Research And Design Of Fast Startup And High Efficiency Boost DC-DC Converter

With the development of science and technology and the widespread application of 5G network,electronic products have become an indispensable part of people’s lives.These portable electronic products are trending towards small size,light weight and long battery life,so small size,low power consumption,high efficiency power management chips emerge.Among them,as a kind of power management chip,DC-DC converter uses high-frequency switching action to guide energy storage devices for energy transmission.Ideally,the switching voltage drop is zero and there is no energy loss.Compared with low dropout regulator（LDO）,DC-DC converter has higher conversion efficiency,so it is widely used in engineering.Firstly,this paper analyzes the basic architecture,working principle,feedback control mode and switching modulation mode of Boost type DC-DC converter.According to the advantages and disadvantages of different architectures and application requirements,a fast start and high efficiency Boost converter is designed.The converter adopts the peak current feedback and voltage feedback double loop control mode,pulse frequency modulation（PFM）mode;Then the paper gives the overall architecture and electrical characteristics of the chip design index,and from the perspective of application analysis,gives the selection rules of peripheral devices,in order to have a better match.The working mode of the chip is given in this paper,and it is divided into startup stage and voltage regulator stage.The startup stage works in continuous on-off mode to accelerate the startup speed of the circuit,and the voltage regulator stage works in discontinuous on-off mode to reduce the working frequency.Based on the analysis of the power loss of Boost converter,the corresponding power optimization scheme is proposed.Compared with the traditional Boost converter,the Boost converter designed in this paper has built-in self-excited oscillation circuit,and its working frequency can be automatically adjusted according to the load size,greatly reducing the power loss.The converter uses two external resistors to set the boost voltage,and the peak inductance current can be programmed through the external resistance R_EXT,improving the flexibility of circuit applications.The paper also introduces the design scheme of the key modules of the chip and the simulation verification of the electrical parameters of the modules,including reference voltage source,charge pump,peak current limit module and zero crossing detection（ZCD）module.In addition,the chip has over temperature protection and undervoltage lock protection module,which can avoid damage during overdrive.Based on DB Hi Tek 0.18um BCD process model,this paper uses Candence software to design and simulate the circuit.The simulation results show that:under the ambient temperature of-40℃～125℃,L=4.7u H,C_IN=100n F,C_OUT=100n F,input voltage in the range of 3V～5V,output voltage can reach 15V～80V,typical output voltage is 55V.When the input voltage is set to 3.6V and the output voltage is set to 55V,the startup time of the Boost converter is 125us and the maximum output voltage ripple is 320m V.Compared with the average output voltage,the ratio is 0.58%.When the load current is set to 0～40m A,the maximum efficiency can reach 90%,and in light load also has a good conversion efficiency,more than 60%.In addition,the load adjustment rate is 2.7%/A,the linear adjustment rate is 0.02%/V,the response characteristics are good,meet the design requirements.