Abstract: A totem-pole PFC and a current-sampling unit of the totem-pole PFC are provided. The totem-pole PFC is electrically connected to an AC power source and a DC-to-DC converter, and is electrically connected to a load through the DC-to-DC converter. The current-sampling unit has a first sampling switch and a second sampling switch. The first sampling switch and the second sampling switch are controlled to be turned on and turned off so that a magnetizing current flows through the magnetizing inductor when a magnetizing inductor is magnetized and a demagnetizing current does not flow through the sampling resistor when the magnetizing inductor is demagnetized, thereby increasing the demagnetization efficiency and overcoming superimposed operations to improve current detection and increase conversion efficiency of the power conversion.

Abstract: A feed forward controlling circuit is used to perform a feed forward controlling method to restrain ripple of the output voltage in a power converter. The power converter is controlled by a control signal outputted from an output terminal of a controller. The method includes steps of: receiving an output voltage from an output terminal of a voltage converter; attenuating the output voltage to generate an electrical signal; acquiring a DC signal from the electrical signal; and obtaining a ripple compensation signal in accordance with the electrical signal and the DC signal to output to an output terminal of a controller. The output terminal of the controller outputs a control signal to control the power converter.

Abstract: A feed forward controlling circuit and a method for voltage ripple restraint are provided. The feed forward controlling circuit is used to perform the feed forward controlling method. The feed forward controlling method is used to restrain ripple of the output voltage in a power converter. The power converter is controlled by a control signal outputted from an output terminal of a controller. The method includes steps of: receiving an output voltage from an output terminal of a voltage converter; attenuating the output voltage to generate an electrical signal; acquiring a DC signal from the electrical signal; and obtaining a ripple compensation signal in accordance with the electrical signal and the DC signal to output to an output terminal of a controller. The output terminal of the controller outputs a control signal to control the power converter.