G.A. Belov, A.V. Serebryannikov

On the basis of consideration of the power factor corrector-s (PFC) control microcircuit-s functioning, analysis and calculation of PFC-s quasistationary mode and transients is given. The quasistationary mode is considered in the assumption that the power part works in a boundary mode when a throttle-s current represents sequence of triangular impulses without pauses between them. Then at performance of the additional condition consisting in a constancy of the power transistor-s on-condition time, average value of throttle-s current changes to proportionally PFC-s input voltage in the absence of a special input current-s average value regulation contour. The nonlinear differential equation for average value of the output condenser-s voltage received here as depends on input power and a load-s current, as well as in PFC with a double-circuit control system. This equation shows presence in PFC-s output voltage of the low-frequency pulsations changing with doubled frequency of a power line which can decrease only increase in capacity of output condenser. These pulsations get on an output of voltage regulator and on an input of the pulse-width modulator, causing additional peak modulation of impulses of throttle-s current and additional distortions of PFC-s input current and a power line current. The analytical parities, allowing organizing fast and exact enough calculation of transients, are proved. Results of calculations well illustrate the basic features of PFC-s considered scheme. Switching frequency of the power transistor is maximum in the beginning and in the end of a power line voltage-s half-period where the switching period is minimum and is approximately equal to necessary duration of the power transistor-s on-condition t1 . Changing of time t1 during the power line voltage-s half-period, necessary for maintenance of a output voltage-s constancy, is slightly, as well as is required on conditions of PFC-s normal work. It is provided with that voltage regulator-s output voltage uvr also slightly changes for the power line voltage-s half-period (apparently from the presented curves, in the beginning of a half-period voltage uvr is supported at level 7 V, in the middle of a half-period - at the rate of about 7,25 V, in the end of a half-period - 7,5 V). Time t1 , as well as voltage uvr , changes for the power line voltage-s half-period approximately on 7 %.