Research On Transient Response Optimization Technology Of Digital DC-DC Converter

With the development of society,people’s demand for portable electronic equipment has increased in recent years.Power supply is an indispensable part of electronic equipment.At present,switching power supplies on the market are gradually being gradually developed due to their superior efficiency.Replace the linear regulator LDO.Switching power supplies can be divided into analog power supplies and digital power supplies according to their control methods.Due to its strong portability,real-time programming control,and short development cycle,digital power supplies have developed their own products by major semiconductor companies such as TI and ADI.This article designs a transient response optimized digital control circuit for a fixedfrequency voltage-mode Buck converter.The digitally controlled Buck converter adopts an adaptive ramp DPWM,and adaptively changes the control clock frequency of the DPWM ramp according to the error voltage,improving the transient response of the loop by increasing the bandwidth of the entire control loop during the transient response.The adaptive ramp DPWM designed in this paper increases the modulation effect of the fixed frequency PWM signal by detecting the error voltage and changing the slope of the ramp Ramp generated by the internal counter,and improves the transient response of the entire system.This article uses two methods to achieve adaptive ramp DPWM,one method is digital adaptive DPWM control(Adaptive DPWM,A-DPWM).A-DPWM control is to adaptively change the control clock frequency of the DPWM ramp after fractional frequency division of the system clock frequency through a pure digital method.Another method is analog auxiliary DPWM control(Analog Assistant DPWM,AADPWM).AA-DPWM adjusts the output clock frequency of the ICO through the error current generated by the error voltage to adaptively change the control clock frequency of the DPWM.A-DPWM and AA-DPWM enhance the regulation effect when the feedback voltage is far away from the reference voltage,which is equivalent to increasing the bandwidth of the control loop,thereby achieving an improvement in response speed.At the same time,it has the bandwidth of the original controller when the feedback voltage is close to the reference voltage,which will not affect the stability of steady-state operation.The Buck converter is simulated and verified when the input voltage is 3.3V,the output voltage is 1.8V,and the switching frequency is 1MHz.The digital-analog hybrid simulation results show that the A-DPWM circuit has a 10-20 A load step,the overshoot is reduced by 5mV,the recovery time is reduced by 10.5μs;the undershoot is reduced by8 mV,and the recovery time is reduced by 9.6μs.Simulink model simulation results show that the digital control Buck converter based on AA-DPWM has an input voltage of 5V,an output voltage of 3.3V,and a load step of 10-20 A,the overshoot is reduced by 30 mV,and the recovery time is reduced by 7.555μs;The undershoot is reduced by 15 mV,and the recovery time is reduced by 5.805μs.