Research Of A Fast Transient Response BUCK Controller Based On Constant On Time Control

At present along with the continuous progress and development of modern electronic science and technology, a variety of new electronic products continue to emerge endlessly, such as intelligent touch-screen mobile phones, smart phones, tablet PCs and others. Thus the requirements of switching power supply are increasingly rising, such as when the power system switches from a sleeping mode to active mode,there is a significant change for load current. Hence the regulator must be able to respond immediately.In view of the above requirements, this thesis designs a fast transient response BUCK controller based on the constant on time. The controller uses a constant on time valley current control mode architecture to deliver low duty factors, and to improve transient response, besides the controller can operate in the discontinuous conduction mode and forced continuous mode. This thesis firstly introduces the background and significance of the research, analyses the research status of switching power supply and the future direction of development at home and abroad; and focuses on pulse frequency modulation mode and the peak current control mode, the average current control mode and so on. Then this thesis puts forward three methods including the inductance value and output capacitance and switching frequency optimization design and the valley current control mode and the constant on time mode to improve the transient response.Then the advantages and disadvantages of several typical constant on time mode circuit are analyzed and a novel constant on time mode module circuit where the switching frequency is almost constant is proposed to simplify the electromagnetic interference shielding equipment. Next, analysis and simulate the whole function module circuit including the constant on time module, valley current module and PLL module and the main parameters of the converter system. Finally, simulation and verification of performance parameters of the entire converter system are presented.Based on 0.35?m BCD process, system function and parameter simulation of the designed circuit module are simulated by Cadence Spectre and Hspice software. The simulation results denote that all the modules are working properly, and the performance parameters of the BUCK controller system are normal. The input supply voltage can range from 5V to 28V, with maximum load current of 10A. The transient recovery time is 65 ?s and over charging voltage is 5 3mV in a step load change between 5A and 10A. The transient recovery time is 54?s and over charging voltage is lOmV when the input power supply voltage changes from 10V to 20V. The whole chip meets the requirements of rapid transient response characteristic, and the performance meets the design and application requirements.