Research On Low Power AC/DC Power Management Chip

With the development of science and technology, requirements of electronic products areincreased. As the power supply equipment for electronic products, the development of poweralso becomes essential. It develops toward the direction of high integration, high conversionefficiency and low power consumption. Based on the intense research of the power supplyefficiency, a low power AC/DC power management chip is designed.The flyback structure and PWM modulation mode are adopted in this switching powersupply management chip, and its main function modules include reference voltage sourcecircuit, PWM generation circuit, oscillator circuit, frequency modulation module circuit, etc.In order to make the system safe and work stably, a variety of protection circuits areintegrated in the chip, which include over-voltage protection circuit, under voltage clampingcircuit, over-current protection circuit, thermal protection circuit and leading edge blankingcircuit, etc. In order to meet the requirements of low power consumption in modern portableelectronic products， a light load efficiency mode is proposed to solve the problem of the lowefficiency under light-load in PWM mode, that makes the chip achieve high efficiency withinthe entire load range.The light-load efficiency mode is mainly consisted of two aspects. Onthe one hand, the system works normally under PWM mode, if it is under the condition of noload or light-load, it enters PFM mode. By reducing switching actions, switching loss can belowered, low power consumption and high conversion efficiency also can be got; On the otherhand, the loop of output power limit is added. This loop not only reduces the conduction lossof the power transistor, but also saves the chip space and cost.CADENCE simulation tools are used to complete simulation and analysis of eachmodule, then the whole circuit of the chip is also verified through simulation, which includingnormal working situation of the chip, PFM mode function during light load，and the efficiencyunder different load conditions. The theoretical analysis and simulation results show that thefunctions of the chip are normal and meeting design specifications. Finally, according to the circuit, the layout is designed; the feasibility of the layout is also verified by the DRC andLVS.