Patent ID: 8144486

Claim:
A power converter comprising: a primary coil configured to receive an input voltage; a switch, including a first electrode, a second electrode coupled to the primary coil, and a control electrode; an output unit, including a secondary coil, the output unit configured to output an output voltage, the primary coil and the secondary coil forming a transformer, and the input voltage being converted to the output voltage by the transformer; and a controller configured to receive a sensing voltage corresponding to a switch current flowing between the first electrode and the second electrode of the switch; to detect a maximum value of the switch current based on the sensing voltage; to detect a valley point of a voltage between the first electrode and the second electrode of the switch based on the sensing voltage; and to transmit a control signal having a first voltage for turning on the switch and a second voltage for turning off the switch to the control electrode of the switch in accordance with the valley point, wherein an off period in which the control signal has the second voltage includes a first period and a second period, and wherein the controller is configured to calculate the first period of the off period based on the maximum value of the switch current, and to detect the valley point by using a third period in which the control signal has the first voltage, the calculated first period, and the second period.