Research On Fully-integrated Digital Control Power Management Chip System Based On PID Algorithm

Digital control power supply has become the mainstream trend of modern switching power supply design with the characteristics of high integration and short design cycle.It is widely used in modern industrial applications such as vehicle chip,smart home and so on.Power Management Integrated Circuit(PMIC)is an indispensable part of the chip.Controlling the chip by fully integrating the digital feedback loop of switching power supply and power devices through MCU has become a new trend of PMIC management chip under the background of the new era.At the same time,highly integrated digital control power supply is also a new challenge in the development trend of power supply in the future.Based on vis150 nm process,a fully integrated digital control DC-DC buck power management chip system based on PID algorithm is designed.The main work is as follows:1.The buck power level is analyzed by the state space average method,and the voltage loop,current loop and double-loop built by the PID compensator are modeled to determine the system transfer function.The power level and double-loop digital feedback loop under synchronous rectification control mode are simulated by Simulink simulator.The model simulation results preliminarily ensure the theoretical feasibility of the design,provide a basis for PID parameter setting,and compensate the loop through the set parameters.2.The digital module includes incremental PID compensator module,DPWM module,sample holder module and clamp comparator module.The compensator of incremental PID algorithm only needs to clamp the output to solve the overshoot problem,which reduces the design difficulty of digital feedback loop.The DPWM module adopts the triangular wave modulation mode.Through the code design,the accurate dead time improves the efficiency under the synchronous rectification control mode,and generates a flag signal to cooperate with the sample and holder module completes the simultaneous sampling of output voltage and inductor current,realizes the design of current loop and double-loop,at the same time,solves the problem of double loop synchronous sampling.A clamp comparator is designed to prevent overshoot caused by data overflow.Finally,the physical implementation of the above modules is completed by code.3.The transient enhanced LDO is used to provide a fast response power supply for the feedback loop of the digital control chip.It has the characteristics of fast transient response,low power consumption and low output ripple.Its static current is 61μA,the establishment time is 4μs,the output voltage is 1.8V,with the load current jumps from0 m A to 20 m A within 1us,the overshoot voltage is 280mv/295 mv.In order to ensure the stability of the circuit under temperature change,a Banba bandgap reference with high temperature suppression coefficient is designed by using the method of secondorder current subsection compensation to provide reference power for LDO,which greatly reduces the influence of temperature drift on the circuit reference voltage.Its input voltage is 5V,output voltage is 1.2V,and the temperature coefficient can reach2.5ppm / ℃4.Combined with the 5V to 2V low output voltage index,the synchronous rectifier control mode is adopted to drive the switch.The current loop with low gain and high bandwidth is used as the inner loop and the voltage loop with high gain and small bandwidth is used as the outer loop,which enhances the driving ability of the loop.The input voltage range of the power management chip system is 3V-12 V,the output voltage is 2.008 V,the maximum load capacity is 1A,the system locking time is 1.24 ms under1A load,and the output voltage ripple is less than 12 mv.Finally,AMS simulator is used to simulate the power supply management system in virtuoso,and the layout of the analog part and the back-end flow of the digital code are completed according to the corresponding process and layout rules.