Patent ID: 7221128

Claim:
A converter comprising: a first switching element being connected to a DC power source through a primary winding of a transformer; a control circuit to conduct ON/OFF control on the first switching element; an output rectifying/smoothing circuit to rectify and smooth a voltage induced on a secondary winding of the transformer and provide a DC output; a voltage supply part to rectify and smooth a voltage induced on a tertiary winding of the transformer and provide the rectified and smoothed voltage as a supply voltage to the control circuit; a start-up circuit having a constant current circuit to supply a constant current to the voltage supply part and a constant voltage circuit to supply a constant voltage to the voltage supply part; and a start-up control circuit to operate the start-up circuit as the constant current circuit until the control circuit starts and to switch the operation of the start-up circuit from the constant current circuit operation to the constant voltage circuit operation after detecting the start of the control circuit according to a voltage generated by the tertiary winding of the transformer.