System Design Of Current Observer Modulated Boost Converter

With the increase of DSP,FPGA and other microprocessor speeds,digitally controlled DC-DC converters can implement a variety of complex algorithms to improve the system’s response speed and performance.Current sensors play a key role in digital current mode control,but there are several major problems: first,the sensor cannot continuously sample the inductor current,and the sampling frequency is limited;secondly,the price of the sensor increases linearly with the increase of the sampling frequency;sampling The delay introduced by the circuit will affect the control effect of the system.So people began to study current observers instead of sensors.In this paper,the Boost converter is modeled by the basic modeling method,and the transfer function of the circuit is derived.The method of coupling the leading edge modulation and the peak current mode eliminates the subharmonic oscillation problem when the duty ratio is greater than 0.5 in the current mode control.The control algorithm can adjust the inductor current to the reference current in the current cycle to improve the dynamics of the system.responding speed.On this basis,according to the variation law of the inductor current,an integrated current observer is proposed to reduce the cost of the system and the noise introduced by sampling.Considering the influence of parasitic parameters on the observed current and output voltage in the actual circuit,it is proposed to add a self-correction module to the inner loop.Simulation and experimental results show that the parasitic parameters of the device cause the observed current to diverge and the output voltage of the converter to have a steady-state error.After adding the self-correction module to the current loop,the integrated current observer can well predict the actual inductor current,and its error is limited to 4.5%,while eliminating the steady-state error of the output voltage.The leading edge modulation coupling peak current mode control strategy proposed in this paper can not only eliminate the subharmonic oscillation,but also eliminate the influence of circuit parasitic parameters on the system and improve the stability of the Boost converter.