The Design Of Low Power Constant Voltage Output BUCK AC/DC Converter With Intergrated 500V Power Transistor

Nowadays,all kinds of electronic products continue to enter our lives and become an indispensable part of life.However,electronic information products can not do without the support of power supply system.Stable power supply is the most basic condition for circuit work.How to get a stable power supply in various environments is a matter that power chip designers have been studying.Moore’s law guides the development direction of increasing the integration of transistors in chips.Under the guidance of this law,the complexity of circuits in chips is increasing day by day,and switching power supply chips are no exception.From the earliest discrete device circuit boards to today’s nanotechnology process,circuits with higher and higher integration bring us more development potential and direction.In order to get stable power supply,this paper designs a low-power buck AC/DC power supply chip integrated with 500 V power transistor.The chip adopts PWM and PFM mixed modulation scheme to reduce power consumption,and the modulation mode of the chip can be switched according to the load change.And the power transistor which can withstand up to 500 V voltage is integrated into the chip as a switch,which effectively simplifies the use conditions of the chip.The chip uses the output current of the system to charge the external VCC capacitor to supply voltage to the chip without auxiliary winding power supply,which simplifies the peripheral circuit design of the chip.Many protection functions are integrated in the chip,such as over temperature,under voltage,overload and so on.The voltage conversion circuit constructed by the chip can output stable 5V/3.5V DC voltage under the condition of input 85v-265 v AC power supply.The module circuit and the whole circuit of the chip are simulated by spectre and hspiced simulators of cadence software in 0.8 μ m CMOS process library.The final system simulation results show that the linear regulation rate of output voltage is about ± 3.9%,and the load regulation rate is about ± 4.5%.The results show that the system has good constant voltage characteristics.This paper analyzes the basic architecture of the power conversion circuit,the modulation mode and feedback control mode of the power chip in detail.According to the requirements and the application scope of the chip,the index parameters of the chip are designed in detail,including the limit parameters and electrical characteristics,and the packaging mode of the chip pin is described.The architecture of the chip is designed by using the top-down design method.The internal modules of the chip architecture,including bandgap reference,oscillator,driver,over temperature and under voltage circuit,are described in detail,and the simulation results are given.The peripheral circuit design and parameter selection of the chip are explained,and the whole circuit is simulated in turn,and the results are explained.Finally,the chip layout design is guided.