Design And Research Of Key Module Of Digital Control Buck Converter

In recent years,the scale of electronic products such as smart phones,tablets and portable electronic products has expanded rapidly,and power supply is an integral part of these portable electronic products.Switching power supply includes analog switching power supply and digital switching power supply.In view of the problems that analog switching power supply does not conform to the portability of power supply,long running time and aging of semiconductor devices,a digital switching power supply is proposed.The advantages of high efficiency,strong anti-interference ability and flexible control mode of digital switching power supply have become the focus of academic research at home and abroad.Starting with the working principle of typical buck converter,this paper analyzes and summarizes the key modules of digital control buck converter,and mainly designs the analog-to-digital converter（ADC）,digital proportion integral derivative（dpid）and Digital pulse width modulation（DPWM）and an OCP overcurrent protection circuit can realize the nonlinear regulation of valley current.Among them,according to the overall design index,the analog-to-digital converter selected in this paper is the successive approximation analog-to-digital converter（SAR ADC）,and the idea of redundancy is added to the ADC.In the design index of the designed SAR ADC,the input range is 0.8-2.8 V,the number of bits is 10 bits,and the sampling frequency is 10 MHz.Finally,the simulation is carried out in cadence virtuoso.Digital compensation network plays a key role in digital switching power supply,and its performance determines the stability of the whole system.Firstly,according to the empirical trial and error method,the dpid coefficients are determined in Simulink MATLAB.When the proportional term coefficient is 100,the integral term coefficient is10000 and the differential term coefficient is 0.01,buck can stably output 1.8 V and the overshoot is 0.39%.When it is discretized,the position PID discretization is selected.After analyzing the principle of digital pulse width modulator,dpid and DPWM are realized by hardware description language（Verilog）.In order to verify the effectiveness of its DPWM module,the clock frequency of DPWM module is set to 50 MHz,and the DPWM simulation waveforms with duty cycle of 7 / 10,1 / 2 and 3 / 10 are obtained.The simulation results show that the function can be realized better.When the OCP overcurrent protection circuit detects the circuit overcurrent,it can quickly adjust the circuit.According to the comparison results of the numerical comparator,the valley current can be adjusted in stages.In case of overcurrent,reduce it to the set multiple.Moreover,the adjustment proportion is different for different voltages.After setting the parameters of OCP,it is listed that the adjustment proportion is 11.1%,20.0% and 25.0%when the output voltage is 12 V,20V and 32 V.This method can improve the circuit efficiency and improve the response speed.