Research And Design Of A Current Mode Buck Converter With A Wide Input Range

With the fast development of electronic science and technology,demands for consumer electronic products are increasing rapidly. Electronic products such as notebook computer, pad computer and intelligent mobile phone have gradually entered people’s life. As the essential part of electronic products, the battery life and service life of electronic products will be directly affected by performance of the power supply. The switching power supply has been widely used in the market of power management and its share is increasing for its advantages such as high transfer efficiency, low cost and small volume.As an important part of switching power supply,DC/DC convert could realize the effective transformation of the input direct voltage. It can realize boost,buck, buck-boost and polarity inversion functions. So DC/DC convert is widely used in pad computer, notebook computer, intelligent mobile phone and MP3/4.A kind of wide input voltage range current mode step-down converter is designed in this paper. The input supply of the converter range from 4.5 V to 38 V. The internal power supply LDO has been modified for the input voltage may be very high. under_voltage protection of inter power is designed to ensure the regular work of LDO. Besides, the converter can deliver up to 20 A output current, from 0.6 V to 5.5 V output supply, from 200 kHz to2 MHz frequency. application of current control mode offers fast transient response, application of technology of synchronous rectification leads to the reduction of conduction losses and the growth of transfer efficiency.First of all, this paper summarizes development and future trend of switching power supply. Then basic categories, related principles, modulation methods and control modes are all introduced. Both the advantages and disadvantages are discussed. At last, function characteristics, key parameters, system architecture and principles are discussed too.designs and simulations of several sub_module circuits have been presented in this thesis, including: LDO voltage regulator circuit, under_voltage protection of inter power, gate driver of synchronous rectifying MOSFET and mode switching circuit. Using H_spice and CSMC 0.25 um BCD technology, the corresponding circuits are both simulated and verified and it turns out that all the results meet the corresponding demands and parameters. Then the whole circuit has been simulated and it turns out it has good performance.