Design Of Fully Integrated BUCK Converter For Vehicle Charger

At present,the trend of electronic products on the market is portability,which are required high integration and performance of the chips used.As the heart of electronic products,power management chip is an important factor restricting the development of electronic products.With the more complexity and less energy of electronic products,power management chips with high performance,high efficiency and high integration are the direction of research by scholars and engineers all over the world.Switching power supply has many advantages,such as less size and weight,higher efficiency and wide output range,so it has become the most important part of current research of power management chip.A fully integrated Buck converter with dual-mode and synchronous rectifier is designed in this paper.The design mainly refers to the design experience of similar mature products in the market,and consults the literature.The original design is carried out by using 0.40 um BCD technology of Taiwan Vis Company.The DC-DC converter chip has these characteristics: peak current detection,PWM/PSM dual-mode modulation,over-temperature and under-voltage protection.The design performance parameter of this paper is that the input voltage is 12 V,the output voltage is 6V,the maximum load capacity is 2A,and the working frequency is 200 kHz.A voltage synchronous rectifier Buck circuit with PWM/PSM dual-mode modulation is adopted.When the circuit working with high load,it uses PWM mode modulation,When the circuit working with light load,PSM mode modulation is used,and the circuit can automatically switch between the two modes according to the load condition,which makes the circuit more efficient in the whole load range.Soft start circuit as a part of the chip avoids the impact of overvoltage and surge current on the chip or even damage.This circuit adopts synchronous rectifier technology,which effectively improves the efficiency of the circuit,and adds a dead-time control module,which effectively avoids the simultaneous working of the power transistor and the Free-wheeling transistor.Based on the analysis of the working principle,circuit system structure and control mode of DC-DC circuit,the main structure of the circuit designed in this paper is presented.Meanwhile,each module of the system,including reference circuit,current detection circuit,protection circuit,oscillator circuit,error amplifier circuit,comparator circuit and bootstrap circuit,is designed particular and adopt Cadence to simulate and adjust the parameters so that all modules achieve the design targets.Finally,the system is simulated and adjusted.The simulation results reveal that the system operates well and achieves the design requirement.