METHOD FOR CONTROLLING SWITCHING BY CHANGING CONTROL MODE AND SWITCHING CONTROLLER AND PFC CONTROLLER USING THE SAME

摘要

A switching controlling method through control mode change and a switching controller and a power factor correction controller using the same are disclosed. The switching controlling method which controls a switching action of a power switch of the power factor correction controller by controlling an inductor current flowing in an inductor with input voltage comprises; a step of detecting that the inductor current becomes 0 so that the power factor correction controller is controlled with a critical conduction mode; a step of detecting the state that an RMS value of the inductor current gets lower than a predetermined value; a step of turning on the power switch so that the state in which the power factor correction controller is controlled with the critical conduction mode is maintained when the inductor current becomes 0 at the state that the RMS value of the inductor current does not get lower than the predetermined value; a step of delaying turn-on timing of the power switch so that the power factor correction controller is controlled with a discontinuous conduction mode when the inductor current becomes 0 at the state that the RMS value of the inductor current gets lower than the predetermined value. The present invention improves a power factor of a power factor correction circuit and relieves a total harmonic distortion problem by sensing the inductor current and changing a control mode around zero current getting out a pure sine wave shape when operating the power factor correction circuit with the critical conduction mode using a fly-back converter.