Buck DC-DC Converter Design With On＿chip Ripple Injection

As time passes,modern technology develops rapidly,micro-electronics products have tended to be portable,low power consumption and high performance.The new energy vehicle field,which is currently developing hot,has more demanding requirements on the performance and stability of the system.The power management chip,on the other hand,determines whether the system can work smoothly and efficiently.So developing into a buck DC-DC converter with higher safety,less interference from external parameters,and higher output voltage accuracy is very exploratory and commercially valuable.In this paper,TSMC 40 nm CMOS(Complementary Metal Oxide Semiconductor)process is selected to design a buck DC-DC converter based on ACOT(Advanced Constant On Time)mode.The main features are: i.It avoids the use of error amplifiers in the DC-DC system loop and does not require the design of an error amplifier compensation network.The response speed of the system is improved.ii.In practical applications,the LDO(Low Dropout Regulator)can be used as a soft-start module for DC-DC,and the LDO is chosen to provide output at light load to improve conversion efficiency.iii.The on-chip ripple injection method is used to reduce the influence of the external environment on the working condition of the ripple injection device,and the smaller size and lower parasitic parameters of ceramic capacitors are considered as output filter capacitors to effectively reduce the size of the output ripple while ensuring the stability of the system.The system is also designed with power-on reset,zero current detection,and over current protection modules to ensure normal and stable operation during the whole phase of use.This paper uses Cadence Virtuoso 6.1.8 simulation tool to simulate each submodule and the system to verify the correctness of the logic and functions,and the results are as follows: under typical conditions,the supply voltage is 3.3 V,the DC-DC system works in discontinuous conduction mode,the ripple size of the output voltage is about 4.5 mV,and the switching frequency of the system is about 1.005 MHz.In the continuous conduction mode,the ripple size of the output voltage is about 2.45 mV and the system switching frequency is about 996 k Hz.The load current completes a fast jump between 0 m A and 300 m A in 1 μs time,and the maximum overshoot and undershoot of the output voltage in the full process corner condition are 42.44 mV and47.09 mV,respectively.The load current is set to 110 m A,and the buck conversion efficiency of the system is about 91 %.