| Power factor correction(PFC)converters are widely used in AC/DC power conversion to achieve high power factor(PF)and low input current total harmonic distortion(THD).The input-side inductance of the boost PFC converter is beneficial to suppress the high-order harmonics of input current,and it is one of the most commonly used PFC converters.The design objective of boost PFC converter usually is wide input range,high power density and high efficiency.This paper studies the control strategy of interleaved DCM boost PFC converter which is suitable for wide input range.This paper analyzes the topology and working principle of interleaved DCM boost PFC converter,and the reasons for the input current distortion and PF reduction of the converter under wide input voltage.A variable duty cycle control method is studied,which can improve the PF of the converter to unity and reduce the input current distortion in a wide input voltage range.At the same time,DCM boost PFC converter can realize ‘automatic current shaping’,which does not need a high-bandwidth current inner loop.DCM boost PFC converter is suitable for modern aviation applications with AC input frequency of up to 800 Hz.When the boost PFC converter starts up,a large inrush current will be generated at the moment of startup.This paper analyzes the causes of the inrush current,and studies a new inrush current limiter circuit with digital controlled bridge,which does not need to use inrush current limiter resistance and improves the power density of the converter.The relationship between startup-time and inrush current is analyzed,the control principle of digital controlled bridge is studied,and the design of trigger circuit is given.In this paper,the power loss model of interleaved DCM boost PFC converter is derived,a phase-shedding control strategy to optimize the light load efficiency of the converter is studied,and a control strategy to improve the phase-shedding transient response performance of the converter is proposed based on nonlinear digital control.The factors which limit the voltage loop bandwidth of the converter are analyzed,and a nonlinear PI transient optimization method is studied.In this paper,the digital implementation method of variable duty cycle control is studied,the small signal analysis of interleaved DCM boost PFC converter is carried out,the small signal transfer function of the control signal to output voltage is deduced;the step-by-step design procedure of voltage control loop realized by digital control is studied.Finally,the voltage and current stress of the power device of the converter are calculated,and the parameters of the boost inductor and the DC bus capacitor are designed,and a 350 W experimental prototype is built.Experimental results show that the control strategy studied in this paper can ensure that the converter has a good performance,i.e.high power factor,low THD,high efficiency,fast transient response and small startup inrush current in a wide input range(85-264 Vac,47-800Hz). |
