontinuous conduction mode (CCM) and discontinuous conduction mode (DCM) are derived indetail. Then, the system design method is introduced in3aspects such as the choice of off-chipcomponents, the analysis of current sensing methods and the analysis of loop stability in Matlab.Isolated module design and simulation are carried on Cadence Spectre. Finally, systemsimulations are preceeded and conclusions are obtained. |
PDF Full Text Request