Design Of A Peak Current Mode Controlled PWM Fly-back AC-DC Converter XD1576

Portable electronic products such as mobile phone, pad, etc. have made great development in recent years, which improves people's life vastly. As the core of their power supply system, the power supply is inevitably affected by people's higher requirement. The Fly-back AC-DC converter has many advantages such as a high conversion efficiency, a low power consumption, a small size, a wide input range, a simple circuit, input and output isolation and a low cost, which make it the first choice for the power adapter, charger, LED driver and other small and medium-sized power equipment.A peak current mode controlled pulse width modulation(PWM) Fly-back AC-DC converter XD1576 is designed in this thesis, which is based on the project of ‘the research and design of key techniques for high performance AC-DC converter', supported by the Key Lab of High-speed Circuit Design and EMC, Ministry of Education of Xi Dian University.The operational principle of Fly-back AC-DC converter is introduced in this thesis, and a theoretical derivation for normal state working analysised in detail. The system function of the chip is designed firstly, and then the computing method of the components selecting for a typical application circuit with XD1576 is illustrated. In addition, the key sub modules of XD1576 together with the circuit designs are presented, which includes the theoretical basis and circuit implementation of the Bandgap reference circuit, the theoretical analysis and circuit design of the over temperature protection function circuit, the necessity analysis and the design scheme of the under voltage lock module, the principle analysis and reliability improvement of the oscillator module.By detecting the load, XD1576 can work in the green mode and active burst mode when the load is light. In the green mode, XD1576 reduces the PWM frequency to minimize power loss, thus increases the conversion efficiency. In heavy load case, the chip enters the overload protection mode, in which the chip close the chip switch operation and protect the safety and service life of the chip and the system. A complete protection system is offered in XD1576, ensuring a safe and high efficiency work state. When XD1576 working in a mode of changeless switching frequency, the chip may suffer a trouble caused by serious electromagnetic interference(EMI). In order to solve this problem, a frequency shuffling technique is implemented in XD1576, which can disperse the harmonic interference energy and also improve its EMI performance.Based on a process of 0.35?m BCDMOS, XD1576 is designed and simulated with the software of Cadence Virtuoso platform Hspice D simulator. The simulation results of sub modules and whole chip show that XD1576 meets the expected specifications and works excellently.