Study Of Boost Converter Based On Predictive Current Control With Current Observer

With the popularity of microcontrollers,field programmable gate arrays and analog-to-digital converters,and the increased demand for power performance in the consumer and industrial markets,digital switching power supply-related products are gaining increasing attention.Compared to analog DC-DC converters,the performance of digital DC-DC converters is limited by factors such as control algorithm run time,analog-to-digital converter rate,and resolution of digital pulse width modulators,resulting in hardware costs and converters Performance between the contradictions.How to increase the dynamic and static performance of the converter without increasing the hardware cost of the system is the hotspot of the current research.In this paper,the small-signal model of boost type DC-DC converter is deduced by using the state space averaging method.The characteristics and existing problems of the existing control method are analyzed.On this basis,the peak current control algorithm is proposed.Using the double-loop control method,the outer loop focus on control accuracy,the inner loop reference current can be calculated through output voltage error.The inner loop foucus on control speed,the duty cycle can be calculated through current error.When the disturbance occurs,the algorithm can adjust the inductor current to the reference current in only two cycles,and has a high response speed.Aiming at the problem of subharmonic oscillation in the traditional current mode,it can not only avoid the subharmonic oscillation effectively by the combination of sampling point and modulation mode,but also increase the resolution of digital pulse width modulation without complicated slope Compensation algorithm.Finally,a current observer is proposed to replace the complex and expensive current sensors required for traditional digital current control.However,due to the presence of parasitic parameters on the switching device and the inductor,the inductor current can not be accurately observed.And the current observer can eliminate the integral part of the outer loop proportional integral controller,which will bring steady-state error to the output voltage.In this paper,the corresponding compensation algorithm is proposed,which not only eliminates the steady-state error of the output voltage,but also improves the observed current accuracy.Simulation and experimental results show that the proposed predictive peak current algorithm based on current observer can effectively eliminate the sub-harmonic oscillation,can greatly enhance the load response speed compared with the traditional digital PID controller.With the parasitic parameters compensation,the output voltage steady state error can be eliminated.Moreover,the inductor current can be accurately observed.In the steady state,the estimation error is less than 5%,which indicate that the current observer can satisfy the application demand.