Abstract: The disclosure provides a method for controlling an equivalent resistance of a converter. The method includes receiving a power source input signal, generating a first control signal according to a voltage level and a state of the power source input signal to adjust an equivalent resistance of the voltage conversion module and cause the voltage conversion module to operate in the damper mode or the converter mode, when the voltage conversion module operates in the converter mode converting the power source input signal to an output signal, and when the voltage conversion module operates in the damper mode detecting the voltage level or the current level of the power source input signal, and adjusting the equivalent resistance so that the voltage conversion module could operate in the bleeder mode or the converter mode to convert the power source input signal to the output signal.

Abstract: A resonant converter with power factor correction includes a power-obtaining circuit, an energy-storage element and an energy-transferred circuit. The power-obtaining circuit is used for receiving an input line voltage. The energy-storage element is coupled between the power-obtaining circuit and the energy-transferred circuit. The energy-transferred circuit is used for generating an output power. In a first time period, based on a first control signal, the energy-storage element and the power-obtaining circuit operate a soft switching so that the energy-storage element is charged to obtain the input line power and generate an energy-storage voltage. In a second time period, based on a second control signal, the energy-storage element and the energy-transferred circuit operate a soft switching so that the energy-storage element is discharged to make the energy-storage voltage converted into the output power.