Patent ID: 6845019

Claim:
A flyback converter, which provides an essentially constant output voltage independent of the size of a load, the flyback converter comprising: a transformer operable to change an input voltage to a predetermined level according to a winding ratio of a primary coil to a secondary coil; an output unit, coupled to the transformer, operable to rectify a voltage signal output from the transformer into a DC signal operable to drive the load; a switch, coupled to the primary coil of the transformer, operable to control an on/off state of a power at the primary coil according to an input switching control signal; a feedback unit, coupled to the transformer, operable to detect the voltage signal output by the transformer to the output unit, generating a feedback signal, detecting a switching current of the switch to correct the feedback signal, and outputting the corrected feedback signal, the feedback unit comprising: a detecting coil operable to detect the power output from the transformer; a driving power generator operable to rectify a detected signal of the detecting coil to generate a driving power for the operation of the switching controller; a switch current operator operable to detect a current variation according to the switching operation of the switch to generate a converted current signal; a gain regulator operable to regulate the gain of the converted current signal output from the switch current operator to generate a corrected current signal; and a feedback signal generator operable to reduce the driving power signal output from the driving power generator by a voltage drop corresponding to the corrected current signal output from the gain regulator to generate a feedback voltage signal to the switching controller; and a switching controller, coupled to the feedback unit and to the switch, operable to receive an output signal of the feedback unit and generating a switching control signal, operable to control the operation of the switch.