| As the key technology to realize "intelligent transportation",autonomous driving has become an inevitable trend of future automobile development.Recently,the vehicle intelligent electronic system has been used in a period of rapid development,and new technologies emerge one after another.As one of the key technologies of the autonomous driving system,the speed of product update and iteration has also increased rapidly,which has brought many new challenges to the corresponding power management,including diversified demands for high power output and low voltage ripple,etc.This paper mainly studies and designs the key power technology of the laser driver for the high-performance requirements of the vehicle laser radar.In order to meet the requirements of the laser drive chip for a wide voltage range,the design of the power converter adopts a four-tube buck-boost structure,which can realize the functions of boost,buck and buck-boost at the same time.According to the current inputoutput relationship,the converter can automatically switch between the three modes of boost,buck and buck-boost.In order to meet the requirements of the laser driver chip for stable voltage,the output voltage ripple of the power converter needs to be small,and the output voltage can be smoothly transitioned when the input voltage changes or the load current suddenly changes.In this design,an output voltage monitoring technology is used,which can limit the overshoot and sag of the output voltage within a certain voltage range when the buck-boost mode is switched and the load current is abruptly changed.In order to meet the high power requirements of the laser driver chip,the power converter needs to have a strong load capacity.In this design,the parameters of the power device are calculated accurately,and combined with the synchronous rectification technology,the conversion efficiency of the converter can be maintained above 85% under heavy load(14W).In order to meet the low power consumption requirements of the laser driver chip in light load or standby state,the reverse current monitoring technology used in this design can effectively avoid the reverse current loss of the switching regulator in the forced continuous conduction mode.Combined with PSM technology,it can further reduce the energy consumption of the chip in the standby state.In view of the use environment of the vehicle laser radar driver chip,the design of buckboost power converter needs to meet the characteristics of miniaturization,low cost,high efficiency and high power.By integrating Bipolar,CMOS and DMOS devices,the BCD process integrates the advantages of high speed,high integration,low power consumption and strong load driving capacity,which is suitable for the design of power converter.Therefore,Tower Jazz 0.18 um BCD process is selected in this design.LDMOS is selected for the output switch tube to withstand high voltage.Compared with ordinary HVMOS,LDMOS has an advantage in the area under the same conduction resistance.Since the onresistance of the N tube is usually smaller than that of the P tube,the selection of LDNMOS can reduce the chip area and improve the conversion efficiency.On this basis,using the relevant knowledge of switching power and integrated circuits,I designed a four-tube buckboost power converter with integrated switching tubes on-chip.The feasibility of the scheme was verified through simulation tests.The performance parameters meet the design requirements,and the layout design has been completed,and the next step of testing is to be conducted after tape-out. |
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