Switching Power Supply PFC Correction Digital Control Algorithm Research

In the development of power electronics,switching power supply,as a kind of low loss,high efficiency,simple circuit,high reliability power supply device,has been widely applied in all kinds of industrial production,electronic equipment and daily life,etc.But its special rectification device structure are connected to the grid,leading to the input current contains a lot of harmonic pollution in power grid.The harmonic is not conducive to the construction of "green" power grid,so the design of power factor correction device for switching power supply is imperative.Therefore avoiding a series of problems brought by the harmonic pollution.Before the 21st century,power factor correction technology is controlled by the analog components or integrated chip.But this way is influenced by aging,temperature and the outside interference,so correction system is not very stable.As the popularity of microprocessors,digital signal processor and field programmable gate array control device,which can realize normal simulation control scheme with digital control ways,and modern control theory can be applied to power factor correction.Its high-speed sampling frequency and fast signal processing speed makes digital control PFC to be researching trend.In this paper,under the hypothesis that the input voltage without harmonic,from the definition of power factor to analysis on the two crucial factors:harmonic factor and phase factor,which is to improve the power factor.There are two ways:one is reducing the phase difference between the input current and the input voltage to increase the value of cos?;another is making the input current waveform well with sinusoidal waveform of input voltage to reduce THD of the input current.Choosing the Boost circuit to be the APFC converter topology.When the Boost is working in CCM mode,the three terminal switching device modeling method is adopted to analyse steady state and small signal disturbance of circuit,and to set up the transfer function between the perturbation parameter.There is a simple summary comparison for the existing power factor correction techniques in paper.Selecting the average current double loop digital control method to achieve PFC.According to the transfer function to design the inner current loop,outer voltage loop and voltage feed-forward part,and to construct simulation model on the MATLAB.The simulation validates the control strategy.In order to improve the correction precision of system,using the Delta operator to continuous the discrete signal obtained by high-speed sampling.The paper is based on the above Delta operator putting forward a kind of APFC which is based on sliding mode PI digital controller,and establishing simulation model on MATLAB platform.The control algorithm can improve the power factor effectively,and verify the high precision,strong anti-interference ability,and strong robustness.The effect is better than the average current double loop digital control mode.