Design Of Current Mode Boost DC-DC Converter

With the advancement of the theory of electronics,the connection of networks,and the entry of smart applications,the popularity of small portable electronic products has become higher and higher.As a medium for energy management in electronic products,the role of power management chips has become increasingly important.It is of great significance to the improvement of the efficiency of the use of electronic products.Based on an LED driver chip,this thesis designs a boost DC-DC converter with peak current control.Its load is a constant current source with variable current,maximum current1.5A,and 128 adjustable.This chip’s technology is simple,small area,low cost,and can achieve boost and pass through two system operating modes under the working condition of the internal clock frequency of 1M and maximum 4M,and through the tape test,the system is stable,the function is normal,and the performance is good.This paper first analyzes various structures and principles of the boost DC-DC converter,and explains why to select the peak current mode as the control mode.The peak current mode boost system is linearized,a small signal model of the system is established,and the transmission function is solved.In view of the occurrence of sub-harmonic oscillations in the peak current mode of the system,the stability analysis of the system provides a basis for system compensation.Based on the MagnaChip HL18 GFL.18um process,this chip designs sub-circuits such as a bandgap reference,an oscillator,an error amplifier,a current detection and slope compensation module,power driver module,and load current drive module.In order to optimize its performance,the oscillator module is designed with a trimming circuit and a new type of current detection circuit is designed to achieve a current detection accuracy of5%.In addition,a leading-edge blanking circuit is added to ensure the accuracy of current detection.A segmented driving circuit was designed to reduce transmission delays and to avoid high currents in the moment of logic change to damage the power MOS.The load current drive circuit uses double loop control in order to confirm the accuracy of the constant current source.The designed sub-module are integrated in the system,and the SPECTRE simulator is used to perform the pre-condition simulation of the conditions and process angles.Thedigital circuit is used to simulate the functions using the AMS simulator and the parameters and the chip functions are normal.After the chip layout design is completed,postsimulation is performed,and its parameter functions are within the normal deviation.Finally,it is made into a mask and factory-stretched.After testing,the packaged chip had a shutdown current of less than 1 uA,current accuracy of 1%,and frequency accuracy of 4%.In the range of load variation,the conversion efficiency of the converter is all above 85%,and the conversion efficiency of the low-current mode is as high as 97%.